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Marini M, Zeynali A, Collini M, Bouzin M, Sironi L, D'Alfonso L, Mantegazza F, Cassina V, Chirico G. Proteinaceous microstructure in a capillary: a study of non-linear bending dynamics. Lab Chip 2022; 22:4917-4932. [PMID: 36382419 DOI: 10.1039/d2lc00697a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
The flap of bendable structures under continuous flow impacts a variety of fields, ranging from energy harvesting to active mixing in microfluidic devices. Similar physical principles determine the flapping dynamics in a variety of systems with different sizes, but a thorough investigation of the bending dynamics at the microscale is still lacking. We employ here two-photon laser polymerization to fabricate elongated proteinaceous flexible microstructures directly within a micro-capillary and we characterize their bending dynamics. The elastic properties of the microstructures with different (circular and square) cross-sections are tested by Atomic Force Microscopy and by studying the deflection-flow dependence in microfluidic experiments at intermediate Reynolds numbers (Rey ≲ 150). The retrieved Young's modulus of the fabricated matrix (100 kPa ≤ E ≤ 4 MPa) falls in the range of most typical biological tissues and solely depends on the laser fabrication intensity. The elastic constant of the microstructures falls in the range of 0.8 nN μm-1 ≤ k ≤ 50 nN μm-1, and fully agrees with the macroscopic Euler Bernoulli theory. For soft microstructures (0.8 nN μm-1 ≤ k ≤ 8 nN μm-1) we reveal undamped bending oscillations under continuous microfluidic flow, corresponding to ∼10% of the total structure deflection. This behavior is ascribed to the coupling of the viscoelasticity and non-linear elasticity of the polymer matrix with non-linear dynamics arising from the time-dependent friction coefficient of the bendable microstructures. We envision that similar instabilities may lead to the development of promising energy conversion nanoplatforms.
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Affiliation(s)
- Mario Marini
- Dipartimento di Fisica, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy.
| | - Amirbahador Zeynali
- Dipartimento di Fisica, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy.
| | - Maddalena Collini
- Dipartimento di Fisica, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy.
- Bionanomedicine Center, BIONANOMIB, Via Follereau 3, 20854, Vedano al Lambro, Italy
| | - Margaux Bouzin
- Dipartimento di Fisica, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy.
| | - Laura Sironi
- Dipartimento di Fisica, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy.
- Bionanomedicine Center, BIONANOMIB, Via Follereau 3, 20854, Vedano al Lambro, Italy
| | - Laura D'Alfonso
- Dipartimento di Fisica, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy.
- Bionanomedicine Center, BIONANOMIB, Via Follereau 3, 20854, Vedano al Lambro, Italy
| | - Francesco Mantegazza
- Dipartimento di Medicina e Chirurgia, Università degli Studi di Milano-Bicocca, Via Follereau 3, 20854, Vedano al Lambro, Italy
- Bionanomedicine Center, BIONANOMIB, Via Follereau 3, 20854, Vedano al Lambro, Italy
| | - Valeria Cassina
- Dipartimento di Medicina e Chirurgia, Università degli Studi di Milano-Bicocca, Via Follereau 3, 20854, Vedano al Lambro, Italy
- Bionanomedicine Center, BIONANOMIB, Via Follereau 3, 20854, Vedano al Lambro, Italy
| | - Giuseppe Chirico
- Dipartimento di Fisica, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy.
- Bionanomedicine Center, BIONANOMIB, Via Follereau 3, 20854, Vedano al Lambro, Italy
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2
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Bouzin M, Marini M, Chirico G, Granucci F, Mingozzi F, Colombo R, D'Alfonso L, Sironi L, Collini M. Melanin concentration maps by label-free super-resolution photo-thermal imaging on melanoma biopsies. Biomed Opt Express 2022; 13:1173-1187. [PMID: 35414966 PMCID: PMC8973199 DOI: 10.1364/boe.445945] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Revised: 11/09/2021] [Accepted: 11/09/2021] [Indexed: 05/04/2023]
Abstract
Surgical excision followed by histopathological examination is the gold standard for melanoma screening. However, the color-based inspection of hematoxylin-and-eosin-stained biopsies does not provide a space-resolved quantification of the melanin content in melanocytic lesions. We propose a non-destructive photo-thermal imaging method capable of characterizing the microscopic distribution and absolute concentration of melanin pigments in excised melanoma biopsies. By exploiting the photo-thermal effect primed by melanin absorption of visible laser light we obtain label-free super-resolution far-infrared thermal images of tissue sections where melanin is spatially mapped at sub-diffraction 40-μm resolution. Based on the finite-element simulation of the full 3D heat transfer model, we are able to convert temperature maps into quantitative images of the melanin molar concentration on B16 murine melanoma biopsies, with 4·10-4 M concentration sensitivity. Being readily applicable to human melanoma biopsies in combination with hematoxylin-and-eosin staining, the proposed approach could complement traditional histopathology in the characterization of pigmented lesions ex-vivo.
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Affiliation(s)
- Margaux Bouzin
- Physics Department, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy
- Equal contribution
| | - Mario Marini
- Physics Department, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy
- Equal contribution
| | - Giuseppe Chirico
- Physics Department, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy
- CNR Institute for Applied Science and Intelligent Systems, Via Campi Flegrei 34, 80078, Pozzuoli, Italy
| | - Francesca Granucci
- Biotechnology and Biosciences Department, Università degli Studi di Milano-Bicocca, Piazza della Scienza 2, 20126, Milano, Italy
| | - Francesca Mingozzi
- Biotechnology and Biosciences Department, Università degli Studi di Milano-Bicocca, Piazza della Scienza 2, 20126, Milano, Italy
| | - Roberto Colombo
- Department of Earth and Environmental Sciences, Università degli Studi di Milano-Bicocca, Piazza della Scienza 1, 20126, Milano, Italy
| | - Laura D'Alfonso
- Physics Department, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy
| | - Laura Sironi
- Physics Department, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy
| | - Maddalena Collini
- Physics Department, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy
- CNR Institute for Applied Science and Intelligent Systems, Via Campi Flegrei 34, 80078, Pozzuoli, Italy
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3
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Scodellaro R, Inverso D, Panzeri D, Bouzin M, D'Alfonso L, Collini M, Chirico G, Sironi L. AI-based pipelines for the automated recognition of hepatocellular carcinoma and the semantic segmentation of virtually stained liver biopsies. Biophys J 2022. [DOI: 10.1016/j.bpj.2021.11.2061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022] Open
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4
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Bouzin M, Marini M, Zeynali A, Borzenkov M, Sironi L, D'Alfonso L, Mingozzi F, Granucci F, Pallavicini P, Chirico G, Collini M. Photo-activated raster scanning thermal imaging at sub-diffraction resolution. Nat Commun 2019; 10:5523. [PMID: 31797931 PMCID: PMC6892803 DOI: 10.1038/s41467-019-13447-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Accepted: 11/07/2019] [Indexed: 12/01/2022] Open
Abstract
Active thermal imaging is a valuable tool for the nondestructive characterization of the morphological properties and the functional state of biological tissues and synthetic materials. However, state-of-the-art techniques do not typically combine the required high spatial resolution over extended fields of view with the quantification of temperature variations. Here, we demonstrate quantitative far-infrared photo-thermal imaging at sub-diffraction resolution over millimeter-sized fields of view. Our approach combines the sample absorption of modulated raster-scanned laser light with the automated localization of the laser-induced temperature variations imaged by a thermal camera. With temperature increments ∼0.5-5 °C, we achieve a six-time gain with respect to our 350-μm diffraction-limited resolution with proof-of-principle experiments on synthetic samples. We finally demonstrate the biological relevance of sub-diffraction thermal imaging by retrieving temperature-based super-resolution maps of the distribution of Prussian blue nanocubes across explanted murine skin biopsies.
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Affiliation(s)
- M Bouzin
- Physics Department, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy
| | - M Marini
- Physics Department, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy
| | - A Zeynali
- Physics Department, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy
| | - M Borzenkov
- Medicine and Surgery Department, Nanomedicine Center, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy
| | - L Sironi
- Physics Department, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy
| | - L D'Alfonso
- Physics Department, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy
| | - F Mingozzi
- Biotechnology and Biosciences Department, Università degli Studi di Milano-Bicocca, Piazza della Scienza 2, 20126, Milano, Italy
| | - F Granucci
- Biotechnology and Biosciences Department, Università degli Studi di Milano-Bicocca, Piazza della Scienza 2, 20126, Milano, Italy
| | - P Pallavicini
- Chemistry Department, Università degli Studi di Pavia, Viale Taramelli 12, 27100, Pavia, Italy
| | - G Chirico
- Physics Department, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy.
- CNR Institute for Applied Science and Intelligent Systems, Via Campi Flegrei 34, 80078, Pozzuoli, Italy.
| | - M Collini
- Physics Department, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy
- CNR Institute for Applied Science and Intelligent Systems, Via Campi Flegrei 34, 80078, Pozzuoli, Italy
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Borzenkov M, D'Alfonso L, Polissi A, Sperandeo P, Collini M, Dacarro G, Taglietti A, Chirico G, Pallavicini P. Novel photo-thermally active polyvinyl alcohol-Prussian blue nanoparticles hydrogel films capable of eradicating bacteria and mitigating biofilms. Nanotechnology 2019; 30:295702. [PMID: 31025630 DOI: 10.1088/1361-6528/ab15f9] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Antibacterial treatment is an essential issue in many diverse fields, from medical device treatments (for example prostheses coating) to food preservation. However, there is a need of novel and light-weight materials with high antibacterial efficiency (preferably due to the physical activation). Utilization of photo-thermally active nanoparticles can lead to novel and re-usable materials that can be remotely activated on-demand to thermally eradicate bacteria and mitigate biofilm formation, therefore meeting the above challenge. In this study polyvinyl alcohol (PVA) hydrogel films containing non-toxic and highly photo-thermally active Prussian blue (PB) nanoparticles were fabricated. The confocal microscopy studies indicated a uniform nanoparticle distribution and a low degree of aggregation. Upon near-infrared (NIR; 700 and 800 nm) light irradiation of PVA-PB films, the local temperature increases rapidly and reaches a plateau (up to ΔT ≅ 78 °C), within ≈6-10 s under relatively low laser intensities, I ≅ 0.3 W cm-2. The high and localized increase of temperature on the fabricated films resulted in an efficient antibacterial effect on Pseudomonas aeruginosa (P. aeruginosa) bacteria. In addition, the localized photo-thermal effect was also sufficient to substantially mitigate biofilms growth.
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Affiliation(s)
- Mykola Borzenkov
- Department of Medicine and Surgery, Nanomedicine Center, University of Milano-Bicocca, Piazza dell' Ateneo Nuovo, I-20126, Milan, Italy
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6
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Scodellaro R, Bouzin M, Mingozzi F, D'Alfonso L, Granucci F, Collini M, Chirico G, Sironi L. Whole-Section Tumor Micro-Architecture Analysis by a Two-Dimensional Phasor-Based Approach Applied to Polarization-Dependent Second Harmonic Imaging. Front Oncol 2019; 9:527. [PMID: 31275857 PMCID: PMC6593899 DOI: 10.3389/fonc.2019.00527] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Accepted: 05/30/2019] [Indexed: 11/17/2022] Open
Abstract
Second Harmonic Generation (SHG) microscopy has gained much interest in the histopathology field since it allows label-free imaging of tissues simultaneously providing information on their morphology and on the collagen microarchitecture, thereby highlighting the onset of pathologies and diseases. A wide request of image analysis tools is growing, with the aim to increase the reliability of the analysis of the huge amount of acquired data and to assist pathologists in a user-independent way during their diagnosis. In this light, we exploit here a set of phasor-parameters that, coupled to a 2-dimensional phasor-based approach (μMAPPS, Microscopic Multiparametric Analysis by Phasor projection of Polarization-dependent SHG signal) and a clustering algorithm, allow to automatically recover different collagen microarchitectures in the tissues extracellular matrix. The collagen fibrils microscopic parameters (orientation and anisotropy) are analyzed at a mesoscopic level by quantifying their local spatial heterogeneity in histopathology sections (few mm in size) from two cancer xenografts in mice, in order to maximally discriminate different collagen organizations, allowing in this case to identify the tumor area with respect to the surrounding skin tissue. We show that the “fibril entropy” parameter, which describes the tissue order on a selected spatial scale, is the most effective in enlightening the tumor edges, opening the possibility of their automatic segmentation. Our method, therefore, combined with tissue morphology information, has the potential to become a support to standard histopathology in diseases diagnosis.
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Affiliation(s)
| | - Margaux Bouzin
- Physics Department, Università degli Studi di Milano-Bicocca, Milan, Italy
| | - Francesca Mingozzi
- Department of Biotechnology and Biosciences, Università degli Studi di Milano-Bicocca, Milan, Italy
| | - Laura D'Alfonso
- Physics Department, Università degli Studi di Milano-Bicocca, Milan, Italy
| | - Francesca Granucci
- Department of Biotechnology and Biosciences, Università degli Studi di Milano-Bicocca, Milan, Italy
| | - Maddalena Collini
- Physics Department, Università degli Studi di Milano-Bicocca, Milan, Italy
| | - Giuseppe Chirico
- Physics Department, Università degli Studi di Milano-Bicocca, Milan, Italy
| | - Laura Sironi
- Physics Department, Università degli Studi di Milano-Bicocca, Milan, Italy
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7
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Ceffa NG, Bouzin M, D'Alfonso L, Sironi L, Marquezin CA, Auricchio F, Marconi S, Chirico G, Collini M. Spatiotemporal Image Correlation Analysis for 3D Flow Field Mapping in Microfluidic Devices. Anal Chem 2018; 90:2277-2284. [PMID: 29266924 DOI: 10.1021/acs.analchem.7b04641] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Microfluidic devices reproducing 3D networks are particularly valuable for nanomedicine applications such as tissue engineering and active cell sorting. There is however a gap in the possibility to measure how the flow evolves in such 3D structures. We show here that it is possible to map 3D flows in complex microchannel networks by combining wide field illumination to image correlation approaches. For this purpose, we have derived the spatiotemporal image correlation analysis of time stacks of single-plane illumination microscopy images. From the detailed analytical and numerical analysis of the resulting model, we developed a fitting method that allows us to measure, besides the in-plane velocity, the out-of-plane velocity component down to vz ≅ 65 μm/s. We have applied this method successfully to the 3D reconstruction of flows in microchannel networks with planar and 3D ramifications. These different network architectures have been realized by exploiting the great prototyping ability of a 3D printer, whose precision can reach few tens of micrometers, coupled to poly dimethyl-siloxane soft-printing lithography.
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Affiliation(s)
- Nicolo' G Ceffa
- Dipartimento di Fisica, Centro di Nanomedicina, Università degli Studi di Milano-Bicocca , Piazza della Scienza 3, 20126, Milano, Italy
| | - Margaux Bouzin
- Dipartimento di Fisica, Centro di Nanomedicina, Università degli Studi di Milano-Bicocca , Piazza della Scienza 3, 20126, Milano, Italy
| | - Laura D'Alfonso
- Dipartimento di Fisica, Centro di Nanomedicina, Università degli Studi di Milano-Bicocca , Piazza della Scienza 3, 20126, Milano, Italy
| | - Laura Sironi
- Dipartimento di Fisica, Centro di Nanomedicina, Università degli Studi di Milano-Bicocca , Piazza della Scienza 3, 20126, Milano, Italy
| | - Cassia A Marquezin
- Instituto de Física, Universidade Federal de Goiás , Goiânia, Goiás 74.690-900, Brazil
| | - Ferdinando Auricchio
- Dipartimento di Ingegneria Civile e Architettura, Università degli Studi di Pavia , 27100 Pavia, Italy
| | - Stefania Marconi
- Dipartimento di Ingegneria Civile e Architettura, Università degli Studi di Pavia , 27100 Pavia, Italy
| | - Giuseppe Chirico
- Dipartimento di Fisica, Centro di Nanomedicina, Università degli Studi di Milano-Bicocca , Piazza della Scienza 3, 20126, Milano, Italy.,CNR-ISASI, Institute of Applied Sciences and Intelligent Systems , Via Campi Flegrei 34, 80078 Pozzuoli, Italy
| | - Maddalena Collini
- Dipartimento di Fisica, Centro di Nanomedicina, Università degli Studi di Milano-Bicocca , Piazza della Scienza 3, 20126, Milano, Italy.,CNR-ISASI, Institute of Applied Sciences and Intelligent Systems , Via Campi Flegrei 34, 80078 Pozzuoli, Italy
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8
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Radaelli F, D'Alfonso L, Collini M, Mingozzi F, Marongiu L, Granucci F, Zanoni I, Chirico G, Sironi L. μMAPPS: a novel phasor approach to second harmonic analysis for in vitro-in vivo investigation of collagen microstructure. Sci Rep 2017; 7:17468. [PMID: 29234132 PMCID: PMC5727101 DOI: 10.1038/s41598-017-17726-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Accepted: 11/28/2017] [Indexed: 12/15/2022] Open
Abstract
Second Harmonic Generation (SHG) is a label-free imaging method used to monitor collagen organization in tissues. Due to its sensitivity to the incident polarization, it provides microstructural information otherwise unreachable by other intensity based imaging methods. We develop and test a Microscopic Multiparametric Analysis by Phasor projection of Polarization-dependent SHG (μMAPPS) that maps the features of the collagen architecture in tissues at the micrometer scale. μMAPPS retrieves pixel-by-pixel the collagen fibrils anisotropy and orientation by operating directly on two coupled phasor spaces, avoiding direct fitting of the polarization dependent SHG signal. We apply μMAPPS to fixed tissue sections and to the study of the collagen microscopic organization in tumors ex-vivo and in-vivo. We develop a clustering algorithm to automatically group pixels with similar microstructural features. μMAPPS can perform fast analyses of tissues and opens to future applications for in-situ diagnosis of pathologies and diseases that could assist histo-pathological evaluation.
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Affiliation(s)
- F Radaelli
- Dipartimento di Fisica, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy
| | - L D'Alfonso
- Dipartimento di Fisica, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy
| | - M Collini
- Dipartimento di Fisica, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy. .,CNR - ISASI, Institute of Applied Sciences & Intelligent Systems, Via Campi Flegrei 34, Pozzuoli, NA, Italy.
| | - F Mingozzi
- Dipartimento di Biotecnologie e Bioscienze, Università degli Studi di Milano-Bicocca, Piazza della Scienza 2, 20126, Milano, Italy
| | - L Marongiu
- Dipartimento di Biotecnologie e Bioscienze, Università degli Studi di Milano-Bicocca, Piazza della Scienza 2, 20126, Milano, Italy
| | - F Granucci
- Dipartimento di Biotecnologie e Bioscienze, Università degli Studi di Milano-Bicocca, Piazza della Scienza 2, 20126, Milano, Italy
| | - I Zanoni
- Dipartimento di Biotecnologie e Bioscienze, Università degli Studi di Milano-Bicocca, Piazza della Scienza 2, 20126, Milano, Italy.,Harvard Medical School and Division of Gastroenterology, Boston Children's Hospital, Boston, MA, USA
| | - G Chirico
- Dipartimento di Fisica, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy.,CNR - ISASI, Institute of Applied Sciences & Intelligent Systems, Via Campi Flegrei 34, Pozzuoli, NA, Italy
| | - L Sironi
- Dipartimento di Fisica, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy.
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9
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Ceffa NG, Cesana I, Collini M, D'Alfonso L, Carra S, Cotelli F, Sironi L, Chirico G. Spatiotemporal image correlation analysis of blood flow in branched vessel networks of zebrafish embryos. J Biomed Opt 2017; 22:1-7. [PMID: 29030941 DOI: 10.1117/1.jbo.22.10.106008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Accepted: 09/26/2017] [Indexed: 05/28/2023]
Abstract
Ramification of blood circulation is relevant in a number of physiological and pathological conditions. The oxygen exchange occurs largely in the capillary bed, and the cancer progression is closely linked to the angiogenesis around the tumor mass. Optical microscopy has made impressive improvements in in vivo imaging and dynamic studies based on correlation analysis of time stacks of images. Here, we develop and test advanced methods that allow mapping the flow fields in branched vessel networks at the resolution of 10 to 20 μm. The methods, based on the application of spatiotemporal image correlation spectroscopy and its extension to cross-correlation analysis, are applied here to the case of early stage embryos of zebrafish.
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Affiliation(s)
- Nicolo G Ceffa
- Università di Milano-Bicocca, Dipartimento di Fisica, Milano, Italy
| | - Ilaria Cesana
- Università di Milano-Bicocca, Dipartimento di Fisica, Milano, Italy
| | - Maddalena Collini
- Università di Milano-Bicocca, Dipartimento di Fisica, Milano, Italy
- Institute of Applied Sciences and Intelligent Systems, CNR-ISASI, Pozzuoli, Italy
- Università di Milano-Bicocca, Nanomedicine Center, Monza, Italy
| | - Laura D'Alfonso
- Università di Milano-Bicocca, Dipartimento di Fisica, Milano, Italy
| | | | | | - Laura Sironi
- Università di Milano-Bicocca, Dipartimento di Fisica, Milano, Italy
| | - Giuseppe Chirico
- Università di Milano-Bicocca, Dipartimento di Fisica, Milano, Italy
- Institute of Applied Sciences and Intelligent Systems, CNR-ISASI, Pozzuoli, Italy
- Università di Milano-Bicocca, Nanomedicine Center, Monza, Italy
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10
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Colombo S, Broggi S, Collini M, D'Alfonso L, Chirico G, Martegani E. Detection of cAMP and of PKA activity in Saccharomyces cerevisiae single cells using Fluorescence Resonance Energy Transfer (FRET) probes. Biochem Biophys Res Commun 2017; 487:594-599. [PMID: 28433631 DOI: 10.1016/j.bbrc.2017.04.097] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Accepted: 04/18/2017] [Indexed: 11/16/2022]
Abstract
In Saccharomyces cerevisiae the second messenger cyclic adenosine monophosphate (cAMP) and protein kinase A (PKA) play a central role in metabolism regulation, stress resistance and cell cycle progression. To monitor cAMP levels and PKA activity in vivo in single S. cerevisiae cells, we expressed an Epac-based FRET probe and a FRET-based A-kinase activity reporter, which were proven to be useful live-cell biosensors for cAMP levels and PKA activity in mammalian cells. Regarding detection of cAMP in single yeast cells, we show that in wild type strains the CFP/YFP fluorescence ratio increased immediately after glucose addition to derepressed cells, while no changes were observed when glucose was added to a strain that is not able to produce cAMP. In addition, we had evidence for damped oscillations in cAMP levels at least in SP1 strain. Regarding detection of PKA activity, we show that in wild type strains the FRET increased after glucose addition to derepressed cells, while no changes were observed when glucose was added to either a strain that is not able to produce cAMP or to a strain with absent PKA activity. Taken together these probes are useful to follow activation of the cAMP/PKA pathway in single yeast cells and for long times (up to one hour).
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Affiliation(s)
- Sonia Colombo
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milan, Italy; SysBio Centre of Systems Biology, Piazza della Scienza 2, I-20126 Milan, Italy
| | - Serena Broggi
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milan, Italy; S.C. di Ematologia e Trapianto di Midollo Osseo, Ospedale Santa Maria della Misericordia, S. Andrea delle Fratte Perugia, Italy
| | | | - Laura D'Alfonso
- Department of Physics, University of Milano-Bicocca, Milan, Italy
| | - Giuseppe Chirico
- Department of Physics, University of Milano-Bicocca, Milan, Italy
| | - Enzo Martegani
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milan, Italy; SysBio Centre of Systems Biology, Piazza della Scienza 2, I-20126 Milan, Italy.
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11
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Galli M, Moschini E, Dozzi MV, Arosio P, Panigati M, D'Alfonso L, Mantecca P, Lascialfari A, D'Alfonso G, Maggioni D. SPIO@SiO2–Re@PEG nanoparticles as magneto-optical dual probes and sensitizers for photodynamic therapy. RSC Adv 2016. [DOI: 10.1039/c6ra04332a] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
A superparamagnetic iron oxide core and a photoluminescent rhenium complex embedded in a silica shell are the active components of a dual magneto-optical nanoprobe, also able to generate singlet oxygen upon irradiation.
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Affiliation(s)
- Marco Galli
- Dipartimento di Chimica
- Università degli Studi di Milano
- 20133 Milano
- Italy
| | - Elisa Moschini
- Dipartimento di Scienze dell'Ambiente e del Territorio e di Scienze della Terra
- Università degli Studi di Milano-Bicocca
- 20126 Milano
- Italy
| | | | - Paolo Arosio
- Dipartimento di Fisica
- Università degli Studi di Milano
- 20133 Milano
- Italy
- Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali
| | - Monica Panigati
- Dipartimento di Chimica
- Università degli Studi di Milano
- 20133 Milano
- Italy
- Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali
| | - Laura D'Alfonso
- Dipartimento di Fisica
- Università degli Studi di Milano-Bicocca
- 20126 Milano
- Italy
| | - Paride Mantecca
- Dipartimento di Scienze dell'Ambiente e del Territorio e di Scienze della Terra
- Università degli Studi di Milano-Bicocca
- 20126 Milano
- Italy
| | - Alessandro Lascialfari
- Dipartimento di Fisica
- Università degli Studi di Milano
- 20133 Milano
- Italy
- Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali
| | - Giuseppe D'Alfonso
- Dipartimento di Chimica
- Università degli Studi di Milano
- 20133 Milano
- Italy
- Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali
| | - Daniela Maggioni
- Dipartimento di Chimica
- Università degli Studi di Milano
- 20133 Milano
- Italy
- Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali
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12
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Pallavicini P, Basile S, Chirico G, Dacarro G, D'Alfonso L, Donà A, Patrini M, Falqui A, Sironi L, Taglietti A. Monolayers of gold nanostars with two near-IR LSPRs capable of additive photothermal response. Chem Commun (Camb) 2015; 51:12928-30. [PMID: 26179941 DOI: 10.1039/c5cc04144a] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Monolayers of photothermally responsive gold nanostars on PEI-coated surfaces display two localized surface plasmon resonances (LSPRs) in the near-IR region that can be laser-irradiated either separately, obtaining two different T jumps, or simultaneously, obtaining a T jump equal to the sum of those obtained with separate irradiations.
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13
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Pallavicini P, Cabrini E, Cavallaro G, Chirico G, Collini M, D'Alfonso L, Dacarro G, Donà A, Marchesi N, Milanese C, Pascale A, Sironi L, Taglietti A. Gold nanostars coated with neutral and charged polyethylene glycols: A comparative study of in-vitro biocompatibility and of their interaction with SH-SY5Y neuroblastoma cells. J Inorg Biochem 2015; 151:123-31. [DOI: 10.1016/j.jinorgbio.2015.05.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Revised: 04/30/2015] [Accepted: 05/02/2015] [Indexed: 01/07/2023]
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14
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Borzenkov M, Chirico G, D'Alfonso L, Sironi L, Collini M, Cabrini E, Dacarro G, Milanese C, Pallavicini P, Taglietti A, Bernhard C, Denat F. Thermal and Chemical Stability of Thiol Bonding on Gold Nanostars. Langmuir 2015; 31:8081-91. [PMID: 26154493 DOI: 10.1021/acs.langmuir.5b01473] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The stability of thiol bonding on the surface of star-shaped gold nanoparticles was studied as a function of temperature in water and in a set of biologically relevant conditions. The stability was evaluated by monitoring the release of a model fluorescent dye, Bodipy-thiol (BDP-SH), from gold nanostars (GNSs) cocoated with poly(ethylene glycol) thiol (PEG-SH). The increase in the BDP-SH fluorescence emission, quenched when bound to the GNSs, was exploited to this purpose. A maximum 15% dye release in aqueous solution was found when the bulk temperature of gold nanostars solutions was increased to T = 42 °C, the maximum physiological temperature. This fraction reduces 3-5% for temperatures lower than 40 °C. Similar results were found when the temperature increase was obtained by laser excitation of the near-infrared (NIR) localized surface plasmon resonance of the GNSs, which are photothermally responsive. Besides the direct impact of temperature, an increased BDP-SH release was observed upon changing the chemical composition of the solvent from pure water to phosphate-buffered saline and culture media solutions. Moreover, also a significant fraction of PEG-SH was released from the GNS surface due to the increase in temperature. We monitored it with a different approach, that is, by using a coating of α-mercapto-ω-amino PEG labeled with tetramethylrhodamine isothiocyanate on the amino group, that after heating was separated from GNS by ultracentrifugation and the released PEG was determined by spectrofluorimetric techniques on the supernatant solution. These results suggest some specific limitations in the use of the gold-thiolate bond for coating of nanomaterials with organic compounds in biological environments. These limitations come from the duration and the intensity of the thermal treatment and from the medium composition and could also be exploited in biological media to modulate the in vivo release of drugs.
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Affiliation(s)
- Mykola Borzenkov
- †Department of Physics "G. Occhialini", University of Milano Bicocca, piazza della Scienza 3, 20126 Milano, Italy
| | - Giuseppe Chirico
- †Department of Physics "G. Occhialini", University of Milano Bicocca, piazza della Scienza 3, 20126 Milano, Italy
| | - Laura D'Alfonso
- †Department of Physics "G. Occhialini", University of Milano Bicocca, piazza della Scienza 3, 20126 Milano, Italy
| | - Laura Sironi
- †Department of Physics "G. Occhialini", University of Milano Bicocca, piazza della Scienza 3, 20126 Milano, Italy
| | - Maddalena Collini
- †Department of Physics "G. Occhialini", University of Milano Bicocca, piazza della Scienza 3, 20126 Milano, Italy
| | - Elisa Cabrini
- ‡Department of Chemistry, University of Pavia, viale Taramelli 12, 27100 Pavia, Italy
| | - Giacomo Dacarro
- ‡Department of Chemistry, University of Pavia, viale Taramelli 12, 27100 Pavia, Italy
| | - Chiara Milanese
- ‡Department of Chemistry, University of Pavia, viale Taramelli 12, 27100 Pavia, Italy
| | | | - Angelo Taglietti
- ‡Department of Chemistry, University of Pavia, viale Taramelli 12, 27100 Pavia, Italy
| | - Claire Bernhard
- §Institut de Chimie Moléculaire de l'Université de Bourgogne, UMR CNRS 6302, Université de Bourgogne, 21078 Dijon, France
| | - Franck Denat
- §Institut de Chimie Moléculaire de l'Université de Bourgogne, UMR CNRS 6302, Université de Bourgogne, 21078 Dijon, France
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15
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Maggioni D, Galli M, D'Alfonso L, Inverso D, Dozzi MV, Sironi L, Iannacone M, Collini M, Ferruti P, Ranucci E, D'Alfonso G. A luminescent poly(amidoamine)-iridium complex as a new singlet-oxygen sensitizer for photodynamic therapy. Inorg Chem 2015; 54:544-53. [PMID: 25554822 DOI: 10.1021/ic502378z] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A polymer complex (1P) was synthesized by binding bis(cyclometalated) Ir(ppy)2(+) fragments (ppy = 2-phenylpyridyl) to phenanthroline (phen) pendants of a poly(amidoamine) copolymer (PhenISA, in which the phen pendants involved ∼6% of the repeating units). The corresponding molecular complex [Ir(ppy)2(bap)](+) (1M, bap = 4-(butyl-4-amino)-1,10-phenanthroline) was also prepared for comparison. In water solution 1P gives nanoaggregates with a hydrodynamic diameter of 30 nm in which the lipophilic metal centers are presumed to be segregated within polymer tasks to reduce their interaction with water. Such confinement, combined with the dilution of triplet emitters along the polymer chains, led to 1P having a photoluminescence quantum yield greater than that of 1M (0.061 vs 0.034, respectively, in an aerated water solution) with a longer lifetime of the (3)MLCT excited states and a blue-shifted emission (595 nm vs 604 nm, respectively). NMR data supported segregation of the metal centers. Photoreaction of O2 with 1,5-dihydroxynaphthalene showed that 1P is able to sensitize (1)O2 generation but with half the quantum yield of 1M. Cellular uptake experiments showed that both 1M and 1P are efficient cell staining agents endowed with two-photon excitation (TPE) imaging capability. TPE microscopy at 840 nm indicated that both complexes penetrate the cellular membrane of HeLa cells, localizing in the perinuclear region. Cellular photodynamic therapy tests showed that both 1M and 1P are able to induce cell apoptosis upon exposure to Xe lamp irradiation. The fraction of apoptotic cells for 1M was higher than that for 1P (74 and 38%, respectively) 6 h after being irradiated for 5 min, but cells incubated with 1P showed much lower levels of necrosis as well as lower toxicity in the absence of irradiation. More generally, the results indicate that cell damage induced by 1M was avoided by binding the iridium sensitizers to the poly(amidoamine).
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Affiliation(s)
- Daniela Maggioni
- Dipartimento di Chimica, Università degli Studi di Milano , Via Golgi 19, 20133 Milano, Italy
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16
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Sironi L, Bouzin M, Inverso D, D'Alfonso L, Pozzi P, Cotelli F, Guidotti LG, Iannacone M, Collini M, Chirico G. In vivo flow mapping in complex vessel networks by single image correlation. Sci Rep 2014; 4:7341. [PMID: 25475129 PMCID: PMC4256590 DOI: 10.1038/srep07341] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2014] [Accepted: 11/17/2014] [Indexed: 01/10/2023] Open
Abstract
We describe a novel method (FLICS, FLow Image Correlation Spectroscopy) to extract flow speeds in complex vessel networks from a single raster-scanned optical xy-image, acquired in vivo by confocal or two-photon excitation microscopy. Fluorescent flowing objects produce diagonal lines in the raster-scanned image superimposed to static morphological details. The flow velocity is obtained by computing the Cross Correlation Function (CCF) of the intensity fluctuations detected in pairs of columns of the image. The analytical expression of the CCF has been derived by applying scanning fluorescence correlation concepts to drifting optically resolved objects and the theoretical framework has been validated in systems of increasing complexity. The power of the technique is revealed by its application to the intricate murine hepatic microcirculatory system where blood flow speed has been mapped simultaneously in several capillaries from a single xy-image and followed in time at high spatial and temporal resolution.
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Affiliation(s)
- Laura Sironi
- Università degli Studi di Milano-Bicocca, Physics Department, Piazza della Scienza 3, I-20126, Milan, Italy
| | - Margaux Bouzin
- Università degli Studi di Milano-Bicocca, Physics Department, Piazza della Scienza 3, I-20126, Milan, Italy
| | - Donato Inverso
- 1] Division of Immunology, Transplantation and Infectious Diseases, IRCCS San Raffaele Scientific Institute, I-20132, Milan, Italy [2] Vita-Salute San Raffaele University, I-20132, Milan, Italy
| | - Laura D'Alfonso
- Università degli Studi di Milano-Bicocca, Physics Department, Piazza della Scienza 3, I-20126, Milan, Italy
| | - Paolo Pozzi
- Università degli Studi di Milano-Bicocca, Physics Department, Piazza della Scienza 3, I-20126, Milan, Italy
| | - Franco Cotelli
- Università degli Studi di Milano, Department of Life Sciences, Via Celoria 26, I-20133, Milan, Italy
| | - Luca G Guidotti
- Division of Immunology, Transplantation and Infectious Diseases, IRCCS San Raffaele Scientific Institute, I-20132, Milan, Italy
| | - Matteo Iannacone
- 1] Division of Immunology, Transplantation and Infectious Diseases, IRCCS San Raffaele Scientific Institute, I-20132, Milan, Italy [2] Vita-Salute San Raffaele University, I-20132, Milan, Italy
| | - Maddalena Collini
- Università degli Studi di Milano-Bicocca, Physics Department, Piazza della Scienza 3, I-20126, Milan, Italy
| | - Giuseppe Chirico
- Università degli Studi di Milano-Bicocca, Physics Department, Piazza della Scienza 3, I-20126, Milan, Italy
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17
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Pozzi P, Sironi L, D'Alfonso L, Bouzin M, Collini M, Chirico G, Pallavicini P, Cotelli F, Foglia EA. Electron multiplying charge-coupled device-based fluorescence cross-correlation spectroscopy for blood velocimetry on zebrafish embryos. J Biomed Opt 2014; 19:067007. [PMID: 24946713 DOI: 10.1117/1.jbo.19.6.067007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Accepted: 05/19/2014] [Indexed: 05/28/2023]
Abstract
Biomedical issues in vasculogenesis and cardiogenesis require methods to follow hemodynamics with high spatial (micrometers) and time (milliseconds) resolution. At the same time, we need to follow relevant morphogenetic processes on large fields of view. Fluorescence cross-correlation spectroscopy coupled to scanning or wide-field microscopy meets these needs but has limited flexibility in the excitation pattern. To overcome this limitation, we develop here a two-photon two-spots setup coupled to an all-reflective near-infrared (NIR) optimized scanning system and to an electron multiplying charge-coupled device. Two NIR laser spots are spaced at adjustable micron-size distances (1 to 50 μm) by means of a Twyman-Green interferometer and repeatedly scanned on the sample, allowing acquisition of information on flows at 4 ms-3 μm time-space resolution in parallel on an extended field of view. We analyze the effect of nonhomogeneous and variable flow on the cross-correlation function by numerical simulations and show exemplary application of this setup in studies of blood flow in zebrafish embryos in vivo. By coupling the interferometer with the scanning mirrors and by computing the cross-correlation function of fluorescent red blood cells, we are able to map speed patterns in embryos' vessels.
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Affiliation(s)
- Paolo Pozzi
- Università degli Studi di Milano-Bicocca, Dipartimento di Fisica, Piazza della Scienza 3, I-20126, Milano, Italy
| | - Laura Sironi
- Università degli Studi di Milano-Bicocca, Dipartimento di Fisica, Piazza della Scienza 3, I-20126, Milano, Italy
| | - Laura D'Alfonso
- Università degli Studi di Milano-Bicocca, Dipartimento di Fisica, Piazza della Scienza 3, I-20126, Milano, Italy
| | - Margaux Bouzin
- Università degli Studi di Milano-Bicocca, Dipartimento di Fisica, Piazza della Scienza 3, I-20126, Milano, Italy
| | - Maddalena Collini
- Università degli Studi di Milano-Bicocca, Dipartimento di Fisica, Piazza della Scienza 3, I-20126, Milano, Italy
| | - Giuseppe Chirico
- Università degli Studi di Milano-Bicocca, Dipartimento di Fisica, Piazza della Scienza 3, I-20126, Milano, Italy
| | | | - Franco Cotelli
- Università degli Studi di Milano, Dipartimento di Bioscienze, Via Celoria 26, I-20133, Milano, Italy
| | - Efrem A Foglia
- Università degli Studi di Milano, Dipartimento di Bioscienze, Via Celoria 26, I-20133, Milano, Italy
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18
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D'Amico M, Schirò G, Cupane A, D'Alfonso L, Leone M, Militello V, Vetri V. High fluorescence of thioflavin T confined in mesoporous silica xerogels. Langmuir 2013; 29:10238-10246. [PMID: 23844566 DOI: 10.1021/la402406g] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Trapping of organic molecules and dyes within nanoporous matrices is of great interest for the potential creation of new materials with tailored features and, thus, different possible applications ranging from nanomedicine to material science. The understanding of the physical basis of entrapment and the spectral properties of the guest molecules within the host matrix is an essential prerequisite for the design and control of the properties of these materials. In this work, we show that a mesoporous silica xerogel can efficiently trap the dye thioflavin T (ThT, a molecule used as a marker of amyloid fibrils and with potential drug benefits), sequestering it from an aqueous solution and producing a highly fluorescent material with a ThT quantum yield 1500 times greater than that of the free molecule. The study of spectroscopical properties of this system and the comparison with fluorescence of an uncharged analogue of ThT give indications about the mechanism responsible for the fluorescence switching-on of ThT molecules during their uptaking into the glass. Diffusion and nanocapillarity are responsible for ThT absorption, whereas electrostatic interaction between positive ThT molecules and negative dangling ≡SiO groups covering the pore surfaces causes the immobilization of ThT molecules inside the pores and the enhancement of its fluorescence, in line with the molecular rotor model proposed for this dye. We also show that entrapment efficiency and kinetics can be tuned by varying the electrostatic properties of the dye and/or the matrix.
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Affiliation(s)
- Michele D'Amico
- Dipartimento di Fisica e Chimica, Università degli Studi di Palermo, Via Archirafi 36, I-90123 Palermo, Italy.
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19
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Freddi S, Sironi L, D'Antuono R, Morone D, Donà A, Cabrini E, D'Alfonso L, Collini M, Pallavicini P, Baldi G, Maggioni D, Chirico G. A molecular thermometer for nanoparticles for optical hyperthermia. Nano Lett 2013; 13:2004-10. [PMID: 23611425 DOI: 10.1021/nl400129v] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We developed an all-optical method to measure the temperature on gold (nanorods and nanostars) and magnetite nanoparticles under near-infrared and radiofrequency excitation by monitoring the excited state lifetime of Rhodamine B that lies within =/~20 nm from the nanoparticle surface. We reached high temperature sensitivity (0.029 ± 0.001 ns/°C) and low uncertainty (±0.3 °C). Gold nanostars are =/~3 and =/~100 times more efficient than gold nanorods and magnetite nanoparticles in inducing localized hyperthermia.
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Affiliation(s)
- Stefano Freddi
- Physics Department, Università degli Studi di Milano Bicocca, Piazza della Scienza 3, I-20126 Milano, Italy
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20
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Campanini B, Pioselli B, Raboni S, Felici P, Giordano I, D'Alfonso L, Collini M, Chirico G, Bettati S. Role of histidine 148 in stability and dynamics of a highly fluorescent GFP variant. Biochim Biophys Acta 2013; 1834:770-9. [PMID: 23357652 DOI: 10.1016/j.bbapap.2013.01.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Revised: 01/11/2013] [Accepted: 01/15/2013] [Indexed: 10/27/2022]
Abstract
The armory of GFP mutants available to biochemists and molecular biologists is huge. Design and selection of mutants are usually driven by tailored spectroscopic properties, but some key aspects of stability, folding and dynamics of selected GFP variants still need to be elucidated. We have prepared, expressed and characterized three H148 mutants of the highly fluorescent variant GFPmut2. H148 is known to be involved in the H-bonding network surrounding the chromophore, and all the three mutants, H148G, H148R and H148K, show increased pKa values of the chromophore. Only H148G GFPmut2 (Mut2G) gave good expression and purification yields, indicating that position 148 is critical for efficient folding in vivo. The chemical denaturation of Mut2G was monitored by fluorescence emission, absorbance and far-UV circular dichroism spectroscopy. The mutation has little effect on the spectroscopic properties of the protein and on its stability in solution. However, the unfolding kinetics of the protein encapsulated in wet nanoporous silica gels, a system that allows to stabilize conformations that are poorly or only transiently populated in solution, indicate that the unfolding pathway of Mut2G is markedly different from the parent molecule. In particular, encapsulation allowed to identify an unfolding intermediate that retains a native-like secondary structure despite a destructured chromophore environment. Thus, H148 is a critical residue not only for the chromophoric and photodynamic properties, but also for the correct folding of GFP, and its substitution has great impact on expression yields and stability of the mature protein.
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Affiliation(s)
- Barbara Campanini
- Dipartimento di Farmacia, Università degli Studi di Parma, Parma, Italy.
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21
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Bosisio C, Quercioli V, Chirico G, D'Alfonso L, Bettati S, Raboni S, Campanini B, Collini M. Effect of the point mutation H148G on GFPmut2 unfolding kinetics by fluorescence spectroscopy. Biophys Chem 2011; 157:24-32. [DOI: 10.1016/j.bpc.2011.04.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2011] [Revised: 04/04/2011] [Accepted: 04/04/2011] [Indexed: 02/09/2023]
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22
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Pallavicini P, Chirico G, Collini M, Dacarro G, Donà A, D'Alfonso L, Falqui A, Diaz-Fernandez Y, Freddi S, Garofalo B, Genovese A, Sironi L, Taglietti A. Synthesis of branched Au nanoparticles with tunable near-infrared LSPR using a zwitterionic surfactant. Chem Commun (Camb) 2011; 47:1315-7. [DOI: 10.1039/c0cc02682d] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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23
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Villa CE, Caccia M, Sironi L, D'Alfonso L, Collini M, Rivolta I, Miserocchi G, Gorletta T, Zanoni I, Granucci F, Chirico G. Accumulative difference image protocol for particle tracking in fluorescence microscopy tested in mouse lymphonodes. PLoS One 2010; 5:e12216. [PMID: 20808918 PMCID: PMC2923183 DOI: 10.1371/journal.pone.0012216] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2010] [Accepted: 07/14/2010] [Indexed: 11/18/2022] Open
Abstract
The basic research in cell biology and in medical sciences makes large use of imaging tools mainly based on confocal fluorescence and, more recently, on non-linear excitation microscopy. Substantially the aim is the recognition of selected targets in the image and their tracking in time. We have developed a particle tracking algorithm optimized for low signal/noise images with a minimum set of requirements on the target size and with no a priori knowledge of the type of motion. The image segmentation, based on a combination of size sensitive filters, does not rely on edge detection and is tailored for targets acquired at low resolution as in most of the in-vivo studies. The particle tracking is performed by building, from a stack of Accumulative Difference Images, a single 2D image in which the motion of the whole set of the particles is coded in time by a color level. This algorithm, tested here on solid-lipid nanoparticles diffusing within cells and on lymphocytes diffusing in lymphonodes, appears to be particularly useful for the cellular and the in-vivo microscopy image processing in which few a priori assumption on the type, the extent and the variability of particle motions, can be done.
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Affiliation(s)
- Carlo E. Villa
- Dipartimento di Fisica, Università degli Studi di Milano Bicocca, Milano, Italy
| | - Michele Caccia
- Dipartimento di Fisica, Università degli Studi di Milano Bicocca, Milano, Italy
| | - Laura Sironi
- Dipartimento di Fisica, Università degli Studi di Milano Bicocca, Milano, Italy
| | - Laura D'Alfonso
- Dipartimento di Fisica, Università degli Studi di Milano Bicocca, Milano, Italy
| | - Maddalena Collini
- Dipartimento di Fisica, Università degli Studi di Milano Bicocca, Milano, Italy
| | - Ilaria Rivolta
- Dipartimento di Medicina Sperimentale, Università degli Studi di Milano Bicocca, Monza, Italy
| | - Giuseppe Miserocchi
- Dipartimento di Medicina Sperimentale, Università degli Studi di Milano Bicocca, Monza, Italy
| | - Tatiana Gorletta
- Dipartimento di Biotecnologie e Bioscienze, Università degli Studi di Milano Bicocca, Milano, Italy
| | - Ivan Zanoni
- Dipartimento di Biotecnologie e Bioscienze, Università degli Studi di Milano Bicocca, Milano, Italy
| | - Francesca Granucci
- Dipartimento di Biotecnologie e Bioscienze, Università degli Studi di Milano Bicocca, Milano, Italy
| | - Giuseppe Chirico
- Dipartimento di Fisica, Università degli Studi di Milano Bicocca, Milano, Italy
- * E-mail:
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24
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Ferri E, Donghi D, Panigati M, Prencipe G, D'Alfonso L, Zanoni I, Baldoli C, Maiorana S, D'Alfonso G, Licandro E. Luminescent conjugates between dinuclear rhenium(I) complexes and peptide nucleic acids (PNA) for cell imaging and DNA targeting. Chem Commun (Camb) 2010; 46:6255-7. [PMID: 20668778 DOI: 10.1039/c0cc00450b] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
New luminescent dinuclear rhenium(I) tricarbonyl complex-PNA conjugates have been synthesized through a reliable solid-phase synthetic methodology. Their photophysical properties have been measured. The most luminescent Re-PNA conjugate 7 showed interesting two-photon absorption (TPA) properties, that were exploited for imaging experiments, to demonstrate its easy uptake into living cells.
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Affiliation(s)
- Elena Ferri
- Dipartimento di Chimica Organica e Industriale, Università degli Studi di Milano, via Venezian 21, I-20133 Milano, Italy
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Quercioli V, Bosisio C, Daglio SC, Rocca F, D'Alfonso L, Collini M, Baldini G, Chirico G, Bettati S, Raboni S, Campanini B. Photoinduced millisecond switching kinetics in the GFPMut2 E222Q mutant. J Phys Chem B 2010; 114:4664-77. [PMID: 20230008 DOI: 10.1021/jp910075b] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
New probes for kinetic intracellular measurements in the millisecond range are desirable to monitor protein biochemical dynamics essential for catalysis, allosteric regulation, and signaling. Good candidates to this aim are the photoswitchable mutants of the green fluorescent protein, whose anionic fluorescence, primed by blue light, is markedly enhanced under an additional excitation at a shorter wavelength and relaxes within a few milliseconds. The aim of this report is to study how the brightness enhancement kinetics depends on the physical-chemical and spectroscopic parameters and to provide proof-of-concept experiments for the use of the fluorescence enhancement in conditions in which the protein diffusion is hindered and thereby photobleaching can be a limiting critical issue. Future, direct applications of photochromic mutants for modulated excitation imaging would in fact require such a detailed knowledge. We present here an extensive study of the photoswitching mechanism of the E222Q mutant of GFPMut2 (Mut2Q), pumped by visible 488 nm light and probed at 400-420 nm, as a function of pH, viscosity, temperature, and light intensity. In solution, two characteristic photoswitching times are found by means of modulated double beam fluorescence correlation spectroscopy in the 1-30 ms range, depending on the solution pH. The photoswitching kinetics is solved in terms of the eigenvalues and the eigenvectors of a specific energy diagram and used directly to fit the data, suggesting that the observed photoswitching amplitudes and kinetics are related to a single three-level transition loop. Finally, we give in vitro examples of the use of modulated excitation microscopy, based on fluorescence enhancement amplitude and kinetics detection, on Mut2Q protein samples immobilized in acrylamide gels.
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Affiliation(s)
- Valentina Quercioli
- Dipartimento di Fisica, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126 Milano, Italy
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26
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Sironi L, Freddi S, D'Alfonso L, Collini M, Gorletta T, Soddu S, Chirico G. p53 Detection by Fluorescence Lifetime on a Hybrid Fluorescein Isothiocyanate Gold Nanosensor. J Biomed Nanotechnol 2009; 5:683-91. [DOI: 10.1166/jbn.2009.1085] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Chirico G, Collini M, D'Alfonso L, Denat F, Diaz-Fernandez YA, Pasotti L, Rousselin Y, Sok N, Pallavicini P. Micelles as Containers for Self-Assembled Nanodevices: A Fluorescent Sensor for Lipophilicity. Chemphyschem 2008; 9:1729-37. [DOI: 10.1002/cphc.200800292] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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28
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Bosisio C, Quercioli V, Collini M, D'Alfonso L, Baldini G, Bettati S, Campanini B, Raboni S, Chirico G. Protonation and conformational dynamics of GFP mutants by two-photon excitation fluorescence correlation spectroscopy. J Phys Chem B 2008; 112:8806-14. [PMID: 18582099 DOI: 10.1021/jp801164n] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
GFP mutants are known to display fluorescence flickering, a process that occurs in a wide time range. Because serine 65, threonine 203, glutamate 222, and histidine 148 have been indicated as key residues in determining the GFP fluorescence photodynamics, we have focused here on the role of histidine 148 and glutamate 222 by studying the fluorescence dynamics of GFPmut2 (S65A, V68L, and S72A GFP) and its H148G (Mut2G) and E222Q (Mut2Q) mutants. Two relaxation components are found in the fluorescence autocorrelation functions of GFPmut2: a 10-100 micros pH-dependent component and a 100-500 micros laser-power-dependent component. The comparison of these three mutants shows that the mutation of histidine 148 to glycine induces a 3-fold increase in the protonation rate, thereby indicating that the protonation-deprotonation of the chromophore occurs via a proton exchange with the solution mediated by the histidine 148 residue. The power-dependent but pH-independent relaxation mode, which is not affected by the E222Q and H148G mutations, is due to an excited-state process that is probably related to conformational rearrangements of the chromophore after the photoexcitation, more than to the chromophore excited-state proton transfer.
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Affiliation(s)
- C Bosisio
- Dipartimento G. Occhialini, Universita di Milano Bicocca
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29
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Collini M, D'Alfonso L, Baldini G. Trehalose-induced Changes of the Ethidium Hydration Shell Detected by Time-resolved Fluorescence ¶. Photochem Photobiol 2007. [DOI: 10.1562/0031-8655(2003)0770376tcoteh2.0.co2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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D'Alfonso L, Collini M, Cannone F, Chirico G, Campanini B, Cottone G, Cordone L. GFP-mut2 proteins in trehalose-water matrixes: spatially heterogeneous protein-water-sugar structures. Biophys J 2007; 93:284-93. [PMID: 17416616 PMCID: PMC1914445 DOI: 10.1529/biophysj.106.090621] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We report investigations on the properties of nanoenvironments around single-GFP-mut2 proteins in trehalose-water matrixes. Single-GFPmut2 molecules embedded in thin trehalose-water films were characterized in terms of their fluorescence brightness, bleaching dynamics, excited state lifetime, and fluorescence polarization. For each property, sets of approximately 100-150 single molecules have been investigated as a function of trehalose content and hydration. Three distinct and interconverting families of proteins have been found which differ widely in terms of bleaching dynamics, brightness, and fluorescence polarization, whose relative populations sizably depend on sample hydration. The reported results evidence the simultaneous presence of different protein-trehalose-water nanostructures whose rigidity increases by lowering the sample hydration. Such spatial inhomogeneity is in line with the well-known heterogeneous dynamics in supercooled fluids and in nonsolid carbohydrate glasses and gives a pictorial representation of the sharp, sudden reorganization of the above structures after uptake <==>release of water molecules.
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Affiliation(s)
- Laura D'Alfonso
- Dipartimento di Fisica, Università di Milano Bicocca, Milano, Italy
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31
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Cannone F, Collini M, D'Alfonso L, Baldini G, Chirico G, Tallarida G, Pallavicini P. Voltage regulation of fluorescence emission of single dyes bound to gold nanoparticles. Nano Lett 2007; 7:1070-5. [PMID: 17346091 DOI: 10.1021/nl0628293] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
An organic dye, SAMSA, bound to gold nanoparticles, displays random photoactivated fluorescence blinking whose rate depends on the size of the nanoparticles. We report experiments indicating that (1) the dye emission wavelength is red-shifted (10-30 nm) by applying an external low voltage (1-10 V) and that (2) the fluorescence emission of single dyes can be resonantly driven by tuning the alternating external bias frequency from 1 to 3 Hz, depending on the nanoparticle size. These properties appear highly valuable and promising for devising light emitting nanostructures.
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Affiliation(s)
- F Cannone
- Laboratory for Advanced BioSpectroscopy (LABS), INFM-CNR, Dipartimento di Fisica, Università degli Studi di Milano-Bicocca, Milano, I-20126, Italy
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Panigati M, Donghi D, D'Alfonso G, Mercandelli P, Sironi A, D'Alfonso L. Luminescent Hydrido-Carbonyl Clusters of Rhenium Containing Bridging 1,2-Diazine Ligands. Inorg Chem 2006; 45:10909-21. [PMID: 17173450 DOI: 10.1021/ic061467z] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The reaction of the electronically unsaturated (56 valence electrons, ve) tetrahedral cluster [Re4(mu3-H)4(CO)12] (1) with pyridazine (pydz) gives as the main initial product the tetranuclear cluster [Re4(mu-H)4(mu-pydz)(pydz)2(CO)12] (2a), with 64 ve and four hydrogen-bridged metal-metal interactions, with a spiked-triangle geometry. One of the three pydz ligands bridges, in a cis configuration, the cluster edge opposite to the vertex bearing the spike, as indicated by the X-ray single-crystal analysis. This species slowly decomposes, affording the dinuclear unsaturated (32 ve) complex [Re2(mu-H)2(mu-pydz)(CO)6] (3a) and two isomers of the tetranuclear cluster [Re4(mu-H)4(mu-pydz)2(CO)12] (64 ve), sharing an unusual square cluster geometry and differing in the trans (major, 85%, 4a) or cis (4a') configuration of the bridging pydz ligands. The structures of 3a and 4a have been ascertained by X-ray analysis, while the characterization of 4a' was hampered by its instability (slowly transforming into 3a in THF solution). Both the dimer and the square cluster 4a are also formed directly (and quickly) from 1, being present in solution since the beginning of the reaction. Cluster 4a is the main final reaction product. The reaction with phthalazine follows a similar course, with some differences in the relative amount of the final products 3b and 4b. Most of the novel complexes are able to emit light in solution at room temperature, and photophysical measurements were performed in CH2Cl2 solution on the main stable reaction products (i.e., the dinuclear species 3a and 3b and the trans square clusters 4a and 4b). The emission was in the range of 580-645 nm, from MLCT excited states, with lifetimes on the order of a hundred nanoseconds (50-473 ns). The quantum yields were 1 order of magnitude higher for the squares (1.7 and 1.3% for 4a and 4b, respectively, in CH2Cl2) than for the dinuclear complexes ( approximately 0.1%). In the case of 4a, a blue shift and an increase of the emission intensity were observed upon decreasing the solvent polarity.
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Affiliation(s)
- Monica Panigati
- Dipartimento di Chimica Inorganica, Metallorganica e Analitica, Università di Milano and INSTM UdR di Milano, Via Venezian 21, 20133 Milan, Italy
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Abbotto A, Baldini G, Beverina L, Chirico G, Collini M, D'Alfonso L, Diaspro A, Magrassi R, Nardo L, Pagani GA. Dimethyl-pepep: a DNA probe in two-photon excitation cellular imaging. Biophys Chem 2004; 114:35-41. [PMID: 15792859 DOI: 10.1016/j.bpc.2004.11.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2004] [Accepted: 11/04/2004] [Indexed: 11/18/2022]
Abstract
Dimethyl-pepep (D-pepep), a newly developed and very efficient two-photon absorber, has been tested here for two-photon excitation (TPE) cellular imaging. The spectral characteristics of the dye following one-photon excitation (OPE) and TPE (excitation and emission spectra, fluorescence lifetime, molecular brightness, saturation intensity) are reported. In vitro interaction studies with biomolecules show that dimethyl-pepep has a large affinity for DNA. A comparison with a widely used DNA stainer, 4-6-diamidino-2-phenylindole (DAPI) bound to DNA shows that the D-pepep brightness is one order of magnitude higher than that of DAPI, making this dye suitable for microscopy and imaging applications. TPE images taken from double-stained yeast Saccharomyces cerevisiae cells have revealed that D-pepep localizes mainly in the nucleus, similarly to DAPI, and in mitochondria, although to a minor extent. Preliminary tests have shown that the dye cellular toxicity is negligible.
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Affiliation(s)
- Alessandro Abbotto
- Dipartimento di Scienza dei Materiali and INSTM, Università di Milano Bicocca, Italy
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D'Alfonso L, Collini M, Ragona L, Ugolini R, Baldini G, Molinari H. Porcine beta-lactoglobulin chemical unfolding: Identification of a non-native α-helical intermediate. Proteins 2004; 58:70-9. [PMID: 15526300 DOI: 10.1002/prot.20309] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The chemical unfolding behavior of porcine beta-lactoglobulin (PLG) has been followed at pH 2 and 6 in the presence of guanidinium hydrochloride. The PLG unfolding transition, monitored by tryptophan fluorescence, far and near UV circular dichroism and 1D-NMR, can be described by a three-state transition suggesting the presence of at least one intermediate state that appears to display an excess of non-native alpha-helical structures. The thermodynamic parameters, as determined through a global analysis fitting procedure, give estimates of the free energy differences of the transitions connecting the native, the intermediate and the unfolded state: DeltaG(NI) (0) = 2.8 +/- 0.7 kcal mol(-1) (pH 2) and 4.2 +/- 0.5 kcal mol(-1) (pH 6) and DeltaG(NU) (0) = 7.2 +/- 0.6 kcal mol(-1) (pH 2) and 6.9 +/- 0.6 kcal mol(-1) (pH 6). CD unfolding data of the bovine species (BLG) have been collected here under the same experimental conditions of PLG to allow a careful comparison of the two beta-lactoglobulins. Intermediates with different characteristics have been identified for BLG and PLG, and their nature has been discussed on a structural analysis basis. The thermodynamic data reported here for PLG and BLG and the comparative analysis with data reported for equine beta lactoglobulin, show that homologous beta-barrel proteins, belonging to the same family and displaying high sequence identity (52-64%) populate unfolding intermediates to different extents, even though a common tendency to the formation of non-native alpha-helical intermediates, can be envisaged. The present results provide a prerequisite foundation of knowledge for the design and interpretation of future folding kinetic studies.
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Affiliation(s)
- Laura D'Alfonso
- Dipartimento di Fisica, Universitá degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milano, Italy
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Collini M, D'Alfonso L, Baldini G, Oldani A, Cellai L, Giordano C, Barone F, Mazzei F, Chirico G. Fluorescence anisotropy in the frequency domain by an optical microscope. Appl Spectrosc 2004; 58:160-165. [PMID: 15000709 DOI: 10.1366/000370204322842887] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Fluorescence anisotropy decay spectroscopy is a suitable tool for investigating the size and the shape of biological molecules. We coupled this technique to an optical microscope in order to reduce the excitation volume and to allow its application to spatially inhomogeneous samples. Phase modulated measurements of the fluorescence anisotropy decay were performed by feeding an intensity modulated linearly polarized laser beam to the epifluorescence port of a microscope. Here we report the test of the dynamic response of the microscope by comparing the lifetime and fluorescence polarization anisotropy decays obtained in cuvettes in a standard phase modulation fluorometer and on tiny drops on the microscope stage. We show that once a correction factor for the objective depolarization is introduced in the best-fit functions for the data analysis of the decays, the results obtained on the two setups are comparable. Some applications are reported here on long DNA tracts as well on short DNA fragments containing structural anomalies.
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Affiliation(s)
- Maddalena Collini
- Istituto Nazionale per la Fisica della Materia, Dipartimento di Fisica, Università di Milano Bicocca, Piazza della Scienza 3, Milano 20126 Italy
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36
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Collini M, D'Alfonso L, Molinari H, Ragona L, Catalano M, Baldini G. Competitive binding of fatty acids and the fluorescent probe 1-8-anilinonaphthalene sulfonate to bovine beta-lactoglobulin. Protein Sci 2003; 12:1596-603. [PMID: 12876309 PMCID: PMC2323946 DOI: 10.1110/ps.0304403] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The use of spectroscopy in the study of fatty acids binding to bovine beta-lactoglobulin (BLG) appears to be a difficult task, as these acid compounds, assumed as the protein natural ligands, do not exhibit favorable optical response such as, for example, absorption or fluorescence. Therefore, the BLG fatty-acid equilibrium has been tackled by exploiting the competition between fatty acids and ANS, a widely used fluorescent hydrophobic probe, whose binding sites on the protein have been characterized recently. Two lifetime decays of the ANS-BLG complex have been found; the longer one has been attributed to the internal binding site and the shorter one to the external site. At increasing fatty acids concentration, the fractional weight associated with ANS bound to the internal site drops, in agreement with a model describing the competition of the dye with fatty acids, whereas the external site occupancy appears to be unaffected by the fatty acids binding to BLG. This model is supported by docking studies. An estimate of the acid-binding affinities for BLG has been obtained by implementing the fitting of the bound ANS intensities with a competitive binding model. A relevant dependence has been found upon the solution pH, in the range from 6 to 8, which correlates with the calyx accessibility modulated by the conformation of the EF loop. Fatty acids with longer aliphatic chains (palmitate and laurate) are found to display larger affinities for the protein and the interaction free energy nicely correlates with the number of contacts inside the protein calyx, in agreement with docking simulations.
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Affiliation(s)
- Maddalena Collini
- Dipartimento di Fisica, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126 Milan, Italy
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37
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Abstract
The stabilizing role of the disaccharide trehalose on beta-lactoglobulin (BLG) against its chemical denaturation both at native and acidic pH has been explored by means of time-resolved fluorescence of the probe acrylodan covalently bound to the unique free cysteine of BLG. The changes in acrylodan fluorescence lifetime with guanidinium chloride concentration reveal BLG sigmoidal denaturation profiles which depend upon the amount of trehalose in solution. When adding trehalose the transition midpoint shifts towards higher denaturant concentration. This effect has been measured by fitting the data with a two-state model whose parameters indicate that an almost 60% increase in the denaturation free energy is induced independently of trehalose concentrations and pH values. Fluorescence anisotropy measurements performed in the same conditions reveal that the internal dynamics are largely affected by the sugar, which makes the acrylodan environment more rigid, and by the denaturant that acts in the opposite way. The overall rotational diffusion of BLG suggests that trehalose affects the hydrodynamic properties of the solution in the proximity of the protein; tentative mechanisms are discussed.
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Affiliation(s)
- Laura D'Alfonso
- Dipartimento di Fisica, Università degli Studi di Milano-Bicocca, and Istituto Nazionale per la Fisica della Materia, Milano, Italy
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Abstract
The fluorescence lifetime of ethidium bromide (EB), a widely used fluorescent dye, has been monitored in water solution versus trehalose concentration in order to learn how the presence of the disaccharide modifies the hydration of EB, which is used in this study as a model probe. The interest in trehalose, a naturally occurring bioprotector (osmolyte), stems from its ability to stabilize biomolecules under stress situations. The observed effects of trehalose on EB fluorescence properties have been compared with those induced by sucrose and glucose. Lifetime measurements have been performed by frequency domain fluorometry (2-40 MHz), and from the analysis of their changes versus sugar concentration, the EB-sugar interaction parameters have been obtained. The effect of trehalose on the EB decay in glasses has also been studied both by exploring the heterogeneity of lifetime decay and by single-molecule imaging. Trehalose appears to be more efficient in changing the EB fluorescence parameters, such as the emission lifetime, and it leads to a degree of heterogeneity higher than that induced by the other sugars. When EB is embedded in trehalose glasses, the heterogeneity of the emission and of the bleaching time is further enhanced.
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Affiliation(s)
- Maddalena Collini
- Dipartimento di Fisica, Universita di Milano-Bicocca, Milano, Italy.
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Abstract
The denaturation of beta-lactoglobulin (BLG) in the presence of urea and GuHCl has been investigated at different pH values with various spectroscopic techniques. The equilibrium denaturation free energy values, obtained by linearly extrapolating the data to vanishing denaturant (DeltaG(D)(H2O)), are compared and discussed. The fit of the spectroscopic data monitoring the denaturation of BLG has been approached, at first, with a two-state model that describes the protein transition from the folded state (at each pH and in the absence of denaturant) to the denatured state, but in particular, along the GuHCl denaturation pathway some evidence is found of the presence of an intermediate state. Time-resolved fluorescence experiments performed on the BLG-ANS (1-anilino-8-naphthalenesulfonate) complex help to understand the results. Fluorescence polarization anisotropy (FPA) measurements accompanying the denaturation process show the presence of a fast rotational diffusion of the ANS probe, and the data are interpreted in terms of local fluctuations of a still structured tract of the denatured protein where the probe is bound.
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Affiliation(s)
- Laura D'Alfonso
- Università degli Studi di Milano-Bicocca and INFM UdR Milano-Bicocca, P.za della Scienza, 3 I-20126 Milano, Italy
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Abstract
The fluorescence time decay parameters of the beta-lactoglobulin-1-anilinonaphthalene-8-sulfonate complex have been investigated under physical and chemical perturbations (2 < pH < 8 and added electrolyte 0 < NaCl < 0.5 M) to obtain new insight on the nature of the protein binding interactions. A double exponential decay of the bound probe lifetime has been confirmed by the presence of a longer component, 11 to 14.5 ns, and a shorter component, 2.5 to 3.5 ns. The two lifetimes are ascribed to different binding modes associated also with different exposure to the solvent; in particular, the longer component is attributed to binding inside the hydrophobic beta barrel, while a "surface" site is suggested for the shorter component. A detailed analysis of the lifetime fractional intensities correlates the binding constants with ionic strength and supports the presence of electrostatic effects at both sites. A Debye-Hückel approach, applied to extrapolate the electrostatic free energy contribution vs. pH at vanishing ionic strength, gives interesting clues on the effective charge felt by the ANS ligands in the proximity of each site. In particular, binding is found to parallel the aspartate and glutamate titrations between pH 3 and pH 4.5; the "surface" site mainly responds to the presence of these local titrating charges while the "internal" site more closely follows the overall protein net charge.
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Affiliation(s)
- M Collini
- Istituto Nazionale per la Fisica della Materia and Università di Milano-Bicocca, Italy
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42
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D'Alfonso L, Collini M, Baldini G. Evidence of heterogeneous 1-anilinonaphthalene-8-sulfonate binding to beta-lactoglobulin from fluorescence spectroscopy. Biochim Biophys Acta 1999; 1432:194-202. [PMID: 10407141 DOI: 10.1016/s0167-4838(99)00105-3] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Steady-state and dynamic fluorescence titrations show that: (a) the complex between beta-lactoglobulin (BLG) and 1-anilinonaphthalene-8-sulfonate (ANS) displays a heterogeneous equilibrium with large changes in the binding strength vs. pH and ion concentration; and (b) the fluorescence response of bound ANS reveals two separate lifetimes that suggest two different sites (or binding modes). While steady-state fluorescence titrations yield effective values of the binding constant and of the bound ANS quantum efficiency, it is shown that, by combining steady-state fluorescence and lifetime decay of ANS, it is possible to give quantitative estimates of the association constants for each site. When heading from the acid (pH approximately 2) to the native state (pH approximately 6) the main result is a very large reduction of the effective binding constant. This and the results of titrations vs. ionic strength suggest that electrostatic interactions are a major contribution to ANS binding to BLG.
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Affiliation(s)
- L D'Alfonso
- Istituto Nazionale per la Fisica della Materia and Università di Milano-Bicocca, via Celoria 16 I-20133, Milan, Italy
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