Three-dimensional characterization of collagen remodeling in cell-seeded collagen scaffolds via polarization second harmonic generation

Assessment of aqueous graphene as a cancer therapeutics delivery system

Graphene is a nanomaterial used in health and oncology settings. However, several reports have raised the alarm about potential toxicity. This study addressed this concern and determined the in vitro cytotoxicity of few-layer graphene (FLG) flakes produced in bespoke ultrasonic reactors using benign methods. The use of graphene flakes as a potential sensitising agent and a carrier for drug delivery in cancer cells was evaluated. To this end, aqueous based FLG suspensions were systematically characterised using UV-Vis, Raman spectroscopy and High-resolution Transmission electron microscopy (HR-TEM). Cell toxicity characterisation (e.g., cell viability assays using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) and cell membrane integrity) of FLG in water were performed together with charge coupled device (CCD) and second harmonic generation (SHG) imaging of live cells in graphene solutions. Collectively, our findings show that NIH 3T3 mouse fibroblast and human fibroblast cells survival was higher than 80% and 90%, respectively upon treatment with the FLG fraction (~ 16 µg/ml ) recovered after centrifugation at 2000 revolutions per minute (RPM). In contrast, the cervical cancer cell line HeLa exposed to similar concentrations of FLG flakes resulted in approximately 30% cell death arguing in favour of a sensitising effect in cervical cancer cells.

Miniaturized Iontronic Micropipettes for Precise and Dynamic Ionic Modulation of Neuronal and Astrocytic Activity

The composition of the extracellular milieu can vary significantly under physiological and pathological conditions, thereby altering the functional set point of brain cells. While global changes in the extracellular milieu are known to affect network activity, a detailed understanding of how specific changes in ion species impact individual cells remains elusive. Current modulation methods involve the use of diluted salts, such as KCl, where lack of precise control complicates data interpretation. This study achieves enhanced resolution by using a miniaturized iontronic micropipette. The micropipette, with a tip filled with polyelectrolyte and an outlet size below 2 µm, allows for on-demand ionic manipulation of single cells, without simultaneous co-delivery of solvents or other solutes. Electrical, chemical, and optical characterizations, supported by computational modeling, confirm the device's high spatial and temporal precision. Validated in hippocampal slices, the device demonstrates iontronic release of potassium ions (K⁺), with a low current (<200 nA), that effectively, rapidly, and reversibly modulates individually targeted neurons and astrocytes. These findings underscore the potential of iontronic micropipettes to elucidate the distinct responses of neuronal and glial cells to specific changes in the local extracellular milieu, offering insights for neuroscience research and therapeutic innovation.

Multiparametric physicochemical analysis of a type 1 collagen 3D cell culture model using light and electron microscopy and mass spectrometry imaging

Three-dimensional cell culture systems underpin cell-based technologies ranging from tissue scaffolds for regenerative medicine to tumor models and organoids for drug screening. However, to realise the full potential of these technologies requires analytical methods able to capture the diverse information needed to characterize constituent cells, scaffold components and the extracellular milieu. Here we describe a multimodal imaging workflow which combines fluorescence, vibrational and second harmonic generation microscopy with secondary ion mass spectrometry imaging and transmission electron microscopy to analyse the morphological, chemical and ultrastructural properties of cell-seeded scaffolds. Using cell nuclei as landmarks we register fluorescence with label-free optical microscopy images and high mass resolution with high spatial resolution secondary ion mass spectrometry images, with an accuracy comparable to the intrinsic spatial resolution of the techniques. We apply these methods to investigate relationships between cell distribution, cytoskeletal morphology, scaffold fiber organisation and biomolecular composition in type I collagen scaffolds seeded with human dermal fibroblasts.

Flow-Induced Shear Stress Combined with Microtopography Inhibits the Differentiation of Neuro-2a Cells

Considering that neurological injuries cannot typically self-recover, there is a need to develop new methods to study neuronal outgrowth in a controllable manner in vitro. In this study, a precise flow-controlled microfluidic system featuring custom-designed chambers that integrate laser-microstructured polyethylene terephthalate (PET) substrates comprising microgrooves (MGs) was developed to investigate the combined effect of shear stress and topography on Neuro-2a (N2a) cells' behavior. The MGs were positioned parallel to the flow direction and the response of N2a cells was evaluated in terms of growth and differentiation. Our results demonstrate that flow-induced shear stress could inhibit the differentiation of N2a cells. This microfluidic system could potentially be used as a new model system to study the impact of shear stress on cell differentiation.

Profiling of collagen and extracellular matrix deposition from cell culture using in vitro ExtraCellular matrix mass spectrometry imaging (ivECM-MSI)

While numerous approaches have been reported towards understanding single cell regulation, there is limited understanding of single cell production of extracellular matrix phenotypes. Collagens are major proteins of the extracellular microenvironment extensively used in basic cell culture, tissue engineering, and biomedical applications. However, identifying compositional regulation of collagen remains challenging. Here, we report the development of In vitro ExtraCellular Matrix Mass Spectrometry Imaging (ivECM-MSI) as a tool to rapidly and simultaneously define collagen subtypes from coatings and basic cell culture applications. The tool uses the mass spectrometry imaging platform with reference libraries to produce visual and numerical data types. The method is highly integrated with basic in vitro strategies as it may be used with conventional cell chambers on minimal numbers of cells and with minimal changes to biological experiments. Applications tested include semi-quantitation of collagen composition in culture coatings, time course collagen deposition, deposition altered by gene knockout, and changes induced by drug treatment. This approach provides new access to proteomic information on how cell types respond to and change the extracellular microenvironment and provides a holistic understanding of both the cell and extracellular response.

Water-Soluble Bimodal Magnetic-Fluorescent Radical Dendrimers as Potential MRI-FI Imaging Probes

Dual or multimodal imaging probes have become potent tools for enhancing detection sensitivity and accuracy in disease diagnosis. In this context, we present a bimodal imaging dendrimer-based structure that integrates magnetic and fluorescent imaging probes for potential applications in magnetic resonance imaging and fluorescence imaging. It stands out as one of the rare examples where bimodal imaging probes use organic radicals as the magnetic source, despite their tendency to entirely quench fluorophore fluorescence. Opting for organic radicals over metal-based contrast agents like gadolinium (Gd3+)-chelates is crucial to mitigate associated toxicity concerns. We utilized an amino-terminated polyamide dendrimer containing a 1,8-naphthalimide (Naft) fluorescent group, amino acid derivatives as linkers to enhance water solubility, and TEMPO organic radicals as terminal groups. The same dendrimer structure, featuring an equivalent number of branches but lacking the fluorophore group, was also functionalized with amino acid and terminal radicals to serve as a reference. Remarkably, we achieved a fully water-soluble dendrimer-based structure exhibiting both magnetic and fluorescent properties simultaneously. The fluorescence of the Naft group in the final structure is somewhat quenched by the organic radicals, likely due to photoinduced electron transfer with the nitroxyl radical acting as an electron acceptor, which has been supported by density functional theory calculations. Molecular dynamics simulations are employed to investigate how the dendrimers' structure influences the electron paramagnetic resonance characteristics, relaxivity, and fluorescence. In summary, despite the influence of the radicals-fluorophore interactions on fluorescence, this bimodal dendrimer demonstrates significant fluorescent properties and effective r1 relaxivity of 1.3 mM-1 s-1. These properties have proven effective in staining the live mesenchymal stem cells without affecting the cell nucleus.

Widefield polarization-resolved second harmonic generation imaging of entire thyroid nodule sections for the detection of capsular invasion

The identification of tumor capsular invasion as a sign of malignancy is currently employed in traditional histopathology routines for thyroid nodules. However, its limitations are associated with the assessment criteria for invasion, which often lead to disagreements among observers. The aim of this paper is to introduce a widefield imaging technique combined with quantitative collagen analysis to identify areas of capsular invasion in thyroid neoplasms. In this study, we introduce the application of widefield polarization-resolved second harmonic generation microscopy for imaging entire thyroid nodule sections on histological slides. We employ a cylindrical collagen model to extract parameters associated with the ultrastructure and orientation of collagen within the entire capsule of the thyroid nodule. We showcase the effectiveness of these parameters in distinguishing between areas of nodule capsule invasion and unaffected regions of the capsule through statistical analysis of individual parameters and employing a machine learning technique that involves generating maps via cluster analysis. Our results suggest that quantitative analysis facilitated by polarization-resolved widefield second harmonic generation microscopy could prove beneficial for the automated evaluation of capsular invasion sites in thyroid pathology.

Assessment of Collagen in Translational Models of Lung Research

The extracellular matrix (ECM) plays an important role in lung health and disease. Collagen is the main component of the lung ECM, widely used for the establishment of in vitro and organotypic models of lung disease, and as scaffold material of general interest for the field of lung bioengineering. Collagen also is the main readout for fibrotic lung disease, where collagen composition and molecular properties are drastically changed and ultimately result in dysfunctional "scarred" tissue. Because of the central role of collagen in lung disease, quantification, determination of molecular properties, and three-dimensional visualization of collagen is important for both development and characterization of translational models of lung research. In this chapter, we provide a comprehensive overview on the various methodologies currently available for quantification and characterization of collagen including their detection principles, advantages, and disadvantages.

Optical Microscopy and the Extracellular Matrix Structure: A Review

Biological tissues are not uniquely composed of cells. A substantial part of their volume is extracellular space, which is primarily filled by an intricate network of macromolecules constituting the extracellular matrix (ECM). The ECM serves as the scaffolding for tissues and organs throughout the body, playing an essential role in their structural and functional integrity. Understanding the intimate interaction between the cells and their structural microenvironment is central to our understanding of the factors driving the formation of normal versus remodelled tissue, including the processes involved in chronic fibrotic diseases. The visualization of the ECM is a key factor to track such changes successfully. This review is focused on presenting several optical imaging microscopy modalities used to characterize different ECM components. In this review, we describe and provide examples of applications of a vast gamut of microscopy techniques, such as widefield fluorescence, total internal reflection fluorescence, laser scanning confocal microscopy, multipoint/slit confocal microscopy, two-photon excited fluorescence (TPEF), second and third harmonic generation (SHG, THG), coherent anti-Stokes Raman scattering (CARS), fluorescence lifetime imaging microscopy (FLIM), structured illumination microscopy (SIM), stimulated emission depletion microscopy (STED), ground-state depletion microscopy (GSD), and photoactivated localization microscopy (PALM/fPALM), as well as their main advantages, limitations.

Airway-On-A-Chip: Designs and Applications for Lung Repair and Disease

The lungs are affected by illnesses including asthma, chronic obstructive pulmonary disease, and infections such as influenza and SARS-CoV-2. Physiologically relevant models for respiratory conditions will be essential for new drug development. The composition and structure of the lung extracellular matrix (ECM) plays a major role in the function of the lung tissue and cells. Lung-on-chip models have been developed to address some of the limitations of current two-dimensional in vitro models. In this review, we describe various ECM substitutes utilized for modeling the respiratory system. We explore the application of lung-on-chip models to the study of cigarette smoke and electronic cigarette vapor. We discuss the challenges and opportunities related to model characterization with an emphasis on in situ characterization methods, both established and emerging. We discuss how further advancements in the field, through the incorporation of interstitial cells and ECM, have the potential to provide an effective tool for interrogating lung biology and disease, especially the mechanisms that involve the interstitial elements.