Single-domain protein A-engineered magnetic nanoparticles: toward a universal strategy to site-specific labeling of antibodies for targeted detection of tumor cells

Curcumin encapsulation in functional PLGA nanoparticles: A promising strategy for cancer therapies

Nanoparticles have emerged as promising drug delivery systems for the treatment of several diseases. Novel cancer therapies have exploited these particles as alternative adjuvant therapies to overcome the traditional limitations of radio and chemotherapy. Curcumin is a natural bioactive compound found in turmeric, that has been reported to show anticancer activity against several types of tumors. Despite some biological limitations regarding its absorption in the human body, curcumin encapsulation in poly(lactic-co-glycolic acid) (PLGA), a non-toxic, biodegradable and biocompatible polymer, represents an effective strategy to deliver a drug to a tumor site. Furthermore, PLGA nanoparticles can be engineered with targeting moieties to reach specific cancer cells, thus enhancing the antitumor effects of curcumin. We herein aim to bring an up-to-date summary of the recently developed strategies for curcumin delivery to different types of cancer cells through encapsulation in PLGA nanoparticles, correlating their effects with those of curcumin on the biological capabilities acquired by cancer cells (cancer hallmarks). We discuss the targeting strategies proposed for advanced curcumin delivery and the respective improvements achieved for each cancer cell analyzed, in addition to exploring the encapsulation techniques employed. The conjugation of correct encapsulation techniques with tumor-oriented targeting design can result in curcumin-loaded PLGA nanoparticles that can successfully integrate the elaborate network of development of alternative cancer treatments along with traditional ones. Finally, the current challenges and future demands to launch these nanoparticles in oncology are comprehensively examined.

Functionalization of colloidal nanoparticles with a discrete number of ligands based on a "HALO-bioclick" reaction

A recombinant HALO-GFP fusion protein was designed and isolated to demonstrate the feasibility of controlling the number and orientation of protein ligands to be conjugated on colloidal gold nanoparticles. AuNPs functionalized with exactly one or exactly two GFP molecules exhibited fully preserved functionality of the protein. The method is very straightforward and generally provides highly bioactive nanoparticle-protein conjugates.

Mechanism of antibodies purification by protein A

Protein A, a major cell wall component of Staphylococcus aureus, is one of the first immunoglobulin-binding proteins that is discovered about 80 years ago. However, a great deal of development in both purification methods and application of antibodies in treatment have been done. There are many publications based on the untargeted (size exclusion, ion exchange and hydrophobic interactions) and targeted (affinity) methods by scientists in academic/industry groups. In this review, we have focused on the study of both native and engineered Protein A to understand its mechanism in the purification of antibodies. What domain of Protein A dose interact with antibody? Where are contact regions? What is the non-covalent interaction mechanism of Protein A and antibody? Does alkaline condition, in the washing step, influence on antibody structure and activity? On the other hand, the immobilization of Protein A on various sorbents such as agarose, silica, polysaccharide, polymers, and magnetic nanoparticles have investigated. Also, the application of Protein A as biosensor for detection of the antibody is discussed. We have tried to find interesting and stimulating answers to all these questions.

Seeking Innovative Affinity Approaches: A Performance Comparison between Magnetic Nanoparticle Agglomerates and Chromatography Resins for Antibody Recovery

Monoclonal antibodies are key molecules in medicine and pharmaceuticals. A potentially crucial drawback for faster advances in research here is their high price due to the extremely expensive antibody purification process, particularly the affinity capture step. Affinity chromatography materials have to demonstrate the high binding capacity and recovery efficiency as well as superior chemical and mechanical stability. Low-cost materials and robust, faster processes would reduce costs and enhance industrial immunoglobulin purification. Therefore, exploring the use of alternative materials is necessary. In this context, we conduct the first comparison of the performance of magnetic nanoparticles with commercially available chromatography resins and magnetic microparticles with regard to immobilizing Protein G ligands and recovering immunoglobulin G (IgG). Simultaneously, we demonstrate the suitability of bare as well as silica-coated and epoxy-functionalized magnetite nanoparticles for this purpose. All materials applied have a similar specific surface area but differ in the nature of their matrix and surface accessibility. The nanoparticles are present as micrometer agglomerates in solution. The highest Protein G density can be observed on the nanoparticles. IgG adsorbs as a multilayer on all materials investigated. However, the recovery of IgG after washing indicates a remaining monolayer, which points to the specificity of the IgG binding to the immobilized Protein G. One important finding is the impact of the ligand-binding stoichiometry (Protein G surface coverage) on IgG recovery, reusability, and the ability to withstand long-term sanitization. Differences in the materials' performances are attributed to mass transfer limitations and steric hindrance. These results demonstrate that nanoparticles represent a promising material for the economical and efficient immobilization of proteins and the affinity purification of antibodies, promoting innovation in downstream processing.

Surface Functionalization of Magnetic Nanoparticles Using a Thiol-Based Grafting-Through Approach

Here we describe a simple and straightforward synthesis of different multifunctional magnetic nanoparticles by using surface bound thiol-groups as transfer agents in a free radical polymerization process. The modification includes a first step of surface silanization with (3-mercaptopropyl)trimethoxysilane to obtain thiol-modified nanoparticles, which are further used as a platform for modification with a broad variety of polymers. The silanization was optimized in terms of shell thickness and particle size distribution, and the obtained materials were investigated by dynamic light scattering (DLS), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDX). Subsequently, the free radical polymerization of different monomers (tert-butyl acrylate (tBA), methyl methacrylate (MMA), styrene, 2-vinyl pyridine (2VP), and N-isopropylacrylamide (NIPAAm)) was examined in the presence of the thiol-modified nanoparticles. During the process, a covalently anchored polymeric shell was formed and the resulting core–shell hybrid materials were analyzed in terms of size (DLS, TEM), shell thickness (TGA, TEM), and the presence of functional groups (attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FT-IR)). Hereby, the shell leads to a different solution behavior of the particles and in some cases an increased stability towards acids. Moreover, we examined the influence of the nanoparticle concentration during polymerization and we found a significant influence on dispersity of the resulting polymers. Finally, we compared the characteristics of the surface bound polymer and polymer formed in solution for the case of polystyrene. The herein presented approach provides straightforward access to a wide range of core–shell nanocomposites.

Does conjugation strategy matter? Cetuximab-conjugated gold nanocages for targeting triple-negative breast cancer cells

The efficient targeting of cancer cells depends on the success of obtaining the active targeting of overexpressed receptors. A very accurate design of nanoconjugates should be done via the selection of the conjugation strategy to achieve effective targeted nanoconjugates. Here, we present a detailed study of cetuximab-conjugated nonspherical gold nanocages for the active targeting of triple-negative breast cancer cells, including MDA-MB-231 and MDA-MB-468. A few different general strategies were selected for monoclonal antibody conjugation to the nanoparticle surface. By varying the bioconjugation conditions, including antibody orientation or the presence of a polymeric spacer or recombinant protein biolinker, we demonstrate the importance of a rational design of nanoconjugates. A quantitative study of gold content via ICP-AES allowed us to compare the effectiveness of cellular uptake as a function of the conjugation strategy and confirmed the active nature of nanoparticle internalization in cancer cells via epidermal growth factor receptor recognition, corroborating the importance of the rational design of nanomaterials for nanomedicine.

Antibody-Oriented Strategy and Mechanism for the Preparation of Fluorescent Nanoprobes for Fast and Sensitive Immunodetection

Nanoprobes have been widely used in biomedical engineering. However, antibodies are generally conjugated onto nanoparticles disorderly, which reduces their antigen recognition ability. The existing antibody orientation approaches are usually complex. Here, we developed and demonstrated a simple antibody-oriented strategy for the lateral flow immunoassay of cardiac troponin I by conjugating antibodies onto polystyrene nanospheres at the optimal pH. The binding amount and orientation of antibodies as well as the detection sensitivity were significantly improved. Although pH regulation is commonly used to optimize antibody conjugation, this paper illustrates the mechanism of its antibody orientation enhancement ability for the first time and reveals the important influences of the density, the charge distribution and hydrophilicity of the antibody, the control of the velocities of physical adsorption and chemical coupling, and other factors on antibody orientation. It is of great significance to understand and regulate antibody conjugation on the surface of micro- or nanospheres to construct high-performance probes for in vitro diagnosis applications.

SPIONs functionalized with small peptides for binding of lipopolysaccharide, a pathophysiologically relevant microbial product

Systemic inflammation such as sepsis represents an acute life-threatening condition, to which often no timely remedy can be found. A promising strategy may be to functionalize magnetic nanoparticles with specific peptides, derived from the binding motives of agglutinating salivary proteins, that allow immobilization of pathogens. In this work, superparamagnetic iron oxide nanoparticles with stable polycondensed aminoalkylsilane layer were developed, to which the heterobifunctional linkers N-succinimidyl 3-(2-pyridyldithio)-propanoate (SDPD) and N-succinimidyl bromoacetate (SBA) were bound. These linkers were further chemoselectively reacted with the thiol group of singularly present cysteines of selected peptides. The resulting functional nanoparticles underwent a detailed physicochemical characterization. The biocompatibility of the primarily coated aminoalkylsilane particles was also investigated. To test the pathogen-binding efficacy of the particles, the lipopolysaccharide-immobilization capacity of the peptide-coated particles was compared with free peptides. Here, one particle-bound peptide species succeeded in capturing 90% of the toxin, whereas the degree of immobilization of the toxin with a system that varied in the sequence of the peptide dropped to 35%. With these promising results, we hope to develop extracorporeal magnetic clearance systems for removing pathogens from the human body in order to accelerate diagnosis and alleviate acute disease conditions such as sepsis.

Targeting strategies for improving the efficacy of nanomedicine in oncology

The use of nanoparticles as drug carriers has provided a powerful weapon in the fight against cancer. These nanocarriers are able to transport drugs that exhibit very different nature such as lipophilic or hydrophilic drugs and big macromolecules as proteins or RNA. Moreover, the external surface of these carriers can be decorated with different moieties with high affinity for specific membrane receptors of the tumoral cells to direct their action specifically to the malignant cells. The selectivity improvement yielded by these nanocarriers provided a significative enhancement in the efficacy of the transported drug, while the apparition of side effects in the host was reduced. Additionally, it is possible to incorporate targeting moieties selective for organelles of the cell, which improves even more the effect of the transported agents. In the last years, more sophisticated strategies such as the use of switchable, hierarchical or double targeting strategies have been proposed for overcoming some of the limitations of conventional targeting strategies. In this review, recent advances in the development of targeted nanoparticles will be described with the aim to present the current state of the art of this technology and its huge potential in the oncological field.

Half-Chain Cetuximab Nanoconjugates Allow Multitarget Therapy of Triple Negative Breast Cancer

The use of therapeutic monoclonal antibodies (mAbs) has revolutionized cancer treatment. The conjugation of mAbs to nanoparticles has been broadly exploited to improve the targeting efficiency of drug nanocarriers taking advantage of high binding efficacy and target selectivity of antibodies for specific cell receptors. However, the therapeutic implications of nanoconjugation have been poorly considered. In this study, half-chain fragments of the anti-EGFR mAb cetuximab were conjugated to colloidal nanoparticles originating stable nanoconjugates that were investigated as surrogates of therapeutic mAbs in triple negative breast cancer (TNBC). Three TNBC cell lines were selected according to EGFR expression, which regulates activation of MAPK/ERK and PI3K/Akt pathways, and to distinctive molecular profiling including KRAS, PTEN, and BRCA1 mutations normally associated with diverse sensitivity to treatment with cetuximab. The molecular mechanisms of action of nanoconjugated half-chain mAb, including cell targeting, interference with downstream signaling pathways, proliferation, cell cycle, and apoptosis, along with triggering of ADCC response, were investigated in detail in sensitive and resistant TNBC cells. We found that half-chain mAb nanoconjugation was able to enhance the therapeutic efficacy and improve the target selectivity against sensitive, but unexpectedly also resistant, TNBC cells. Viability assays and signaling transduction modulation suggested a role of BRCA1 mutation in TNBC resistance to cetuximab alone, whereas its effect could be circumvented using half-chain cetuximab nanoconjugates, suggesting that nanoconjugation not only improved the antibody activity but also exerted different mechanisms of action. Our results provide robust evidence of the potential of half-chain antibody nanoconjugates in the treatment of TNBC, which could offer a new paradigm for therapeutic antibody administration, potentially allowing improved curative efficiency and reduced minimal effective dosages in both sensitive and resistant tumors.

Recent advances in magnetic fluid hyperthermia for cancer therapy

Recently, magnetic fluid hyperthermia using biocompatible magnetic nanoparticles as heat mediators for cancer therapy has been extensively investigated due to its high efficiency and limited side effects. However, the development of more efficient heat nanomediators that exhibit very high specific absorption rate (SAR) value is essential for clinical application to overcome the several restrictions previously encountered due to the large quantity of nanomaterial required for effective treatment. In this review, we focus on the current progress in the development of magnetic nanoparticles based hyperthermia therapy as well as combined therapy harnessing hyperthermia with heat-mediated drug delivery for cancer treatment. We also address the fundamental principles of magnetic hyperthermia, basics of magnetism including the effect of several parameters on heating capacity, synthetic methods and nanoparticle surface chemistry needed to design and develop an ideal magnetic nanoparticle heat mediator suitable for clinical translation in cancer therapy.

How can nanotechnology help the fight against breast cancer?

In this review we provide a broad overview on the use of nanotechnology for the fight against breast cancer (BC). Nowadays, detection, diagnosis, treatment, and prevention may be possible thanks to the application of nanotechnology to clinical practice. Taking into consideration the different forms of BC and the disease status, nanomaterials can be designed to meet the most forefront objectives of modern therapy and diagnosis. We have analyzed in detail three main groups of nanomaterial applications for BC treatment and diagnosis. We have identified several types of drugs successfully conjugated with nanomaterials. We have analyzed the main important imaging techniques and all nanomaterials used to help the non-invasive, early detection of the lesions. Moreover, we have examined theranostic nanomaterials as unique tools, combining imaging, detection, and therapy for BC. This state of the art review provides a useful guide depicting how nanotechnology can be used to overcome the current barriers in BC clinical practice, and how it will shape the future scenario of treatments, prevention, and diagnosis, revolutionizing the current approaches, e.g., reducing the suffering related to chemotherapy.

Redox-responsive dextran based theranostic nanoparticles for near-infrared/magnetic resonance imaging and magnetically targeted photodynamic therapy

Photodynamic therapy (PDT) is a site-specific treatment of cancer using much lower optical power densities with minimal nonspecific damage to normal tissues. To improve the therapeutic efficiency of PDT, we fabricated a multifunctional theranostic nanoparticle system (DSSCe6@Fe₃O₄ NPs) by loading Fe₃O₄ nanoparticles in redox-responsive chlorin e6 (Ce6)-conjugated dextran nanoparticles for near-infrared (NIR)/magnetic resonance (MR) dual-modality imaging and magnetic targeting. The obtained DSSCe6@Fe₃O₄ NPs demonstrated a uniform nanospherical morphology consisting of Fe₃O₄ clusters. The fluorescence signal of Ce6 of this theranostic system could turn "ON" from a self-quenching state in a reductive intracellular environment. T₂-Weighted MR imaging revealed a high transverse relaxivity (r₂) measured to be 194.4 S^-1 mM^-1, confirming that it was also a distinctive contrast agent in T₂-weighted MR imaging. Confocal images and flow cytometry results showed that the cellular uptake of DSSCe6@Fe₃O₄ NPs was enhanced effectively under an extra magnetic field, which resulted in promoted PDT therapeutic efficiency. In vivo MR imaging showed that DSSCe6@Fe₃O₄ NPs effectively accumulated in tumors under an extra magnetic field. These results illustrated that the DSSCe6@Fe₃O₄ NPs could be a promising theranostic system for both NIR/MR imaging-guided PDT precision therapy.

Trastuzumab- and Fab' fragment-modified curcumin PEG-PLGA nanoparticles: preparation and evaluation in vitro and in vivo

Introduction

Nanoparticles (NPs) modified with bio-ligands represent a promising strategy for active targeted drug delivery to tumour. However, many targeted ligands, such as trastuzumab (TMAB), have high molecular weight, limiting their application for targeting. In this study, we prepared Fab' (antigen-binding fragments cut from TMAB)-modified NPs (Fab'-NPs) with curcumin (Cur) as a model drug for more effective targeting of human epidermal growth factor receptor 2 (HER2/ErbB2/Neu), which is overexpressed on breast cancer cells.

Material and methods

The release kinetics was conducted by dialysis bags. The ability to kill HER2-overexpressing BT-474 cells of Fab'-Cur-NPs compared with TMAB-Cur-NPs was conducted by cytotoxicity experiments. Qualitative and quantitative cell uptake studies using coumarin-6 (fluorescent probe)-loaded NPs were performed by fluorescence microscopy and flow cytometry. Pharmacokinetics and biodistribution experiments in vivo were assessed by liquid chromatography-tandem mass spectrometry (LC-MS/MS).

Results

The release kinetics showed that both Fab'-Cur-NPs and TMAB-Cur-NPs provided continuous, slow release of curcumin for 72 h, with no significant difference. In vitro cytotoxicity experiments showed that Fab'-Cur-NPs manifested prominent ability to kill HER2-overexpressing BT-474 cells compared with TMAB-Cur-NPs. Qualitative and quantitative cell uptake studies indicated that the accumulation of Fab'-NPs was greater than that of TMAB-NPs in BT-474 (HER2+) cells; However, there was no significant difference in MDA-MB-231 (HER2-) cells. Pharmacokinetics and biodistribution experiments in vivo demonstrated that the half-life (t1/2) and area under the blood concentration-time curve (AUC0-t) of Fab'-Cur-NPs increased 5.30-fold and 1.76-fold relative to those of TMAB-Cur-NPs, respectively. Furthermore, the tumor accumulation of Fab'-Cur-NPs was higher than that of TMAB-Cur-NPs.

Conclusion

Fab' fragment has greater capacity than the intact antibody to achieve tumor targeting through NP-based delivery.

PMIDA-Modified Fe3O4 Magnetic Nanoparticles: Synthesis and Application for Liver MRI

The surface modification of Fe₃O₄-based magnetic nanoparticles (MNPs) with N-(phosphonomethyl)iminodiacetic acid (PMIDA) was studied, and the possibility of their use as magnetic resonance imaging contrast agents was shown. The effect of the added PMIDA amount, the reaction temperature and time on the degree of immobilization of this reagent on MNPs, and the hydrodynamic characteristics of their aqueous colloidal solutions have been systematically investigated for the first time. It has been shown that the optimum condition for the modification of MNPs is the reaction at 40 °C with an equimolar amount of PMIDA for 3.5 h. The modified MNPs were characterized by X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric, and CHN elemental analyses. The dependence of the hydrodynamic characteristics of the MNP colloidal solutions on the concentration and pH of the medium was studied by the dynamic light scattering method. On the basis of the obtained data, we can assume that the PMIDA molecules are fixed on the surface of the MNPs as a monomolecular layer. The modified MNPs had good colloidal stability and high magnetic properties. The calculated relaxivities r₂ and r₁ were 341 and 102 mmol^-1 s^-1, respectively. The possibility of using colloidal solutions of PMIDA-modified MNPs as a T₂ contrast agent for liver studies in vivo (at a dose of 0.6 mg kg^-1) was demonstrated for the first time.

Gelatinase activity imaged by activatable cell-penetrating peptides in cell-based and in vivo models of stroke

Matrix metalloproteinases (MMPs), particularly gelatinases (MMP-2/-9), are involved in neurovascular impairment after stroke. Detection of gelatinase activity in vivo can provide insight into blood-brain barrier disruption, hemorrhage, and nerve cell injury or death. We applied gelatinase-activatable cell-penetrating peptides (ACPP) with a cleavable l-amino acid linker to examine gelatinase activity in primary neurons in culture and ischemic mouse brain in vivo We found uptake of Cy5-conjugated ACPP (ACPP-Cy5) due to gelatinase activation both in cultured neurons exposed to n-methyl-d-aspartate and in mice after cerebral ischemia. Fluorescence intensity was significantly reduced when cells or mice were treated with MMP inhibitors or when a cleavage-resistant ACPP-Cy5 was substituted. We also applied an ACPP dendrimer (ACPPD) conjugated with multiple Cy5 and/or gadolinium moieties for fluorescence and magnetic resonance imaging (MRI) in intact animals. Fluorescence analysis showed that ACPPD was detected in sub-femtomole range in ischemic tissues. Moreover, MRI and inductively coupled plasma mass spectrometry revealed that ACPPD produced quantitative measures of gelatinase activity in the ischemic region. The resulting spatial pattern of gelatinase activity and neurodegeneration were very similar. We conclude that ACPPs are capable of tracing spatiotemporal gelatinase activity in vivo, and will therefore be useful in elucidating mechanisms of gelatinase-mediated neurodegeneration after stroke.

Tumour homing and therapeutic effect of colloidal nanoparticles depend on the number of attached antibodies

Active targeting of nanoparticles to tumours can be achieved by conjugation with specific antibodies. Specific active targeting of the HER2 receptor is demonstrated in vitro and in vivo with a subcutaneous MCF-7 breast cancer mouse model with trastuzumab-functionalized gold nanoparticles. The number of attached antibodies per nanoparticle was precisely controlled in a way that each nanoparticle was conjugated with either exactly one or exactly two antibodies. As expected, in vitro we found a moderate increase in targeting efficiency of nanoparticles with two instead of just one antibody attached per nanoparticle. However, the in vivo data demonstrate that best effect is obtained for nanoparticles with only exactly one antibody. There is indication that this is based on a size-related effect. These results highlight the importance of precisely controlling the ligand density on the nanoparticle surface for optimizing active targeting, and that less antibodies can exhibit more effect.

A common strategy to target nanoparticles to tumours is conjugation with specific antibodies, targeting protein expressed preferentially by cancer cells. Here the authors show that the number of antibodies bound to the nanoparticle influences the targeting ability in vitro and in vivo.

Affinity Maturation of a Cyclic Peptide Handle for Therapeutic Antibodies Using Deep Mutational Scanning

Meditopes are cyclic peptides that bind in a specific pocket in the antigen-binding fragment of a therapeutic antibody such as cetuximab. Provided their moderate affinity can be enhanced, meditope peptides could be used as specific non-covalent and paratope-independent handles in targeted drug delivery, molecular imaging, and therapeutic drug monitoring. Here we show that the affinity of a recently reported meditope for cetuximab can be substantially enhanced using a combination of yeast display and deep mutational scanning. Deep sequencing was used to construct a fitness landscape of this protein-peptide interaction, and four mutations were identified that together improved the affinity for cetuximab 10-fold to 15 nm Importantly, the increased affinity translated into enhanced cetuximab-mediated recruitment to EGF receptor-overexpressing cancer cells. Although in silico Rosetta simulations correctly identified positions that were tolerant to mutation, modeling did not accurately predict the affinity-enhancing mutations. The experimental approach reported here should be generally applicable and could be used to develop meditope peptides with low nanomolar affinity for other therapeutic antibodies.

Novel Hybrid Compound of a Plinabulin Prodrug with an IgG Binding Peptide for Generating a Tumor Selective Noncovalent-Type Antibody-Drug Conjugate

Although several approaches for making antibody-drug conjugates (ADC) have been developed, it has yet to be reported that an antibody binding peptide such as Z33 from protein A is utilized as the pivotal unit to generate the noncovalent-type ADC (NC-ADC). Herein we aim to establish a novel probe for NC-ADC by synthesizing the Z33-conjugated antitumor agent, plinabulin. Due to the different solubility of two components, including hydrophobic plinabulin and hydrophilic Z33, an innovative method with a solid-supported disulfide coupling reagent is required for the synthesis of the target compounds with prominent efficiency (29% isolated yield). We demonstrate that the synthesized hybrid exhibits a binding affinity against the anti-HER2 antibody (Herceptin) and the anti-CD71 antibody (6E1) (Kd = 46.6 ± 0.5 nM and 4.5 ± 0.56 μM, respectively) in the surface plasmon resonance (SPR) assay. In the cell-based assays, the hybrid provides a significant cytotoxicity in the presence of Herceptin against HER2 overexpressing SKBR-3 cells, but not against HER2 low-expressing MCF-7 cells. Further, it is noteworthy that the hybrid in combination with Herceptin induces cytotoxicity against Herceptin-resistant SKBR-3 (SKBR-3HR) cells. Similar results are obtained with the 6E1 antibody, suggesting that the synthesized hybrid can be widely applicable for NC-ADC using the antibody of interest. In summary, a series of evidence presented here strongly indicate that NC-ADCs have high potential for the next generation of antitumor agents.

Covalent conjugation of cysteine-engineered scFv to PEGylated magnetic nanoprobes for immunotargeting of breast cancer cells

Orientation- and site-directed covalent conjugation of cysteine-engineered scFv to PEGylated SPIONs allows antigen recognition while preserving colloidal properties of nanoprobes.

Multimodal theranostic nanomaterials derived from phthalocyanine-based organic salt

This study represents a one pot simplistic approach towards development of multimodal theranostic nanomaterials.

Polymer decorated magnetite materials as smart protein separators to manipulate the high loading of heme proteins

Polymer decorated magnetite materials using polyvinyl imidazole were successfully fabricated, which could separate high-abundance heme proteins from blood efficiently.

Immobilization of carboxypeptidase from Sulfolobus solfataricus on magnetic nanoparticles improves enzyme stability and functionality in organic media

Background

Superparamagnetic iron oxide nanoparticles (MNP) offer several advantages for applications in biomedical and biotechnological research. In particular, MNP-based immobilization of enzymes allows high surface-to-volume ratio, good dispersibility, easy separation of enzymes from the reaction mixture, and reuse by applying an external magnetic field. In a biotechnological perspective, extremophilic enzymes hold great promise as they often can be used under non-conventional harsh conditions, which may result in substrate transformations that are not achievable with normal enzymes. This prompted us to investigate the effect of MNP bioconjugation on the catalytic properties of a thermostable carboxypeptidase from the hyperthermophilic archaeon Sulfolobus solfataricus (CPSso), which exhibits catalytic properties that are useful in synthetic processes.

Results

CPSso was immobilized onto silica-coated iron oxide nanoparticles via NiNTA-His tag site-directed conjugation. Following the immobilization, CPSso acquired distinctly higher long-term stability at room temperature compared to the free native enzyme, which, in contrast, underwent extensive inactivation after 72 h incubation, thus suggesting a potential utilization of this enzyme under low energy consumption. Moreover, CPSso conjugation also resulted in a significantly higher stability in organic solvents at 40°C, which made it possible to synthesize N-blocked amino acids in remarkably higher yields compared to those of free enzyme.

Conclusions

The nanobioconjugate of CPSso immobilized on silica-coated magnetic nanoparticles exhibited enhanced stability in aqueous media at room temperature as well as in different organic solvents. The improved stability in ethanol paves the way to possible applications of immobilized CPSso, in particular as a biocatalyst for the synthesis of N-blocked amino acids. Another potential application might be amino acid racemate resolution, a critical and expensive step in chemical synthesis.

Facile method for the site-specific, covalent attachment of full-length IgG onto nanoparticles

Antibodies, most commonly IgGs, have been widely used as targeting ligands in research and therapeutic applications due to their wide array of targets, high specificity and proven efficacy. Many of these applications require antibodies to be conjugated onto surfaces (e.g. nanoparticles and microplates); however, most conventional bioconjugation techniques exhibit low crosslinking efficiencies, reduced functionality due to non-site-specific labeling and random surface orientation, and/or require protein engineering (e.g. cysteine handles), which can be technically challenging. To overcome these limitations, we have recombinantly expressed Protein Z, which binds the Fc region of IgG, with an UV active non-natural amino acid benzoylphenyalanine (BPA) within its binding domain. Upon exposure to long wavelength UV light, the BPA is activated and forms a covalent link between the Protein Z and the bound Fc region of IgG. This technology was combined with expressed protein ligation (EPL), which allowed for the introduction of a fluorophore and click chemistry-compatible azide group onto the C-terminus of Protein Z during the recombinant protein purification step. This enabled the crosslinked-Protein Z-IgG complexes to be efficiently and site-specifically attached to aza-dibenzocyclooctyne-modified nanoparticles, via copper-free click chemistry.

Delivering colloidal nanoparticles to mammalian cells: a nano-bio interface perspective

Understanding the behavior of multifunctional colloidal nanoparticles capable of biomolecular targeting remains a fascinating challenge in materials science with dramatic implications in view of a possible clinical translation. In several circumstances, assumptions on structure-activity relationships have failed in determining the expected responses of these complex systems in a biological environment. The present Review depicts the most recent advances about colloidal nanoparticles designed for use as tools for cellular nanobiotechnology, in particular, for the preferential transport through different target compartments, including cell membrane, cytoplasm, mitochondria, and nucleus. Besides the conventional entry mechanisms based on crossing the cellular membrane, an insight into modern physical approaches to quantitatively deliver nanomaterials inside cells, such as microinjection and electro-poration, is provided. Recent hypotheses on how the nanoparticle structure and functionalization may affect the interactions at the nano-bio interface, which in turn mediate the nanoparticle internalization routes, are highlighted. In addition, some hurdles when this small interface faces the physiological environment and how this phenomenon can turn into different unexpected responses, are discussed. Finally, possible future developments oriented to synergistically tailor biological and chemical properties of nanoconjugates to improve the control over nanoparticle transport, which could open new scenarios in the field of nanomedicine, are addressed.

Antibody-engineered nanoparticles selectively inhibit mesenchymal cells isolated from patients with chronic lung allograft dysfunction

AIMS

Chronic lung allograft dysfunction represents the main cause of death after lung transplantation, and so far there is no effective therapy. Mesenchymal cells (MCs) are primarily responsible for fibrous obliteration of small airways typical of chronic lung allograft dysfunction. Here, we engineered gold nanoparticles containing a drug in the hydrophobic section to inhibit MCs, and exposing on the outer hydrophilic surface a monoclonal antibody targeting a MC-specific marker (half-chain gold nanoparticles with everolimus).

MATERIALS & METHODS

Half-chain gold nanoparticles with everolimus have been synthesized and incubated with MCs to evaluate the effect on proliferation and apoptosis.

RESULTS & DISCUSSION

Drug-loaded gold nanoparticles coated with the specific antibody were able to inhibit proliferation and induce apoptosis without stimulating an inflammatory response, as assessed by in vitro experiments.

CONCLUSION

These findings demonstrate the effectiveness of our nanoparticles in inhibiting MCs and open new perspectives for a local treatment of chronic lung allograft dysfunction.

Biotechnological approaches toward nanoparticle biofunctionalization

Nanomedicine has emerged in the past decade as a promising tool for several therapeutic and diagnostic applications. The development of nanoconjugates containing bioactive ligands specific for targeting cancer cell receptors has become a primary objective of modern nanotechnology. The design of ideal nanoconjugates requires optimization of fundamental parameters including size, shape, ligand shell composition, and reduction in nonspecific protein adsorption. Of great importance is the choice of bioconjugation approach, given that it affects the orientation, accessibility, and bioactivity of the targeting molecule. We provide an overview of recent advances in the immobilization of targeting proteins, focusing on methods to control ligand orientation and density, and highlight criteria for nanoparticle design and development required to achieve enhanced receptor-targeting efficiency.

A universal DNA-based protein detection system

Protein immune detection requires secondary antibodies which must be carefully selected in order to avoid interspecies cross-reactivity, and is therefore restricted by the limited availability of primary/secondary antibody pairs. Here we present a versatile DNA-based protein detection system using a universal adapter to interface between IgG antibodies and DNA-modified reporter molecules. As a demonstration of this capability, we successfully used DNA nano-barcodes, quantum dots, and horseradish peroxidase enzyme to detect multiple proteins using our DNA-based labeling system. Our system not only eliminates secondary antibodies but also serves as a novel method platform for protein detection with modularity, high capacity, and multiplexed capability.

Multiple morphologies of gold-magnetite heterostructure nanoparticles are effectively functionalized with protein for cell targeting

Nanoparticles composed of a magnetic iron oxide core surrounded by a metal shell have utility in a broad range of biomedical applications. However, the presence of surface energy differences between the two components makes wetting of oxide with metal unfavorable, precluding a "core-shell" structure of an oxide core completely surrounded by a thin metal shell. Three-dimensional island growth followed by island coalescence into thick shells is favored over the two-dimensional layer-by-layer growth of a thin, continuous metal coating of a true core-shell. Aqueous synthesis of gold-coated magnetite nanoparticles with analysis by infrared, energy-dispersive X-ray, and electron energy loss spectroscopies; high-resolution transmission electron microscopy; selected area electron diffraction; and high-angle annular dark-field scanning transmission electron microscopy showed two distinct morphologies that are inconsistent with an idealized core-shell. The majority were isolated ~16-22-nm-diameter nanoparticles consisting of ~7-nm-diameter magnetite and a thick deposition of gold, most often discontinuous, with some potentially "sandwiched" morphologies. A minority were aggregates of agglomerated magnetite decorated with gold but displaying significant bare magnetite. Both populations were successfully conjugated to fibrinogen and targeted to surface-activated platelets, demonstrating that iron oxide-gold nanoparticles produced by aqueous synthesis do not require an ideal core-shell structure for biological activity in cell labeling and targeting applications.

Assessing the in vivo targeting efficiency of multifunctional nanoconstructs bearing antibody-derived ligands

A great challenge in nanodiagnostics is the identification of new strategies aimed to optimize the detection of primary breast cancer and metastases by the employment of target-specific nanodevices. At present, controversial proof has been provided on the actual importance of surface functionalization of nanoparticles to improve their in vivo localization at the tumor. In the present paper, we have designed and developed a set of multifunctional nanoprobes, modified with three different variants of a model antibody, that is, the humanized monocolonal antibody trastuzumab (TZ), able to selectively target the HER2 receptor in breast cancer cells. Assuming that nanoparticle accumulation in target cells is strictly related to their physicochemical properties, we performed a comparative study of internalization, trafficking, and metabolism in MCF7 cells of multifunctional nanoparticles (MNP) functionalized with TZ or with alternative lower molecular weight variants of the monoclonal antibody, such as the half-chain (HC) and scFv fragments (scFv). Hence, to estimate to what extent the structure of the surface bioligand affects the targeting efficiency of the nanoconjugate, three cognate nanoconstructs were designed, in which only the antibody form was differentiated while the nanoparticle core was maintained unvaried, consisting of an iron oxide spherical nanocrystal coated with an amphiphilic polymer shell. In vitro, in vivo, and ex vivo analyses of the targeting efficiency and of the intracellular fate of MNP-TZ, MNP-HC, and MNP-scFv suggested that the highly stable MNP-HC is the best candidate for application in breast cancer detection. Our results provided evidence that, in this case, active targeting plays an important role in determining the biological activity of the nanoconstruct.

Cysteine-terminated B-domain of Staphylococcus aureus protein A as a scaffold for targeting GABA(A) receptors

This study reports the preparation and characterization of cysteine-terminated B-domain (Bd-cys) of Staphylococcus aureus protein A, in combination with immunoglobulin G (IgG) antibodies directed against the ρ1 and α1 subunits of GABA(A) receptors, for localizing reagents of interest to the target receptor. A cysteine residue was inserted at the C terminus of the cysteine-lacking B-domain (Bd) and used for conjugating maleimide-containing compounds. As determined by enzyme-linked immunosorbent assay (ELISA), binding of a Bd-cys-S-fluorescein conjugate to polyclonal guinea pig anti-GABA(A)-ρ1 and rabbit anti-GABA(A)-α1 IgG was similar to that exhibited by full-length protein A. Surface plasmon resonance analysis of the interaction of Bd-cys-S-PEG3400-biotin conjugate (where PEG is polyethylene glycol) with anti-GABA(A)-ρ1 and anti-GABA(A)-α1 yielded K(D) values of 6.4 ± 1.9 and 0.4 ± 0.1 nM, respectively. Fluorescence anisotropy analysis of the binding of Bd-cys-S-fluorescein to the two antibodies yielded EC50 values of 65 and 18 nM, respectively. As determined with biotin-reactive fluorescent reagents, Bd-cys-S-PEG3400-biotin specifically bound to the plasma membrane of Xenopus laevis oocytes that expressed α1β2γ2 or homomeric ρ1 GABA(A) receptors and were pretreated with the corresponding anti-GABA(A) IgG. The IgG-binding specificity and high affinity of Bd-cys conjugates illustrate the potential of these conjugates, in combination with a selected IgG, to localize compounds of interest at specific cell surface proteins.

Protein oriented ligation on nanoparticles exploiting O6-alkylguanine-DNA transferase (SNAP) genetically encoded fusion

A bimodular genetic fusion comprising a delivery module (scFv) and a capture module (SNAP) is proposed as a novel strategy for the site-specific covalent conjugation of targeting peptides to nanoparticles. An scFv mutant selective for HER2 tumor antigen is chosen as the targeting ligand. SNAP-scFv is immobilized on magnetofluorescent nanoparticles and its targeting efficiency against HER2-positive cells is assessed by flow cytometry and immunofluorescence.

Tailor-made magnetic Fe3O4@mTiO2 microspheres with a tunable mesoporous anatase shell for highly selective and effective enrichment of phosphopeptides

Selective enrichment of phosphoproteins or phosphopeptides from complex mixtures is essential for MS-based phosphoproteomics, but still remains a challenge. In this article, we described an unprecedented approach to synthesize magnetic mesoporous Fe(3)O(4)@mTiO(2) microspheres with a well-defined core/shell structure, a pure and highly crystalline TiO(2) layer, high specific surface area (167.1 m(2)/g), large pore volume (0.45 cm(3)/g), appropriate and tunable pore size (8.6-16.4 nm), and high magnetic susceptibility. We investigated the applicability of Fe(3)O(4)@mTiO(2) microspheres in a study of the selective enrichment of phosphopeptides. The experiment results demonstrated that the Fe(3)O(4)@mTiO(2) possessed remarkable selectivity for phosphopeptides even at a very low molar ratio of phosphopeptides/non-phosphopeptides (1:1000), large enrichment capacity (as high as 225 mg/g, over 10 times as that of the Fe(3)O(4)@TiO(2) microspheres), extreme sensitivity (the detection limit was at the fmol level), excellent speed (the enrichment can be completed in less than 5 min), and high recovery of phosphopeptides (as high as 93%). In addition, the high magnetic susceptibility allowed convenient separation of the target peptides by magnetic separation. These outstanding features give the Fe(3)O(4)@mTiO(2) composite microspheres high benefit for mass spectrometric analysis of phosphopeptides.

Biological applications of magnetic nanoparticles

In this review an overview about biological applications of magnetic colloidal nanoparticles will be given, which comprises their synthesis, characterization, and in vitro and in vivo applications. The potential future role of magnetic nanoparticles compared to other functional nanoparticles will be discussed by highlighting the possibility of integration with other nanostructures and with existing biotechnology as well as by pointing out the specific properties of magnetic colloids. Current limitations in the fabrication process and issues related with the outcome of the particles in the body will be also pointed out in order to address the remaining challenges for an extended application of magnetic nanoparticles in medicine.

Targeting of primary breast cancers and metastases in a transgenic mouse model using rationally designed multifunctional SPIONs

Breast cancer remains one of the most prevalent and lethal malignancies in women. The inability to diagnose small volume metastases early has limited effective treatment of stage 4 breast cancer. Here we report the rational development and use of a multifunctional superparamagnetic iron oxide nanoparticle (SPION) for targeting metastatic breast cancer in a transgenic mouse model and imaging with magnetic resonance (MR). SPIONs coated with a copolymer of chitosan and polyethylene glycol (PEG) were labeled with a fluorescent dye for optical detection and conjugated with a monoclonal antibody against the neu receptor (NP-neu). SPIONs labeled with mouse IgG were used as a nontargeting control (NP-IgG). These SPIONs had desirable physiochemical properties for in vivo applications such as near neutral zeta potential and hydrodynamic size around 40 nm and were highly stable in serum containing medium. Only NP-neu showed high uptake in neu expressing mouse mammary carcinoma (MMC) cells which was reversed by competing free neu antibody, indicating their specificity to the neu antigen. In vivo, NP-neu was able to tag primary breast tumors and significantly, only NP-neu bound to spontaneous liver, lung, and bone marrow metastases in a transgenic mouse model of metastatic breast cancer, highlighting the necessity of targeting for delivery to metastatic disease. The SPIONs provided significant contrast enhancement in MR images of primary breast tumors; thus, they have the potential for MRI detection of micrometastases and provide an excellent platform for further development of an efficient metastatic breast cancer therapy.

Hybrid polyethylenimine and polyacrylic acid-bound iron oxide as a magnetoplex for gene delivery

Low transfection efficiency is always an issue when cationic polymers are used as a nonviral gene vector in the physiological condition, especially in the presence of proteins. A cationic magnetic nanoparticle (MNP) may be an alternative to solve this problem because a magnetic field can help to attract the MNP and internalize it into cells. The aim of this study was to determine the potency of polyethylenimine (PEI)-decorated MNPs for efficiently complexing and delivering plasmid DNA in vitro with the help of a magnetic field. PEI is associated with poly(acrylic acid)-bound superparamagnetic iron oxide (PAAIO) through electrostatic interactions (PEI-PAAIO). PEI-PAAIO formed stable polyplexes with pDNA in the presence and absence of 10% fetal bovine serum (FBS) and could be used for magnetofection. The effect of a static magnetic field on the cytotoxicity, cellular uptake, and transfection efficiency of PEI-PAAIO/pDNA was evaluated with and without 10% FBS. Magnetofection efficacy in HEK 293T cells and U87 cells containing 10% FBS was significantly improved in the presence of an external magnetic field. The amount of internalized iron was quantitatively measured using an inductively coupled plasma-optical emission spectrometer and directly visualized using Prussian blue staining. The internalized pDNA was visualized using a confocal laser scanning microscope.