Visualization of the protein corona: towards a biomolecular understanding of nanoparticle-cell-interactions

In Situ Measurement of Nanoparticle-Blood Protein Adsorption and Its Heterogeneity with Single-Nanoparticle Resolution via Dual Fluorescence Quantification

The formation of a protein corona gives nanomedicines a distinct biological identity, profoundly influencing their fate in the body. Nonspecific nanoparticle-protein interactions are typically highly heterogeneous, which can lead to unique biological behaviors and in vivo fates for individual nanoparticles that remain underexplored. To address this, we have established an in situ approach that allows quantitative examination of nanoparticle-protein adsorption at the individual nanoparticle level. This method integrates dual fluorescence quantification techniques, wherein the nanoparticles are first individually analyzed via nanoflow cytometry to detect fluorescent signals from adsorbed proteins. The obtained fluorescence intensity is then translated into protein quantities through calibration with microplate reader quantification. Consequently, this approach enables analysis of interparticle heterogeneity of nano-protein interactions, as well as in situ monitoring of protein adsorption kinetics and nanoparticle aggregation status in blood serum, preconditioning for a comprehensive understanding of nano-bio interactions, and predicting in vivo fate of nanomedicines.

Analysis of nanomaterial biocoronas in biological and environmental surroundings

A biomolecular coating, or biocorona, forms on the surface of engineered nanomaterials (ENMs) immediately as they enter biological or environmental systems, defining their biological and environmental identity and influencing their fate and performance. This biomolecular layer includes proteins (the protein corona) and other biomolecules, such as nucleic acids and metabolites. To ensure a meaningful and reproducible analysis of the ENMs-associated biocorona, it is essential to streamline procedures for its preparation, separation, identification and characterization, so that studies in different labs can be easily compared, and the information collected can be used to predict the composition, dynamics and properties of biocoronas acquired by other ENMs. Most studies focus on the protein corona as proteins are easier to monitor and characterize than other biomolecules and play crucial roles in receptor engagement and signaling; however, metabolites play equally critical roles in signaling. Here we describe how to reproducibly prepare and characterize biomolecule-coated ENMs, noting especially the steps that need optimization for different types of ENMs. The structure and composition of the biocoronas are characterized using general methods (transmission electron microscopy, dynamic light scattering, capillary electrophoresis-mass spectrometry and liquid chromatography-mass spectrometry) as well as advanced techniques, such as transmission electron cryomicroscopy, synchrotron-based X-ray absorption near edge structure and circular dichroism. We also discuss how to use molecular dynamic simulation to study and predict the interaction between ENMs and biomolecules and the resulting biocorona composition. The application of this protocol can provide mechanistic insights into the formation, composition and evolution of the ENM biocorona, ultimately facilitating the biomedical and agricultural application of ENMs and a better understanding of their impact in the environment.

Deposition of Human-Serum-Albumin-Functionalized Spheroidal Particles on Abiotic Surfaces: Reference Kinetic Results for Bioparticles

Human serum albumin (HSA) corona formation on polymer microparticles of a spheroidal shape was studied using dynamic light scattering and Laser Doppler Velocimetry (LDV). Physicochemical characteristics of the albumin comprising the zeta potential and the isoelectric point were determined as a function of pH for various ionic strengths. Analogous characteristics of the polymer particles were analyzed. The adsorption of albumin on the particles was in situ monitored by LDV. The stability of the HSA-functionalized particle suspensions under various pHs and their electrokinetic properties were also determined. The deposition kinetics of the particles on mica, silica and gold sensors were investigated by optical microscopy, AFM and quartz microbalance (QCM) under diffusion and flow conditions. The obtained results were interpreted in terms of the random sequential adsorption model that allowed to estimate the range of applicability of QCM for determining the deposition kinetics of viruses and bacteria at abiotic surfaces.

Interfacial Denaturation at the Droplet Simplifies the Formation of Drug-Loaded Protein Nanocapsules to Enhance Immune Response of Cells

Nanocapsules enable multicomponent encapsulation of therapeutic cargoes with high encapsulation content and efficiency, which is vital for cancer immunotherapy. In the past, chemical crosslinking is used to synthesize nanocapsules, which can impede the regulatory approval process. Therefore, a new class of protein nanocapsules is developed by eliminating the need for chemical crosslinking by utilizing protein denaturation through a process that is referred to as "baking at the droplet interface". Such protein nanocapsules with antigens incorporated in the shell and a combination of encapsulated drugs showed an enhancement in the immune response of cells.

Concepts and Approaches to Reduce or Avoid Protein Corona Formation on Nanoparticles: Challenges and Opportunities

This review describes the formation of a protein corona (or its absence) on different classes of nanoparticles, its basic principles, and its consequences for nanomedicine. For this purpose, it describes general concepts to control (guide/minimize) the interaction between artificial nanoparticles and plasma proteins to reduce protein corona formation. Thereafter, methods for the qualitative or quantitative determination of protein corona formation are presented, as well as the properties of nanoparticle surfaces, which are relevant for protein corona prevention (or formation). Thereby especially the role of grafting density of hydrophilic polymers on the surface of the nanoparticle is discussed to prevent the formation of a protein corona. In this context also the potential of detergents (surfactants) for a temporary modification as well as grafting-to and grafting-from approaches for a permanent modification of the surface are discussed. The review concludes by highlighting several promising avenues. This includes (i) the use of nanoparticles without protein corona for active targeting, (ii) the use of synthetic nanoparticles without protein corona formation to address the immune system, (iii) the recollection of nanoparticles with a defined protein corona after in vivo application to sample the blood proteome and (iv) further concepts to reduce protein corona formation.

Artificial protein coronas: directing nanoparticles to targets

The protein corona surrounding nanoparticles (NPs) offers exciting possibilities for targeted drug delivery. However, realizing this potential requires direct evidence of corona-receptor interactions in vivo; a challenge hampered by the limitations of in vitro settings. This opinion proposes that utilizing engineered protein coronas can address this challenge. Artificial coronas made of selected plasma proteins retain their properties in vivo, enabling manipulation for specific receptor targeting. To directly assess corona-receptor interactions mimicking in vivo complexity, we propose testing artificial coronas with recently adapted quartz crystal microbalance (QCM) setups whose current limitations and potential advancements are critically discussed. Finally, the opinion proposes future experiments to decipher corona-receptor interactions and unlock the full potential of the protein corona for NP-based drug delivery.

Optimizing Transfection Efficiency in CAR-T Cell Manufacturing through Multiple Administrations of Lipid-Based Nanoparticles

The existing manufacturing protocols for CAR-T cell therapies pose notable challenges, particularly in attaining a transient transfection that endures for a significant duration. To address this gap, this study aims to formulate a transfection protocol utilizing multiple lipid-based nanoparticles (LNPs) administrations to enhance transfection efficiency (TE) to clinically relevant levels. By systematically fine-tuning and optimizing our transfection protocol through a series of iterative refinements, we have accomplished a remarkable one-order-of-magnitude augmentation in TE within the immortalized T-lymphocyte Jurkat cell line. This enhancement has been consistently observed over 2 weeks, and importantly, it has been achieved without any detrimental impact on cell viability. In the subsequent phase of our study, we aimed to optimize the gene delivery system by evaluating three lipid-based formulations tailored for DNA encapsulation using our refined protocol. These formulations encompassed two LNPs constructed from ionizable lipids and featuring systematic variations in lipid composition (iLNPs) and a cationic lipoplex (cLNP). Our findings showcased a notable standout among the three formulations, with cLNP emerging as a frontrunner for further refinement and integration into the production pipeline of CAR-T therapies. Consequently, cLNP was scrutinized for its potential to deliver CAR-encoding plasmid DNA to the HEK-293 cell line. Confocal microscopy experiments demonstrated its efficiency, revealing substantial internalization compared to iLNPs. By employing a recently developed confocal image analysis method, we substantiated that cellular entry of cLNP predominantly occurs through macropinocytosis. This mechanism leads to heightened intracellular endosomal escape and mitigates lysosomal accumulation. The successful expression of anti-CD19-CD28-CD3z, a CAR engineered to target CD19, a protein often expressed on the surface of B cells, was confirmed using a fluorescence-based assay. Overall, our results indicated the effectiveness of cLNP in gene delivery and suggested the potential of multiple administration transfection as a practical approach for refining T-cell engineering protocols in CAR therapies. Future investigations may focus on refining outcomes by adjusting transfection parameters like nucleic acid concentration, lipid-to-DNA ratio, and incubation time to achieve improved TE and increased gene expression levels.

Looking back, moving forward: protein corona of lipid nanoparticles

Lipid nanoparticles (LNPs) are commonly employed for drug delivery owing to their considerable drug-loading capacity, low toxicity, and excellent biocompatibility. Nevertheless, the formation of protein corona (PC) on their surfaces significantly influences the drug's in vivo fate (such as absorption, distribution, metabolism, and elimination) upon administration. PC denotes the phenomenon wherein one or multiple strata of proteins adhere to the external interface of nanoparticles (NPs) or microparticles within the biological milieu, encompassing ex vivo fluids (e.g., serum-containing culture media) and in vivo fluids (such as blood and tissue fluids). Hence, it is essential to claim the PC formation behaviors and mechanisms on the surface of LNPs. This overview provided a comprehensive examination of crucial aspects related to such issues, encompassing time evolution, controllability, and their subsequent impacts on LNPs. Classical studies of PC generation on the surface of LNPs were additionally integrated, and its decisive role in shaping the in vivo fate of LNPs was explored. The mechanisms underlying PC formation, including the adsorption theory and alteration theory, were introduced to delve into the formation process. Subsequently, the existing experimental outcomes were synthesized to offer insights into the research and application facets of PC, and it was concluded that the manipulation of PC held substantial promise in the realm of targeted delivery.

Advancing In Situ Analysis of Biomolecular Corona: Opportunities and Challenges in Utilizing Field-Flow Fractionation

The biomolecular corona, a complex layer of biological molecules, envelops nanoparticles (NPs) upon exposure to biological fluids including blood. This dynamic interface is pivotal for the advancement of nanomedicine, particularly in areas of therapy and diagnostics. In situ analysis of the biomolecular corona is crucial, as it can substantially improve our ability to accurately predict the biological fate of nanomedicine and, therefore, enable development of more effective, safe, and precisely targeted nanomedicines. Despite its importance, the repertoire of techniques available for in situ analysis of the biomolecular corona is surprisingly limited. This tutorial review provides an overview of the available techniques for in situ analysis of biomolecular corona with a particular focus on exploring both the advantages and the limitations inherent in the use of field-flow fractionation (FFF) for in situ analysis of the biomolecular corona. It delves into how FFF can unravel the complexities of the corona, enhancing our understanding and guiding the design of next-generation nanomedicines for medical use.

Unveiling the challenges of engineered protein corona from the proteins' perspective

It is well known that protein corona affects the "biological identity" of nanoparticles (NPs), which has been seen as both a challenge and an opportunity. Approaches have moved from avoiding protein adsorption to trying to direct it, taking advantage of the formation of a protein corona to favorably modify the pharmacokinetic parameters of NPs. Although promising, the results obtained with engineered NPs still need to be completely understood. While much effort has been put into understanding how the surface of nanomaterials affects protein absorption, less is known about how proteins can affect corona formation due to their specific physicochemical properties. This review addresses this knowledge gap, examining key protein factors influencing corona formation, highlighting current challenges in studying protein-protein interactions, and discussing future perspectives in the field.

The In Vivo Biological Fate of Protein Corona: A Comparative PET Study of the Fate of Soft and Hard Protein Corona in Healthy Animal Models

Radiolabeling and nuclear imaging techniques are used to investigate the biodistribution patterns of the soft and hard protein corona around poly (lactic-co-glycolic acid) nanoparticles (PLGA NPs) after administration to healthy mice. Soft and hard protein coronas of 131I-labeled BSA or 131I-labeled serum are formed on PLGA NPs functionalized with either polyehtylenimine (PEI) or bovine serum albumin (BSA). The exchangeability of hard and soft corona is assessed in vitro by gamma counting exposing PLGA NPs with corona to non-labeled BSA, serum, or simulated body fluid. PEI PLGA NPs form larger and more stable coronas than BSA PLGA NPs. Soft coronas are more exchangeable than hard ones. The in vivo fate of PEI PLGA NPs coated with preformed 18F-labeled BSA hard and soft coronas is assessed by positron emission tomography (PET) following intravenous administration. While the soft corona shows a biodistribution similar to free 18F BSA with high activity in blood and kidney, the hard corona follows patterns characteristic of nanoparticles, accumulating in the lungs, liver, and spleen. These results show that in vivo fates of soft and hard corona are different, and that soft corona is more easily exchanged with proteins from the body, while hard corona is largely retained on the nanoparticle surface.

Development of a fast and simple method for the isolation of superparamagnetic iron oxide nanoparticles protein corona from protein-rich matrices

The adsorption of proteins onto the surface of nanoparticle (NP) leads to the formation of the so-called "protein corona" as consisting both loosely and tightly bound proteins. It is well established that the biological identity of NPs that may be acquired after exposure to a biological matrix is mostly provided by the components of the hard corona as the pristine surface is generally less accessible for binding. For that reason, the isolation and the characterisation of the NP-corona complexes and identification of the associated biomolecules can help in understanding its biological behaviour. Established methods for the isolation of the NP-HC complexes are time-demanding and can lead to different results based on the isolation method applied. Herein, we have developed a fast and simple method using ferromagnetic beads isolated from commercial MACS column and used for the isolation of superparamagnetic NP following exposure to different types of biological milieu. We first demonstrated the ability to easily isolate superparamagnetic iron oxide NPs (IONPs) from different concentrations of human blood plasma, and also tested the method on the corona isolation using more complex biological matrices, such as culture medium containing pulmonary mucus where the ordinary corona methods cannot be applied. Our developed method showed less than 20% difference in plasma corona composition when compared with centrifugation. It also showed effective isolation of NP-HC complexes from mucus-containing culture media upon comparing with centrifugation and MACS columns, which failed to wash out the unbound proteins. Our study was supported with a full characterisation profile including dynamic light scattering, nanoparticle tracking analysis, analytical disk centrifuge, and zeta potentials. The biomolecules/ proteins composing the HC were separated by vertical gel electrophoresis and subsequently analysed by liquid chromatography-tandem mass spectrometry. In addition to our achievements in comparing different isolation methods to separate IONPs with corona from human plasma, this is the first study that provides a complete characterisation profile of particle protein corona after exposure in vitro to pulmonary mucus-containing culture media.

Chiral nanomaterials in tissue engineering

Addressing significant medical challenges arising from tissue damage and organ failure, the field of tissue engineering has evolved to provide revolutionary approaches for regenerating functional tissues and organs. This involves employing various techniques, including the development and application of novel nanomaterials. Among them, chiral nanomaterials comprising non-superimposable nanostructures with their mirror images have recently emerged as innovative biomaterial candidates to guide tissue regeneration due to their unique characteristics. Chiral nanomaterials including chiral fibre supramolecular hydrogels, polymer-based chiral materials, self-assembling peptides, chiral-patterned surfaces, and the recently developed intrinsically chiroptical nanoparticles have demonstrated remarkable ability to regulate biological processes through routes such as enantioselective catalysis and enhanced antibacterial activity. Despite several recent reviews on chiral nanomaterials, limited attention has been given to the specific potential of these materials in facilitating tissue regeneration processes. Thus, this timely review aims to fill this gap by exploring the fundamental characteristics of chiral nanomaterials, including their chiroptical activities and analytical techniques. Also, the recent advancements in incorporating these materials in tissue engineering applications are highlighted. The review concludes by critically discussing the outlook of utilizing chiral nanomaterials in guiding future strategies for tissue engineering design.

Modulating the toxicity of engineered nanoparticles by controlling protein corona formation: Recent advances and future prospects

With the rapid development and widespread application of engineered nanoparticles (ENPs), understanding the fundamental interactions between ENPs and biological systems is essential to assess and predict the fate of ENPs in vivo. When ENPs are exposed to complex physiological environments, biomolecules quickly and inevitably adsorb to ENPs to form a biomolecule corona, such as a protein corona (PC). The formed PC has a significant effect on the physicochemical properties of ENPs and gives them a brand new identity in the biological environment, which determines the subsequent ENP-cell/tissue/organ interactions. Controlling the formation of PCs is therefore of utmost importance to accurately predict and optimize the behavior of ENPs within living organisms, as well as ensure the safety of their applications. In this review, we provide an overview of the fundamental aspects of the PC, including the formation mechanism, composition, and frequently used characterization techniques. We comprehensively discuss the potential impact of the PC on ENP toxicity, including cytotoxicity, immune response, and so on. Additionally, we summarize recent advancements in manipulating PC formation on ENPs to achieve the desired biological outcomes. We further discuss the challenges and prospects, aiming to provide valuable insights for a better understanding and prediction of ENP behaviors in vivo, as well as the development of low-toxicity ENPs.

Cytotoxicity prediction of nano metal oxides on different lung cells via Nano-QSAR

In recent years, nanomaterials have found extensive applications across diverse domains owing to their distinctive physical and chemical characteristics. It is of great importance in theoretical and practical terms to carry out the relationship between structural characteristics of nanomaterials and different cytotoxicity and to achieve practical assessment and prediction of cytotoxicity. This study investigated the intrinsic quantitative constitutive relationships between the cytotoxicity of nano-metal oxides on human normal lung epithelial cells and human lung adenocarcinoma cells. We first employed quasi-SMILES-based nanostructural descriptors by selecting the five physicochemical properties that are most closely related to the cytotoxicity of nanometal oxides, then established SMILES-based descriptors that can effectively describe and characterize the molecular structure of nanometal oxides, and then built the corresponding Nano-Quantitative Structure-Activity Relationship (Nano-QSAR) prediction models, finally, combined with the theory of reactive oxygen species (ROS) biotoxicity, to reveal the mechanism of toxicity and differences between the two cell types. The established model can efficiently and accurately predict the properties of targets, reveal the corresponding toxicity mechanisms, and guide the safe design, synthesis, and application of nanometal oxides.

Formation of extracellular polymeric substances corona on TiO2 nanoparticles: Roles of crystalline phase and exposed facets

Nanoparticles (NPs) in the environment can interact with macromolecules in the surrounding environment to form eco-corona on their surfaces, which in turn affects the environmental fate and toxicity of nanoparticles. Wastewater treatment plants containing large amounts of microbial extracellular polymeric substances (EPS) are an important source of NPs into the environment, where the formation of EPS coronas on NPs is critical. However, it remains unclear how the crystalline phase and exposed facets, which are intrinsic properties of NPs, affect the formation of EPS coronas on NPs. This study investigated the formation of EPS corona on three TiO2 NPs (representing the most widely used engineered NPs) with different crystalline phases and exposed facets. The protein type and abundance in EPS coronas on TiO2 NPs varied depending on the crystalline phase and exposed facets. Anatase with {101} facets and {001} facets preferred to adsorb proteins with lower molecular weights and higher H-bonding relevant amino acids, respectively, while EPS corona on rutile with {110} facets had proteins with higher hydrophobicity. In addition, the selective adsorption of proteins was primarily determined by steric hindrance, hydrogen bonding, and hydrophobic interaction between TiO2 NPs and proteins, which were affected by changes in aggregation state, surface hydroxyl density, and hydrophobicity of TiO2 NPs induced by crystalline phase and exposed facets. Moreover, crystalline phase and exposed facets-induced EPS corona changes altered the aggregation state and oxidation potential of TiO2-EPS corona complexes. These findings emphasize the important role of crystalline phase and exposed facets in the environmental behavior of nanoparticles and may provide insights into the safe design of nanoparticles.

Nanocarrier-based localized and effective treatment of renal disorders: currently employed targeting strategies

Renal disorders pose a global health threat, with targeted drug-delivery systems emerging as a promising strategy to enhance therapy safety and efficacy. Recent efforts have harnessed targeted nanomaterials for kidney disease treatment. While some systems remain in the early stages, they show immense potential in delivering cargo to specific sites. Through animal model experimentations, it has been demonstrated to reduce systemic side effects and enhance treatment effectiveness. This review presents current strategies for kidney disorder treatment, emphasizing site-specific targeting critical to renal disease pathophysiology. Recent advancements in nano-drug delivery systems for kidney targeting are explored. Finally, toxicological aspects and prospects of the most promising kidney-targeting delivery systems are discussed in this review article.

Understanding protein-nanoparticle interactions leading to protein corona formation: In vitro - in vivo correlation study

Nanoparticles (NPs) in contact with biological fluids form a biomolecular corona through interactions with proteins, lipids, and sugars, acquiring new physicochemical properties. This work explores the interaction between selected proteins (hemoglobin and fetuin-A) that may alter NP circulation time and NPs of different surface charges (neutral, positive, and negative). The interaction with key proteins albumin and transferrin, the two of the most abundant proteins in plasma was also studied. Binding affinity was investigated using quartz crystal microbalance and fluorescence quenching, while circular dichroism assessed potential conformational changes. The data obtained from in vitro experiments were compared to in vivo protein corona data. The results indicate that electrostatic interactions primarily drive protein-NP interactions, and higher binding affinity does not necessarily translate into more significant structural changes. In vitro and single protein-NP studies provide valuable insights that can be correlated with in vivo observations, opening exciting possibilities for future protein corona studies.

Uptake of extracellular vesicles into immune cells is enhanced by the protein corona

The influence of a protein corona on the uptake of nanoparticles in cells has been demonstrated in various publications over the last years. Extracellular vesicles (EVs), can be seen as natural nanoparticles. However, EVs are produced under different cell culture conditions and little is known about the protein corona forming on EVs and its influence on their uptake by target cells. Here, we use a proteomic approach in order to analyze the protein composition of the EVs themselves and the protein composition of a human blood plasma protein corona around EVs. Moreover, we analyze the influence of the protein corona on EV uptake into human monocytes and compare it with the influence on the uptake of engineered liposomes. We show that the presence of a protein corona increases the uptake of EVs in human monocytes. While for liposomes this seems to be triggered by the presence of immunoglobulins in the protein corona, for EVs blocking the Fc receptors on monocytes did not show an influence of uptake. Therefore, other mechanisms of docking to the cell membrane and uptake are most like involved, demonstrating a clear difference between EVs and liposomes as technically produced nanocarriers.

Proteomics reveals time-dependent protein corona changes in the intracellular pathway

The intracellular protein corona has not been fully investigated in the field of nanotechnology-biology (nano-bio) interactions. To effectively understand intracellular protein corona formation and dynamics, we established a workflow to isolate the intracellular protein corona at different uptake times of two nanoparticles - magnetic hydroxyethyl starch nanoparticles (HES-NPs) and magnetic human serum albumin nanocapsules (HSA-NCs). We performed label-free quantitative LC-MS proteomics to analyze the composition of the intracellular protein corona and correlated our findings with results from conventional methods for intracellular trafficking of nanocarriers, such as flow cytometry, transmission electron microscopy (TEM), and confocal microscopy (cLSM). We determined the evolution of the intracellular protein corona. At different time stages the protein corona of the HES-NPs with a slower uptake changed, but there were fewer changes in that of the HSA-NCs with a more rapid uptake. We identified proteins that are involved in macropinocytosis (RAC1, ASAP2) as well as caveolin. This was confirmed by blocking experiments and by TEM studies. The investigated nanocarrier predominantly trafficked from early endosomes as determined by RAB5 identification in proteomics and in cLSM to late endosomes/lysosomes (RAB7, LAMP1, cathepsin K and HSP 90-beta) We further demonstrated differences between nanoparticles with slower and faster uptake kinetics and determined the associated proteome at different time points. Analysis of the intracellular protein corona provides us with effective data to examine the intracellular trafficking of nanocarriers used in efficient drug delivery and intracellular applications. STATEMENT OF SIGNIFICANCE: Many research papers focus on the protein corona on nanoparticles formed in biological fluids, but there are hardly any articles dealing with proteins that come in contact with nanoparticles inside cells. The "intracellular protein corona" studied here is a far more complex and highly demanding field. Most nanocarriers are designed to be taken up into cells. Given this, we chose two different nanocarriers to reveal changes in the proteins in dendritic cells during contact at specific times. Further studies will allow us to examine molecular target proteins using these methods. Our research is a significant addition towards the goal of understanding and thus improving the efficacy of drug nanocarriers.

Real-Time Optical Tracking of Protein Corona Formation on Single Nanoparticles in Serum

The formation of a protein corona, where proteins spontaneously adhere to the surface of nanomaterials in biological environments, leads to changes in their physicochemical properties and subsequently affects their intended biomedical functionalities. Most current methods to study protein corona formation are ensemble-averaging and either require fluorescent labeling, washing steps, or are only applicable to specific types of particles. Here we introduce real-time all-optical nanoparticle analysis by scattering microscopy (RONAS) to track the formation of protein corona in full serum, at the single-particle level, without any labeling. RONAS uses optical scattering microscopy and enables real-time and in situ tracking of protein adsorption on metallic and dielectric nanoparticles with different geometries directly in blood serum. We analyzed the adsorbed protein mass, the affinity, and the kinetics of the protein adsorption at the single particle level. While there is a high degree of heterogeneity from particle to particle, the predominant factor in protein adsorption is surface chemistry rather than the underlying nanoparticle material or size. RONAS offers an in-depth understanding of the mechanisms related to protein coronas and, thus, enables the development of strategies to engineer efficient bionanomaterials.

Protein corona investigations of polyplexes with varying hydrophobicity - From method development to in vitro studies

In the field of non-viral drug delivery, polyplexes (PXs) represent an advanced investigated and highly promising tool for the delivery of nucleic acids. Upon encountering physiological fluids, they adsorb biological molecules to form a protein corona (PC), that influence PXs biodistribution, transfection efficiencies and targeting abilities. In an effort to understand protein - PX interactions and the effect of PX material on corona composition, we utilized cationic branched 10 kDa polyethyleneimine (b-PEI) and a hydrophobically modified nylon-3 polymer (NM0.2/CP0.8) within this study to develop appropriate methods for PC investigations. A centrifugation procedure for isolating hard corona - PX complexes (PCPXs) from soft corona proteins after incubating the PXs in fetal bovine serum (FBS) for PC formation was successfully optimized and the identification of proteins by a liquid chromatography-tandem mass spectrometry (LC-MS-MS) method clearly demonstrated that the PC composition is affected by the underlying PXs material. With regard to especially interesting functional proteins, which might be able to induce active targeting effects, several candidates could be detected on b-PEI and NM0.2/CP0.8 PXs. These results are of high interest to better understand how the design of PXs impacts the PC composition and subsequently PCPXs-cell interactions to enable precise adjustment of PXs for targeted drug delivery.

Tuning the Cross-Linking Density and Cross-Linker in Core Cross-Linked Polymeric Micelles and Its Effects on the Particle Stability in Human Blood Plasma and Mice

Core cross-linked polymeric micelles (CCPMs) are designed to improve the therapeutic profile of hydrophobic drugs, reduce or completely avoid protein corona formation, and offer prolonged circulation times, a prerequisite for passive or active targeting. In this study, we tuned the CCPM stability by using bifunctional or trifunctional cross-linkers and varying the cross-linkable polymer block length. For CCPMs, amphiphilic thiol-reactive polypept(o)ides of polysarcosine-block-poly(S-ethylsulfonyl-l-cysteine) [pSar-b-pCys(SO2Et)] were employed. While the pCys(SO2Et) chain lengths varied from Xn = 17 to 30, bivalent (derivatives of dihydrolipoic acid) and trivalent (sarcosine/cysteine pentapeptide) cross-linkers have been applied. Asymmetrical flow field-flow fraction (AF4) displayed the absence of aggregates in human plasma, yet for non-cross-linked PM and CCPMs cross-linked with dihydrolipoic acid at [pCys(SO2Et)]17, increasing the cross-linking density or the pCys(SO2Et) chain lengths led to stable CCPMs. Interestingly, circulation time and biodistribution in mice of non-cross-linked and bivalently cross-linked CCPMs are comparable, while the trivalent peptide cross-linkers enhance the circulation half-life from 11 to 19 h.

Stabilizing Polymer Coatings Alter the Protein Corona of DNA Origami and Can Be Engineered to Bias the Cellular Uptake

With DNA-based nanomaterials being designed for applications in cellular environments, the need arises to accurately understand their surface interactions toward biological targets. As for any material exposed to protein-rich cell culture conditions, a protein corona will establish around DNA nanoparticles, potentially altering the a-priori designed particle function. Here, we first set out to identify the protein corona around DNA origami nanomaterials, taking into account the application of stabilizing block co-polymer coatings (oligolysine-1kPEG or oligolysine-5kPEG) widely used to ensure particle integrity. By implementing a label-free methodology, the distinct polymer coating conditions show unique protein profiles, predominantly defined by differences in the molecular weight and isoelectric point of the adsorbed proteins. Interestingly, none of the applied coatings reduced the diversity of the proteins detected within the specific coronae. We then biased the protein corona through pre-incubation with selected proteins and show significant changes in the cell uptake. Our study contributes to a deeper understanding of the complex interplay between DNA nanomaterials, proteins, and cells at the bio-interface.

Harnessing sortase A transpeptidation for advanced targeted therapeutics and vaccine engineering

The engineering of potent prophylactic and therapeutic complexes has always required careful protein modification techniques with seamless capabilities. In this light, methods that favor unobstructed multivalent targeting and correct antigen presentations remain essential and very demanding. Sortase A (SrtA) transpeptidation has exhibited these attributes in various settings over the years. However, its applications for engineering avidity-inspired therapeutics and potent vaccines have yet to be significantly noticed, especially in this era where active targeting and multivalent nanomedications are in great demand. This review briefly presents the SrtA enzyme and its associated transpeptidation activity and describes interesting sortase-mediated protein engineering and chemistry approaches for achieving multivalent therapeutic and antigenic responses. The review further highlights advanced applications in targeted delivery systems, multivalent therapeutics, adoptive cellular therapy, and vaccine engineering. These innovations show the potential of sortase-mediated techniques in facilitating the development of simple plug-and-play nanomedicine technologies against recalcitrant diseases and pandemics such as cancer and viral infections.

Mechanistic Understanding of Protein Corona Formation around Nanoparticles: Old Puzzles and New Insights

Although a wide variety of nanoparticles (NPs) have been engineered for use as disease markers or drug delivery agents, the number of nanomedicines in clinical use has hitherto remained small. A key obstacle in nanomedicine development is the lack of a deep mechanistic understanding of NP interactions in the bio-environment. Here, the focus is on the biomolecular adsorption layer (protein corona), which quickly enshrouds a pristine NP exposed to a biofluid and modifies the way the NP interacts with the bio-environment. After a brief introduction of NPs for nanomedicine, proteins, and their mutual interactions, research aimed at addressing fundamental properties of the protein corona, specifically its mono-/multilayer structure, reversibility and irreversibility, time dependence, as well as its role in NP agglomeration, is critically reviewed. It becomes quite evident that the knowledge of the protein corona is still fragmented, and conflicting results on fundamental issues call for further mechanistic studies. The article concludes with a discussion of future research directions that should be taken to advance the understanding of the protein corona around NPs. This knowledge will provide NP developers with the predictive power to account for these interactions in the design of efficacious nanomedicines.

The protein corona from nanomedicine to environmental science

The protein corona spontaneously develops and evolves on the surface of nanoscale materials when they are exposed to biological environments, altering their physiochemical properties and affecting their subsequent interactions with biosystems. In this Review, we provide an overview of the current state of protein corona research in nanomedicine. We next discuss remaining challenges in the research methodology and characterization of the protein corona that slow the development of nanoparticle therapeutics and diagnostics, and we address how artificial intelligence can advance protein corona research as a complement to experimental research efforts. We then review emerging opportunities provided by the protein corona to address major issues in healthcare and environmental sciences. This Review details how mechanistic insights into nanoparticle protein corona formation can broadly address unmet clinical and environmental needs, as well as enhance the safety and efficacy of nanobiotechnology products.

Differences in protein distribution, conformation, and dynamics in hard and soft coronas: dependence on protein and particle electrostatics

We perform all-atom molecular dynamics simulations of a 9 nm-thick protein layer, which consists of serum albumin (SA) or a mixture of SA and immunoglobulin gamma-1, formed on 10 nm-sized cationic, anionic, and neutral polystyrene particles. More than half of the proteins are densely concentrated within a distance of ∼3 nm from the particle surface, while fewer proteins are broadly distributed in the range of 3-9 nm from the particle. This compares favorably with the experimental observations of a hard corona as the first layer adjacent to the particle and a soft corona as a loose protein-network. The conformation and diffusivity of the proteins vary in different positions of the layer, and are to an extent dependent on the protein and particle electrostatics. These, combined with free energy calculations, show that the protein and particle charges do not significantly modify the strength of protein-particle binding but do influence the distribution of proteins in the layer. In particular, a free protein more strongly binds to the complex of a protein and particle than to either one, showing the synergistic effect of already adsorbed proteins and a particle. This helps explain the experimental observation regarding the formation of a denser protein layer and the stronger protein-protein interaction in the hard corona than the soft corona.

Systematic modulation of the lipid composition enables the tuning of liposome cellular uptake

As liposomes have been widely explored as drug delivery carriers over the past decades, they are one of the most promising platforms due to their biocompatibility and versatility for surface functionalization. However, to improve the specific design of liposomes for future biomedical applications such as nanovaccines, it is necessary to understand how these systems interact with cell membranes, as most of their potential applications require them to be internalized by cells. Even though several investigations on the cellular uptake of liposomes were conducted, the effect of the liposome membrane properties on internalization in different cell lines remains unclear. Here, we demonstrate how the cellular uptake behavior of liposomes can be driven towards preferential interaction with dendritic cells (DC2.4) as compared to macrophages (RAW264.7) by tuning the lipid composition with varied molar ratios of the lipid 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE). Cellular internalization efficiency was analyzed by flow cytometry, as well as liposome-cell membrane co-localization by confocal laser scanning microscopy. The corresponding proteomic analysis of the protein corona was performed in order to unravel the possible effect on the internalization. The obtained results of this work reveal that it is possible to modulate the cellular uptake towards enhanced internalization by dendritic cells just by modifying the applied lipids and, thus, mainly the physico-chemical properties of the liposomes. STATEMENT OF SIGNIFICANCE: In the field of nanomedicine, it is of key importance to develop new specific and efficient drug carriers. In this sense, liposomes are one of the most widely known carrier types and used in clinics with good results. However, the exact interaction mechanisms of liposomes with cells remain unclear, which is of great importance for the design of new drug delivery platforms. Therefore, in this work we demonstrate that cellular uptake depends on the lipid composition. We are able to enhance the uptake in a specific cell type just by tuning the content of a lipid in the liposome membrane. This finding could be a step towards the selective design of liposomes to be internalized by specific cells with promising applications in biomedicine.

Nanocarrier design–function relationship: The prodigious role of properties in regulating biocompatibility for drug delivery applications

The concept of drug delivery systems as a magic bullet for the delivery of bioactive compounds has emerged as a promising approach in the treatment of different diseases with significant advantages over the limitations of traditional methods. While nanocarrier-based drug delivery systems are the main advocates of drug uptake because they offer several advantages including reduced non-specific biodistribution, improved accumulation, and enhanced therapeutic efficiency; their safety and biocompatibility within cellular/tissue systems are therefore important for achieving the desired effect. The underlying power of "design-interplay chemistry" in modulating the properties and biocompatibility at the nanoscale level will direct the interaction with their immediate surrounding. Apart from improving the existing nanoparticle physicochemical properties, the balancing of the hosts' blood components interaction holds the prospect of conferring newer functions altogether. So far, this concept has been remarkable in achieving many fascinating feats in addressing many challenges in nanomedicine such as immune responses, inflammation, biospecific targeting and treatment, and so on. This review, therefore, provides a diverse account of the recent advances in the fabrication of biocompatible nano-drug delivery platforms for chemotherapeutic applications, as well as combination therapy, theragnostic, and other diseases that are of interest to scientists in the pharmaceutical industries. Thus, careful consideration of the "property of choice" would be an ideal way to realize specific functions from a set of delivery platforms. Looking ahead, there is an enormous prospect for nanoparticle properties in regulating biocompatibility.

Aging of Nanoplastics Significantly Affects Protein Corona Composition Thus Enhancing Macrophage Uptake

Nanoplastics (NPs), as emerging contaminants, have attracted increasing attention for their effects on human exposure and potential health risks. The protein corona formed on the surface of NPs affects the biological activity and fate of the NPs in vivo. However, how environmental aging, an inevitable process once NPs enter the environment, affects the formation of protein corona on NPs is still unclear. This study investigated the changes in the compositions of protein corona formed on photo-aged polystyrene (PS) NPs in human bronchoalveolar lavage fluid (BALF), corresponding to the inhalation exposure pathway. The results demonstrated that both the species and abundance of proteins in the BALF protein corona on the surface of PS NPs were altered by aging. In addition, the aged PS NPs are more hydrophilic and less electronegative than the pristine PS NPs; hence, there is an increased sorption of more negatively charged hydrophilic proteins. Moreover, aging-induced alterations in BALF protein corona enhanced the uptake of aged PS NPs by lung macrophages J774A.1 through phagocytosis and clathrin-mediated endocytosis. These findings highlight the importance of environmental aging processes in the biosafety assessment of nanoplastics.

Protein-Nanoparticle Interactions Govern the Interfacial Behavior of Polymeric Nanogels: Study of Protein Corona Formation at the Air/Water Interface

Biomedical applications of nanoparticles require a fundamental understanding of their interactions and behavior with biological interfaces. Protein corona formation can alter the morphology and properties of nanomaterials, and knowledge of the interfacial behavior of the complexes, using in situ analytical techniques, will impact the development of nanocarriers to maximize uptake and permeability at cellular interfaces. In this study we evaluate the interactions of acrylamide-based nanogels, with neutral, positive, and negative charges, with serum-abundant proteins albumin, fibrinogen, and immunoglobulin G. The formation of a protein corona complex between positively charged nanoparticles and albumin is characterized by dynamic light scattering, circular dichroism, and surface tensiometry; we use neutron reflectometry to resolve the complex structure at the air/water interface and demonstrate the effect of increased protein concentration on the interface. Surface tensiometry data suggest that the structure of the proteins can impact the interfacial properties of the complex formed. These results contribute to the understanding of the factors that influence the bio-nano interface, which will help to design nanomaterials with improved properties for applications in drug delivery.

Endosomal sorting results in a selective separation of the protein corona from nanoparticles

The formation of the protein corona is a well-known effect when nanoparticles (NP) are exposed to biological environments. The protein corona is the most important factor, which determines the rate and route of endocytosis, and decisively impacts cellular processes and even the release of the active pharmaceutical ingredient from the nanoparticles. While many studies concentrate on the effect of the protein corona formation extracellularly or the uptake consequences, little is known about the fate of the protein corona inside of cells. Here, we reconstruct for the first time the separation of the protein corona from the NPs by the cell and their further fate. Ultimately, the NPs and protein corona are separated from each other and end up in morphologically different cellular compartments. The cell directs the NPs towards recycling endosomes, whereas the protein corona gathers in multivesicular bodies. From this, we conclude that the NPs are prepared for subsequent exocytosis, while the protein corona remains in the cell and is finally metabolized there.

Overcoming Cytosolic Delivery Barriers of Proteins Using Denatured Protein-Conjugated Mesoporous Silica Nanoparticles

Intracellular delivery of therapeutic proteins has increased advantages over current small-molecule drugs and gene therapies, especially in therapeutic efficacies for a broad spectrum of diseases. Hence, developing the protein therapeutics approach provides a needed alternative. Here, we designed a mesoporous silica nanoparticle (MSN)-mediated protein delivery approach and demonstrated effective intracellular delivery of the denatured superoxide dismutase (SOD) protein, overcoming the delivery challenges and achieving higher enzymatic activity than native SOD-conjugated MSNs. The denatured SOD-conjugated MSN delivery strategy provides benefits of reduced size and steric hindrance, increased protein flexibility without distorting its secondary structure, exposure of the cell-penetrating peptide transactivator of transcription for enhanced efficient delivery, and a change in the corona protein composition, enabling cytosolic delivery. After delivery, SOD displayed a specific activity around threefold higher than in our previous reports. Furthermore, the in vivo biosafety and therapeutic potential for neuron therapy were evaluated, demonstrating the biocompatibility and the effective antioxidant effect in Neuro-2a cells that protected neurite outgrowth from paraquat-induced reactive oxygen species attack. This study offers an opportunity to realize the druggable possibility of cytosolic proteins using MSNs.

Silver nanoparticles with excellent biocompatibility block pseudotyped SARS-CoV-2 in the presence of lung surfactant

Silver (Ag) is known to possess antimicrobial properties which is commonly attributed to soluble Ag ions. Here, we showed that Ag nanoparticles (NPs) potently inhibited SARS-CoV-2 infection using two different pseudovirus neutralization assays. We also evaluated a set of Ag nanoparticles of different sizes with varying surface properties, including polyvinylpyrrolidone (PVP)-coated and poly (ethylene glycol) (PEG)-modified Ag nanoparticles, and found that only the bare (unmodified) nanoparticles were able to prevent virus infection. For comparison, TiO₂ nanoparticles failed to intercept the virus. Proteins and lipids may adsorb to nanoparticles forming a so-called bio-corona; however, Ag nanoparticles pre-incubated with pulmonary surfactant retained their ability to block virus infection in the present model. Furthermore, the secondary structure of the spike protein of SARS-CoV-2 was perturbed by the Ag nanoparticles, but not by the ionic control (AgNO₃) nor by the TiO₂ nanoparticles. Finally, Ag nanoparticles were shown to be non-cytotoxic towards the human lung epithelial cell line BEAS-2B and this was confirmed by using primary human nasal epithelial cells. These results further support that Ag nanoparticles may find use as anti-viral agents.

Protein-coated microplastics corona complex: An underestimated risk of microplastics

Traditionally, toxicity of microplastics is ascribed to the chemicals adsorbed on them. However, microplastics can also interact with biomolecules, such as secretory proteins from aquatic organisms, and form protein-coated microplastics corona complex with unknown toxic effects. Here, we investigated the toxic effects of polystyrene microplastics (PS) and bovine serum albumin (BSA) coated PS corona complex (PS + BSA) on adult zebrafish (Danio rerio) intestines. The food intake ratio, accumulation and distribution of microplastics, histopathological changes, and molecular effects related to the antioxidant system in the intestine were studied. For the first time, we observed that PS + BSA aggregated on the inner surface of the zebrafish intestine, whereas PS dispersed. The aggregation of PS + BSA resulted in increased microplastics accumulation and longer residence time in the zebrafish intestine, which inhibited food intake and generated reactive oxygen species (ROS) in the intestine. Furthermore, the functions of the Keap1-Nrf2-ARE antioxidant signaling pathway and the activation of antioxidant enzymes were significantly affected by PS + BSA after a 21-day exposure. Ultimately, a higher accumulation of ROS and stronger inhibition of antioxidants led to more severe intestinal injury. These results suggest that the increased toxicity of protein-coated microplastics corona complex may be affected by oxidative damage and can result in the inhibition of digestion due to their aggregation and longer residence time in the intestine. Therefore, the ecological risk of microplastics may be underestimated owing to the interactive mechanisms of microplastics and protein coronas.

Macromolecules Absorbed from Influenza Infection-Based Sera Modulate the Cellular Uptake of Polymeric Nanoparticles

Optimizing the biological identity of nanoparticles (NPs) for efficient tumor uptake remains challenging. The controlled formation of a protein corona on NPs through protein absorption from biofluids could favor a biological identity that enables tumor accumulation. To increase the diversity of proteins absorbed by NPs, sera derived from Influenza A virus (IAV)-infected mice were used to pre-coat NPs formed using a hyperbranched polyester polymer (HBPE-NPs). HBPE-NPs, encapsulating a tracking dye or cancer drug, were treated with sera from days 3-6 of IAV infection (VS3-6), and uptake of HBPE-NPs by breast cancer cells was examined. Cancer cells demonstrated better uptake of HBPE-NPs pre-treated with VS3-6 over polyethylene glycol (PEG)-HBPE-NPs, a standard NP surface modification. The uptake of VS5 pre-treated HBPE-NPs by monocytic cells (THP-1) was decreased over PEG-HBPE-NPs. VS5-treated HBPE-NPs delivered a cancer drug more efficiently and displayed better in vivo distribution over controls, remaining stable even after interacting with endothelial cells. Using a proteomics approach, proteins absorbed from sera-treated HBPE-NPs were identified, such as thrombospondin-1 (TSP-1), that could bind multiple cancer cell receptors. Our findings indicate that serum collected during an immune response to infection is a rich source of macromolecules that are absorbed by NPs and modulate their biological identity, achieving rationally designed uptake by targeted cell types.

Mimicking Pseudo-Virion Interactions with Abiotic Surfaces: Deposition of Polymer Nanoparticles with Albumin Corona

Adsorption of human serum albumin (HSA) molecules on negatively charged polystyrene microparticles was studied using the dynamic light scattering, the electrophoretic and the solution depletion methods involving atomic force microscopy. Initially, the physicochemical characteristics of the albumin comprising the hydrodynamic diameter, the zeta potential and the isoelectric point were determined as a function of pH. Analogous characteristics of the polymer particles were acquired, including their size and zeta potential. The formation of albumin corona on the particles was investigated in situ by electrophoretic mobility measurements. The size, stability and electrokinetic properties of the particles with the corona were also determined. The particle diameter was equal to 125 nm, which coincides with the size of the SARS-CoV-2 virion. The isoelectric point of the particles appeared at a pH of 5. The deposition kinetics of the particles was determined by atomic force microscopy (AFM) under diffusion and by quartz microbalance (QCM) under flow conditions. It was shown that the deposition rate at a gold sensor abruptly vanished with pH following the decrease in the zeta potential of the particles. It is postulated that the acquired results can be used as useful reference systems mimicking virus adsorption on abiotic surfaces.

Differential aggregation of polystyrene and titanium dioxide nanoparticles under various salinity conditions and against multiple proteins types

The interaction of nanoplastics (NPls) and engineered nanoparticles (ENPs) with organic matter and environmental pollutants is particularly important. Therefore, their behavior should be investigated under the different salinity conditions, mimicking rivers and coastal environments, to understand this phenomenon in those areas. In this work, we analyzed the elementary characteristics of polystyrene-PS (unmodified surface and modified with amino or carboxyl groups) and titanium dioxide-TiO2 nanoparticles. The effect of salinity on their colloidal properties was studied too. Also, the interaction with different types of proteins (bovine serum albumin-BSA and tilapia proteins), as well as the formation of the BSA corona and its effect on the colloidal stability of nanoparticles, were evaluated. The morphology and dispersion of sizes were more uniform in unmodified-surface PS-NPs (70.5 ± 13.7 nm) than in TiO2-NPs (131.2 ± 125.6 nm). Likewise, Rama spectroscopy allowed recognizing peaks associated with the PS phenyl group aromatic ring in unmodified-surface PS-NPs (621, 1002, 1582, and 1602 cm^-1). For TiO2-NPs, the data suggest belonging to the tetragonal form, also known as rutile (445, 610 cm^-1). The elevation of salinity dose-dependently decreased NP colloid stability, with more significant variation in the PS-NPs compared to TiO2-NPs. The organic matter is also involved in this phenomenon, differentially as a function of time compared to its absence (unmodified-surface PS-NPs 30 psu/TOC 5 mgL^-1/24 h: 2876.6 ± 378.03 nm; unmodified-surface PS-NPs 30 psu/24 h: 2133 ± 49.57 nm). In general, the TiO2-NPs demonstrated greater affinity with all proteins tested (0.066 g/L). It was observed that morphology, size, and surface chemical modification intervene in a relevant way in the interaction of the nanoparticles with bovine serum albumin (unmodified-surface PS-NPs 298 K: 6.08E⁺⁰²; 310 K: 6.63E⁺⁰²; TiO2-NPs 298 K: 8.76E⁺⁰²; 310 K: 1.05E⁺⁰³ L mol^-1) and tilapia tissues proteins (from blood, gills, liver, and brain). Their morphology and size also determined the protein corona formation and the NPs' agglomeration. These findings can provide references during knowledge transfer between NPls and ENPs.

Multivalent ACE2 engineering-A promising pathway for advanced coronavirus nanomedicine development

The spread of coronavirus diseases has resulted in a clarion call to develop potent drugs and vaccines even as different strains appear beyond human prediction. An initial step that is integral to the viral entry into host cells results from an active-targeted interaction of the viral spike (S) proteins and the cell surface receptor, called angiotensin-converting enzyme 2 (ACE2). Thus, engineered ACE2 has been an interesting decoy inhibitor against emerging coronavirus infestation. This article discusses promising innovative ACE2 engineering pathways for current and emerging coronavirus therapeutic development. First, we provide a brief discussion of some ACE2-associated human coronaviruses and their cell invasion mechanism. Then, we describe and contrast the individual spike proteins and ACE2 receptor interactions, highlighting crucial hotspots across the ACE2-associated coronaviruses. Lastly, we address the importance of multivalency in ACE2 nanomedicine engineering and discuss novel approaches to develop and achieve multivalent therapeutic outcomes. Beyond coronaviruses, these approaches will serve as a paradigm to develop new and improved treatment technologies against pathogens that use ACE2 receptor for invasion.

In situ analysis of nanoparticle soft corona and dynamic evolution

How soft corona, the protein corona’s outer layer, contributes to biological identity of nanomaterials is largely because capturing protein composition of the soft corona in situ remains challenging. We herein develop an in situ Fishing method that can monitor the dynamic formation of protein corona on ultra-small chiral Cu₂S nanoparticles (NPs) allowing us to directly separate and identify the corona protein composition. Our method detects spatiotemporal processes in the evolution of hard and soft coronas on chiral NPs, revealing subtle differences in NP − protein interactions even within several minutes. This study highlights the importance of in situ and dynamic analysis of soft/hard corona, provides insights into the role of soft corona in mediating biological responses of NPs, and offers a universal strategy to characterize soft corona to guide the rational design of biomedical nanomaterials.

Characterizing the soft protein corona on nanoparticles i.e. the outer layer of the corona, remains a longstanding challenge. Here, the authors develop an in situ method to monitor the dynamic processes of multilayered corona formation and evolution that offers a universal strategy to characterize the soft corona proteome.

Multicolor Super-Resolution Microscopy of Protein Corona on Single Nanoparticles

Nanoparticles represent a promising class of material for nanomedicine and molecular biosensing. The formation of a protein corona due to nonspecific particle-protein interactions is a determining factor for the biological fate of nanoparticles in vivo and strongly impacts the performance of nanoparticles when used as biosensors. Nonspecific interactions are usually highly heterogeneous, yet little is known about the heterogeneity of the protein corona that may lead to inter- and intraparticle differences in composition and protein distribution. Here, we present a super-resolution microscopic approach to study the protein corona on single silica nanoparticles and subsequent cellular interactions using multicolor stimulated emission depletion (STED) microscopy. We demonstrate that STED resolves structural features of protein corona on single particles including the distribution on the particle surface and the degree of protein internalization in porous particles. Using multicolor measurements of multiple labeled protein species, we determine the composition of the protein corona at the single-particle level. We quantify particle-to-particle differences in the composition and find that the composition is considerably influenced by the particle geometry. In a subsequent cellular uptake measurement, we demonstrate multicolor STED of protein corona on single particles internalized by cells. Our study shows that STED microscopy opens the window toward mechanistic understanding of protein coronas and aids in the rational design of nanoparticles as nanomedicines and biosensors.

Protein coronas coating polymer-stabilized silver nanocolloids attenuate cytotoxicity with minor effects on antimicrobial performance

Silver nanoparticles are versatile platforms with a variety of applications in the biomedical field. In this framework, their presence in biological media inevitably leads to the interaction with proteins thus conducting to the formation of biomolecular coronas. This feature alters the identity of the nanomaterial and may affect many biological events. These considerations motivated the investigation of protein adsorption onto the surface of polymer-stabilized AgNPs. The metallic colloids were coated by polyethyleneimine (PEI), polyvinylpyrrolidone (PVP), and poly(2-vinyl pyridine)-b-poly(ethylene oxide) (PEO-b-P2VP), and nanoparticle-protein interaction was probed by using a library of analytical techniques. The experimental data revealed a higher extent of protein adsorption at the surface of AgNPs@PVP whereas PEO-b-P2VP coating conducted to the least amount. The main component of the protein coronas was evidenced to be bovine serum albumin (BSA), which is indeed the protein at the highest abundancy in the model biological media. We have further demonstrated reduced cytotoxicity of the silver colloids coated by biomolecular coronas as compared to the pristine counterparts. Nevertheless, the protein coatings did not notably reduce the antimicrobial performance of the polymer-stabilized AgNPs. Accordingly, although the protein-repelling property is frequently targeted towards longer in vivo circulation of nanoparticles, we herein underline that protein coatings, which are commonly treated as artifacts to be avoided, may indeed enhance the biological performance of nanomaterials. These findings are expected to be highly relevant in the design of polymer-stabilized metallic colloids intended to be used in healthcare.

“Soft Protein Corona” as the Stabilizer of the Methionine-Coated Silver Nanoparticles in the Physiological Environment: Insights into the Mechanism of the Interaction

The study of the interactions between nanoparticles (NPs) and proteins has had a pivotal role in facilitating the understanding of biological effects and safe application of NPs after exposure to the physiological environment. Herein, for the first time, the interaction between L-methionine capped silver nanoparticles (AgMet), and bovine serum albumin (BSA) is investigated in order to predict the fate of AgMet after its contact with the most abundant blood transport protein. The detailed insights into the mechanism of interaction were achieved using different physicochemical techniques. The UV/Vis, TEM, and DLS were used for the characterization of the newly formed “entity”, while the kinetic and thermodynamic parameters were utilized to describe the adsorption process. Additionally, the fluorescence quenching and synchronous fluorescence studies enabled the prediction of the binding affinity and gave us insight into the influence of the adsorption on the conformation state of the BSA. According to the best of our knowledge, for the first time, we show that BSA can be used as an external stabilizer agent which is able to induce the peptization of previously agglomerated AgMet. We believe that the obtained results could contribute to further improvement of AgNPs’ performances as well as to the understanding of their in vivo behavior, which could contribute to their potential use in preclinical research studies.

Renally Excretable Silver Telluride Nanoparticles as Contrast Agents for X-ray Imaging

The use of nanoparticles in the biomedical field has gained much attention due to their applications in biomedical imaging, drug delivery, and therapeutics. Silver telluride nanoparticles (Ag₂Te NPs) have been recently shown to be highly effective computed tomography (CT) and dual-energy mammography contrast agents with good stability and biocompatibility, as well as to have potential for many other biomedical purposes. Despite their numerous advantageous properties for diagnosis and treatment of disease, the clinical translation of Ag₂Te NPs is dependent on achieving high levels of excretion, a limitation for many nanoparticle types. In this work, we have synthesized and characterized a library of Ag₂Te NPs and identified conditions that led to 3 nm core size and were renally excretable. We found that these nanoparticles have good biocompatibility, strong X-ray contrast generation, and rapid renal clearance. Our CT data suggest that renal elimination of nanoparticles occurred within 2 h of administration. Moreover, biodistribution data indicate that 93% of the injected dose (%ID) has been excreted from the main organs in 24 h, 95% ID in 7 days, and 97% ID in 28 days with no signs of acute toxicity in the tissues studied under histological analysis. To our knowledge, this renal clearance is the best reported for Ag₂Te NP, while being comparable to the highest renal clearance reported for any type of nanoparticle. Together, the results herein presented suggest the use of GSH-Ag₂Te NPs as an X-ray contrast agent with the potential to be clinically translated in the future.

PEG Spacer Length Substantially Affects Antibody-Based Nanocarrier Targeting of Dendritic Cell Subsets

Successful cell targeting depends on the controlled positioning of cell-type-specific antibodies on the nanocarrier’s (NC) surface. Uncontrolled antibody immobilization results in unintended cell uptake due to Fc-mediated cell interaction. Consequently, precise immobilization of the Fc region towards the nanocarrier surface is needed with the Fab regions staying freely accessible for antigen binding. Moreover, the antibody needs to be a certain distance from the nanocarrier surface, influencing the targeting performance after formation of the biomolecular corona. This can be achieved by using PEG linker molecules. Here we demonstrate cell type-specific targeting for dendritic cells (DC) as cellular key regulators of immune responses. However, to date, dendritic cell targeting experiments using different linker lengths still need to be conducted. Consequently, we focused on the surface modification of nanocarriers with different molecular weight PEG linkers (0.65, 2, and 5 kDa), and their ability to reduce undesired cell uptake, while achieving efficient DC targeting via covalently immobilized antibodies (stealth targeting). Our findings demonstrate that the PEG linker length significantly affects active dendritic cell targeting from cell lines (DC2.4) to primary cells (BMDCs, splenocytic conventional DCs type 1 (cDC1)). While antibody-functionalized nanocarriers with a shorter PEG length (0.65 kDa) showed the best targeting in DC2.4, a longer PEG length (5 kDa) was required to specifically accumulate in BMDCs and splenocytic cDC1. Our study highlights that these crucial aspects must be considered when targeting dendritic cell subsets, which are of great importance in the fields of cancer immunotherapy and vaccine development.