Adsorption of a Protein Monolayer via Hydrophobic Interactions Prevents Nanoparticle Aggregation under Harsh Environmental Conditions

A hybrid nanoparticle-protein hydrogel system for prolonged local anesthesia

Local anesthetics are effective in relieving pain, but their duration of action is short. Therefore, the development of injectable sustained release systems to prolong the effect of local anesthetics has been of interest. In such systems delivering conventional local anesthetics, it has been challenging to achieve long durations of effect, particularly without incurring tissue toxicity. To overcome these challenges, we created a platform comprising a protein hydrogel incorporating hydrophobic local anesthetic (bupivacaine) nanoparticles. The nanoparticles were prepared by anti-solvent precipitation stabilized with bovine serum albumin (BSA), followed by crosslinking with glutaraldehyde (GA). The resulting BSA hydrogels prolonged release of bupivacaine in vitro. When bupivacaine nanoparticles within crosslinked BSA were injected at the sciatic nerve in rats, a duration of nerve block of 39.9 h was obtained, compared to 5.5 h for the commercial bupivacaine liposome suspension EXPAREL®. Tissue reaction was benign. We further demonstrated that this system could control the release of the amphiphilic drug diphenhydramine and the hydrophobic paclitaxel.

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.

Colloidal stability and aggregation behavior of CdS colloids in aquatic systems: Effects of macromolecules, cations, and pH

Redox-dynamic environments such as river floodplains and paddy fields have been demonstrated to be important sources of CdS colloids. To date, the aggregation kinetics of CdS colloids had not yet been studied, and the structure and properties of macromolecules on the interaction between different macromolecules and CdS colloids, as well as the aggregation behavior of CdS colloids are unclear. This study investigated the colloidal stability of CdS colloids in model aqueous systems with various solution chemistry and representative of macromolecules. The results showed that increased electrolyte concentration destabilized CdS colloids by charge screening, with the cationic effect following Ca²⁺ > Mg²⁺ > K⁺ > Na⁺; Higher solution pH stabilized CdS colloids by raising the critical coagulation concentration from 33 to 56 mM NaCl. Electron microscopy and spectroscopy verified the strong interaction between macromolecules and CdS colloids, and macromolecule adsorbed on the surface of CdS to form a protective layer called "NOM corona". The interaction between macromolecules and CdS induced distinct aggregation behaviors in NaCl and CaCl₂ solutions. The steric repulsion generated by "NOM corona" significantly stabilized CdS colloids in NaCl solution, and the stabilizing order was consistent with the adsorbing capacity of macromolecules on CdS colloids, namely Bovine serum albumin (BSA) > sodium alginate (SA) > calf thymus DNA (DNA) > Suwannee River humic acid (HA). BSA and DNA also inhibited CdS colloids aggregation in the CaCl₂ solution due to the balance of steric hindrance, cation bridging, and electrostatic repulsion. For HA and SA, Ca²⁺ bridging and EDL compression contributed to their destabilization of CdS colloids in CaCl₂ solution. Macromolecules concentration affect corona formation that alter stability of CdS colloids. There results showed that the complex influences of solution chemistry and macromolecules on fate and transport of CdS colloids in environment. The findings will help to understand the potential risks of CdS colloids in environment.

Proteolysis modification targeting protein corona affects ultrasound-induced membrane homeostasis of saccharomyces cerevisiae: Analysis of lipid relative contributions on membrane properties

Introduction

Protein corona (PCN) adsorbed on the surface of nanoparticles has brought new research perspectives for the interaction between nanoparticles and microorganisms. In this study, the responses of saccharomyces cerevisiae' membrane lipid composition, the average length of the fatty acyl chains and the average number of unsaturation of fatty acids to ultrasound combined with nano-Fe₃O₄@PCN with time-limited proteolysis (nano-Fe₃O₄@TLP-PCN) was investigated.

Methods

Lipidomic data was obtained using Ultra-high performance liquid chromatography coupled with a Q-Exactive plus mass spectrometer. The membrane potential, proton motive force assay and the membrane lipid oxidation were measured using Di-BAC₄(3), DISC₃(5) and C11-BODIPY^581/591 as the probes. Combined with the approach of feasible virtual samples generation, the back propagation artificial neural network (BP-ANN) model was adopted to establish the mapping relationship between lipids and membrane properties.

Results

The time-limited proteolysis targeting wheat PCN-coated Fe₃O₄ nanoparticles resulted in regular changes of hydrodynamic diameters, ζ-potentials, and surface hydrophobicity. In addition, with the prolongation of PCN proteolysis time, disturbances of 3 S.cerevisiae membrane characteristics, and membrane lipidomic remodeling in response to ultrasound+ nano-Fe₃O₄@PCN were observed. The analysis of relative importance which followed revealed that ergosterol, phosphatidylserine, and phosphatidylinositol phosphate had the greatest influence on membrane potential. For membrane lipid oxidation, ceramide, phosphatidylethanolamine, and sitosterol ester contribute 16.2, 14.9, and 13.1%, respectively. The relative contributions of six lysolecithins to the dissipation of proton motive force remained limited.

Discussion

An adaptation mechanism of cell membrane to proteolyzed PCN, wherein lipidome remodeling could preserved functional membrane phenotypes was revealed. Furthermore, it is highlighted that the relative importances of SiE, Cer, PE and PIP in determining membrane potential, PMF dissipation and membrane lipid oxidation by establishing FVSG-BP-ANN model.

Supercharged Protein Nanosheets for Cell Expansion on Bioemulsions

Cell culture at liquid-liquid interfaces, for example, at the surface of oil microdroplets, is an attractive strategy to scale up adherent cell manufacturing while replacing the use of microplastics. Such a process requires the adhesion of cells at interfaces stabilized and reinforced by protein nanosheets displaying not only high elasticity but also presenting cell adhesive ligands able to bind integrin receptors. In this report, supercharged albumins are found to form strong elastic protein nanosheets when co-assembling with the co-surfactant pentafluorobenzoyl chloride (PFBC) and mediate extracellular matrix (ECM) protein adsorption and cell adhesion. The interfacial mechanical properties and elasticity of supercharged nanosheets are characterized by interfacial rheology, and behaviors are compared to those of native bovine serum albumin, human serum albumin, and α-lactalbumin. The impact of PFBC on such assembly is investigated. ECM protein adsorption to resulting supercharged nanosheets is then quantified via surface plasmon resonance and fluorescence microscopy, demonstrating that the dual role supercharged albumins are proposed to play as scaffold protein structuring liquid-liquid interfaces and substrates for the capture of ECM molecules. Finally, the adhesion and proliferation of primary human epidermal stem cells are investigated, at pinned droplets, as well as on bioemulsions stabilized by corresponding supercharged nanosheets. This study demonstrates the potential of supercharged proteins for the engineering of biointerfaces for stem cell manufacturing and draws structure-property relationships that will guide further engineering of associated systems.

In Situ Characterization of the Protein Corona of Nanoparticles In Vitro and In Vivo

A new theoretical framework that enables the use of differential dynamic microscopy (DDM) in fluorescence imaging mode to quantify in situ protein adsorption onto nanoparticles (NP) while simultaneously monitoring for NP aggregation is proposed. This methodology is used to elucidate the thermodynamic and kinetic properties of the protein corona (PC) in vitro and in vivo. The results show that protein adsorption triggers particle aggregation over a wide concentration range and that the formed aggregate structures can be quantified using the proposed methodology. Protein affinity for polystyrene (PS) NPs is observed to be dependent on particle concentration. For complex protein mixtures, this methodology identifies that the PC composition changes with the dilution of serum proteins, demonstrating a Vroman effect never quantitatively assessed in situ on NPs. Finally, DDM allows monitoring of the evolution of the PC in vivo. This results show that the PC composition evolves significantly over time in zebrafish larvae, confirming the inherently dynamic nature of the PC. The performance of the developed methodology allows to obtain quantitative insights into nano-bio interactions in a vast array of physiologically relevant conditions that will serve to further improve the design of nanomedicine.

Dynamic process, mechanisms, influencing factors and study methods of protein corona formation

Nanoparticles interacting with proteins to form protein corona represent one of the most fundamental problems in the rapid development of nanotechnology. In the past decade, thousands of studies have pointed out this issue. Within multi-protein systems, the formation of protein corona is a homeostasis process in which proteins compete for the limited surface sites of nanoparticles. Besides, the formation of protein corona generally shows a tendency of evolving with time and involves many different driving forces controlled by properties of nanoparticles, proteins and environment. Therefore, recent research on the dynamic process and mechanisms of protein corona formation in both animals and plants are summarized in this review. The factors that affect the formation and the techniques that commonly used for protein corona analysis are proposed. Furthermore, in order to provide reference for the future research, the limitations and challenges in protein corona studies are assessed and the future perspectives are proposed.

Screening of Estrogenic-Disrupting Compounds in Dairy Products Based on the Estrogen Receptor Cocktail

The residue of estrogenic-disrupting compounds (EDCs) that are secreted by cows, added as drugs, and present in the feed may exist in dairy products. A gold nanoparticles (AuNPs)-estrogen receptor (ER) cocktail colorimetric assay equipped with ER cocktail solid phase extraction (SPE) was established to screen EDCs. Nine EDCs with high, moderate, and low estrogenic activity were selected to be the representative targets. The recognition range of the colorimetric assay combined with the ER cocktail SPE was wider than that of a single ERα or ERβ. The lowest detection limit of the established assay was about 10^-9 mg·mL^-1. The detection limits of estrone, bisphenol A, and bisphenol B were about one order of magnitude lower than the method based on a single ER. The recoveries of the spiked nine EDCs were between 80.0% and 110.0%, and daidzein was identified in the dairy product. The developed method has potential application prospects in food safety and environmental monitoring.

Protein adsorption onto nanomaterials engineered for theranostic applications

The key role of biomolecule adsorption onto engineered nanomaterials for therapeutic and diagnostic purposes has been well recognized by the nanobiotechnology community, and our mechanistic understanding of nano-bio interactions has greatly advanced over the past decades. Attention has recently shifted to gaining active control of nano-bio interactions, so as to enhance the efficacy of nanomaterials in biomedical applications. In this review, we summarize progress in this field and outline directions for future development. First, we briefly review fundamental knowledge about the intricate interactions between proteins and nanomaterials, as unraveled by a large number of mechanistic studies. Then, we give a systematic overview of the ways that protein-nanomaterial interactions have been exploited in biomedical applications, including the control of protein adsorption for enhancing the targeting efficiency of nanomedicines, the design of specific protein adsorption layers on the surfaces of nanomaterials for use as drug carriers, and the development of novel nanoparticle array-based sensors based on nano-bio interactions. We will focus on particularly relevant and recent examples within these areas. Finally, we conclude this topical review with an outlook on future developments in this fascinating research field.

Ultrasmall Manganese Ferrites for In Vivo Catalase Mimicking Activity and Multimodal Bioimaging

Manganese ferrite nanoparticles display interesting features in bioimaging and catalytic therapies. They have been recently used in theranostics as contrast agents in magnetic resonance imaging (MRI), and as catalase-mimicking nanozymes for hypoxia alleviation. These promising applications encourage the development of novel synthetic procedures to enhance the bioimaging and catalytic properties of these nanomaterials simultaneously. Herein, a cost-efficient synthetic microwave method is developed to manufacture ultrasmall manganese ferrite nanoparticles as advanced multimodal contrast agents in MRI and positron emission tomography (PET), and improved nanozymes. Such a synthetic method allows doping ferrites with Mn in a wide stoichiometric range (Mn_x Fe_3-x O₄ , 0.1 ≤ x ≤ 2.4), affording a library of nanoparticles with different magnetic relaxivities and catalytic properties. These tuned magnetic properties give rise to either positive or dual-mode MRI contrast agents. On the other hand, higher levels of Mn doping enhance the catalytic efficiency of the resulting nanozymes. Finally, through their intracellular catalase-mimicking activity, these ultrasmall manganese ferrite nanoparticles induce an unprecedented tumor growth inhibition in a breast cancer murine model. All of these results show the robust characteristics of these nanoparticles for nanobiotechnological applications.

Spectroscopic study of L-DOPA and dopamine binding on novel gold nanoparticles towards more efficient drug-delivery system for Parkinson's disease

Nano-drug delivery systems may potentially overcome current challenges in the treatment of Parkinson's disease (PD) by enabling targeted delivery and more efficient blood-brain penetration ability. This study investigates novel gold nanoparticles (AuNPs) to be used as delivery systems for L-DOPA and dopamine by considering their binding capabilities in the presence and absence of a model protein, bovine serum albumin (BSA). Four different AuNPs were prepared by surface functionalization with polyethylene glycol (PEG), 1-adamantylamine (Ad), 1-adamantylglycine (AdGly), and peptidoglycan monomer (PGM). Fluorescence and UV-Vis measurements demonstrated the strongest binding affinity and L-DOPA/dopamine loading efficiency for PGM-functionalized AuNPs with negligible impact of the serum protein presence. Thermodynamic analysis revealed a spontaneous binding process between L-DOPA or dopamine and AuNPs that predominantly occurred through van der Waals interactions/hydrogen bonds or electrostatic interactions. These results represent PGM-functionalized AuNPs as the most efficient at L-DOPA and dopamine binding with a potential to become a drug-delivery system for neurodegenerative diseases. Detailed investigation of L-DOPA/dopamine interactions with different AuNPs was described here for the first time. Moreover, this study highlights a cost- and time-effective methodology for evaluating drug binding to nanomaterials.

Scratching the Surface of the Protein Corona: Challenging Measurements and Controversies

This Review aims to provide a systematic analysis of the literature regarding ongoing debates in protein corona research. Our goal is to portray the current understanding of two fundamental and debated characteristics of the protein corona, namely, the formation of mono- or multilayers of proteins and their binding (ir)reversibility. The statistical analysis we perform reveals that these characterisitics are strongly correlated to some physicochemical factors of the NP-protein system (particle size, bulk material, protein type), whereas the technique of investigation or the type of measurement (in situ or ex situ) do not impact the results, unlike commonly assumed. Regarding the binding reversibility, the experimental design (either dilution or competition experiments) is also shown to be a key factor, probably due to nontrivial protein binding mechanisms, which could explain the paradoxical phenomena reported in the literature. Overall, we suggest that to truly predict and control the protein corona, future efforts should be directed toward the mechanistic aspects of protein adsorption.

Simultaneous Influence of Gradients in Natural Organic Matter and Abiotic Parameters on the Behavior of Silver Nanoparticles in the Transition Zone from Freshwater to Saltwater Environments

As nanoparticles have been found to cause a range of harmful impacts in biota, understanding processes and transformations which may stabilize and increase their persistence time in the environment are of great importance. As nanoparticles carried in riverine or wastewaters will eventually reach estuaries, understanding their behavior and transport potential in this transition zone from fresh to marine waters is essential, particularly as estuaries are sensitive ecological zones, oftentimes encompassing ornithologically important areas. In this direction, we report on the influence of combined gradients of riverine and marine natural organic matter (NOM) on the temporal stability of biocorona-encapsulated silver nanoparticles in terms of ion release kinetics. In parallel, salinity, pH and oxygen saturation were simultaneously varied to create a model to mimic the complex estuarine environment. While humic acid (HA) and alginate (Alg) disrupted the stabilizing ability of the nanoparticle protein corona to a greater and lesser degree, respectively, they slowed the rate of ion release in freshwater at pH 6.6 and in saltwater at pH 8, respectively, while oxygen saturation was also found to be an important factor. Thus, as the type of NOM changes with pH along a salinity gradient in an estuary, conditions required to increase the persistence time of nanoparticles are serendipitously met, with greater colloidal stability achieved in cases where there is more rapid replacement of HA with Alg. Despite the strong gradients in ionic strength, pH and oxygen saturation, the protein corona was not sufficiently disrupted at the nanoparticle surface to be substituted by NOM indicating the greater adsorption energy of the protein's hydrophobic domains. Ultimately, it is the specific NOM profile of individual estuaries that may provide the best indicator for predicting the stability and persistence of silver nanoparticles as they transition from fresh to salt water environments.

Size and macromolecule stabilizer-dependent performance of gold colloids in immuno-PCR

Gold nanoparticles (GNPs) are well-documented for their size and surface chemistry-dependent electronic and optical properties that are extensively utilized to develop highly sensitive immunoassays. GNP-based immuno-polymerase chain reaction (immuno-PCR) is especially interesting due to the facile loading of biomolecules on the surface of GNP probes and has been utilized to develop analyte-specific assays. In this study, the role of size and surface chemistry of GNPs is explored in detail to develop a highly sensitive and reproducible immuno-PCR assay for specific detection of biotinylated analytes. Our results indicate that smaller-sized gold nanoparticles outperform the larger ones in terms of their sensitivity in immuno-PCR assay and show superior loading of proteins and oligonucleotides on the surface of nanoparticles. Furthermore, the role of different macromolecular stabilizers (such as polyethylene glycol (PEG), bovine serum albumin (BSA), and PEGylated BSA) was compared to optimize the loading of biomolecules and to improve the signal-to-noise ratio of GNP probes. mPEG-BSA-functionalized GNP probes of 15 nm were found to be highly sensitive at low concentrations of analytes and significantly (~ 30 fold) improve the limit of detection of analytes in comparison with ELISA assay.

SARS-CoV-2 detection with aptamer-functionalized gold nanoparticles

A rapid detection test for SARS-CoV-2 is urgently required to monitor virus spread and containment. Here, we describe a test that uses nanoprobes, which are gold nanoparticles functionalized with an aptamer specific to the spike membrane protein of SARS-CoV-2. An enzyme-linked immunosorbent assay confirms aptamer binding with the spike protein on gold surfaces. Protein recognition occurs by adding a coagulant, where nanoprobes with no bound protein agglomerate while those with sufficient bound protein do not. Using plasmon absorbance spectra, the nanoprobes detect 16 nM and higher concentrations of spike protein in phosphate-buffered saline. The time-varying light absorbance is examined at 540 nm to determine the critical coagulant concentration required to agglomerates the nanoprobes, which depends on the protein concentration. This approach detects 3540 genome copies/μl of inactivated SARS-CoV-2.

Sensing nanoparticle-protein corona using nanoparticle enhanced Laser Induced Breakdown Spectroscopy signal enhancement

Recently nanoparticle enhanced Laser Induced Breakdown Spectroscopy (NELIBS) is getting a growing interest as an effective alternative method for improving the analytical performance of LIBS. On the other hand, the plasmonic effect during laser ablation can be used for a different task rather than elemental analysis. In this paper, the dependence of NELIBS emission signal enhancement on nanoparticle-protein solutions dried on a reference substrate (metallic titanium) was investigated. Two proteins were studied: Human Serum Albumin (HSA) and Cytochrome C (CytC). Both proteins have a strong affinity for the gold nanoparticles (AuNPs) due to the bonding between the single free exterior thiol (associated with a cysteine residue) and the gold surface to form a stable protein corona. Then, since the protein sizes are vastly different, a different number of protein units is needed to cover AuNP surface to form a protein layer. The NP-protein solution was dropped and dried onto the titanium substrate. Then the NELIBS signal enhancement of Ti emission lines was correlated to the solution characteristics as determined with Dynamic Light Scattering (DLS), Surface Plasmon Resonance (SPR) spectroscopy and Laser Doppler Electrophoresis (LDE) for ζ-potential determination. Moreover, the dried solutions were studied with TEM (Transmission Electron Microscopy) for the inspection of the inter-particle distance. The structural effect of the NP-protein conjugates on the NELIBS signal reveals that NELIBS can be used to determine the number of protein units required to form the nanoparticle-protein corona with good accuracy. Although the investigated NP-protein systems are simple cases in biological applications, this work demonstrates, for the first time, a different use of NELIBS that is beyond elemental analysis and it opens the way for sensing the nanoparticle protein corona.

Corona protein impacts on alternating current biosusceptometry signal and circulation times of differently coated MnFe2O4 nanoparticles

Background: We evaluated the impacts of corona protein (CP) formation on the alternating current biosusceptometry (ACB) signal intensity and in vivo circulation times of three differently coated magnetic nanoparticles (MNP): bare, citrate-coated and bovine serum albumin-coated MNPs. Methods: We employed the ACB system, gel electrophoresis and mass spectrometry analysis. Results: Higher CP formation led to a greater reduction in the in vitro ACB signal intensity and circulation time. We found fewer proteins forming the CP for the bovine serum albumin-coated MNPs, which presented the highest circulation time in vivo among the MNPs studied. Conclusion: These data showed better biocompatibility, stability and magnetic signal uniformity in biological media for bovine serum albumin-coated MNPs than for citrate-coated MNPs and bare MNPs.

The protein corona and its effects on nanoparticle-based drug delivery systems

In most cases, once nanoparticles (NPs) enter the blood, their surface is covered by biological molecules, especially proteins, forming a so-called protein corona (PC). As a result, what the cells of the body "see" is not the NPs as formulated by the chemists, but the PC. In this way, the PC can influence the effects of the NPs and even mask the desired effects of the NP components. While this can argue for trying to inhibit protein-nanomaterial interactions, encapsulating NPs in an endogenous PC may increase their clinical usefulness. In this review, we briefly introduce the concept of the PC, its formation and its effects on the behavior of NPs. We also discuss how to reduce the formation of PCs or exploit them to enhance NP functions. Studying the interactions between proteins and NPs will provide insights into their clinical activity in health and disease. STATEMENT OF SIGNIFICANCE: The formation of protein corona (PC) will affect the operation of nanoparticles (NPs) in vivo. Since there are many proteins in the blood, it is impossible to completely overcome the formation of PC. Therefore, the use of PCs to deliver drug is the best choice. De-opsonins adsorbed on NPs can reduce macrophage phagocytosis and cytotoxicity of NPs, and prolong their circulation in blood. Albumin, apolipoprotein and transferrin are typical de-opsonins. In present review, we mainly discuss how to optimize the delivery of nanoparticles through the formation of albumin corona, transferrin corona and apolipoprotein corona in vivo or in vitro.

Mechanisms of transport enhancement for self-propelled nanoswimmers in a porous matrix

Micro/nanoswimmers convert diverse energy sources into directional movement, demonstrating significant promise for biomedical and environmental applications, many of which involve complex, tortuous, or crowded environments. Here, we investigated the transport behavior of self-propelled catalytic Janus particles in a complex interconnected porous void space, where the rate-determining step involves the escape from a cavity and translocation through holes to adjacent cavities. Surprisingly, self-propelled nanoswimmers escaped from cavities more than 20× faster than passive (Brownian) particles, despite the fact that the mobility of nanoswimmers was less than 2× greater than that of passive particles in unconfined bulk liquid. Combining experimental measurements, Monte Carlo simulations, and theoretical calculations, we found that the escape of nanoswimmers was enhanced by nuanced secondary effects of self-propulsion which were amplified in confined environments. In particular, active escape was facilitated by anomalously rapid confined short-time mobility, highly efficient surface-mediated searching for holes, and the effective abolition of entropic and/or electrostatic barriers at the exit hole regions by propulsion forces. The latter mechanism converted the escape process from barrier-limited to search-limited. These findings provide general and important insights into micro/nanoswimmer mobility in complex environments.

Quantification of Tumor Protein Biomarkers from Lung Patient Serum Using Nanoimpact Electrochemistry

Protein quantification with high throughput and high sensitivity is essential in the early diagnosis and elucidation of molecular mechanisms for many diseases. Conventional approaches for protein assay often suffer from high costs, long analysis time, and insufficient sensitivity. The recently emerged nanoimpact electrochemistry (NIE), as a contrast, allows in situ detection of analytes one at a time with simplicity, fast response, high throughput, and the potential of reducing the detection limits down to the single entity level. Herein, we propose a NIE-enabled electrochemical immunoassay using silver nanoparticles (AgNPs) as labels for the detection of CYFRA21-1, a typical protein marker for lung carcinoma. This strategy is based on the measurement of the impact frequency and the charge intensity of the electrochemical oxidation of individual AgNPs before and after they are modified with anti-CYFRA21-1 and in turn immunocomplexed with CYFRA21-1. Both the frequency and intensity modes of single-nanoparticle electrochemistry correlate well with each other, resulting in a self-validated immunoassay that provides linear ranges of two orders of magnitude and a limit of detection of 0.1 ng/mL for CYFRA21-1 analysis. The proposed immunoassay also exhibits excellent specificity when challenged with other possible interfering proteins. In addition, the CYFRA21-1 content is validated by a conventional, well-known enzyme-linked immunosorbent assay and successfully quantified in a diluted healthy serum with a satisfactory recovery. Moreover, CYFRA21-1 detection in serum samples of lung cancer patients is successfully demonstrated, suggesting the feasibility of the NIE-based immunoassay in clinically relevant diagnosis. To the best of our knowledge, this is the first report to construct NIE-based electrochemical immunoassays for the specific detection of tumor protein biomarkers.

A simplified model for gel electrophoresis of a hydrophobic rigid colloid

Electrophoresis of a charged dielectric hydrophobic colloid embedded in a charged hydrogel medium is addressed. A slip velocity condition at the particle surface is considered. The characteristic of the gel electrophoresis is different compared with the free-solution electrophoresis due to the presence of immobile charges of the gel medium, which induces a strong background electroosmotic flow and modifies the Debye layer of the colloid. The gel electrophoresis of the dielectric hydrophobic charged colloid is made based on first-order perturbation analysis. A closed form solution involving simple exponential integrals for the mobility is derived, which reduces to several existing mobility expressions under limiting conditions such as for the gel electrophoresis of hydrophilic particles and a hydrophobic colloid in free-solution electrophoresis. We find that the mobility reversal is achieved by varying the Debye length or gel permeability. For the present first-order perturbation analysis, unlike free-solution electrophoresis, the particle dielectric permittivity is found to influence the mobility. One of the intriguing features of the present study is the derivation of the simplified mobility expression, which can be easily computed for a given set of parameter values.

Simple colorimetric screening of paraquat residue in vegetables evaluated by localized surface plasmon resonance of gold nanoparticles

The contamination of paraquat in vegetables is widely connected with human health risks, leading to the research interest in developing a paraquat sensing system. This work reports a simple detection method of paraquat based on the electrostatic interaction of paraquat and the negatively charged gold nanoparticles (AuNPs), resulting in the changes of colors from red to blue and the shifting of localized surface plasmon resonance (LSPR) peaks of AuNPs. The limit of detection concentration (C_LOD ) of this system was 100 μM paraquat. Moreover, among eight cationic salts tested, NaCl was selective to enhance the detection sensitivity of the system, resulting in the reduction of C_LOD to 0.10 μM. This system selectively detected paraquat, but not other tested herbicides (ametryn, atrazine, glyphosate, and 2,4-D-dimethyl ammonium). The paraquat-spiking experiment in kale demonstrated the significant recovery rate of paraquat at 96.0-103.0%, and the relative standard deviations were less than 4%. The developed system was efficient for screening contaminated paraquat in vegetables under unwashed and washed conditions. Three out of five unwashed vegetables had a significant level of paraquat as determined by LSPR values. These results suggested the potential application of this system for a simple screening of contaminated paraquat in vegetables. Simple paraquat-screening system was developed based on the negatively charged gold nanoparticles. The limit of paraquat detection of this system was 0.10 μM. This system was potentially used for a simple screening of contaminated paraquat in vegetables.

An overview of therapeutic anticancer drug monitoring based on surface enhanced (resonance) Raman spectroscopy (SE(R)RS)

Therapeutic drug monitoring (TDM) is important for many therapeutic regimens and has particular relevance for anticancer drugs which often have serious effects and whose optimum dosage can vary significantly between different patients. Many of the features of surface enhanced (resonance) Raman spectroscopy (SE(R)RS) suggest it should be very suitable for TDM of anticancer drugs and some initial studies which explore the potential of SE(R)RS for TDM of anticancer drugs have been published. This review brings this work together in an attempt to draw some general observations about key aspects of the approach, including the nature of the substrate used, matrix interference effects and factors governing adsorption of the target molecules onto the enhancing surface. There is now sufficient evidence to suggest that none of these pose real difficulties in the context of TDM. However, some issues, particularly the need to carry out multiplex measurements for TDM of combination therapies, have yet to be addressed.

Protein corona formation and its influence on biomimetic magnetite nanoparticles

Biomimetic magnetite nanoparticles (BMNPs) synthesized in the presence of MamC, a magnetosome-associated protein from Magnetoccus marinus MC-1, have gained interest for biomedical applications because of their unique magnetic properties. However, their behavior in biological systems, like their interaction with proteins, still has to be evaluated prior to their use in clinics. In this study, doxorubicin (DOXO) as a model drug was adsorbed onto BMNPs to form nanoassemblies. These were incubated with human plasma to trigger protein corona (PC) formation. Proteins from the human plasma stably attached to either BMNPs or DOXO-BMNP nanoassemblies. In particular, fibrinogen was detected as the main component in the PC of DOXO-BMNPs that potentially provides advantages, e.g. protecting the particles from phagocytosis, thus prolonging their circulation time. Adsorption of PC to the BMNPs did not alter their magnetic properties but improved their colloidal stability, thus reducing their toxicity in human macrophages. In addition, PC formation enhanced cellular internalization and did not interfere with DOXO activity. Overall, our data indicate that the adsorption of PC onto DOXO-BMNPs in biological environment even increases their efficiency as drug carrier systems.

Insights into colloidal nanoparticle-protein corona interactions for nanomedicine applications

Colloidal nanoparticles (NPs) have attracted significant attention due to their unique physicochemical properties suitable for diagnosing and treating different human diseases. Nevertheless, the successful implementation of NPs in medicine demands a proper understanding of their interactions with the different proteins found in biological fluids. Once introduced into the body, NPs are covered by a protein corona (PC) that determines the biological behavior of the NPs. The formation of the PC can eventually favor the rapid clearance of the NPs from the body before fulfilling the desired objective or lead to increased cytotoxicity. The PC nature varies as a function of the different repulsive and attractive forces that govern the NP-protein interaction and their colloidal stability. This review focuses on the phenomenon of PC formation on NPs from a physicochemical perspective, aiming to provide a general overview of this critical process. Main issues related to NP toxicity and clearance from the body as a result of protein adsorption are covered, including the most promising strategies to control PC formation and, thereby, ensure the successful application of NPs in nanomedicine.

Fabrication of Bovine Serum Albumin@Au Particles for Colorimetric Detection of Glutathione

Abnormal concentrations of glutathione (GSH) are important indicators of many human diseases such as cancers, liver damage, AIDS, and Alzheimer's disease. In this work, a kind of bovine serum albumin (BSA)@Au core-shell particles were fabricated using 110 nm BSA aggregates as a template, onto which gold shells composed of Au nanoparticles (NPs) were grown through a seeded growth approach. The morphology of the Au shells deposited on BSA aggregates was tuned from sparse to dense distribution of Au NPs by increasing the concentration of silver ions contained in the growth solutions. Surface plasmon resonance (SPR) peaks of BSA@Au particles were tunable in the range from 550 to 620 nm, corresponding to evolution in color from red to blue due to the enhanced plasmonic coupling among the Au NPs in the shell. The blue BSA@Au particles were qualified for colorimetric detection of GSH since GSH may act as a swelling agent for BSA@Au particles by breaking the intermolecular disulfide bonds in BSA aggregates. With an increased amount of GSH presented, the color of BSA@Au particles evolved from blue to red attributed to gradual swelling of BSA@Au particles and thus increased the distance among the Au NPs in the shell, which was readily recognized by naked eyes or recorded by ultraviolet-visible (UV-vis) spectroscopy. This colorimetric method exhibited good selectivity and anti-interference capability in the analysis of GSH in real samples. In addition, a solid sensing system for the detection of GSH was designed and fabricated by dispersing BSA@Au particles into an agarose hydrogel.

Corn derivative mesoporous carbon microspheres supported hydrophilic polydopamine for development of new membrane: Water treatment containing bovine serum albumin

A new mixed matrix membrane (MMM) was prepared by incorporating biological mesoporous carbon microspheres (mCMSs) from corn starch polysaccharide-supported hydrophilic polydopamine (PDA), as a mesoporous and large-surface area filler, selective modifier, and pore-forming agent, into polyvinylidene fluoride (PVDF) matrix in presence of polyethylene glycol (PEG) as a hydrophilic agent. The structural parameters of the prepared membranes were characterized via FE-SEM, BET/BJH, XRD, FT-IR, and AFM analyses, sorption experiments, water permeability assessments, porosimetry tests, flux recovery ratio (FRR) evaluations, and contact angle measurements, with the so-called central composite design (CCD) been successfully applied for optimization and investigation of the effects of the operational parameters. The results were then applied to treat double-distilled water containing bovine serum albumin (BSA) utilizing a cross-module set-up. Based on the findings, the content of the mCMS-PDA in the PVDF matrix significantly affected the contact angle, pure water flux (PWF), FRR, and BSA removal. In this respect, the PWF of the PVDF-PEG-mCMS-PDA increased from 10.25 to 27.78 L/m² h with increasing the mCMS-PDA content, with the peak FRR (93.84%) of the PVDF-PEG-mCMS-PDA seen at maximum surface hydrophilicity of the membrane.

Influence of environmental and biological macromolecules on aggregation kinetics of nanoplastics in aquatic systems

Nanoplastics derived from degradation of micro- or macroplastics are emerging contaminants in aquatic environments, where their fate and transport as well as toxicity are affected by aggregation. This study employed time-resolved dynamic light scattering to investigate the aggregation kinetics of polystyrene nanoplastics (PSNPs) in the presence of four macromolecules (sodium alginate (SA), bovine serum albumin (BSA), extracellular polymeric substance (EPS), and Suwannee River humic acid (HA)) in solutions containing monovalent (NaCl) and divalent (CaCl₂) salts at different pH. Our results showed that the macromolecules enhanced PSNP stability in NaCl solutions but destabilized PSNPs in CaCl₂ solutions at pH 6. In NaCl solutions, macromolecules inhibited PSNP aggregation due to steric hindrance originated from macromolecular layer adsorbed on PSNPs. The strongest stabilization effect was observed for BSA having the greatest hydrodynamic adsorption layer thickness of 21.9 nm, followed by HA, EPS, and SA. In CaCl₂ solutions, SA significantly destabilized PSNPs via alginate bridging with Ca²⁺, which enhanced with concentrations of SA and CaCl₂. The destabilization effects of other three macromolecules in CaCl₂ solutions were governed by the interplay among molecular bridging, charge screening, and steric hindrance. An increased pH in NaCl or CaCl₂ solutions containing macromolecules all stabilized PSNPs due to elevated electrostatic repulsion, except that SA destabilized PSNPs in CaCl₂ solutions via enhanced molecular bridging. The stabilization effect of macromolecules may also compete with the destabilization effect under seawater condition. This study suggested that PSNP aggregation in aquatic environments could be strongly affected by macromolecules and solution chemistry.

Relating the composition and interface interactions in the hard corona of gold nanoparticles to the induced response mechanisms in living cells

Understanding the formation of the intracellular protein corona of nanoparticles is essential for a wide range of bio- and nanomedical applications. The innermost layer of the protein corona, the hard corona, directly interacts with the nanoparticle surface, and by shielding the surface, it has a deterministic effect on the intracellular processing of the nanoparticle. Here, we combine a direct qualitative analysis of the hard corona composition of gold nanoparticles with a detailed structural characterization of the molecules in their interaction with the nanoparticle surface and relate both to the effects they have on the ultrastructure of living cells and the processing of the gold nanoparticles. Cells from the cell lines HCT-116 and A549 were incubated with 30 nm citrate-stabilized gold nanoparticles and with their aggregates in different culture media. The combined results of mass spectrometry based proteomics, cryo soft X-ray nanotomography and surface-enhanced Raman scattering experiments together revealed different uptake mechanisms in the two cell lines and distinct levels of induced cellular stress when incubation conditions were varied. The data indicate that the different incubation conditions lead to changes in the nanoparticle processing via different protein-nanoparticle interfacial interactions. Specifically, they suggest that the protein-nanoparticle surface interactions depend mainly on the surface properties of the gold nanoparticles, that is, the ζ-potential and the resulting changes in the hydrophilicity of the nanoparticle surface, and are largely independent of the cell line, the uptake mechanism and intracellular processing, or the extent of the induced cellular stress.

A Systematic comparison of in vitro cell uptake and in vivo biodistribution for three classes of gold nanoparticles with saturated PEG coatings

A great deal of attention has been focused on nanoparticles for cancer therapy, with the promise of tumor-selective delivery. However, despite intense work in the field over many years, the biggest obstacle to this vision remains extremely low delivery efficiency of nanoparticles into tumors. Due to the cost, time, and impact on the animals for in vivo studies, the nanoparticle field predominantly uses cellular uptake assays as a proxy to predict in vivo outcomes. Extensive research has focused on decreasing macrophage uptake in vitro as a proxy to delay nanoparticle accumulation in the mononuclear phagocytic system (MPS), mainly the liver and spleen, and thereby increase tumor accumulation. We have recently reported novel synthetic methods employing small molecule crosslinkers for the controlled assembly of small nanoparticles into larger aggregates and found that these nanoaggregates had remarkably high surface coverage and low cell uptake, even in macrophages. We further found that this extremely low cellular uptake could be recapitulated on solid gold nanoparticles by densely coating their surface with small molecules. Here we report our studies on the biodistribution and clearance of these materials in comparison to more conventional PEGylated gold nanoparticles. It was expected that the remarkably low macrophage uptake in vitro would translate to extended blood circulation time in vivo, but instead we found no correlation between either surface coverage or in vitro macrophage cell uptake and in vivo blood circulation. Gold nanoaggregates accumulate more rapidly and to a higher level in the liver compared to control gold nanoparticles. The lack of correlation between in vitro macrophage uptake and in vivo blood circulation suggests that the field must find other in vitro assays to use as a primary proxy for in vivo outcomes or use direct in vivo experimentation as a primary assay.

Rapid and specific detection of oxidized LDL/β2GPI complexes via facile lateral flow immunoassay

β2-Glycoprotein I (β2GPI) forms indissociable complex with oxidized LDL (oxLDL) into proatherogenic oxLDL/β2GPI complex through a specific ligand known as 7-ketocholesteryl-9-carboxynonanoate (oxLig-1). Recent discoveries have demonstrated the atherogenicity of these complexes in patients of both systemic and non-systemic autoimmune diseases. Hence, serological level of oxLDL/β2GPI complexes may represent one crucial clinical parameter for disease prognosis of atherosclerosis-related diseases. Herein, we established a simple, specific and rapid gold nanoparticle (GNP) based lateral flow immunoassay (LFIA) to quantify oxLDL/β2GPI complexes from test samples. Specificities of hybridoma cell-derived monoclonal antibodies against antigen, optimal conditions for conjugation of antibody with GNP, and sensitivity of oxLDL/β2GPI LFIA in comparison to an ELISA-based detection method were assessed accordingly. The established oxLDL/β2GPI LFIA was capable of detecting oxLDL/β2GPI specifically without interference from autoantibodies and solitary components of oxLDL/β2GPI present in test samples. A significant correlation (R² > 0.8) was also obtained with the oxLDL/β2GPI LFIA when compared to the ELISA-based detection. On the whole, the oxLDL/β2GPI LFIA remains advantageous over the oxLDL/β2GPI ELISA. The unnecessary washing step, short developmental and analytical time support facile and rapid detection of oxLDL/β2GPI as opposed to the laborious ELISA system.

Attaching DNA to Gold Nanoparticles With a Protein Corona

DNA-functionalized gold nanoparticles (AuNPs) have been widely used in directed assembly of materials, biosensors, and drug delivery. This conjugate may encounter proteins in these applications and proteins may affect not only DNA adsorption but also the function of the attached DNA. Bovine serum albumin (BSA) with many cysteine residues can strongly adsorb on AuNPs and this conjugate showed high colloidal stability against salt, acid and base. Similar protection effects were also observed with a few other common proteins including catalase, hemoglobin, glucose oxidase, and horseradish peroxidase. DNA oligonucleotides without a thiol label can hardly displace adsorbed BSA, and BSA cannot displace pre-adsorbed DNA either, indicating a strongly kinetically controlled system. Thiolated DNA can be attached at a low density on the AuNPs with a BSA corona. The BSA corona did not facilitate the hybridization of the conjugated DNA, while a smaller peptide, glutathione allowed faster hybridization. Overall, proteins increase the colloidal stability of AuNPs, and they do not perturb the gold-thiol bond in the DNA conjugate, although a large protein corona may inhibit the hybridization function of DNA.

Nanoscale Surface-Induced Unfolding of Single Fibronectin Is Restricted by Serum Albumin Crowding

Understanding nanoscale protein conformational changes at solid-liquid interfaces is critical for predicting how proteins will impact the performance of biomaterials in vivo. Crowding is an important contributor to conformational stability. Here we apply single-molecule high resolution imaging with photobleaching to directly measure dye-conjugated fibronectin's unfolding in varying conditions of crowding with human serum albumin on aminosilanized glass. Using this approach, we identify serum albumin's crowding mechanism. We find that fibronectin achieves larger degrees of unfolding when not crowded by coadsorbed serum albumin. Serum albumin does not as effectively constrict fibronectin's conformation if it is sequentially, rather than simultaneously, introduced, suggesting that serum albumin's crowding mechanism is dependent on its ability to sterically block fibronectin's unfolding during the process of adsorption. Because fibronectin's conformation is dependent on interfacial macromolecular crowding under in vitro conditions, it is important to consider the role of in vivo crowding on protein activity.

Platinum(II) Drug-Loaded Gold Nanoshells for Chemo-Photothermal Therapy in Colorectal Cancer

In the present study, we utilize a poly[2-(N,N-dimethylamino)ethyl methacrylate]-poly(ε-caprolactone) (PDMA-PCL) micellar template-based gold nanoshell as a nanocarrier of a platinum-based chemotherapeutic drug, dichloro(1,2-diaminocyclohexane)platinum(II) (DACHPt). The gold nanoshells not only function as a drug delivery platform but also provide a remarkable photothermal effect, resulting in synergistically combined chemo-photothermal therapy. With the positively charged outstretched hydrophilic PDMA segments, chloroauric anions are attracted to the PDMA-PCL micellar surface and reduced to gold atoms in situ, forming small seeds that nucleate the subsequent growth of gold nanoshells. The DACHPt-loaded gold nanoshells possess strong absorption in the near-infrared (NIR) region and outstanding photothermal conversion effect; thus, they can promote a temperature increase that is sufficient to ablate tumor cells under NIR laser irradiation at a moderate power density (1 W/cm²). Furthermore, by exploiting the synergistic effects of platinum-based chemotherapy and photothermal therapy, the DACHPt-loaded gold nanoshells exhibited a profound inhibition of tumor growth compared to chemotherapy or photothermal therapy alone. Therefore, the platinum(II)-loaded gold nanoshells that we proposed herein may be a potential alternative for efficient curative therapy for colorectal cancer.

Facile synthesis of SnO2shell followed by microwave treatment for high environmental stability of Ag nanoparticles

This study describes a new method for passivating Ag nanoparticles (AgNPs) with SnO₂ layer and their further treatment by microwave irradiation. The one-step process of SnO₂ layer formation was carried out by adding sodium stannate to the boiling aqueous AgNPs solution, which resulted in the formation of core@shell Ag@SnO₂ nanoparticles. The coating formation was a tunable process, making it possible to obtain an SnO₂ layer thickness in the range from 2 to 13 nm. The morphology, size, zeta-potential, and optical properties of the Ag@SnO₂NPs were studied. The microwave irradiation significantly improved the environmental resistance of Ag@SnO₂NPs, which remained stable in different biological solutions such as NaCl at 150 mM and 0.1 M, Tris-buffered saline buffer at 0.1 M, and phosphate buffer at pH 5.6, 7.0, and 8.0. Ag@SnO₂NPs after microwave irradiation were also stable at biologically relevant pH values, both highly acidic (1.4) and alkaline (13.2). Moreover, AgNPs covered with a 13 nm-thick SnO₂ layer were resistant to cyanide up to 0.1 wt%. The microwave-treated SnO₂ shell can facilitate the introduction of AgNPs in various solutions and extend their potential application in biological environments by protecting the metal nanostructures from dissolution and aggregation.

This study describes a new method for passivating Ag nanoparticles (AgNPs) with SnO₂ layer and their further treatment by microwave irradiation.

Graphene oxide-based nanomaterial interaction with human breast cancer cells

Graphene and graphene-based nanomaterials have great potential for various biomedical applications due to their unique physicochemical properties. However, how graphene-based nanomaterials interact with biological systems has not been thoroughly studied. This study shows that 24, 48, and 72 hr exposure of 2.4 μg/cm² of graphene oxide (GOX) and GOX modified with DAB-AM-16 and PAMAM dendrimers (GOXD and GOXP, respectively) did not exhibit toxicity to MCF-7 cells. However, higher graphene concentrations, such as 24 and 48 μg/cm² , induced low cytotoxic effects. The GOX, GOXD, and GOXP particles have a strong affinity with the cellular membrane. Cells that internalized the nanomaterials presented morphological alterations and modifications in the organization of microfilaments and microtubules compared with control cells. Then, cells were treated with 24 μg/cm² of GOX, GOXD or GOXP for 24 hr and recovered for an additional period of 24 hr in normal medium. Nanoparticles remained in the cytoplasm of some cells, apparently with no effect on cellular morphology, being consistent with the data found in the cell proliferation experiment, which showed that the cells remained alive up to 72 hr.

Enhanced stability of an intrinsically disordered protein against proteolytic cleavage through interactions with silver nanoparticles

Intrinsically disordered proteins (IDPs), being sensitive to proteolytic degradation both in vitro and in vivo, can be stabilized by the interactions with various binding partners. Here, we show for the first time that silver nanoparticles (AgNPs) have the ability to enhance the half-life of an IDP, thereby rendering it stable for a month against proteolytic degradation. The conjugate of the unstructured linker domain of human insulin-like growth factor binding protein-2 (L-hIGFBP2) with 10 nm citrate-capped AgNPs was studied using two-dimensional NMR spectroscopy and other biophysical techniques. Our studies reveal the extent and nature of residue-specific interactions of the IDP with AgNPs. These interactions mask proteolysis-prone sites of the IDP and stabilize it. This study opens new avenues for the design of appropriate nanoparticles targeting IDPs and for storage, stabilization and delivery of IDPs into cells in a stable form.

Protein corona-resistant SERS tags for live cell detection of integrin receptors

Chemical signals are conveyed to cells through ligand-receptor binding, triggering cascades of biochemical reactions and resulting in pivotal cellular functions. These binding events are important in understanding membrane signaling and drug interactions. To probe ligand-receptor binding, surface enhanced Raman scattering (SERS) tags are a promising tool. SERS tags are plasmonic nanostructures functionalized with a protective coating, a Raman reporter molecule, and a biorecognition element. In biological fluids, native proteins have affinity for bare nanoparticles and form a protein corona. SERS tags have a protective shell which eliminates this complication. It is important to analyze ligand-receptor binding with SERS tags in live cells since cell fixatives alter protein structure, leading to spectral changes and data misinterpretation. In this study, we synthesized a novel SERS tag by creating a mixed monolayer of the small cyclic arginine-glycine-aspartic acid-phenylalanine-cysteine (RGDFC) peptide and 4-mercaptobenzonitrile (MBN) on the surface of spherical gold nanoparticles (Au NP). Au-RGDFC-MBN NP showed resistance to PC formation and were successfully detected in both fixed and living human metastatic colon cancer cells.

Influence of macromolecules on aggregation kinetics of diesel soot nanoparticles in aquatic environments

Soot nanoparticles (SNPs) produced from incomplete combustion have strong impacts on aquatic environments as they eventually reach surface water, where their environmental fate and transport are largely controlled by aggregation. This study investigated the aggregation kinetics of SNPs in the presence of macromolecules including fulvic acid (FA), humic acid (HA), alginate polysaccharide, and bovine serum albumin (BSA, protein) under various environmentally relevant solution conditions. Our results showed that increasing salt concentrations induced SNP aggregation by suppressing electrostatic repulsion and that CaCl₂ exhibited stronger effect than NaCl in charge neutralization, which is in agreement with the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. The aggregation rates of SNPs were variously reduced by macromolecules, and such stabilization effect was the greatest by BSA, followed by HA, alginate, and FA. Steric repulsion resulting from macromolecules adsorbed on SNP surfaces was mainly responsible for enhancing SNP stability. Such steric repulsion appeared to be affected by macromolecular structure, as BSA having a more compact globular structure on SNP surfaces imparted long-range steric repulsive forces and retarded the SNP aggregation rate by 10-100 times. In addition, alginate was shown to enhance SNP aggregation by ∼10 times at high CaCl₂ concentrations due to alginate gel formation via calcium bridging. The results may bear strong significance for the fate and transport of SNPs in both natural and controlled environmental systems.

Protein-Nanoparticle Interactions: What Are the Protein-Corona Thickness and Organization?

Protein adsorption on a surface is generally evaluated in terms of the evolution of the proteins' structures and functions. However, when the surface is that of a nanoparticle, the protein corona formed around it possesses a particular supramolecular structure that gives a "biological identity" to the new object. Little is known about the actual shape of the protein corona. Here, the protein corona formed by the adsorption of model proteins (myoglobin and hemoglobin) on silica nanoparticles was studied. Small-angle neutron scattering and oxygenation studies were combined to assess both the structural and functional impacts of the adsorption on proteins. Large differences in the oxygenation properties could be found while no significant global shape changes were seen after adsorption. Moreover, the structural study showed that the adsorbed proteins form an organized yet discontinuous monolayer around the nanoparticles.