Understanding the Chemical Nature of Nanoparticle-Protein Interactions

Fluorescent Labeling of Human Serum Albumin by Thiol-Cyanimide Addition and Its Application in the Fluorescence Quenching Method for Nanoparticle-Protein Interactions

A boron-dipyrromethene (BODIPY)-based fluorescent probe, BDP-CN, was synthesized in this work. It had a fluorescence emission maximum at 512 nm and a high quantum yield (48%). As evidenced by agarose gel electrophoresis and liquid chromatography-mass spectrometry, it could realize the fluorescent labeling of human serum albumin (HSA) through a thiol-cyanimide addition. Interestingly, f-HSA, defined as HSA labeled by BDP-CN, had an even higher quantum yield (77%). In addition, BDP-CN would not affect the secondary structure of HSA. Based on the successful formation of f-HSA, it was further applied to study the interactions with nanoparticles. The fluorescence quenching of f-HSA by dihydrolipoic acid-coated gold nanoclusters (DHLA-AuNCs) obeyed a dynamic mechanism, consistent with the intrinsic fluorescence quenching of HSA by DHLA-AuNCs. The association constant K_a between f-HSA and DHLA-AuNCs at 298 K was 1.5 × 10⁵ M^-1, which was the same order of magnitude as that between HSA and DHLA-AuNCs. Moreover, the interactions of f-HSA with glutathione-coated gold nanoclusters confirmed that the labeled fluorescence could replace the intrinsic fluorescence to monitor the interactions between proteins and nanoparticles. By this method, strong fluorescence ensures better stability and reproducibility, excitation at a longer wavelength reduces the damage to the proteins, and covalent conjugation with cysteine residues eliminates the inner filter effects to a great extent. Therefore, the strategy for the fluorescent labeling of HSA can be expanded to investigate a broad class of nanoparticle-protein interactions and inspire even more fluorescent labeling methods with organic dyes.

Inhibiting mTTR Aggregation/Fibrillation by a Chaperone-like Hydrophobic Amino Acid-Conjugated SPION

Transthyretin (TTR) aggregation via misfolding of a mutant or wild-type protein leads to systemic or partial amyloidosis (ATTR). Here, we utilized variable biophysical assays to characterize two distinct aggregation pathways for mTTR (a synthesized monomer TTR incapable of association into a tetramer) at pH 4.3 and also pH 7.4 with agitation, referred to as mTTR aggregation and fibrillation, respectively. The findings suggest that early-stage conformational changes termed monomer activation here determine the aggregation pathway, resulting in developing either amorphous aggregates or well-organized fibrils. Less packed partially unfolded monomers consisting of more non-regular secondary structures that were rapidly produced via a mildly acidic condition form amorphous aggregates. Meanwhile, more hydrophobic and packed monomers consisting of rearranged β sheets and increased helical content developed well-organized fibrils. Conjugating superparamagnetic iron oxide nanoparticles (SPIONs) with leucine and glutamine (L-SPIONs and G-SPIONs in order) via a trimethoxysilane linker provided the chance to study the effect of hydrophobic/hydrophilic surfaces on mTTR aggregation. The results indicated a powerful inhibitory effect of hydrophobic L-SPIONs on both mTTR aggregation and fibrillation. Monomer depletion was introduced as the governing mechanism for inhibiting mTTR aggregation, while a chaperone-like property of L-SPIONs by maintaining an mTTR native structure and adsorbing oligomers suppressed the progression of further fibril formation.

Rearrangement of protein structures on a gold nanoparticle surface is regulated by ligand adsorption modes

With development of the nanomedicine field and increasing hazards of exposure to nanobiological materials, research on the protein corona is urgently required. In particular, the understanding of the mechanism of structural changes of protein on a nanosurface should be improved. Herein, we focus on exploring the role of ligand adsorption modes (physiosorbed citrates or chemisorbed GSH) in the regulation of conformational rearrangement of three blood proteins (serum albumin, globulin, and fibrinogen) on the surface of gold nanoparticles. Through experimental measurements, protein adsorption features (thermodynamics, kinetics, adsorption orientation, and structural changes) were estimated. Molecular dynamics simulations further indicated that physiosorbed citrates could be gradually peeled off by approaching proteins and that the bare Au surface provided a stronger interface interaction than the chemisorbed GSH layer. Protein structure rearrangements were due to the reduction in protein internal energy, with an increase in H-bond formation involving a decrease in the α-helical content and an increase in the β-sheet content, to offset the high interfacial energy. Rearrangement of protein structures could occur either intramolecularly or intermolecularly. These findings enhanced our understanding of nano-protein interaction in the biological milieu and facilitate biomedical exploration of engineered nanomaterials.

Enhanced lipid accumulation in microalgae through nanoparticle-mediated approach, for biodiesel production: A mini-review

Nanoparticle application in microalgae for enhanced lipid production is an ongoing work that leads towards the contribution in biodiesel production. During this decade, metal nanoparticles are constantly being reported to have numerous applications in diverse fields, because of their unique optical, electrical, and magnetic properties. They can interact with the biomolecules of cells and thereby alters cellular metabolisms, which in turn reflects their ability to regulate some primary or secondary metabolic pathways. Nanoparticles derived from metals like Fe, Cu, and Se are taking part in redox processes and their presence in many enzymes may modulate algal metabolisms. Besides by upregulating or downregulating the expression of several genes, nanoparticle exposure can alter gene expressions in many organisms. In microalgae such as Chlorella vulgaris, C. pyrenoidosa, Scenedesmus obliquus, S. rubescens, Trachydiscus minut u s, Parachlorella kessleri, and Tetraselmis suecica; metal nanoparticle exposure in different environmental conditions have impacts on various physiological or molecular changes, thereby increasing the growth rate, biomass and lipid production. The present mini-review gives an insight into the various advantages and a future outlook on the application of nanoparticles in microalgae for biofuel production. Also, it can be proposed that nanoparticles could be useful in blocking or deactivating the AGPase enzyme (involved in the glucose to starch conversion pathway), binding to its active site, thereby increasing lipid production in microalgae that could be utilized for enhanced biodiesel production.

Detection of Circulating Serum Protein Biomarkers of Non-Muscle Invasive Bladder Cancer after Protein Corona-Silver Nanoparticles Analysis by SWATH-MS

Because cystoscopy is expensive and invasive, a new method of detecting non-invasive muscular bladder cancer (NMIBC) is needed. This study aims to identify potential serum protein markers for NMIBC to improve diagnosis and to find treatment approaches that avoid disease progression to a life-threatening phenotype (muscle-invasive bladder cancer, MIBC). Here, silver nanoparticles (AgNPs, 9.73 ± 1.70 nm) as a scavenging device together with sequential window acquisition of all theoretical mass spectra (SWATH-MS) were used to quantitatively analyze the blood serum protein alterations in two NMIBC subtypes, T1 and Ta, and they were compared to normal samples (HC). NMIBC’s analysis of serum samples identified three major groups of proteins, the relative content of which is different from the HC content: proteins implicated in the complement and coagulation cascade pathways and apolipoproteins. In conclusion, many biomarker proteins were identified that merit further examination to validate their useful significance and utility within the clinical management of NMIBC patients.

Size Dependence Unveiling the Adsorption Interaction of High-Density Lipoprotein Particles with PEGylated Gold Nanoparticles in Biomolecular Corona Formation

Apolipoproteins have been often found to be highly enriched in the serum protein coronas produced on various engineered nanoparticles (NPs), which is also known to greatly influence the behaviors of protein corona NPs in the biological systems. As most of the apolipoproteins in blood are associated with lipoproteins, it suggests the active involvement of lipoproteins in the formation of biomolecular coronas on NPs. However, the interactions of lipoprotein complexes with NPs in the corona formation have been rarely understood. In this study, to obtain insights into the interactions, the formation of biomolecular coronas of high-density lipoproteins (HDLs) on the PEGylated gold NPs (PEG-AuNPs) of various sizes (20-150 nm dia.) was investigated as a model system. The results of this study revealed a noticeable size dependence, which is a drastic increase in the affinity of HDL for larger NPs and thus less-curved NP surfaces. For example, only a few HDLs per NP, which correspond to 5% surface coverage, were found to constitute the hard coronas of HDLs on 20 nm PEG-AuNPs, whereas 73% surface coverage was assessed for larger 150 nm PEG-AuNPs. However, the relative affinities of HDL and apolipoprotein A-1 (APOA1) examined in competition with human serum albumin exhibited the opposite size dependences, which suggests that the adsorption of HDLs is not driven by the constituent protein, APOA1. In fact, the total strength of non-covalent intermolecular interactions between a HDL particle and a NP relies on the physical contact between the two particles, which thus depends on the varying curvatures of spherical NPs in this case. Therefore, it was concluded that it is whole HDL complex that interacts with the spherical PEG-AuNPs in the initial stage of adsorption toward biomolecular coronas, which is unveiled by the distinct size dependence observed in this study.

How Do Proteins Associate with Nanoscale Metal-Organic Framework Surfaces?

It is well known that colloidal nanomaterials, upon exposure to a complex biological medium, acquire biomolecules on their surface to form coronas. Porous nanomaterials present an opportunity to sequester biomolecules and/or control their orientation at the surface. In this report, a metal-organic framework (MOF) shell around gold nanorods was compared to MOF nanocrystals as potential protein sponges to adsorb several common proteins (lysozyme, beta-lactoglobulin-A, and bovine serum albumin) and potentially control their orientation at the surface. Even after correction for surface area, MOF shell/gold nanorod materials adsorbed more protein than the analogous nanoMOFs. For the set of proteins and nanomaterials in this study, all protein-surface interactions were exothermic, as judged by isothermal titration calorimetry. Protein display at the surfaces was determined from limited proteolysis experiments, and it was found that protein orientation was dependent both on the nature of the nanoparticle surface and on the nature of the protein, with lysozyme and beta-lactoglobulin-A showing distinct molecular positioning.

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.

High-Affinity Points of Interaction on Antibody Allow Synthesis of Stable and Highly Functional Antibody-Gold Nanoparticle Conjugates

Many emerging nanobiotechnologies rely on the proper function of proteins immobilized on gold nanoparticles. Often, the surface chemistry of the AuNP is engineered to control the orientation, surface coverage, and structure of the adsorbed protein to maximize conjugate function. Here, we chemically modified antibody to investigate the effect of protein surface chemistries on adsorption to AuNPs. A monoclonal anti-horseradish peroxidase IgG antibody (anti-HRP) was reacted with N-succinimidyl acrylate (NSA) or reduced dithiobissuccinimidyl propionate (DSP) to modify lysine residues. Zeta potential measurements confirmed that both chemical modifications reduced the localized regions of positive charge on the protein surface, while the DSP modification incorporated additional free thiols. Dynamic light scattering confirmed that native and chemically modified antibodies adsorbed onto AuNPs to form bioconjugates; however, adsorption kinetics revealed that the NSA-modified antibody required significantly more time to allow for the formation of a hard corona. Moreover, conjugates formed with the NSA-modified antibody lost antigen-binding function, whereas unmodified and DSP-modified antibodies adsorbed onto AuNPs to form functional conjugates. These results indicate that high-affinity functional groups are required to prevent protein unfolding and loss of function when adsorbed on the AuNP surface. The reduced protein charge and high-affinity thiol groups on the DSP-modified antibody enabled pH-dependent control of protein orientation and the formation of highly active conjugates at solution pHs (<7.5) that are inaccessible with unmodified antibody due to conjugate aggregation. This study establishes parameters for protein modification to facilitate the formation of highly functional and stable protein-AuNP conjugates.

Thermodynamic and kinetic insights into the interactions between functionalized CdTe quantum dots and human serum albumin: A surface plasmon resonance approach

To explore in vivo application of quantum dots (QDs), it is essential to understand the dynamics and energetics of interactions between QDs and proteins. Here, surface plasmon resonance (SPR) and molecular docking were employed to investigate the kinetics and thermodynamics of interactions between human serum albumin (HSA) and CdTe QDs (~3 nm) functionalized with mercaptopropionic acid (MPA) or thioglycolic acid (TGA). Kinetic analysis showed that HSA-QD interactions involved transition-complex formation. Despite the structural similarities between MPA and TGA, the [HSA-CdTe@TGA]^‡ formation by association of free HSA and QDs demanded 70% more energy and higher entropic gain (E_a-TGA^‡= 65.10 and T∆S_a-TGA^‡= 28.62 kJ mol^-1) than the formation of [HSA-CdTe@MPA]^‡ (E_a-MPA^‡ = 38.13 and T∆S_a-MPA^‡ = 0.53kJ mol^-1). While the [HSA-CdTe@MPA]^° dissociation required higher energy and lower entropy loss (E_d-MPA^‡ = 49.96 and T∆S_d-MPA^‡ = - 32.18kJ mol^-1) than the [HSA-CdTe@TGA]^° dissociation (E_d-TGA^‡= 30.78 and T∆S_d-TGA^‡= - 51.12 kJ mol^-1). The stability of [HSA-QDs]^° was independent of the temperature and functionalizing group. However, the enthalpic and entropic components were highly affected by the substitution of MPA (ΔH° = - 11.83 and TΔS° = 32.72 kJ mol^-1) with TGA (ΔH° = 34.31 and TΔS° = 79.73 kJ mol^-1). Furthermore, molecular docking results indicated that the metal site on the QDs contributes to the stabilization of [HSA-QDs]^°. Therefore, differences in QD functionalization and surface coverage densities can alter the HSA-QD interaction, thus their application.

Influence of Poly(ethylene glycol) Molecular Architecture on Particle Assembly and Ex Vivo Particle-Immune Cell Interactions in Human Blood

Poly(ethylene glycol) (PEG) is widely used in particle assembly to impart biocompatibility and stealth-like properties in vivo for diverse biomedical applications. Previous studies have examined the effect of PEG molecular weight and PEG coating density on the biological fate of various particles; however, there are few studies that detail the fundamental role of PEG molecular architecture in particle engineering and bio-nano interactions. Herein, we engineered PEG particles using a mesoporous silica (MS) templating method and investigated how the PEG building block architecture impacted the physicochemical properties (e.g., surface chemistry and mechanical characteristics) of the PEG particles and subsequently modulated particle-immune cell interactions in human blood. Varying the PEG architecture from 3-arm to 4-arm, 6-arm, and 8-arm generated PEG particles with a denser, stiffer structure, with increasing elastic modulus from 1.5 to 14.9 kPa, inducing an increasing level of immune cell association (from 15% for 3-arm to 45% for 8-arm) with monocytes. In contrast, the precursor PEG particles with the template intact (MS@PEG) were stiffer and generally displayed higher levels of immune cell association but showed the opposite trend-immune cell association decreased with increasing PEG arm numbers. Proteomics analysis demonstrated that the biomolecular corona that formed on the PEG particles minimally influenced particle-immune cell interactions, whereas the MS@PEG particle-cell interactions correlated with the composition of the corona that was abundant in histidine-rich glycoproteins. Our work highlights the role of PEG architecture in the design of stealth PEG-based particles, thus providing a link between the synthetic nature of particles and their biological behavior in blood.

Protein nanoparticles in drug delivery: animal protein, plant proteins and protein cages, albumin nanoparticles

In this article, we will describe the properties of albumin and its biological functions, types of sources that can be used to produce albumin nanoparticles, methods of producing albumin nanoparticles, its therapeutic applications and the importance of albumin nanoparticles in the production of pharmaceutical formulations. In view of the increasing use of Abraxane and its approval for use in the treatment of several types of cancer and during the final stages of clinical trials for other cancers, to evaluate it and compare its effectiveness with conventional non formulations of chemotherapy Paclitaxel is paid. In this article, we will examine the role and importance of animal proteins in Nano medicine and the various benefits of these biomolecules for the preparation of drug delivery carriers and the characteristics of plant protein Nano carriers and protein Nano cages and their potentials in diagnosis and treatment. Finally, the advantages and disadvantages of protein nanoparticles are mentioned, as well as the methods of production of albumin nanoparticles, its therapeutic applications and the importance of albumin nanoparticles in the production of pharmaceutical formulations.

Biomolecular interactions of ultrasmall metallic nanoparticles and nanoclusters

The use of nanoparticles (NPs) in biomedicine has made a gradual transition from proof-of-concept to clinical applications, with several NP types meeting regulatory approval or undergoing clinical trials. A new type of metallic nanostructures called ultrasmall nanoparticles (usNPs) and nanoclusters (NCs), while retaining essential properties of the larger (classical) NPs, have features common to bioactive proteins. This combination expands the potential use of usNPs and NCs to areas of diagnosis and therapy traditionally reserved for small-molecule medicine. Their distinctive physicochemical properties can lead to unique in vivo behaviors, including improved renal clearance and tumor distribution. Both the beneficial and potentially deleterious outcomes (cytotoxicity, inflammation) can, in principle, be controlled through a judicious choice of the nanocore shape and size, as well as the chemical ligands attached to the surface. At present, the ability to control the behavior of usNPs is limited, partly because advances are still needed in nanoengineering and chemical synthesis to manufacture and characterize ultrasmall nanostructures and partly because our understanding of their interactions in biological environments is incomplete. This review addresses the second limitation. We review experimental and computational methods currently available to understand molecular mechanisms, with particular attention to usNP-protein complexation, and highlight areas where further progress is needed. We discuss approaches that we find most promising to provide relevant molecular-level insight for designing usNPs with specific behaviors and pave the way to translational applications.

Phagocytosis of polymeric nanoparticles aided activation of macrophages to increase atherosclerotic plaques in ApoE-/- mice

The unique physiochemical properties of nanomaterials have been widely used in drug delivery systems and diagnostic contrast agents. The safety issues of biomaterials with exceptional biocompatibility and hemo-compatibility have also received extensive attention at the nanoscale, especially in cardiovascular disease. Therefore, we conducted a study of the effects of poly (lactic-co-glycolic acid) nanoparticles (PLGA NPs) on the development of aortic atherosclerotic plaques in ApoE^−/− mice. The particle size of PLGA NPs was 92.69 ± 3.1 nm and the zeta potential were − 31.6 ± 2.8 mV, with good blood compatibility. ApoE^−/− mice were continuously injected with PLGA NPs intravenously for 4 and 12 weeks. Examination of oil red O stained aortic sinuses confirmed that the accumulation of PLGA NPs caused a significantly higher extension of atherosclerotic plaques and increasing the expression of associated inflammatory factors, such as TNF-α and IL-6. The combined exposure of ox-LDL and PLGA NPs accelerated the conversion of macrophages to foam cells. Our results highlight further understanding the interaction between PLGA NPs and the atherosclerotic plaques, which we should consider in future nanomaterial design and pay more attention to the process of using nano-medicines on cardiovascular diseases.

Current Strategies in Assessment of Nanotoxicity: Alternatives to In Vivo Animal Testing

Millions of experimental animals are widely used in the assessment of toxicological or biological effects of manufactured nanomaterials in medical technology. However, the animal consciousness has increased and become an issue for debate in recent years. Currently, the principle of the 3Rs (i.e., reduction, refinement, and replacement) is applied to ensure the more ethical application of humane animal research. In order to avoid unethical procedures, the strategy of alternatives to animal testing has been employed to overcome the drawbacks of animal experiments. This article provides current alternative strategies to replace or reduce the use of experimental animals in the assessment of nanotoxicity. The currently available alternative methods include in vitro and in silico approaches, which can be used as cost-effective approaches to meet the principle of the 3Rs. These methods are regarded as non-animal approaches and have been implemented in many countries for scientific purposes. The in vitro experiments related to nanotoxicity assays involve cell culture testing and tissue engineering, while the in silico methods refer to prediction using molecular docking, molecular dynamics simulations, and quantitative structure-activity relationship (QSAR) modeling. The commonly used novel cell-based methods and computational approaches have the potential to help minimize the use of experimental animals for nanomaterial toxicity assessments.

An environmental ecocorona influences the formation and evolution of the biological corona on the surface of single-walled carbon nanotubes

Nanomaterials (NMs) taken up from the environment carry a complex ecocorona consisting of dissolved organic matter. An ecocorona is assumed to influence the interactions between NMs and endogenous biomolecules and consequently affects the formation of a biological corona (biocorona) and the biological fate of the NMs. This study shows that biomolecules in fish plasma attach immediately (within <5 min) to the surface of SWCNTs and the evolution of the biocorona is a size dependent phenomenon. Quantitative proteomics data revealed that the nanotube size also influences the plasma protein composition on the surface of SWCNTs. The presence of a pre-attached ecocorona on the surface of SWCNTs eliminated the influence of nanotube size on the formation and evolution of the biocorona. Over time, endogenous biomolecules from the plasma partially replaced the pre-attached ecocorona as measured using a fluorescently labelled ecocorona. The presence of an ecocorona offers a unique surface composition to each nanotube. This suggests that understanding the biological fate of NMs taken up from the environment by organisms to support the environmental risk assessment of NMs is a challenging task because each NM may have a unique surface composition in the body of an organism.

Dendrimers based cancer nanotheranostics: An overview

Cancer is a known deadliest disease that requires a judicious diagnostic, targeting, and treatment strategy for an early prognosis and selective therapy. The major pitfalls of the conventional approach are non-specificity in targeting, failure to precisely monitor therapy outcome, and cancer progression leading to malignancies. The unique physicochemical properties offered by nanotechnology derived nanocarriers have the potential to radically change the landscape of cancer diagnosis and therapeutic management. An integrative approach of utilizing both diagnostic and therapeutic functionality using a nanocarrier is termed as nanotheranostic. The nanotheranostics platform is designed in such a way that overcomes various biological barriers, efficiently targets the payload to the desired locus, and simultaneously supports planning, monitoring, and verification of treatment delivery to demonstrate an enhanced therapeutic efficacy. Thus, a nanotheranostic platform could potentially assist in drug targeting, image-guided focal therapy, drug release and distribution monitoring, predictionof treatment response, and patient stratification. A class of highly branched nanocarriers known as dendrimers is recognized as an advanced nanotheranostic platform that has the potential to revolutionize the oncology arena by its unique and exciting features. A dendrimer is a well-defined three-dimensional globular chemical architecture with a high level of monodispersity, amenability of precise size control, and surface functionalization. All the dendrimer properties exhibit a reproducible pharmacokinetic behavior that could ensure the desired biodistribution and efficacy. Dendrimers are thus being exploited as a nanotheranostic platform embodying a diverse class of therapeutic, imaging, and targeting moieties for cancer diagnosis and treatment.

Thermodynamic Implications and Time Evolution of the Interactions of Near-Infrared PbS Quantum Dots with Human Serum Albumin

Near-infrared (NIR)-emitting PbS quantum dots (QDs) are endowed with good stability, high quantum yield, and long lifetime in the body, so they are promising agents in biological imaging. They quickly form the so-called "protein corona" through nonspecific adsorption with proteins in biological fluids once upon exposure to the biological system. Here, PbS QDs and human serum albumin (HSA) were selected as the model system. Fluorescence quenching spectroscopic studies indicated a static quenching process caused by the addition of PbS QDs, which was corroborated by the UV-vis absorption spectroscopy and fluorescence lifetime. Thermodynamic parameters were obtained by the fluorescence quenching method. The enthalpy change and entropy change were well correlated with the "enthalpy-entropy compensation" (EEC) equation summarized in this work. The slope (α = 1.08) and the intercept (TΔS ₀ = 34.44 kJ mol^-1) indicated that the interaction resembled a protein-protein association. The both negative signs of enthalpy change and entropy change were elucidated by a proposed "two-step association-interaction" (TSAI) model. Agarose gel electrophoresis (AGE) and dynamic light scattering (DLS) showed that the binding ratio was roughly 2:1 (HSA/QDs), resembling sandwich-like structures. Furthermore, the secondary structure of HSA depended on the concentration of added QDs and the incubation time. The results preliminarily uncovered the physicochemical properties of QDs in the presence of proteins and elucidated the role of time evolution. These will inspire us to make the fluorescent QDs more biocompatible and use them in a proper way.

Can nanoparticles and nano‒protein interactions bring a bright future for insulin delivery?

Insulin therapy plays an essential role in the treatment of diabetes mellitus. However, frequent injections required to effectively control the glycemic levels lead to substantial inconvenience and low patient compliance. In order to improve insulin delivery, many efforts have been made, such as developing the nanoparticles (NPs)-based release systems and oral insulin. Although some improvements have been achieved, the ultimate results are still unsatisfying and none of insulin-loaded NPs systems have been approved for clinical use so far. Recently, nano‒protein interactions and protein corona formation have drawn much attention due to their negative influence on the in vivo fate of NPs systems. As the other side of a coin, such interactions can also be used for constructing advanced drug delivery systems. Herein, we aim to provide an insight into the advance and flaws of various NPs-based insulin delivery systems. Particularly, an interesting discussion on nano‒protein interactions and its potentials for developing novel insulin delivery systems is initiated.

•

Insulin therapy plays essential roles in treating diabetes.

•

Optimizing insulin delivery enhances insulin therapy.

•

Nanoparticles are promising systems for delivery of insulin.

•

Nano-protein interactions influence the delivery of nanoparticles.

•

Nano-protein interactions can be used for advanced delivery of insulin.

Effects of Surface Protein Adsorption on the Distribution and Retention of Intratumorally Administered Gold Nanoparticles

The heterogeneous distribution of delivery or treatment modalities within the tumor mass is a crucial limiting factor for a vast range of theranostic applications. Understanding the interactions between a nanomaterial and the tumor microenvironment will help to overcome challenges associated with tumor heterogeneity, as well as the clinical translation of nanotheranostic materials. This study aims to evaluate the influence of protein surface adsorption on gold nanoparticle (GNP) biodistribution using high-resolution computed tomography (CT) preclinical imaging in C57BL/6 mice harboring Lewis lung carcinoma (LLC) tumors. LLC provides a valuable model for study due to its highly heterogenous nature, which makes drug delivery to the tumor challenging. By controlling the adsorption of proteins on the GNP surface, we hypothesize that we can influence the intratumoral distribution pattern and particle retention. We performed an in vitro study to evaluate the uptake of GNPs by LLC cells and an in vivo study to assess and quantify the GNP biodistribution by injecting concentrated GNPs citrate-stabilized or passivated with bovine serum albumin (BSA) intratumorally into LLC solid tumors. Quantitative CT and inductively coupled plasma optical emission spectrometry (ICP-OES) results both confirm the presence of particles in the tumor 9 days post-injection (n = 8 mice/group). A significant difference is highlighted between citrate-GNP and BSA-GNP groups (** p < 0.005, Tukey's multiple comparisons test), confirming that the protein corona of GNPs modifies intratumoral distribution and retention of the particles. In conclusion, our investigations show that the surface passivation of GNPs influences the mechanism of cellular uptake and intratumoral distribution in vivo, highlighting the spatial heterogeneity of the solid tumor.

The combined impact of protein corona-free property of starch coated poly (methyl methacrylate) nanoparticles: Amylose content and surface charge

The protein corona on nano drug carriers is an important well-known biological issue that often induce biological incompatibility and screens the targeting molecules on the surfaces of carriers, therefore, the design of NPs with good protein corona-free property is highly desired and challenged. The natural polysaccharide has been demonstrated as one types of stealth materials after the functional group modification process, but the types and structures of their chains has never been considered. Here, we have designed five types of core-shell starch-coated poly (methyl methacrylate) nanoparticles and we found the starch coated NPs with low amylose content (<15%) could exhibit the excellent protein corona-free property without any modification and the starch with high amylose content coated NPs can also exhibit protein corona-free property after etherifying the surface of NPs to positive surface charge. Therefore, the combined impact of both low amylose content and positive surface charges by etherification modification of the starch can provide the excellent protein corona-free property for starch coated polymer NPs, that is very promising for highly efficient nano drug carries and marine coatings.

Solid Lipid Nanoparticles for Drug Delivery: Pharmacological and Biopharmaceutical Aspects

In the golden age of pharmaceutical nanocarriers, we are witnessing a maturation stage of the original concepts and ideas. There is no doubt that nanoformulations are extremely valuable tools for drug delivery applications; the current challenge is how to optimize them to ensure that they are safe, effective and scalable, so that they can be manufactured at an industrial level and advance to clinical use. In this context, lipid nanoparticles have gained ground, since they are generally regarded as non-toxic, biocompatible and easy-to-produce formulations. Pharmaceutical applications of lipid nanocarriers are a burgeoning field for the transport and delivery of a diversity of therapeutic agents, from biotechnological products to small drug molecules. This review starts with a brief overview of the characteristics of solid lipid nanoparticles and discusses the relevancy of performing systematic preformulation studies. The main applications, as well as the advantages that this type of nanovehicles offers in certain therapeutic scenarios are discussed. Next, pharmacokinetic aspects are described, such as routes of administration, absorption after oral administration, distribution in the organism (including brain penetration) and elimination processes. Safety and toxicity issues are also addressed. Our work presents an original point of view, addressing the biopharmaceutical aspects of these nanovehicles by means of descriptive statistics of the state-of-the-art of solid lipid nanoparticles research. All the presented results, trends, graphs and discussions are based in a systematic (and reproducible) bibliographic search that considered only original papers in the subject, covering a 7 years range (2013-today), a period that accounts for more than 60% of the total number of publications in the topic in the main bibliographic databases and search engines. Focus was placed on the therapeutic fields of application, absorption and distribution processes and current efforts for the translation into the clinical practice of lipid-based nanoparticles. For this, the currently active clinical trials on lipid nanoparticles were reviewed, with a brief discussion on what achievements or milestones are still to be reached, as a way of understanding the reasons for the scarce number of solid lipid nanoparticles undergoing clinical trials.

Navigating the Biological-Material Interface with the Guide of Chemical Biology

Research at the biological-material interface often has translation in mind, with applications in medical implants, drug delivery, and regenerative medicine. While the clinical impact of this research is undeniable, a clearer picture of the in vivo behavior of materials is needed to address longstanding limitations in performance and function. Advances in chemical biology and biotechnology have propelled our understanding of how small molecules and biologics behave in living systems. Adapting these techniques to the study of synthetic materials, enabled by modern polymer chemistry, will bring molecular resolution to biological-material interactions and guide the development of next-generation biomaterials for therapeutic and diagnostic applications.

Impact of Protein Corona on Noncovalent Molecule-Gold Nanoparticle-Based Sensing

Gold nanoparticle (AuNP)-based sensors have been extensively applied for sensing or imaging. It is known that a protein shell named protein corona (PC) formed around the nanomaterials could not only block the desired function of nanomaterials but also affect their behavior, which is a hot and important issue needing consideration. Therefore, we hypothesize that the formation of PC around AuNPs could inevitably affect the AuNP-based target assay. In this work, the effects of PC on the detection results in sensors based on AuNPs were studied. Three types of noncovalent molecule-AuNP sensors including AuNP-dichlorofluorescein, AuNP-aptamer, and AuNP-antibody-DNA were constructed, and several typical proteins (bovine serum albumin, fibrinogen, hemoglobin, and β-lactoglobulin), milk, and fetal bovine serum were selected as models for the formation of PCs. This study shows that the PC could cause the loss of detection signals (up to 80%) and result in positive deviation of the measuring value compared with the true value. Moreover, the loss of detection signals could also increase the limits of detection (almost 10 times), decreasing the sensitivity of the three types of sensors, as proposed in this work compared to that without PC. Moreover, the polyethylene glycol backfilling strategy could not resolve the negative effects of PC on noncovalent molecule-AuNP sensors. The impacts of PC on detection results from noncovalent molecule-AuNP sensors would cause misdiagnosis or wasted production, which needs careful reconsideration of the AuNP-based detection in application fields like clinic diagnosis, food safety control, and so forth.

Formation of a Highly Stable and Nontoxic Protein Corona upon Interaction of Human α-1-Acid Glycoprotein (AGP) with Citrate-Stabilized Silver Nanoparticles

Given the importance of protein corona in determining cellular responses to nanoparticles, numerous studies have been devoted to finding stable, biocompatible, and nontoxic protein corona. In this work, the interaction between human α-1-acid glycoprotein (AGP) and citrate-stabilized silver (Ag-CIT) nanoparticles of about 10 nm was methodically studied using molecular docking simulation approach and various experimental techniques. It could be shown that a stable Ag-CIT/AGP bioconjugate was formed with a high binding constant of 10⁹ M^-1, several orders of magnitude larger than that of other highly abundant serum proteins. Formation of AGP corona was accompanied by conserving the native conformation of the protein and further associated with a considerable decrease in the cytotoxicity of the silver nanoparticles.

Protein-Nanoparticle Interaction: Corona Formation and Conformational Changes in Proteins on Nanoparticles

Nanoparticles (NPs) are highly potent tools for the diagnosis of diseases and specific delivery of therapeutic agents. Their development and application are scientifically and industrially important. The engineering of NPs and the modulation of their in vivo behavior have been extensively studied, and significant achievements have been made in the past decades. However, in vivo applications of NPs are often limited by several difficulties, including inflammatory responses and cellular toxicity, unexpected distribution and clearance from the body, and insufficient delivery to a specific target. These unfavorable phenomena may largely be related to the in vivo protein-NP interaction, termed "protein corona." The layer of adsorbed proteins on the surface of NPs affects the biological behavior of NPs and changes their functionality, occasionally resulting in loss-of-function or gain-of-function. The formation of a protein corona is an intricate process involving complex kinetics and dynamics between the two interacting entities. Structural changes in corona proteins have been reported in many cases after their adsorption on the surfaces of NPs that strongly influence the functions of NPs. Thus, understanding of the conformational changes and unfolding process of proteins is very important to accelerate the biomedical applications of NPs. Here, we describe several protein corona characteristics and specifically focus on the conformational fluctuations in corona proteins induced by NPs.

Optimizing Quantum Dot Probe Size for Single-Receptor Imaging

Quantum dots (QDs) are nanocrystals with bright fluorescence and long-term photostability, attributes particularly beneficial for single-molecule imaging and molecular counting in the life sciences. The size of a QD nanocrystal determines its physicochemical and photophysical properties, both of which dictate the success of imaging applications. Larger nanocrystals typically have better optical properties, with higher brightness, red-shifted emission, reduced blinking, and greater stability. However, larger nanocrystals introduce molecular-labeling biases due to steric hindrance and nonspecific binding. Here, we systematically analyze the impact of nanocrystal size on receptor labeling in live and fixed cells. We designed three (core)shell QDs with red emission (600-700 nm) and crystalline sizes of 3.2, 5.5, and 8.3 nm. After coating with the same multidentate polymer, hydrodynamic sizes were 9.2 nm (QD9.2), 13.3 nm (QD13.3), and 17.4 nm (QD17.4), respectively. The QDs were conjugated to streptavidin and applied as probes for biotinylated neurotransmitter receptors. QD9.2 exhibited the highest labeling specificity for receptors in the narrow synaptic cleft (∼20-30 nm) in living neurons. However, for dense receptor labeling for molecular counting in live and fixed HeLa cells, QD13.3 yielded the highest counts. Nonspecific binding rose sharply for hydrodynamic sizes larger than 13.3 nm, with QD17.4 exhibiting particularly diminished specificity. Our comparisons further highlight needs to continue engineering the smallest QDs to increase single-molecule intensity, suppress blinking frequency, and inhibit nonspecific labeling in fixed and permeabilized cells. These results lay a foundation for designing QD probes with further reduced sizes to achieve unbiased labeling for quantitative and single-molecule imaging.

In Situ Analysis of Weakly Bound Proteins Reveals Molecular Basis of Soft Corona Formation

Few experimental techniques allow the analysis of the protein corona in situ. As a result, little is known on the effects of nanoparticles on weakly bound proteins that form the soft corona. Despite its biological importance, our understanding of the molecular bases driving its formation is limited. Here, we show that hemoglobin can form either a hard or a soft corona on silica nanoparticles depending on the pH conditions. Using cryoTEM and synchrotron-radiation circular dichroism, we show that nanoparticles alter the structure and the stability of weakly bound proteins in situ. Molecular dynamics simulation identified the structural elements driving protein-nanoparticle interaction. Based on thermodynamic analysis, we show that nanoparticles stabilize partially unfolded protein conformations by enthalpy-driven molecular interactions. We suggest that nanoparticles alter weakly bound proteins by shifting the equilibrium toward the unfolded states at physiological temperature. We show that the classical approach based on nanoparticle separation from the biological medium fails to detect destabilization of weakly bound proteins, and therefore cannot be used to fully predict the biological effects of nanomaterials in situ.

Protein electrostatics: From computational and structural analysis to discovery of functional fingerprints and biotechnological design

Computationally driven engineering of proteins aims to allow them to withstand an extended range of conditions and to mediate modified or novel functions. Therefore, it is crucial to the biotechnological industry, to biomedicine and to afford new challenges in environmental sciences, such as biocatalysis for green chemistry and bioremediation. In order to achieve these goals, it is important to clarify molecular mechanisms underlying proteins stability and modulating their interactions. So far, much attention has been given to hydrophobic and polar packing interactions and stability of the protein core. In contrast, the role of electrostatics and, in particular, of surface interactions has received less attention. However, electrostatics plays a pivotal role along the whole life cycle of a protein, since early folding steps to maturation, and it is involved in the regulation of protein localization and interactions with other cellular or artificial molecules. Short- and long-range electrostatic interactions, together with other forces, provide essential guidance cues in molecular and macromolecular assembly. We report here on methods for computing protein electrostatics and for individual or comparative analysis able to sort proteins by electrostatic similarity. Then, we provide examples of electrostatic analysis and fingerprints in natural protein evolution and in biotechnological design, in fields as diverse as biocatalysis, antibody and nanobody engineering, drug design and delivery, molecular virology, nanotechnology and regenerative medicine.

Cytotoxic or Not? Disclosing the Toxic Nature of Carbonaceous Nanomaterials through Nano-Bio Interactions

The cytotoxic influence of two different carbonaceous nanomaterials on human mesenchymal stem cells (MSCs) cultured in vitro was compared in the short (1-3 days) and long term (up to 60 days). Amorphous carbon and single-walled carbon nanotubes were chosen and evaluated due to their contrasting physicochemical properties. Both materials, though supposed similarly low-toxic in basic short-term cytotoxicity assays, demonstrated dramatically different properties in the long-term study. The surface chemistry and biomolecule-adsorption capacity turned out to be crucial factors influencing cytotoxicity. We proved that amorphous carbon is able to weakly bind a low-affinity protein coat (so-called soft corona), while carbon nanotubes behaved oppositely. Obtained results from zeta-potential and adsorption measurements for both nanomaterials confirmed that a hard protein corona was present on the single-walled carbon-nanotube surface that aggravated their cytotoxic influence. The long-term exposure of the mesenchymal stem cells to carbon nanotubes, coated by the strongly bound proteins, showed a significant decrease in cell-growth rate, followed by cell senescence and death. These results are of great importance in the light of increasing nanomaterial applications in biomedicine and cell-based therapies. Our better understanding of the puzzling cytotoxicity of carbonaceous nanomaterials, reflecting their surface chemistry and interactions, is helpful in adjusting their properties when tailored for specific applications.

Targeted drug delivery therapies inspired by natural taxes

A taxis is the movement responding to a stimulus of an organism. This behavior helps organisms to migrate, to find food or to avoid dangers. By mimicking and using natural taxes, many bio-inspired and bio-hybrid drug delivery systems have been synthesized. Under the guidance of physical and chemical stimuli, drug-loaded carriers are led to a target, for example tumors, then locally release the drug, inducing a therapeutic effect without influencing other parts of the body. On the other hand, for moving targets, for example metastasis cancer cells or bacteria, taking advantage of their taxes behavior is a solution to capture and to eliminate them. For instance, several traps and ecological niches have been fabricated to attract cancer cells by releasing chemokines. Cancer cells are then eliminated by drug loaded inside the trap, by radiotherapy focusing on the trap location or by simply removing the trap. Further research is needed to deeply understand the taxis behavior of organisms, which is essential to ameliorate the performance of taxes-inspired drug delivery application.

Recent advances in the analysis of nanoparticle-protein coronas

In spite of radical advances in nanobiotechnology, the clinical translation of nanoparticle (NP)-based agents is still a major challenge due to various physiological factors that influence their interactions with biological systems. Recent decade witnessed meticulous investigation on protein corona (PC) that is the first surrounds NPs once administered into the body. Formation of PC around NP surface exhibits resilient effects on their circulation, distribution, therapeutic activity, toxicity and other factors. Although enormous literature is available on the role of PC in altering pharmacokinetics and pharmacodynamics of NPs, understanding on its analytical characterization methods still remains shallow. Therefore, the current review summarizes the impact of PC on biological fate of NPs and stressing on analytical methods employed for studying the NP-PC.

Protein Binding Affinity of Polymeric Nanoparticles as a Direct Indicator of Their Pharmacokinetics

Polymeric nanoparticles (NPs) are an important category of drug delivery systems, and their in vivo fate is closely associated with delivery efficacy. Analysis of the protein corona on the surface of NPs to understand the in vivo fate of different NPs has been shown to be reliable but complicated and time-consuming. In this work, we establish a simple approach for predicting the in vivo fate of polymeric NPs. We prepared a series of poly(ethylene glycol)-block-poly(d,l-lactide) (PEG-b-PLA) NPs with different protein binding behaviors by adjusting their PEG densities, which were determined by analyzing the serum protein adsorption. We further determined the protein binding affinity, denoted as the equilibrium association constant (K_A), to correlate with in vivo fate of NPs. The in vivo fate, including blood clearance and Kupffer cell uptake, was studied, and the maximum concentration (C_max), the area under the plasma concentration-time curve (AUC), and the mean residence time (MRT) were negatively linearly dependent, while Kupffer cell uptake was positively linearly dependent on K_A. Subsequently, we verified the reliability of the approach for in vivo fate prediction using poly(methoxyethyl ethylene phosphate)-block-poly(d,l-lactide) (PEEP-b-PLA) and poly(vinylpyrrolidone)-block-poly(d,l-lactide) (PVP-b-PLA) NPs, and the linear relationship between the K_A value and their PK parameters further suggests that the protein binding affinity of polymeric NPs can be a direct indicator of their pharmacokinetics.

Amphoteric natural starch-coated polymer nanoparticles with excellent protein corona-free and targeting properties

The protein corona on nano drug carriers is an important well-known biological issue that often induces biological incompatibility and screens the targeting molecules on the surfaces of carriers, thus causing a loss of targeting specificity. Although polyethylene glycol (PEG) and zwitterionic polymers have been widely used as anti-fouling materials, there still remain critical challenges for their use as protein-corona agents for drug delivery and targeting. Here, we have designed novel amphoteric natural starch-stabilized core-shell colloidal nanoparticles with more efficient protein corona-free properties, under long term circulation, at different protein concentrations and in different protein charge environments, compared to typical anti-fouling materials such as PEG and zwitterionic polymers. More importantly, the starch-coated polymer nanoparticles can be further functionalized by antibodies to achieve additional excellent targeting and cell internalization capabilities for their use in photodynamic therapy. Our findings demonstrate a novel protein-free or anti-fouling natural material that is very promising for use as highly efficient nano drug carriers and marine coatings.

Recent Developments in the Design of Non-Biofouling Coatings for Nanoparticles and Surfaces

Biofouling is a major issue in the field of nanomedicine and consists of the spontaneous and unwanted adsorption of biomolecules on engineered surfaces. In a biological context and referring to nanoparticles (NPs) acting as nanomedicines, the adsorption of biomolecules found in blood (mostly proteins) is known as protein corona. On the one hand, the protein corona, as it covers the NPs' surface, can be considered the biological identity of engineered NPs, because the corona is what cells will "see" instead of the underlying NPs. As such, the protein corona will influence the fate, integrity, and performance of NPs in vivo. On the other hand, the physicochemical properties of the engineered NPs, such as their size, shape, charge, or hydrophobicity, will influence the identity of the proteins attracted to their surface. In this context, the design of coatings for NPs and surfaces that avoid biofouling is an active field of research. The gold standard in the field is the use of polyethylene glycol (PEG) molecules, although zwitterions have also proved to be efficient in preventing protein adhesion and fluorinated molecules are emerging as coatings with interesting properties. Hence, in this review, we will focus on recent examples of anti-biofouling coatings in three main areas, that is, PEGylated, zwitterionic, and fluorinated coatings.

Spherical Nucleic Acids with Tailored and Active Protein Coronae

Spherical nucleic acids (SNAs) are nanomaterials typically consisting of a nanoparticle core and a functional, dense, and highly oriented oligonucleotide shell with unusual biological properties that make them appealing for many applications, including sequence-specific gene silencing, mRNA quantification, and immunostimulation. When placed in biological fluids, SNAs readily interact with serum proteins, leading to the formation of ill-defined protein coronae on the surface, which can influence the targeting capabilities of the conjugate. In this work, SNAs were designed and synthesized with functional proteins, such as antibodies and serum albumin, deliberately adsorbed onto their surfaces. These particles exhibit increased resistance to protease degradation compared with native SNAs but still remain functional, as they can engage in hybridization with complementary oligonucleotides. SNAs with adsorbed targeting antibodies exhibit improved cellular selectivity within mixed cell populations. Similarly, SNAs coated with the dysopsonizing protein serum albumin show reduced macrophage uptake, providing a strategy for tailoring selective SNA delivery. Importantly, the protein coronae remain stable on the SNAs in human serum, exhibiting a less than 45% loss of protein through exchange after 12 h at 37 °C. Taken together, these results show that protein-SNA complexes and the method used to prepare them provide a new avenue for enhancing SNA stability, targeting, and biodistribution.

Recent Patents Concerning the use of Nanotechnology-based Delivery Systems as Skin Penetration Enhancers

Nanotechnology-based delivery systems have been considered a promising approach for topical application, considering their characteristics of penetration into/across the skin. The present review aimed to evaluate the recent international scenario of patents concerning the use of nanotechnology- based delivery systems as skin penetration enhancers. A survey of recent patent documents was conducted by using the Espacenet patent database including the terms "skin" in the title and "promot* or enhanc* and penetrat* or absorp* or permeat*" and "nano*" with the truncation symbol (*) in the abstract of documents. A total of 110 patents were published from 2008 to 2018, with 94 technologies being considered. The results demonstrated an increase in innovations concerning nanotechnologybased delivery systems as skin penetration enhancers in recent years. Most patent applicants are from China (60.6%) and Korea (21.3%), and companies (68%) were the most prominent owners. The majority of patent applications (76%) were intended for cosmetic purposes; the types of products and nanostructures were also investigated. Overall results demonstrated the increased interest around the world in patenting products involving skin permeation promotion and nanotechnology for pharmaceutical and, mainly, for cosmetics purposes.