Further study on particle size, stability, and complexation of silver nanoparticles under the composite effect of bovine serum protein and humic acid

Silver nanoparticles (AgNPs) are widely used due to their unique antibacterial properties and excellent photoelectric properties. Wastewater treatment plants form a pool of AgNPs due to the social cycle of wastewater. During biological treatment processes, the particle size and stability of AgNPs change. We studied the particle size changes and stability of silver nanoparticles in the presence of bovine serum albumin (BSA) and humic acid (HA). The experimental results indicated that silver nanoparticles can complex with the functional groups in BSA. For AgNP-BSA composites, as the BSA concentration increases, the size of the silver nanoparticles first decreases and then increases. AgNPs can combine with the amide, amino, and carboxyl groups in HA. As the concentration of HA increases, the particle size and large particle size distribution of AgNPs increase. This increasing trend is more obvious when the HA concentration is lower than 20 mg L-1. When HA and BSA exist at the same time, HA will occupy the adsorption sites of BSA on the surface of AgNPs, and the AgNP-HA complex will dominate the system. This study aims to provide key operational control strategies for the process operation of wastewater treatment plants containing AgNPs and theoretical support for promoting water environment improvement and economic development such as tourism.

Albumin Retains Its Transport Function after Interaction with Cerium Dioxide Nanoparticles

The interaction of inorganic nanomaterials with biological fluids containing proteins can lead not only to the formation of a protein corona and thereby to a change in the biological activity of nanoparticles but also to a significant effect on the structural and functional properties of the biomolecules themselves. This work studied the interaction of nanoscale CeO2, the most versatile nanozyme, with human serum albumin (HSA). Fourier transform infrared spectroscopy, MALDI-TOF mass spectrometry, UV-vis spectroscopy, and fluorescence spectroscopy confirmed the formation of HSA-CeO2 nanoparticle conjugates. Changes in protein conformation, which depend on the concentration of both citrate-stabilized CeO2 nanoparticles and pristine CeO2 nanoparticles, did not affect albumin drug-binding sites and, accordingly, did not impair the HSA transport function. The results obtained shed light on the biological consequences of the CeO2 nanoparticles' entrance into the body, which should be taken into account when engineering nanobiomaterials to increase their efficiency and reduce the side effects.

The Morphology Dependent Interaction between Silver Nanoparticles and Bovine Serum Albumin

Biological applications of silver nanoparticles (AgNPs) depend on the covalently attached or adsorbed proteins. A series of biological effects of AgNPs within cells are determined by the size, shape, aspect ratio, surface charge, and modifiers. Herein, the morphology dependent interaction between AgNPs and protein was investigated. AgNPs with three different morphologies, such as silver nanospheres, silver nanorods, and silver nanotriangles, were employed to investigate the morphological effect on the interaction with a model protein: bovine serum albumin (BSA). The adsorptive interactions between BSA and the AgNPs were probed by UV-Vis spectroscopy, fluorescence spectroscopy, dynamic light scattering (DLS), Fourier transform infrared spectrometry (FTIR), transmission electron microscopy (TEM), and circular dichroism (CD) techniques. The results revealed that the particle size, shape, and dispersion of the three types of AgNPs markedly influence the interaction with BSA. Silver nanospheres and nanorods were capsulated by protein coronas, which led to slightly enlarged outer size. The silver nanotriangles evolved gradually into nanodisks in the presence of BSA. Fluorescence spectroscopy confirmed the static quenching the fluorescence emission of BSA by the three AgNPs. The FTIR and CD results suggested that the AgNPs with different morphologies had different effects on the secondary structure of BSA. The silver nanospheres and silver nanorods induced more pronounced structural changes than silver nanotriangles. These results suggest that the formation of a protein corona and the aggregation behaviors of AgNPs are markedly determined by their inherent morphologies.

Biophysical study of cisplatin loaded albumin-gold nanoparticle and its interaction with glycans of gp60 receptor

The biophysical study provides a quantitative understanding of biomolecular interaction. The interaction of protein-nanoparticle has been critically examined using various biophysical and biochemical tools. The present investigation focussed on the biophysical characterization of anticancer drug cisplatin (CPT) with Bovine Serum Albumin (BSA) - Gold nanoparticles (GNP) conjugate; and BSA-CPT-GNP interaction with glycan sugars of glycoprotein receptor. Spectroscopic study (UV visible and fluorescence) showed strong binding of CPT loaded BSA with GNP. The binding between BSA-CPT-GNP and glycan sugars of gp60 receptor was estimated. Circular Dichroism (CD) spectroscopy study revealed weak alteration in the secondary structure of BSA upon CPT and GNP binding. Dynamic Light Scattering (DLS) data indicated the changes in the size of conjugates; zeta potential data showed the stability of conjugates. Biocompatible studies showed no toxicity to RBCs and chorioallantoic membrane (CAM). The mechanisms of interaction have been explored at the molecular and cellular levels. This investigation can be effectively extrapolated for in-vivo and in-vitro targeted drug delivery studies for cancer therapy.

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

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

Thermodynamic and Kinetic Binding Behaviors of Human Serum Albumin to Silver Nanoparticles

A nanoparticle, under biological milieu, is inclined to be combined with various biomolecules, particularly protein, generating an interfacial corona which provides a new biological identity. Herein, the binding interaction between silver nanoparticles (AgNPs) and human serum albumin (HSA) was studied with transmission electron microscopy (TEM), circular dichroism (CD), and multiple spectroscopic techniques. Due to the ground state complex formed mainly through hydrophobic interactions, the fluorescence titration method proved that intrinsic fluorescence for HSA was probably statically quenched by AgNPs. The complete thermodynamic parameters were derived, indicating that the interaction between HSA and AgNPs is an entropy-driven process. Additionally, synchronous fluorescence and CD spectrum results suggested the conformational variation it has upon binding to AgNPs and the α-helix content has HSA visibly decreased. The kinetic experiments proved the double hysteresis effect has in HSA’s binding to the AgNPs surface. Moreover, the binding has between HSA and AgNPs follows the pseudo-second-order kinetic characteristic and fits the Freundlich model for multilayer adsorption. These results facilitate the comprehension about NPs’ underlying biological effects under a physiological environment and promote the secure applications of NPs biologically and medically.

Multiscale Modeling of Bio-Nano Interactions of Zero-Valent Silver Nanoparticles

Understanding the specifics of interaction between the protein and nanomaterial is crucial for designing efficient, safe, and selective nanoplatforms, such as biosensor or nanocarrier systems. Routing experimental screening for the most suitable complementary pair of biomolecule and nanomaterial used in such nanoplatforms might be a resource-intensive task. While a range of computational tools are available for prescreening libraries of proteins for their interactions with small molecular ligands, choices for high-throughput screening of protein libraries for binding affinities to new and existing nanomaterials are very limited. In the current work, we present the results of the systematic computational study of interaction of various biomolecules with pristine zero-valent noble metal nanoparticles, namely, AgNPs, by using the UnitedAtom multiscale approach. A set of blood plasma and dietary proteins for which the interaction with AgNPs was described experimentally were examined computationally to evaluate the performance of the UnitedAtom method. A set of interfacial descriptors (log P^NM, adsorption affinities, and adsorption affinity ranking), which can characterize the relative hydrophobicity/hydrophilicity/lipophilicity of the nanosized silver and its ability to form bio(eco)corona, was evaluated for future use in nano-QSAR/QSPR studies.

Silver nanoparticle-protein interactions and the role of lysozyme as an antagonistic antibacterial agent

The photoreductive synthesis and antibacterial activity of silver nanoparticles (AgNP) prepared in the presence of bovine serum albumin (BSA) and lysozyme (LZ) were evaluated. AgNP@BSA showed similar antibacterial activity to those stabilized with citrate (AgNP@CIT) and to an AgNO₃ solution, suggesting the releases of Ag⁺ as the mechanism of death. In contrast, AgNP@LZ solutions showed no activity, although LZ behaves as a moderately antibacterial peptide. Furthermore, the addition of LZ to the AgNP@CIT or AgNP@BSA solutions induced their agglomeration and suppressed their original antibacterial efficacy. This antagonistic antibacterial effect exerted by LZ on AgNPs is associated with electrostatic interactions exerted by LZ. Specific metal-LZ interactions produce a harder protein corona on AgNP@LZ that retains Ag⁺, while LZ acts as a glue for AgNP@CIT or AgNP@LZ due to its opposite electrical charge, besides strong binding to Ag⁺avoiding the bactericide effect. Therefore, bactericidal effects of AgNP in biological media may be modulated by specific protein interactions.

Recovered fluorescence of the Cd-nanocluster-Hg(II) system based on experimental results and computational methods

Human Serum Albumin, a plasma protein existing in abundance, was selected as a template and reducing agent for the formation of CdNCs due to two factors: its stability and low cost. In the presence of human serum albumin (HSA), a selective and sensitive, low-cost, environmental friendly, and label-free off-on fluorescent sensor was synthesized and characterized for a bioaccumulating and toxic heavy metal, Hg²⁺ and biothiols. HSA - CdNCs can specifically recognize Hg²⁺ through aggregating NCs and causing fluorescence quenching. Subsequently, with increase in the concentration of biothiols, Hg²⁺ was eliminated from the surface of NC, while the fluorescence was restored. The calculated limits of detection (LOD) were 55 pM for Hg(II) and 14 nM for GSH, respectively. The assay was capable of detecting Hg²⁺ ions and GHS at different concentrations in the range of 0.008 to 8530 nM and 7.5-5157 nM, respectively. Furthermore, the appropriate molecular mechanics (MM) as well as quantum mechanical (QM) methods were performed to optimize and the theoretical investigation of the discussed HSA-profile structures and its interactions with the Cd-NCs (one atom of Cd), Hg²⁺ and glutathione (G).

Synthesis, Characterization and Fluorescence Properties of Novel Porous Fe/ZnO Nano-Hybrid Assemblies by Using Berberis thunbergii Extract

In this work, novel Fe/ZnO nanocomposites (NCs) and Fe nanoparticles loaded onto porous ZnO nanostructures have been synthesized via a simple biotechnological route by using Berberis thunbergii extract. In this direction, the as-synthesized bio-based porous ZnO derivatives and human serum albumin (HSA), as a biopolymeric model, form nano-hybrid assemblies. The effect of loading Fe on properties of porous ZnO nanostructures as well as the behavior of the nano-hybrid assemblies were evaluated by using XRD, SEM, EDX, DLS, PL, CD, FTIR and UV/Visible-diffuse reflectance spectra (UV/Vis-DRS) techniques. The fluorescence results revealed that the interaction of Fe/ZnO NCs with HSA biopolymer led to the formation of a ground state complexes as nano-hybrid assemblies. The calculated thermodynamic parameters indicated that the binding process occurred spontaneously. The CD and FTIR spectra confirmed the changes in helicity of HSA as well as the random coil and β-turn in the secondary structure of HSA upon interaction with Fe/ZnO NCs.

Adsorption of bovine serum albumin on gold nanoprisms: interaction and effect of NIR irradiation on protein corona

Because of their photothermal properties, gold nanoparticles (AuNPs) have gained attention regarding their use in drug delivery and therapeutic applications. In this sense, it is interesting to consider their interactions with biologically available proteins, such as serum albumin, as well as the effects of irradiation and photothermal conversion on the protein structure that can lead to a loss of function or generate an immune response. Gold nanoprisms (AuNPrs) have gained interest due to their low toxicity, ease of synthesis, and excellent stability, promoting their use in bioapplications such as surface-enhanced Raman spectroscopy (SERS), drug delivery, and photothermal therapy. The interaction between AuNPrs, with plasmon bands centred in the near-infrared region (NIR), and bovine serum albumin (BSA) has not been explored yet. UV-Vis spectroscopy, dynamic light scattering (DLS) and fluorescence spectroscopy were used to study the interaction between AuNPrs and BSA in addition to estimation of the adsorption rate and kinetic and thermodynamic parameters (K, ΔH°, ΔG°, ΔS°, and Ea) using adsorption isotherms and Langmuir and Freundlich models. The results suggest spontaneous cooperative binding in multilayer adsorption, achieved by the chemisorption of BSA on the AuNPr surface through the S-Au interaction, as confirmed by Raman spectroscopy. On the other hand, the photothermal conversion efficiency (PE) of the coated nanoparticles after NIR irradiation was assessed, resulting in a slight decrease in the PE of BSA coated on AuNPrs in comparison with that of noncapped nanoparticles. The effect of the irradiation on the protein conformation of capped nanoparticles was also assessed; circular dichroism showed BSA unfolding upon interaction with AuNPrs, with a decrease in the α-helix and β-sheet contents, as well as an increase in random coil conformations. Changes in the Raman spectrum suggest a modification of the disposition of the protein residues exposed to the gold surface after NIR irradiation; but at the secondary structure level, no relevant changes were observed. This provides possibilities for the use of NPs-BSA for bioapplications based on the photothermal effect promoted by laser irradiation, since the biological identity of the protein is preserved after NIR irradiation.

Glutathione-S-transferase Fusion Protein Nanosensor

Fusion protein tags are widely used to capture and track proteins in research and industrial bioreactor processes. Quantifying fusion-tagged proteins normally requires several purification steps coupled with classical protein assays. Here, we developed a broadly applicable nanosensor platform that quantifies glutathione-S-transferase (GST) fusion proteins in real-time. We synthesized a glutathione-DNA-carbon nanotube system to investigate glutathione-GST interactions via semiconducting single-walled carbon nanotube (SWCNT) photoluminescence. We found that SWCNT fluorescence wavelength and intensity modulation occurred specifically in response to GST and GST-fusions. The sensor response was dependent on SWCNT structure, wherein mod(n - m, 3) = 1 nanotube wavelength and intensity responses correlated with nanotube diameter distinctly from mod(n - m, 3) = 2 SWCNT responses. We also found broad functionality of this sensor to diverse GST-tagged proteins. This work comprises the first label-free optical sensor for GST and has implications for the assessment of protein expression in situ, including in imaging and industrial bioreactor settings.

Stoichiometric Tuning of PNA Probes to Au0.8Ag0.2 Alloy Nanoparticles for Visual Detection of Nucleic Acids in Plasma

Standard detection methods for nucleic acids, an important class of diagnostic biomarkers, are often laborious and cumbersome. In need for development of facile methodologies, localized surface plasmon resonance (LSPR) assays have been widely explored for both spectroscopic and visual detection of nucleic acids. Our sensing approach is based on monitoring changes in the LSPR band due to interaction between peptide nucleic acid (PNA) and plasmonic nanoparticles (NPs) in the presence/absence of target nucleic acid. We have investigated the importance of tuning the stoichiometry of PNA to NPs to enable "naked-eye" detection of nucleic acids at clinically relevant concentration ranges. Assaying in plasma is achieved by incorporation of silver in gold NPs (AuNPs) via an alloying process. The synthesized gold/silver alloy NPs reduce nonspecific adsorption of proteinaceous interferents in plasma. Furthermore, the gold/silver alloy NPs absorb in the most sensitive cyan to green transition zone (∼500 nm) yielding highly competitive visual limits of detection (LODs). The visual LOD (calculated objectively using the ΔE algorithm) for a model microRNA (mir21) using a productive combination of stoichiometric tuning of the PNA to NP ratio and compositional tuning of the NPs in buffer and plasma extract equals 200 pM (∼250 times lower than existing reports) and 3 nM, respectively. We envision that the proposed LSPR assay based on Au_0.8Ag_0.2NPs offers an avenue for rapid and sensitive on-site detection of nucleic acids in complex matrixes in combination with efficient target extraction kits.

Impact of oppositely charged shell and cores on interaction of core-shell colloids with differently charged proteins as a route for tuning of the colloids cytotoxicity

The present work represents interactions between the core-shell nanoparticles and different proteins, exemplified by lysozyme (LSZ), pepsin, bovine serum albumin (BSA), thioredoxin (TRX) and yellow fluorescent protein (YFP). The core-shell morphology derives from the non-covalent deposition of polyethyleneimine (PEI) onto nanoprecipitated luminescent complex (AuCl)₂L (L is cyclic PNNP ligand). Analysis of the data obtained by DLS, CD spectroscopy, luminescence derived from both (AuCl)₂L and YFP reveal the electrostatically driven interaction of negatively charged proteins with the shell of PEI-(AuCl)₂L. The fluorescence of YFP enables to reveal the inclusion of the protein molecules into the shell. The lack of any luminescent response of PEI-(AuCl)₂L on TRX conforms its electrostatically driven interactions with the shell which, in turn, excludes a binding of the exposed thiol moieties with (AuCl)₂L. The negatively charged surface of pepsin provides the greatest recharging of the PEI-based shell versus the other proteins, which is followed by the enhanced luminescence of (AuCl)₂L. The significant effect of PEI-(AuCl)₂L on the CD spectra of LSZ followed by the decreased intensity of (AuCl)₂L-based luminescence points to specific interaction mode of PEI-(AuCl)₂L with LSZ. The flow cytometry and fluorescent microscopy measurements revealed efficient internalization of PEI-(AuCl)₂L into the Wi-38 cell samples resulting in the efficient staining of all cell organelles. The concentration dependent cytotoxicity of PEI-(AuCl)₂L is detectably enhanced by LSZ, which is correlated with its interaction mode with the 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.

The Food Matrix and the Gastrointestinal Fluids Alter the Features of Silver Nanoparticles

Silver nanoparticles (AgNPs) are used in the agri-food sector, which can lead to their ingestion. Their interaction with food and their passage through the gastrointestinal tract can alter their properties and influence their fate upon ingestion. Therefore, this study aims at developing an in vitro method to follow the fate of AgNPs in the gastrointestinal tract. After incorporation of AgNPs into a standardized food matrix, a precolonic digestion is simulated and AgNPs are characterized by different techniques. The presence of food influences the AgNPs properties by forming a corona around nanoparticles. Even if the salivary step does not impact significantly the AgNPs, the pH decrease and the digestive enzymes induce the agglomeration of AgNPs during the gastric phase, while the addition of intestinal fluids disintegrates these clusters. AgNPs can thus reach the intestinal cells under nanometric form, although the presence of food and gastrointestinal fluids modifies their properties compared to pristine AgNPs. They can form a corona around the nanoparticles and act as colloidal stabilizer, which can impact the interaction of AgNPs with intestinal epithelium. This study demonstrates the importance of taking the fate of AgNPs in the gastrointestinal tract into account to perform an accurate risk assessment of nanomaterials.

Comparative Analysis of Au and Au@SiO2 Nanoparticle-Protein Interactions for Evaluation as Platforms in Theranostic Applications

Gold nanoparticles are utilized in a variety of sensing and detection technologies because of their unique physiochemical properties. Their tunable size, shape, and surface charge enable them to be used in an array of platforms. The purpose of this study is to conduct a thorough spectroscopic characterization of Au and functionalized hybrid Au@SiO₂ nanoparticles under physiological conditions and in the presence of two proteins known to be abundant in serum, bovine serum albumin and human ubiquitin. The information obtained from this study will enable us to develop design principles to synthesize an array of surface-enhanced Raman spectroscopy-based nanoparticles as platforms for theranostic applications. We are particularly interested in tailoring the surface chemistry of the Au@SiO₂ nanoparticles for applications in theranostic technologies. We employ common spectroscopic techniques, with particular emphasis on circular dichroism and heteronuclear single quantum correlation nuclear magnetic resonance (HSQC NMR) spectroscopy, as combinatorial tools to understand protein conformational dynamics, binding site interactions, and protein corona for the design of nanoparticles capable of reaching their intended target in vivo. Our results conclude that protein adsorption onto the nanoparticle surface prevents nanoparticle aggregation. We observed that varying the ionic strength and type of ion influences the aggregation and aggregation rate of each respective nanoparticle. The conformation of proteins and the absorption of proteins on the surface of Au nanoparticles are also influenced by ionic strength. Using two-dimensional [¹⁵N-¹H]-HSQC NMR experiments to compare the interactions of Au and Au@SiO₂ nanoparticles with ¹⁵N-ubiquitin, we observed small chemical shift perturbations in some amino acid peaks and differences in binding site interactions with ubiquitin and respective nanoparticles.

Probing protein adsorption onto polymer-stabilized silver nanocolloids towards a better understanding on the evolution and consequences of biomolecular coronas

The use of noble metal nanoparticles in biomedical and biotechnological applications is nowadays well established. Particularly, silver nanoparticles (AgNPs) were proven to be effective for instance as a biocide agent. They also find applications in tumor therapies and sensing applications being encouraging tools for in-vivo imaging. In this framework, whenever they are in contact with living systems, they are rapidly coated by a protein corona thereby influencing a variety of biological events including cellular uptake, blood circulation lifetime, cytotoxicity and, ultimately, the therapeutic effect. Taking these considerations into account, we have explored the behavior of polymer-coated AgNPs in model protein environments focusing on the self-development of protein coronas. The polymers polyethyleneimine (PEI), polyvinylpyrrolidone (PVP) and poly(2-vinyl pyridine)-b-poly(ethylene oxide) (PEO-b-P2VP) were used as stabilizing agents. The chemical nature of the polymer capping remarkably influences the behavior of the hybrid nanomaterials in protein environments. The PEO-b-P2VP and PVP-stabilized AgNPs are essentially inert to the model proteins adsorption. On the other hand, the PEI-stabilized AgNPs interact strongly with bovine serum albumin (BSA). Nevertheless, the same silver colloids were evidenced to be stable in IgG and lysozyme environments. The BSA adsorption into the PEI-stabilized AgNPs is most probably driven by hydrogen bonding and van der Waals interactions as suggested by isothermal titration calorimetry data. The development of protein coronas around the AgNPs may have relevant implications in a variety of biological events. Therefore, further investigations are currently underway to evaluate the influence of its presence on the cytotoxicity, hemolytic effects and biocide properties of the produced hybrid nanomaterials.

Biophysical interactions between silver nanoparticle-albumin interface and curcumin

Active targeted drug delivery methods facilitate effective uptake of functionalized nanoparticles through receptor-mediated transcytosis. In recent years, albumin-nanoparticle interaction has been critically examined so that this functionalized nanoparticle can be efficiently loaded with drugs. The present investigation aims at understanding the adsorption of Bovine Serum Albumin (BSA) on Silver Nanoparticle (SNP) surface, preparation of soft conjugates (SC) and hard conjugates (HC) of BSA-functionalized SNP (SNP-BSA), and their interaction with curcumin (CUR). HC contains tightly bound BSA whereas SC involves tightly and loosely bound BSA. Increase in the hydrodynamic radii of conjugates was observed upon SNP incubation with increased concentration of BSA. Three different SNP-BSA conjugate ratios were selected to study their interaction with CUR. Fluorescence spectroscopy showed a strong association between CUR and SNP:BSA conjugates. However, binding varied with a change in the conjugate ratio. Circular Dichroism (CD)/Fourier Transform Infrared (FTIR) spectroscopy revealed the alterations in the secondary structure of BSA upon CUR binding to the conjugates. Zeta potential data indicated stable conjugate formation. CUR in SNP:BSA conjugate was found to have a higher half-life as compared to the control. We believe that this is the first biophysical characterization report of conjugates that can be effectively extrapolated for targeted drug delivery.

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Soft Conjugates (SC) and Hard conjugates (HC) of Bovine Serum Albumin (BSA) and Silver nanoparticles (SNP) were prepared and interaction with anticancer drug CUR was explored.

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Binding number and adsorption capacity of drug was identified.

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Conformational and microenvironment changes in adsorbed BSA upon SNP and CUR interaction were investigated.

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Best possible conjugates were identified for efficient loading of CUR drug.

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Drug designed can be further studied for its interaction with glycoprotein receptor present on the diseased (cancerous) cell.

Structure, stability and chaperone function of Mycobacterium leprae Heat Shock Protein 18 are differentially affected upon interaction with gold and silver nanoparticles

Gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs) have several biomedical applications. However, the effective usage of these two nanoparticles is impeded due to limited understanding of their interaction with proteins including small heat shock proteins (sHSPs). Specifically, no evidences of interaction of these two nanoparticles with HSP18 (an antigenic protein) which is an important factor for the growth and survival of M. leprae (the causative organism of leprosy) are available in the literature. Here, we report for the first time evidences of "HSP18-AuNPs/AgNPs interaction" and its impact on the structure and chaperone function of HSP18. Interaction of citrate-capped AuNPs/AgNPs (~20 nm diameter) to HSP18 alters the secondary and tertiary structure of HSP18 in a distinctly opposite manner; while "HSP18-AuNPs interaction" leads to oligomeric association, "HSP18-AgNPs interaction" results in oligomeric dissociation of the protein. Surface hydrophobicity, thermal stability, chaperone function of HSP18 and survival of thermally stressed E. coli harbouring HSP18 are enhanced upon AuNPs interaction, while all of them are reduced upon interaction with AgNPs. Altogether, our study reveals that HSP18 is an important drug target in leprosy and its chaperone function may possibly plays a vital role in the growth and survival of M. leprae pathogen in infected hosts.

Bovine Serum Albumin Enhances Silver Nanoparticle Dissolution Kinetics in a Size- and Concentration-Dependent Manner

The dissolution of silver nanoparticles (AgNPs) to release Ag(I)(aq) is an important mechanism in potentiating AgNP cytotoxicity and imparting their antibacterial properties. However, AgNPs can undergo other simultaneous biophysicochemical transformations, such as protein adsorption, which can mediate AgNP dissolution behaviors. We report the comprehensive analysis of AgNP dissolution and protein adsorption behaviors with monolayer surface coverage of AgNPs by bovine serum albumin (BSA). AgNP dissolution rate constants, k_dissolution, were quantified over several particle sizes (10, 20, and 40 nm) and BSA concentrations (0-2 nM) using linear sweep stripping voltammetry. Across all particle sizes, the dissolution rate constant increased with increasing BSA concentrations. However, protein-enhanced dissolution behaviors were most pronounced for 10 nm AgNPs, which exhibited 3.6-fold and 7.7-fold relative enhancement when compared to 20 and 40 nm AgNPs, respectively. Changes to AgNP surface properties upon interaction with BSA were monitored using dynamic light scattering and zeta potential measurements, while BSA-AgNP complex formation was evaluated using UV-vis spectroscopy and circular dichroism spectroscopy. A subtle increase in the BSA-AgNP association constant was observed with an increase in the AgNP size. Together, these results suggest that the AgNP size dependence of BSA-enhanced dissolution of AgNPs is possibly mediated through both displacement of Ag(I)(aq)-loaded BSA by excess protein in the bulk solution and minimized accessibility of the AgNP surface because of BSA adsorption.

Influence of pH on interaction of silver nanoparticles - protein: Analyses by spectroscopic and thermodynamic ideology

To investigate the interaction between bovine serum albumin (BSA) and silver nanoparticles (AgNPs) at five different pHs (below (3.0 and 4.0), above (7.4 and 9.2) and at the isoelectric point (4.7) of BSA) by spectroscopic (viz., UV-vis, fluorescence, circular dichroism (CD)), microscopic (viz., atomic force microscopy (AFM), transmission electron microscopy (TEM), field emission scanning electron microscope (FESEM)) and thermodynamic (viz., isothermal titration calorimetry (ITC)) methods. The fluorescence quenching spectra provided binding constants via Stern-Volmer plot, quenching constant (K_sv) and rate constant (K_q) were calculated. From the CD spectra, it is clear that the α-helix decreases by increasing the AgNP's concentration. However, at isoelectric point (pH = 4.7), BSA shows more helicity in the presence of AgNPs, which indicates that the structures of BSA become more ordered and stable, and aggregation occurs at strong acidic (3.0), and basic medium (9.2) Fluorescence spectra also indicate the aggregation of the protein at strong acidic (pH = 3.0) and basic medium (pH = 9.2). Furthermore, the morphological and topographical evolute ion upon the interaction was examined using TEM, FESEM, and AFM. The studies conclude the effect of the pH in the medium and behavior of AgNPs with BSA by using different spectroscopic and microscopic techniques.

Development of pH-responsive organic-inorganic hybrid nanocomposites as an effective oral delivery system of protein drugs

This research aimed to develop a pH-responsive organic-inorganic hybrid nanocomposite as an effective oral delivery system for protein drugs. Three different nanocomposites were prepared by using bovine serum albumin (BSA) as a model protein. A nanocomplex of BSA with 3-aminopropyl functionalized magnesium phyllosilicate (AC-BSA) was obtained via the spontaneous co-assembly and then sequentially coated with glycol-chitosan (GAC-BSA) and the pH sensitive polymer, Eudragit®L100-55 (EGAC-BSA). These organic-inorganic hybrid nanocomposites exhibited high entrapment efficiency (86-99%) and their structural characteristics were confirmed by using energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and circular dichroism analysis, indicating that the secondary structure of BSA was well retained in the nanocomposites. At pH 1.2, AC-BSA achieved rapid drug release of about 80% within 2 h, while GAC-BSA and EGAC-BSA exhibited slow drug release of 30% and 15%, respectively, indicating that the surface-coated nanocomposites were more stable in the gastric condition. Furthermore, the conformational stability of BSA entrapped in EGAC-BSA was well retained in the presence of proteolytic enzymes, suggesting that EGAC-BSA should be effective in protecting the protein against gastrointestinal harsh environment. Compared to free BSA, all of tested nanocomposites demonstrated 2.1-3.8-fold higher cellular uptake in Caco-2 cells. Furthermore, energy-dependent endocytosis and paracellular pathway contributed to the cellular transport of nanoparticles. After oral administration in rats, EGAC-BSA significantly enhanced the intestinal permeation of BSA compared to free BSA. In conclusion, EGAC-BSA appears to be promising as an effective oral delivery system for proteins with enhanced intestinal absorption.

Biofunctionalization of Silver Nanoparticles With Lactonase Leads to Altered Antimicrobial and Cytotoxic Properties

Background: N-acylated homoserine lactone lactonase which cleave the Acyl homoserine lactone molecules produced by biofilm-forming pathogens and silver nano-particles (AgNPs), are known for their antibacterial effect against several Gram-positive and Gram-negative bacteria. In this study, AgNPs were coated with N-acylated homoserine lactonase protein (AgNPs-AiiA) isolated from Bacillus sp. ZA12. Results: The AgNPs-AiiA complex was characterized by UV-visible spectra, Dynamic light Scattering, Fourier transform infrared spectroscopy (FTIR), and Field Emission Scanning Electron Microscope (Fe-SEM). The synthesized nano-particles were found to be spherical in shape and had an approximate size of 22.4 nm. Treatment with AiiA coated AgNPs showed a significant reduction in exopolysaccharide production, metabolic activity, cell surface hydrophobicity of bacterial cells, and anti-biofilm activity against multidrug-resistant K. pneumoniae as compared to treatment with AiiA protein and neat AgNPs. AgNPs-AiiA complex exhibited potent antibiofilm activity at sub-optimal concentration of 14.4 μg/mL without being harmful to the macrophages and to the various tissues including kidney, liver, spleen and lungs of BALB/c mice upon intra-venous administration. Conclusion: It is concluded that at a concentration of 14.4 μg/mL, AgNPs coated with AiiA kill bacteria without harming the host tissue and provides a suitable template to design novel anti-biofilm drug to circumvent the issue of drug resistance.

Self-assembly of plant protein fibrils interacting with superparamagnetic iron oxide nanoparticles

In situ fibrillation of plant proteins in presence of the superparamagnetic iron oxide nanoparticles (NP) promoted formation of a hybrid nanocomposite. The morphology of NP-fibril composite was revealed using ex-situ atomic force microscopy (AFM) in air. The NP-fibrils were associated into extended multi-fibril structures, indicating that the addition of NPs promoted protein association via β-sheet assembly. Real-time movement of NPs attached to fibrils under an external magnetic field was visualized using in-situ AFM in liquid, revealing that composite structures were stable at low pH, and displaying dipolar property of the NPs in the composite at high pH. Changes in magnetic properties of NPs when interacting with protein fibrils were quantitatively mapped using magnetic force microscopy (MFM). The magnetic moment of the NPs in composite was increased by co-existing with protein at low pH, while their dipolar nature was maintained at high pH. Self-assembly of the protein into fibrils is accelerated with increasing NP concentration within an optimal range, which is attributed to a fibrillation-competent conformation of the peptides. The latter was explained by the formation of favorable hydrogen bonds, electrostatic interactions, and efficient surface energy transfer between NPs and proteins.

Quenching of Luminol Fluorescence at Nano-Bio Interface: Towards the Development of an Efficient Energy Transfer System

Surface modified colloidal gold (Au) and silver (Ag) nanoparticles (NPs) were used as efficient quenchers of luminol (LH₂) fluorescence either in homogeneous aqueous medium or its noncovalent assembly with bovine serum albumin (BSA). The mechanism as well as the extent of fluorescence quenching was found to be strongly dependent on the nature of the nanoparticles. While simple static type fluorescence quenching mechanism was perceived with AuNP, a more complex protocol involving quenching sphere model was envisaged for AgNP quenching. Nevertheless, the magnitude of Stern-Volmer (SV) quenching constant (K_SV ~ 10⁸-10¹⁰ M^-1) was calculated to be ca. 10⁴ times more for surface quoted NPs in comparison with BSA-NP bioconjugates system. On the other hand, a highly efficient (E ≈ 95%) energy transfer (ET) process was predicted for LH₂ captured in the hydrophobic assembly with BSA in presence of AgNP as an acceptor. The ET efficiency is critically dependent on the concentration of BSA and nicely correlated with the extent of NP surface coverage. However, fluorescence quenching on AuNP surface is relatively less responsive towards protein concentration, primarily due to the difference in surface activity as well as the mode of interaction of the protein with NPs. Graphical Abstract Energy transfer from excited luminol to metal nanoparticles is strongly modulated in presence of serum albumins.

The interactions of CdTe quantum dots with serum albumin and subsequent cytotoxicity: the influence of homologous ligands

With spreading applications of fluorescent quantum dots (QDs) in biomedical fields in recent years, there is increasing concern over their toxicity. Among various factors, surface ligands play critical roles. Previous studies usually employed QDs with different kinds of surface ligands, but general principles were difficult to be obtained since it was hard to compare these surface ligands with varied chemical structures without common features. Herein, the physicochemical properties of two types of CdTe QDs were kept very similar, but different in the surface ligands with mercaptoacetic acid (TGA) and 3-mercaptopropionic acid (MPA), respectively. These two types of homologous ligands only had a difference in one methylene group (-CH2-). The interactions of the two types of CdTe QDs with bovine serum albumin (BSA), which was one of the main components of cell culture, were studied by fluorescence, UV-vis absorption, and circular dichroism spectroscopy. It was found that the fluorescence quenching of BSA by CdTe QDs followed a static quenching mechanism, and there was no obvious difference in the Stern-Volmer quenching constants and binding constants. The thermodynamic parameters of the two types of QDs were similar. BSA underwent conformational changes upon association with these QDs. By comparing the cytotoxicity of these two types of QDs, TGA-capped QDs were found to be less cytotoxic than MPA-capped QDs. Besides, in the presence of serum proteins, the cytotoxicity of the QDs was reduced. QDs in the absence of serum proteins had a higher internalization efficiency, compared with those in the medium with serum. To the best of our knowledge, this is a rare study focusing on surface ligands with such small variations at the biomolecular and cellular levels. These findings can provide new insights for the design and applications of QDs in complex biological media.

The interaction of silver nanoparticles with papain and bromelain

These fundamental studies will provide some new insights into the safe and effective application of AgNPs in biological and medical areas.

Nanoparticle-Protein Interactions: Therapeutic Approaches and Supramolecular Chemistry

Research on nanoparticles has evolved into a major topic in chemistry. Concerning biomedical research, nanoparticles have decisively entered the field, creating the area of nanomedicine where nanoparticles are used for drug delivery, imaging, and tumor targeting. Besides these functions, scientists have addressed the specific ways in which nanoparticles interact with biomolecules, with proteins being the most prominent example. Depending on their size, shape, charge, and surface functionality, specifically designed nanoparticles can interact with proteins in a defined way. Proteins have typical dimensions of 5-20 nm. Ultrasmall nanoparticles (size about 1-2 nm) can address specific epitopes on the surface of a protein, for example, an active center of an enzyme. Medium-sized nanoparticles (size about 5 nm) can interact with proteins on a 1:1 basis. Large nanoparticles (above 20 nm) are big in comparison to many proteins and therefore are at the borderline to a two-dimensional surface onto which a protein will adsorb. This can still lead to irreversible structural changes in a protein and a subsequent loss of function. However, as most cells readily take up nanoparticles of almost any size, it is easily possible to use nanoparticles as transporters for proteins into a cell, for example, to address an internal receptor. Much work has been dedicated to this approach, but it is constrained by two processes that can only be observed in living cells or organisms. First, nanoparticles are usually taken up by endocytosis and are delivered into an intracellular endosome. After fusion with a lysosome, a degradation or denaturation of the protein cargo by the acidic environment or by proteases may occur before it can enter the cytoplasm. Second, nanoparticles are rapidly coated with proteins upon contact with biological media like blood. This so-called protein corona influences the contact with other proteins, cells, or tissue and may prevent the desired interaction. Essentially, these effects cannot be understood in purely chemical approaches but require biological environments and systems because the underlying processes are simply too complicated to be modeled in nonbiological systems. The area of nanoparticle-protein interactions strongly relies on different approaches: Synthetic chemistry is involved to prepare, stabilize, and functionalize nanoparticles. High-end analytical chemistry is required to understand the nature of a nanoparticle surface and the steps of its interaction with proteins. Concepts from supramolecular chemistry help to understand the complex noncovalent interactions between the surfaces of proteins and nanoparticles. Protein chemistry and biophysical chemistry are required to understand the behavior of a protein in contact with a nanoparticle. Finally, all chemical concepts must live up to the "biological reality", first in cell culture experiments in vitro and finally in animal or human experiments in vivo, to open new therapies in the 21st century. This interdisciplinary approach makes the field highly exciting but also highly demanding for chemists who, however, have to learn to understand the language of other areas.

Enzyme-mediated formulation of stable elliptical silver nanoparticles tested against clinical pathogens and MDR bacteria and development of antimicrobial surgical thread

BACKGROUND

Silver nanoparticles (AgNPs) are believed to be emerging tool against various infectious diseases including multi-drug resistant (MDR) bacteria. In the present study, in vitro synthesis of AgNPs was optimized using 1:50 ratio of macerozyme (25 μg/μl) and 1 mM AgNO₃ incubated at 80 °C for 8 h. AgNPs were characterized by UV-Visible spectroscopy, dynamic light scattering (DLS), scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy (TEM) and X-ray diffraction (XRD).

RESULTS

Characterization studies suggest the synthesis of elliptical, stable and crystalline AgNPs with an average size of 38.26 ± 0.4 nm calculated using TEM. The XRD pattern revealed the face-centered-cubic (fcc) form of metallic silver. Good shape integrity and dispersion of AgNPs after 1 year of incubation confirmed their stability. AgNPs were exibited the antimicrobial property against ten pathogenic bacteria, three molds and one yeast. The AgNPs also revealed remarkable antimicrobial activity against three MDR strains i.e. Extended spectrum beta-lactamase positive Escherichia coli, Staphylococcus aureus (MRSA) and Teicoplanin resistant Streptococcus Pneumoniae. The AgNPs coated surgical threads (suture) were revealed the remarkble antibacterial activity against three MDR strains. This is the first report to synthesize antimicrobial elliptical AgNPs using enzymes.

CONCLUSION

The results suggest the possibilities to develop the nanoparticles coated antimicrobial medical fabric to combat against MDR infection.