Study of silver nanoparticle-hemoglobin interaction and composite formation

Green Synthesis of Silver Nanoparticles Using Drymaria cordata and Their Biocompatibility with Hemoglobin: A Therapeutic Potential Approach

In this study, we present the synthesis and characterization of AgNPs using Drymaria cordata along with an assessment of their antioxidant, antibacterial, and antidiabetic activities. Antibacterial activities using four bacterial strains, free radical scavenging assays (DPPH and ABTS), and carbohydrate hydrolyzing enzyme inhibition assays were done to examine the therapeutic efficacy of AgNPs. Additionally, herein, we also evaluated the biocompatibility of the AgNPs using hemoglobin (Hb) as a model protein. A comprehensive analysis of Hb and AgNP interactions was carried out by using various spectroscopic, imaging, and size determination studies. Spectroscopic results showed that the secondary structure of Hb was not altered after its interaction with AgNPs. Furthermore, the thermal stability was also well maintained at different concentrations of nanoparticles. This study demonstrated a low-cost, quick, and eco-friendly method for developing AgNPs using D. cordata, and the biocompatible nature of AgNPs was also established. D. cordata-mediated AgNPs have potential applications against bacteria and diabetes and may be utilized for targeted drug delivery.

Blood proteins self-assembly, staphylococcal enterotoxins-interaction, antibacterial synergistic activities of biogenic carbon/FeSO4/Cu/CuO nanocomposites modified with three antibiotics

INTRODUCTION

Nanocomposites based on copper, iron, and carbon materials are novel nanomaterials with both antibacterial and biocompatibility properties considerable to fight against multidrug-resistant bacteria.

METHODS

In this study, phytogenic carbon/FeSO4/Cu/CuO nanocomposites modified by three antibiotics including tetracycline, amoxicillin, and penicillin were employed to hinder antibiotic resistant bacteria of Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. Interaction of albumin and hemoglobin as major blood proteins with these nanocomposites were evaluated by SEM, FTIR, and AFM techniques. As in silico study, molecular docking properties of staphylococcal enterotoxin toxin A and B with (Z)-α-Bisabolene epoxide, (E)-Nerolidol, α-Cyperone, daphnauranol C, nootkatin, and nootkatone as major secondary metabolites of Daphne mucronata were obtained by AutoDock Vina program.

RESULTS

Physicochemical characterization of nanocomposites showed (Zeta potential (- 5.09 mV), Z-average (460.2 d.nm), polydispersity index (0.293), and size range of 44.58 ± 6.78 nm). Results of both in vitro and in silico surveys disclosed significant antibacterial activity of antibiotic functionalized carbon/FeSO4/Cu/CuO nanocomposites compared to antibiotics alone towards Gram-negative and Gram-positive bacteria.

CONCLUSION

Synergistic activity of bio-fabricated carbon/FeSO4/Cu/CuO nanocomposites with antibiotics may be affected by main parameters of concentration and ratio of antibacterial agents, physicochemical properties of nanocomposites, bacterial type (Gram-negative or Gram-positive), antibacterial mechanisms, and chemical structure of antibiotics.

Metal-organic framework-based oxygen carriers with antioxidant activity resulting from the incorporation of gold nanozymes

Blood transfusions are a life-saving procedure since they can preserve the body's oxygen levels in patients suffering from acute trauma, undergoing surgery, receiving chemotherapy or affected by severe blood disorders. Due to the central role of hemoglobin (Hb) in oxygen transport, so-called Hb-based oxygen carriers (HBOCs) are currently being developed for situations where donor blood is not available. In this context, an important challenge that needs to be addressed is the oxidation of Hb into methemoglobin (metHb), which is unable to bind and release oxygen. While several research groups have considered the incorporation of antioxidant enzymes to create HBOCs with minimal metHb conversion, the use of biological enzymes has important limitations related to their high cost, potential immunogenicity or low stability in vivo. Thus, nanomaterials with enzyme-like properties (i.e., nanozymes (NZs)) have emerged as a promising alternative. Amongst the different NZs, gold (Au)-based metallic nanoparticles are widely used for biomedical applications due to their biocompatibility and multi-enzyme mimicking abilities. Thus, in this work, we incorporate Au-based NZs into a type of HBOC previously reported by our group (i.e., Hb-loaded metal-organic framework (MOF)-based nanocarriers (NCs)) and investigate their antioxidant properties. Specifically, we prepare MOF-NCs loaded with Au-based NZs and demonstrate their ability to catalytically deplete over multiple rounds of two prominent reactive oxygen species (ROS) that exacerbate Hb's autoxidation (i.e., hydrogen peroxide and the superoxide radical). Importantly, following loading with Hb, we show how these ROS-scavenging properties translate into a decrease in metHb content. All in all, these results highlight the potential of NZs to create novel HBOCs with antioxidant protection which may find applications as a blood substitute in the future.

Nanoparticle Effects on Stress Response Pathways and Nanoparticle-Protein Interactions

Nanoparticles (NPs) are increasingly used in a wide variety of applications and products; however, NPs may affect stress response pathways and interact with proteins in biological systems. This review article will provide an overview of the beneficial and detrimental effects of NPs on stress response pathways with a focus on NP-protein interactions. Depending upon the particular NP, experimental model system, and dose and exposure conditions, the introduction of NPs may have either positive or negative effects. Cellular processes such as the development of oxidative stress, the initiation of the inflammatory response, mitochondrial function, detoxification, and alterations to signaling pathways are all affected by the introduction of NPs. In terms of tissue-specific effects, the local microenvironment can have a profound effect on whether an NP is beneficial or harmful to cells. Interactions of NPs with metal-binding proteins (zinc, copper, iron and calcium) affect both their structure and function. This review will provide insights into the current knowledge of protein-based nanotoxicology and closely examines the targets of specific NPs.

The Emerging Roles of Silver nanoparticles to Target Viral Life-Cycle and Detect Viral Pathogens

Along the line of recent vaccine advancements, new antiviral therapeutics are compelling to combat viral infection‐related public health crises. Several properties of silver nanoparticles (AgNPs) such as low level of cytotoxicity, ease of tunability of the AgNPs in the ultra‐small nanoscale size and shape through different convenient bottom‐up chemistry approaches, high penetration of the composite with drug formulations into host cells has made AgNPs, a promising candidate for developing antivirals. In this review, we have highlighted the recent advancements in the AgNPs based nano‐formulations to target cellular mechanisms of viral propagation, immune modulation of the host, and the ability to synergistically enhance the activity of existing antiviral drugs. On the other hand, we have discussed the recent advancements on AgNPs based detection of viral pathogens from clinical samples using inherent physicochemical properties. This article will provide an overview of our current knowledge on AgNPs based formulations that has promising potential for developing a counteractive strategy against emerging and existing viruses.

Contrasting spectroscopic response of human hemoglobin in presence of graphene oxides and its reduced form: Comparative approach with carbon quantum dots

Recently, a considerable amount of research is being directed towards study of graphene oxide (GO) and its reduced form (RGO) since their exposed functional groups make them better candidates in nanobiotechnolgy. In order to assess their biocompatibility, the nature of interactions between Human Hemoglobin (HHb) and GO/RGO are monitored since a comparative spectroscopic approach towards understanding their nature of interactions has not been investigated previously. UV-vis spectroscopy reveals hyperchromicity for HHb-GO system and hypochromicity for HHb-RGO system in the region of absorption of tryptophan/tyrosine residues. Notably, although steady-state fluorescence static quenching of HHb for GO and enhancement of fluorescence for RGO is noticed, but average fluorescence-lifetime is remaining unchanged in presence of GO/RGO. Calorimetric data illustrates three-site and five-site binding model to be the best-fit model for GO and RGO respectively. Also, synchronous fluorescence quenching corresponding to alterations in microenvironment of tryptophan/ tyrosine residues is observed only in presence of GO. Likewise FTIR spectroscopy elucidates involvement of both amide I and amide II bond of HHb backbone through H-bonding interaction only for GO. Furthermore RLS spectra demonstrate an increase and a decrease in signal for GO and RGO respectively. Surprisingly, secondary structure of HHb is maintained upon interaction with both GO/RGO, as revealed by CD spectroscopy, thus supporting their potential application in biological microenvironment. Thus it appears that the spectroscopic properties of HHb upon interaction with GO is altered upon its reduction to RGO. Furthermore the role of HHb as good candidate for bimolecular interaction has been highlighted.

Interactions of Gallic Acid with Porcine Hemoglobin: Effect on the Redox State and Structure of Hemoglobin

The effect of gallic acid (GA) on the redox state of hemoglobin (Hb) and the structural mechanism upon the Hb-GA interaction were investigated. Results indicated that GA exhibited antioxidant and pro-oxidant effects on Hb, which depended on its concentration and the redox state of Hb. The antioxidant capacity of GA contributed to the inhibition of free iron release from Hb. GA could bind to the central cavity of Hb and interacted with the heme moiety through direct hydrophobic contacts as indicated by docking analysis, but GA did not disrupt the heme structure. Conversely, GA increased the compactness of the Hb molecule and might narrow the crevice around the heme pocket, which contributed to the inhibition of Hb autoxidation and the free iron release. Results provided significant insights into the interaction of GA with redox-active Hb, which is beneficial to the application of GA in relative meat and blood products.

Molecular interaction of fluorescent carbon dots from mature vinegar with human hemoglobin: Insights from spectroscopy, thermodynamics and AFM

Foodborne nanoparticles have attracted considerable interest due to their distinctive fluorescence and physicochemical properties. The discovery of vinegar carbon dots (VCDs) has drawn our attention to study their effect on human plasma protein. Herein, spectral, constructional, morphological, and enzymatic activity assessments were carried out to investigate the interaction of VCDs with human hemoglobin (HHb). The intrinsic fluorescence of HHb was quenched significantly by the VCDs through a static quenching process. Furthermore, binding constants and important thermodynamic parameters were calculated, the negative enthalpy and entropy changes were accompanied by a negative Gibbs energy, which proposed the binding between VCDs with HHb was spontaneous. Moreover, negative enthalpy and entropy change corroborated the involvement of van der Waals force and hydrogen bonds in the binding process. Results from FTIR, atomic force microscopy and circular dichroism revealed change of HHB after binding with VCDs although their essential morphological features were unaffected. The esterase activity of HHb decreased after VCDs treatment in a dose-dependent manner, which further confirmed the effect of VCDs on HHb. The results offered detailed information about the interaction between VCDs and HHb.

c-Phycocyanin primed silver nano conjugates: Studies on red blood cell stress resilience mechanism

Green synthesis of metal-encased nutraceutical nano-hybrids has been a target for research over the last few years. In the present investigation, we have reported temperature dependent facile synthesis of silver nanoparticles using FDA approved c phycocyanin (cPC). The cPC conjugated silver nanoparticles (AgcPCNPs) were characterized by TEM, Zeta Potential, UV-vis, XPS, FTIR, and CD Spectroscopy. The temperature optimization studies suggested the synthesis of stable AgcPCNPs at 40 °C while at higher temperature system shows aggregated appearance. Molecular docking studies predicted the exclusive interaction of C, D, I, and J chains of cPC with the surface of AgNPs. Moreover, AgcPCNPs significantly (p < 0.1 %) counteract the toxic nature of AgNPs on red blood cell by measuring parameters like total RBC count, % hemolysis, % hematocrit, coagulation time, pH, electrolyte concentrations and degree of blood cell lipid peroxidation by the anti-oxidation mechanism. Skin fibroblast in vitro cell migration result suggeststhat AgcPCNPs enhanced the degree of cell movement towards the wound area. Data obtained collectively demonstrate that AgcPCNPs can be a better agent in the dermal wound healing with reduced toxicity with the bi-phasic advantage of cPC as a wound healer and Ag nano-metal as an anti-bacterial agent.

Fluorescence enhancement via aggregation effect due to microenvironmental alterations in human hemoglobin protein in presence of carbon quantum dots (CQD): Comparative spectroscopic approach

CQDs have emerged with outstanding properties as a star member of carbon nanomaterial family and in order to reveal its wide-range of application in biological microenvironment the interactions between human hemoglobin (HHb) and CQD and also with ethylenediamine-functionalized CQD (NCQD) are assessed using several techniques. Firstly, UV-vis absorption spectra of HHb reveal hyperchromic effect in the region of absorbance of tryptophan and tyrosine residues and also hypochromicity of Soret band in presence of CQD and NCQD. Interestingly, steady-state fluorescence spectroscopy reveal distinct fluorescence enhancement of HHb with significant red shift thereby indicating exposures of tryptophan and tyrosine residues to a more hydrophilic environment. However synchronous fluorescence spectra reveal that the microenvironment of tryptophan and tyrosine residues is altered in opposite manner, i.e. exposure of tryptophan residues to a more hydrophilic environment and the tyrosine residues to a more hydrophobic environment. Moreover the fluorescence enhancement is observed to be accompanied by increase in average fluorescence-lifetime and decrease in steady-state anisotropy thus signifying a decrease in restriction of rotational motion. Furthermore tryptophan residues within HHb appear to interact more with CQD compared to NCQD. Thermodynamic parameters as revealed by Isothermal Titration Calorimetry (ITC) demonstrate that electrostatic, hydrogen bonding and hydrophobic interactions are the predominant modes of interactions in presence of CQD. Whereas hydrophobic and hydrogen bonding interactions are the major interacting forces in presence of NCQD with five-site sequential binding as best-fit model in both the cases. Such interactions also appear to be associated with an increase in aggregation of HHb as evident from the measurements by atomic force microscopy (AFM) and dynamic light scattering (DLS) study. Although FT-IR spectra display alteration of amide I band, but the overall secondary structure of HHb seems to be nearly retained even in presence of CQDs, as evident in the CD spectra. These observations thus highlight the potential biomedical application of CQDs in biological microenvironment of human especially as drug-delivery system. Also bimolecular interaction of HHb as a model protein with other nanoparticles at the nano bio-interface has been outlined.

Silver and Copper Acute Effects on Membrane Proteins and Impact on Photosynthetic and Respiratory Complexes in Bacteria

The use of metal ions represents a serious threat to the environment and to all living organisms because of the acute toxicity of these ions. Nowadays, silver nanoparticles are one of the most widely used nanoparticles in various industrial and health applications. The antimicrobial effect of nanoparticles is in part related to the released Ag⁺ ions and their ability to interact with bacterial membranes. Here, we identify, both in vitro and in vivo, specific targets of Ag⁺ ions within the membrane of bacteria. This include complexes involved in photosynthesis, but also complexes involved in respiration.

Silver (Ag⁺) and copper (Cu⁺) ions have been used for centuries in industry, as well as antimicrobial agents in agriculture and health care. Nowadays, Ag⁺ is also widely used in the field of nanotechnology. Yet, the underlying mechanisms driving toxicity of Ag⁺ ions in vivo are poorly characterized. It is well known that exposure to excess metal impairs the photosynthetic apparatus of plants and algae. Here, we show that the light-harvesting complex II (LH2) is the primary target of Ag⁺ and Cu⁺ exposure in the purple bacterium Rubrivivax gelatinosus. Ag⁺ and Cu⁺ specifically inactivate the 800-nm absorbing bacteriochlorophyll a (B800), while Ni²⁺ or Cd²⁺ treatment had no effect. This was further supported by analyses of CuSO₄- or AgNO₃-treated membrane proteins. Indeed, this treatment induced changes in the LH2 absorption spectrum related to the disruption of the interaction of B800 molecules with the LH2 protein. This caused the release of B800 molecules and subsequently impacted the spectral properties of the carotenoids within the 850-nm absorbing LH2. Moreover, previous studies have suggested that Ag⁺ can affect the respiratory chain in mitochondria and bacteria. Our data demonstrated that exposure to Ag⁺, both in vivo and in vitro, caused a decrease of cytochrome c oxidase and succinate dehydrogenase activities. Ag⁺ inhibition of these respiratory complexes was also observed in Escherichia coli, but not in Bacillus subtilis.

Silver nanoparticle-human hemoglobin interface: time evolution of the corona formation and interaction phenomenon

In this paper, we have used spectroscopic and electron microscopic analysis to monitor the time evolution of the silver nanoparticles (Ag NP)-human hemoglobin (Hb) corona formation and to characterize the interaction of the Ag NPs with Hb. The time constants for surface plasmon resonance binding and reorganization are found to be 9.51 and 118.48 min, respectively. The drop of surface charge and the increase of the hydrodynamic diameter indicated the corona of Hb on the Ag NP surface. The auto correlation function is found to broaden with the increasing time of the corona formation. Surface zeta potential revealed that positively charged Hb interact electrostatically with negatively charged Ag NP surfaces. The change in α helix and β sheet depends on the corona formation time. The visualization of the Hb corona from HRTEM showed large number of Hb domains aggregate containing essentially Ag NPs and without Ag NPs. Emission study showed the tertiary deformation, energy transfer, nature of interaction and quenching under three different temperatures.

Size Dependent Uptake and Hemolytic Effect of Zinc Oxide Nanoparticles on Erythrocytes and Biomedical Potential of ZnO-Ferulic acid Conjugates

Despite zinc oxide nanoparticles (ZnONPs) being increasingly used as carriers in biomedical fields due to their multifaceted properties and therapeutic importance, better understanding of the mechanisms and cellular consequences resulting from their interaction with cells and cellular components has been warranted. In the present study, we investigate the size-dependent interaction of ZnONPs on RBCs, and its impact on cell viability, DNA damage, ROS generation and morphological changes, employing cellular and analytical methods. Size, charge, stability and solubility were confirmed by DLS, zeta potential, ICP-AES and TEM analysis. Further ICP-AES, TEM, spectroscopic observations and cell based assays showed that ZnONPs exhibited a size dependent impact on RBCs and haemoglobin (Hb), particularly size <50 nm. Conversely, ferulic acid (FA) conjugates and serum albumin significantly reduced the adverse effects exhibited by ZnONPs. The extent of DNA damage and ROS generation is comparatively low in ZnONPs-FA than in ZnONPs alone treated cells. Thus our study documents a novel conceptualization delineating the influence of size on the material properties and therapeutic potential of nanoparticle.

Structure and Function of Adsorbed Hemoglobin on Silica Nanoparticles: Relationship between the Adsorption Process and the Oxygen Binding Properties

The connection between the mechanisms of protein adsorption on nanoparticles and the structural and functional properties of the adsorbed protein often remains unclear. We investigate porcine hemoglobin adsorption on silica nanoparticles, and we analyze the structural and functional modifications of adsorbed hemoglobin by UV-vis spectrophotometry, circular dichroism, and oxygen binding measurement. The structural analysis of adsorbed hemoglobin on silica nanoparticles reveals a significant loss of secondary structure and a preservation of the heme electronic structure. However, adsorbed hemoglobin retains its quaternary structure and exhibits an enhanced oxygen affinity with cooperative binding. Moreover, the structural and functional modifications are fully reversible after complete desorption from silica nanoparticles at pH 8.7. The tunable adsorption and desorption of hemoglobin on SNPs with pH change, and the full control of hemoglobin activity by pH, temperature, and the addition of inorganic phosphate effectors opens the way to an interesting system whereby protein adsorption on nanoparticles can allow for full control over hemoglobin oxygen binding activity. Our results suggest that adsorption of hemoglobin on silica nanoparticles leads to a new structural, functional, and dynamic state with full reversibility in a way that significantly differs from protein denaturation.

Multispectroscopic and calorimetric studies on the binding of the food colorant tartrazine with human hemoglobin

Interaction of the food colorant tartrazine with human hemoglobin was studied using multispectroscopic and microcalorimetric techniques to gain insights into the binding mechanism and thereby the toxicity aspects. Hemoglobin spectrum showed hypochromic changes in the presence of tartrazine. Quenching of the fluorescence of hemoglobin occurred and the quenching mechanism was through a static mode as revealed from temperature dependent and time-resolved fluorescence studies. According to the FRET theory the distance between β-Trp37 of hemoglobin and bound tartrazine was evaluated to be 3.44nm. Synchronous fluorescence studies showed that tartrazine binding led to alteration of the microenvironment around the tryptophans more in comparison to tyrosines. 3D fluorescence and FTIR data provided evidence for conformational changes in the protein on binding. Circular dichroism studies revealed that the binding led to significant loss in the helicity of hemoglobin. The esterase activity assay further complemented the circular dichroism data. Microcalorimetric study using isothermal titration calorimetry revealed the binding to be exothermic and driven largely by positive entropic contribution. Dissection of the Gibbs energy change proposed the protein-dye complexation to be dominated by non-polyelectrolytic forces. Negative heat capacity change also corroborated the involvement of hydrophobic forces in the binding process.

Binding of fluorescent acridine dyes acridine orange and 9-aminoacridine to hemoglobin: Elucidation of their molecular recognition by spectroscopy, calorimetry and molecular modeling techniques

The molecular interaction between hemoglobin (HHb), the major human heme protein, and the acridine dyes acridine orange (AO) and 9-aminoacridine (9AA) was studied by various spectroscopic, calorimetric and molecular modeling techniques. The dyes formed stable ground state complex with HHb as revealed from spectroscopic data. Temperature dependent fluorescence data showed the strength of the dye-protein complexation to be inversely proportional to temperature and the fluorescence quenching was static in nature. The binding-induced conformational change in the protein was investigated using circular dichroism, synchronous fluorescence, 3D fluorescence and FTIR spectroscopy results. Circular dichroism data also quantified the α-helicity change in hemoglobin due to the binding of acridine dyes. Calorimetric studies revealed the binding to be endothermic in nature for both AO and 9AA, though the latter had higher affinity, and this was also observed from spectroscopic data. The binding of both dyes was entropy driven. pH dependent fluorescence studies revealed the existence of electrostatic interaction between the protein and dye molecules. Molecular modeling studies specified the binding site and the non-covalent interactions involved in the association. Overall, the results revealed that a small change in the acridine chromophore leads to remarkable alteration in the structural and thermodynamic aspects of binding to HHb.

A new route for SERS analysis of intact erythrocytes using polydisperse silver nanoplatelets on biocompatible scaffolds

We provided mutual survival of anisotropic silver nanoparticles and intact erythrocyte in salines to record SERS spectra on biocompatible cellulose scaffolds after replacement of chloride ions with nitrates.

Implications of Volume Exclusion: A Look at Thermodynamic Perspective of DNA-Hemoglobin Complexes and Their Reconstitutes Under Macromolecular Crowding

Live cells contain high concentrations of macromolecules, but almost all experimental biochemical data have been generated from dilute solutions that do not reflect conditions in vivo. To understand biomolecular behavior in vivo, properties studied in vitro are extrapolated to conditions in vivo. Another significant factor which is overlooked is the effects of macromolecular crowding and its consequences in the actual biochemical and physiological environment. Such influences of crowding, its modification and physiological parameters have been reported. The present study investigates the effect of molecular crowding on binding characteristics of Salmon sperm DNA with Bovine hemoglobin and their reconstitutes in presence of molecular crowders viz., Poly ethylene glycol (PEG) and Dextran of different molecular weight by fluorescence, UV visible spectroscopic technique at different temperatures. The results showed that BHb fluorescence was quenched by sDNA through static quenching mechanism which is enhanced in presence of polymers. The number of binding sites 'n' and binding constants 'K' were determined at different temperatures based on fluorescence quenching. The thermodynamic parameters namely ∆H°, ∆G°, T∆S° were studied at different temperatures and the results indicate that hydrophobic forces are predominant in the sDNA-BHb complex. Negative ∆G° values imply that the binding process is spontaneous.

Interaction of toxic azo dyes with heme protein: biophysical insights into the binding aspect of the food additive amaranth with human hemoglobin

A biophysical study on the interaction of the food colorant amaranth with hemoglobin was undertaken. Spectrophotometric and spectrofluorimetric studies proposed for an intimate binding interaction between the dye and the protein. The dye quenched the fluorescence of the protein remarkably and the mechanism of quenching was found to be static in nature. Synchronous fluorescence studies suggested that the polarity around the tryptophan residues was altered in the presence of amaranth whereas the polarity around tyrosine residues remained largely unaltered. 3D fluorescence, FTIR and circular dichroism results suggested that the binding reaction caused conformational changes in hemoglobin. The negative far-UV CD bands exhibited a significantly large decrease in magnitude in the presence of amaranth. From calorimetry studies it was established that the binding was driven by a large positive entropic contribution and a small but favorable enthalpy change.

Quantum-mechanical DFT calculation supported Raman spectroscopic study of some amino acids in bovine insulin

In this article Quantum mechanical (QM) calculations by Density Functional Theory (DFT) have been performed of all amino acids present in bovine insulin. Simulated Raman spectra of those amino acids are compared with their experimental spectra and the major bands are assigned. The results are in good agreement with experiment. We have also verified the DFT results with Quantum mechanical molecular mechanics (QM/MM) results for some amino acids. QM/MM results are very similar with the DFT results. Although the theoretical calculation of individual amino acids are feasible, but the calculated Raman spectrum of whole protein molecule is difficult or even quite impossible task, since it relies on lengthy and costly quantum-chemical computation. However, we have tried to simulate the Raman spectrum of whole protein by adding the proportionate contribution of the Raman spectra of each amino acid present in this protein. In DFT calculations, only the contributions of disulphide bonds between cysteines are included but the contribution of the peptide and hydrogen bonds have not been considered. We have recorded the Raman spectra of bovine insulin using micro-Raman set up. The experimental spectrum is found to be very similar with the resultant simulated Raman spectrum with some exceptions.

Molecular toxicity mechanism of nanosilver

Silver is an ancient antibiotic that has found many new uses due to its unique properties on the nanoscale. Due to its presence in many consumer products, the toxicity of nanosilver has become a hot topic. This review summarizes recent advances, particularly the molecular mechanism of nanosilver toxicity. The surface of nanosilver can easily be oxidized by O₂ and other molecules in the environmental and biological systems leading to the release of Ag⁺, a known toxic ion. Therefore, nanosilver toxicity is closely related to the release of Ag⁺. In fact, it is difficult to determine what portion of the toxicity is from the nano-form and what is from the ionic form. The surface oxidation rate is closely related to the nanosilver surface coating, coexisting molecules, especially thiol-containing compounds, lighting conditions, and the interaction of nanosilver with nucleic acids, lipid molecules, and proteins in a biological system. Nanosilver has been shown to penetrate the cell and become internalized. Thus, nanosilver often acts as a source of Ag⁺ inside the cell. One of the main mechanisms of toxicity is that it causes oxidative stress through the generation of reactive oxygen species and causes damage to cellular components including DNA damage, activation of antioxidant enzymes, depletion of antioxidant molecules (e.g., glutathione), binding and disabling of proteins, and damage to the cell membrane. Several major questions remain to be answered: (1) the toxic contribution from the ionic form versus the nano-form; (2) key enzymes and signaling pathways responsible for the toxicity; and (3) effect of coexisting molecules on the toxicity and its relationship to surface coating.

SERS reveals the specific interaction of silver and gold nanoparticles with hemoglobin and red blood cell components

The interaction of nanoparticles with hemoglobin (Hb), a major constituent of red blood cells, is important in nanotoxicity research. We report SERS spectra of Hb using gold and silver nanoparticles at very small nanoparticle : Hb molecule ratios, that is, under conditions relevant for SERS-based nanotoxicity experiments with red blood cells at high sensitivity. We show that the structural information obtained from the experiment is highly dependent on the type of SERS substrate and the conditions under which the interaction of nanoparticles with Hb molecules takes place. In experiments with isolated red blood cells, we demonstrate that the dependence of the spectra on the type of nanoparticle used as the SERS substrate extends to whole red blood cells and red blood cell components. Regarding the applicability of SERS to red blood cells in vivo, evidence is provided that the molecular information contained in the spectra is highly dependent on the material and size of the nanoparticles. The results indicate specific interactions of gold and silver nanoparticles with Hb and the red blood cell membrane, and reflect the hemolytic activity of silver nanoparticles. The results of this study help improve our understanding of the interactions of silver and gold nanoparticles with red blood cells.

Facile synthesis of silver nanoparticles stabilized by cationic polynorbornenes and their catalytic activity in 4-nitrophenol reduction

We report the facile one-pot single-phase syntheses of silver nanoparticles stabilized by norbornene type cationic polymers. Silver nanoparticles (AgNPs) stabilized by polyguanidino oxanorbornenes (PG) at 5 and 25 kDa and polyamino oxanorbornenes (PA) at 3 and 15 kDa have been synthesized by the reduction of silver ions with NaBH4 in aqueous solutions at ambient temperature. The four different silver nanoparticles have been characterized by UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), and transmission electron microscopy (TEM) for their particle size distributions. Interestingly, PG stabilizes the silver nanoparticles better than PA as evident from our spectroscopic data. Furthermore, the AgNP-PG-5K (5K = 5 kDa) was found to serve as an effective catalyst for the reduction of 4-nitrophenol to 4-aminophenol in the presence of NaBH4. The reduction has a pseudo-first-order rate constant of 5.50 × 10(-3) s(-1) and an activity parameter of 1375 s(-1) g(-1), which is significantly higher than other systems reported in the literature.

Molecular interaction of proteins and peptides with nanoparticles

The interaction of proteins in living cells is one of the key processes in the maintenance of their homeostasis. Introduction of additional agents into the chain of these interactions may influence homeostatic processes. Recent advances in nanotechnologies have led to a wide use of nanoparticles (NPs) in industrial and biomedical applications. NPs are small enough to enter almost all compartments of the body, including cells and organelles, and to complicate the pattern of protein interactions. In some cases, interaction of nanoscale objects with proteins leads to hazardous consequences, such as abnormal conformational changes leading to exposure of cryptic peptide epitopes or the appearance of abnormal functions caused by structural modifications. In addition, the high local protein concentration resulting from protein adsorption on NPs may provoke avidity effects arising from close spatial repetition of the same protein. Finally, the interaction of NPs with proteins is known to induce cooperative effects, such as promotion or inhibition of protein fibrillation or self-assembling of NPs on macromolecules serving as a template. It is obvious that better understanding of the molecular mechanisms of nano-bio interactions is crucial for further advances in all nanotechnological applications. This review summarizes recent progress in understanding the molecular mechanisms of the interactions between proteins or peptides and NPs in order to predict the structural, functional, and/or nanotoxic consequences of these interactions.

Drug targeting to infectious diseases by nanoparticles surface functionalized with special biomolecules

The potential to deliver nanoparticles directly into the targeted cells is important in the therapeutic applications for infectious diseases. The possibility of therapeutic agent being attached to the nanoparticles by chemical modification has provided a novel drug delivery option. Interestingly, the discovery of carbon nanotubes and graphene has given an excellent imaging and therapeutic agent for the biomedical applications. In spite of continuous advancement in pharmaceutical drug delivery viz. micelles, vesicles, liquid crystals, etc., during the past decades, their prohibitive production has limited their use. Nanomaterials with their properties of biodegradation, equal biodistribution, mass production, and long time storage make them attractive alternatives for future biomedical applications. Nanoparticles surface functionalized with specific biomolecules based drug delivery has driven new direction for modulating the pharmacokinetics, pharmacodynamics, biorecognition, and increasing the efficacy of targeted drugs. These new strategies are likely to minimize drug degradation and loss, increase drug availability, and opens up new vistas for drug delivery.