Functionalizing silver nanoparticles (AgNPs) with biomolecules have a number of applications in catalysis, sensing, pharmaceutics and therapy. For the first time, herein we report the interaction of amylase-AgNPs through various spectroscopic techniques. AgNPs are synthesized and characterized by UV-vis spectroscopy, transmission electron microscopy (TEM) and Dynamic Light Scattering (DLS). The binding of AgNPs to α-amylase are investigated by UV-vis, fluorescence, circular dichroism and FTIR spectroscopic techniques. Absorption intensity and Stern-Volmer plots confirmed the formation of the ground state complex with AgNPs. The quenching of the intrinsic protein fluorescence in the presence of different concentrations of AgNP was observed. The apparent binding constant (K) and number of binding sites (n) was calculated from the Stern-Volmer plot was found to be 4.92×103, 3.8×103 and 1.57, 1.3 for porcine pancreas and Bacillus subtilis α-amylase, respectively. Far-UV CD studies revealed the characteristic dichoric band at 222 nm for α-helical structure was shifted to 215 nm in porcine pancreatic α-amylase upon AgNP binding. Further, structural conformation change with peak shifts and the possible binding residues was confirmed through FTIR spectroscopy. © 2013 Elsevier B.V. All rights reserved.

Amitava Mukherjee

Centre for Nanobiotechnology

Vellore Campus

Chandra Sekaran N

Ernest V

Sekar G

Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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VIT University

Journal of Luminescence

Biocompatibility of nanoparticles depends on their binding behavior with biomolecules. Herein, we have reported the interaction of three different biological macromolecules such as hemoglobin, gamma globulin and transferrin with hydroxyl group functionalized Multi-Walled Carbon Nanotubes (OH-MWCNTs). Multiple spectroscopic methods were utilized to identify the binding cum structural changes in biomolecules upon their interaction. Hyperchromic effect observed in the UV-visible spectra, and the quenching behavior from fluorescence emission evidences the existence of bio-nanotube complex formation. Synchronous and three-dimensional fluorescence spectra of biomolecules, in correspondence with Trp and Tyr residues showed the possible disturbance towards their aromatic micro-environment. Changes observed in the FTIR and FT-Raman amide bands, and amino acid residue position of biomolecules upon interaction with CNTs showed the possible effect towards their secondary structure. Further studies with CD spectroscopy indicated the loss of alpha-helical structures quantitatively. The study remains significant in evaluating the biosafety profile of functionalized MWCNTs for their in vivo biomedical applications.

Journal of Photochemistry and Photobiology B: Biology

Binding studies of hydroxylated Multi-Walled Carbon Nanotubes to hemoglobin, gamma globulin and transferrin

CONTEXT: The conjugation of silver nanoparticles (AgNPs) with biomolecules such as oligosaccharides, DNA, proteins has attracted great attention of scientists recently. OBJECTIVE: In this study, lysozyme-AgNP conjugates were evaluated for its synergic antimicrobial effect. MATERIALS AND METHODS: AgNPs were synthesized and characterized using UV-Visible, X-ray diffraction analysis (XRD) and atomic force microscopy (AFM). AgNP (0-1 mM) was interacted with lysozyme for multi-spectrophotometric studies. Lysozyme was immobilized on AgNP at different ratios and the resulting nano-bio-conjugate was tested against Escherichia coli for potent synergic antibacterial effects. RESULTS AND DISCUSSION: A surface plasmon peak at 420 nm confirmed the presence of AgNPs and spherical to oval-shaped AgNPs were observed by AFM. The particle size was calculated to be 25 nm by XRD analysis. The maximum immobilization efficiency (98%) was achieved at 0.01:1 ratio of enzyme:AgNP. UV-Visible and fluorescence spectral studies revealed the binding of AgNPs to lysozyme by the formation of ground-state complex and the binding parameters were calculated. Circular dichroism studies confirmed decrease by 11% in the α-helical and 29.32% in β-sheets of lysozyme upon AgNP interaction. FTIR spectra revealed the binding of AgNP through thiol (-SH) linkages of lysozyme. Our results showed that the antimicrobial activity of lysozyme-AgNP conjugate was enhanced up to 86% decrease in the cell growth. CONCLUSION: In summary, the immobilization of lysozyme on AgNP has yielded a nano-bio-conjugate with synergistic antibacterial properties.

Artificial Cells, Nanomedicine, and Biotechnology

Enhanced activity of lysozyme-AgNP conjugate with synergic antibacterial effect without damaging the catalytic site of lysozyme

Silver nanoparticles (AgNPs) are best known for its catalytic activity. With the current knowledge of biophysics and spectroscopy techniques, we have attempted to study the changes in the structure of amylase upon interaction with AgNPs. Alpha-amylase interacted with AgNPs were investigated by UV-visible, Fourier transform infrared (FTIR), fluorescence and circular dichroism (CD) spectroscopic techniques. UV-Vis spectra showed a plasmon shift towards the lower wavelength indicating structural changes with increased solvent exposure to Trp residues. FTIR studies revealed Ag O bond formation via Trp residues. Fluorescence spectral intensity pertaining to Tryptophan (Trp) residue decreased with an increase in AgNP concentration and a hypsochromic shift from 0.6 mM AgNP. The content of α-helix was decreased by 26.87% while the turns were increased by 49.5% as analyzed by CD studies. The enzyme activity of AgNP-amylase was assayed by Nelson-Somogyi method. AgNP-amylase showed higher catalytic activity with 10 times higher production of reducing sugars at a concentration of 0.6 mM AgNP within fifteen minutes. The conformational change in the structure of amylase had a potential for the higher enzymatic activity for starch breakdown. These studies revealed that the protein structure had changes from UV-Vis, FTIR, CD and fluorescence spectroscopy which helped in increasing the enzyme activity. Copyright © 2013 American Scientific Publishers. All rights reserved.

Journal of Bionanoscience

Biophysical Investigation of α-Amylase Conjugated Silver Nanoparticles Proves Structural Changes Besides Increasing Its Enzyme Activity

Understanding the characteristics of cysteine on a solid surface is an important issue in protein study and amino acid analysis. Therefore, cysteine was selected as a model biomolecule to study the interaction with plasmonic silver nanoparticles. In this study, we report the differential interaction of cysteine with silver nanoparticles synthesised by Lee and Meisel (using citrate as reductant), and modified Creighton (citrate and borohydride as reductant) methods. In Lee and Meisel's method, the red-shifting of silver plasmon resonance in the UV-vis spectra and the aggregation of the particles occurred owing to a decrease in stability of silver nanoparticles upon interaction with cysteine. In contrast, the other method did not cause any aggregation or significant spectral changes. The differential behaviour may be due to surface chemical changes on cysteine with pH, which plays a major role in the nanoparticle-biomolecule interaction. The synthesis of silver nanoparticles applying two sol gel methods followed by interactions with cysteine induces different functionalities on the nanoparticles, which may find specific applications in bio-sensing and drug delivery. © 2013 Copyright Taylor and Francis Group, LLC.

Fulltext

Journal of Experimental Nanoscience

Differential interaction of silver nanoparticles with cysteine

Silver nanoparticles (AgNPs) are proven to be an effective catalytic material for various applications due to their excellent optical and electronic properties. In this paper, we describe a novel approach for the degradation of starch using the catalytic behaviour of AgNPs in an enzyme catalysed reaction of starch hydrolysis by α-amylase. AgNPs were synthesized by soluble starch reducing silver nitrate to silver atoms. An increase of 4.7-fold in reducing sugar formation and 1.5 times faster enzyme activity confirmed the catalytic activity of AgNPs as a nanocatalyst. Surprisingly, starch degradation tests revealed that 9.9 mg of starch was hydrolysed within 5 min, which corroborates with the reducing sugar assay. In short, the present study paves way for the faster degradation of starch by immobilizing the enzyme onto the surface of the AgNP, which could be a promising application in the food industry. © 2012 Elsevier Ltd. All rights reserved.

Carbohydrate Research

Silver nanoparticles: a potential nanocatalyst for the rapid degradation of starch hydrolysis by α-amylase

Biofunctionalization of noble metal nanoparticles like Ag, Au is essential to obtain biocompatibility for specific biomedical applications. Silver nanoparticles are being increasingly used in bio-sensing applications owing to excellent optoelectronic properties. Among the serum albumins, the most abundant proteins in plasma, a wide range of physiological functions of Bovine Serum Albumin (BSA) has made it a model system for biofunctionalization. In absence of adequate prior reports, this study aims to investigate the interaction between silver nanoparticles and BSA. The interaction of BSA [0.05-0.85% concentrations] with Ag nanoparticles [50 ppm concentration] in aqueous dispersion was studied through UV-vis spectral changes, morphological and surface structural changes. At pH 7, which is more than the isoelectric point of BSA, a decrease in absorbance at plasmon peak of uninteracted nanoparticles (425 nm) was noted till 0.45% BSA, beyond that a blue shift towards 410 nm was observed. The blue shift may be attributed to enhanced electron density on the particle surfaces. Increasing pH to 12 enhanced the blue shift further to 400 nm. The conformational changes in BSA at alkaline pH ranges and consequent hydrophobic interactions also played an important role. The equilibrium adsorption data fitted better to Freundlich isotherm compared to Langmuir curve. The X-ray diffraction study revealed complete coverage of Ag nanoparticles by BSA. The scanning electron microscopic study of the interacted nanoparticles was also carried out to decipher morphological changes. This study established that tailoring the concentration of BSA and pH of the interaction it was possible to reduce aggregation of nanoparticles. Biofunctionalized Ag nanoparticles with reduced aggregation will be more amenable towards bio-sensing applications. © 2009 Elsevier B.V. All rights reserved.

Journal	Data powered by TypesetJournal of Luminescence
Publisher	Data powered by TypesetElsevier BV
ISSN	0022-2313
Open Access	0