Use of silver nanoparticles (SNPs) is increasing in a large number of consumer products. Thus, the possible build-up of the nanoparticles in the environment is becoming a major concern. Aeromonas punctata isolated from sewage showed tolerance to 200 μg/ml SNPs. The growth kinetics data for A. punctata treated with nanoparticles were similar to those in the absence of nanoparticles. There was a reduction in the amount of exopolysaccharides (EPS) in bacterial culture supernatant after nanoparticle-supernatant interaction. EPS capping of the nanoparticles was confirmed by UV-visible, XRD and comparative FTIR analysis. The EPS-capped SNPs showed less toxicity to Escherichia coli, Staphylococcus aureus and Micrococcus luteus compared to the uncapped ones. The study suggests capping of nanoparticles by bacterially produced EPS as a probable physiological defense mechanism. © 2011 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim.

Chandra Sekaran N

Centre for Nanobiotechnology

Vellore Campus

Amitava Mukherjee

Sudheer Khan S

Bharath Kumar E

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 Basic Microbiology

Silver and zinc oxide nanoparticles (Ag and ZnO NPs) are widely used as antimicrobial agents. However, their potential toxicological impact on environmental microorganisms is largely unexplored. The aim of this work was to investigate the sensitivity and adaptability of five bacterial species isolated from sewage towards Ag and ZnO NPs. The bacterial species were exposed to increasing concentration of nanoparticles and the growth inhibitory effect, exopolysaccharides (EPSs) and extracellular proteins (ECPs) productions were determined. The involvement of surface charge in nanoparticles toxicity was also determined. The bacterial species were constantly exposed to nanoparticles to determine the adaptation behavior toward nanoparticles. The nanoparticles exhibited remarkable growth inhibitory effect on tested bacterial species. The toxicity of nanoparticles was found to be strongly dependent on surface charge effects. Though, these organisms are highly sensitive to Ag and ZnO NPs, the continuous exposure to these nanoparticles leads to moderate adaptation of bacterial species and the adapted bacterial species convert the highly toxic nano form to less toxic microform. Finally we predict that the continuing applications of nanoparticles in consumer products may lead to the development of nanoparticles resistant bacterial strains in future. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Toxic behavior of silver and zinc oxide nanoparticles on environmental microorganisms

Silver nanoparticles (SNPs) are being increasingly used in many consumer products and industrial application. The release of SNPs to the environment is a major concern. Here we have studied the adsorptive removal of SNPs by a SNP resistant bacterial species Aeromonas punctata, isolated from the sewage environment. The influence of zeta potential on adsorption was investigated at acidic, neutral and alkaline pH and with varying salt (NaCl) concentrations. The rate of adsorption and removal of SNPs was decreases with increase in pH and salt concentration. The zeta potential study suggests that, the adsorption of SNPs on the cell surface was related to electrostatic force of attraction. The equilibrium adsorption isotherm and kinetics of adsorption were also studied. The adsorption equilibrium isotherms fitted well to the Langmuir model. The kinetics of adsorption fitted best to pseudo-first-order. A. punctata was able to remove 4.42 and 3.85. mg/L of SNPs at pH 5 and 7 respectively. The present study can be used for the effective removal of SNPs which is released into the environment and sewage treatment systems. © 2011 Elsevier B.V.

Colloids and Surfaces B: Biointerfaces

Adsorptive removal of silver nanoparticles (SNPs) from aqueous solution by Aeromonas punctata and its adsorption isotherm and kinetics

Indiscriminate and increased use of silver nanoparticles (SNPs) in consumer products leads to the release of it into the environment. The fate and transport of SNPs in environment remains unknown. We have studied the interaction of SNPs with extracellular protein (ECP) produced by two environmental bacterial species and the adsorption behavior in aqueous solutions. The effect of pH and salt concentrations on the adsorption was also investigated. The adsorption process was found to be dependent on surface charge (zeta potential). The capping of SNPs by ECP was confirmed by Fourier transform infrared spectroscopy and X-ray diffraction. The adsorption of ECP on SNPs was analyzed by Langmuir and Freundlich models, suggesting that the equilibrium adsorption data fitted well with Freundlich model. The equilibrium adsorption data were modeled using the pseudo-first-order and pseudo-second-order kinetic equations. The results indicated that pseudo-second-order kinetic equation would better describe the adsorption kinetics. The capping was stable at environmental pH and salt concentration. The destabilization of nanoparticles was observed at alkaline pH. The study suggests that the stabilization of nanoparticles in the environment might lead to the accumulation and transport of nanomaterials in the environment, and ultimately destabilizes the functioning of the ecosystem. © 2011 Elsevier B.V.

Journal of Hazardous Materials

Interaction of silver nanoparticles (SNPs) with bacterial extracellular proteins (ECPs) and its adsorption isotherms and kinetics

The adsorption of exopolysaccharides (EPS) on silver nanoparticles (SNPs) was influenced by pH, salt concentration, and zeta potential. In this paper, SNPs were stabilized using exopolysaccharides (EPS) produced by Aeromonas punctata as the capping agent. The effects of EPS concentration on the adsorption was studied by UV-visible absorption spectra. During interaction, a decrease in absorbance at plasmon peak of SNPs (425. nm) was observed till 50. mg/L of EPS, beyond that a blue shift towards 411. nm was observed. The capping of SNPs by EPS was confirmed by Fourier Transform Infrared Spectroscopy. The adsorption of EPS on nanoparticles was found to be strongly dependent on zeta potential. The equilibrium adsorption data fitted well by Langmuir isotherm compared to Freundlich curve. The kinetics of adsorption was fitted by pseudo-second-order. Desorption of EPS from SNPs was observed at alkaline pH 12. The stabilized silver nanoparticles could be more amenable towards applications in biotechnology and bioengineering. © 2011 Elsevier B.V.

Colloids and Surfaces A: Physicochemical and Engineering Aspects

Interaction of colloidal silver nanoparticles (SNPs) with exopolysaccharides (EPS) and its adsorption isotherms and kinetics

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 Basic Microbiology
Publisher	Data powered by TypesetWiley
ISSN	0233-111X
Open Access	0