Preethy Chandran

Biofunctionalized silver nanoparticles: advances and prospects.

The unique size-dependent properties of nano scale materials have significantly impacted all spheres of human life making nanotechnology a promising field for biomedical applications. Metal nanoparticles like silver have gained significant interest over the years due to their remarkable optical, electrical and antimicrobial properties. However, the toxic nature and aggregation of these nanoparticles has limited its use in more optimized applications. Rational selection of therapeutically active biomolecules for functionalizing the surface of these particles will certainly increase the biocompatibility and biological applicability. The current review attempts to stress on the application domains of silver nanoparticles and also extends an overview on the current strategies involved in biofunctionalizing these particles for specific applications. This review is divided into three sections. The first section emphasizes the importance of silver nanoparticles and its biomedical applications. The need for functionalization and the various concepts and techniques involved in creating surface modified silver nanoparticles will be described in the second section; and the last section throws light on the various applications of the functionalized silver nanoparticles.

Interaction of colloidal zinc oxide nanoparticles with bovine serum albumin and its adsorption isotherms and kinetics

Zinc oxide nanoparticles (ZnO NPs) are widely used in medical, industrial and household application owing to excellent antimicrobial property. The biocompatibility of nanoparticles is important for specific biomedical applications. The aim of this study was to stabilize and biofunctionalize ZnO NPs using bovine serum albumin (BSA). Here we have investigated the adsorption behavior of BSA onto ZnO NPs in aqueous solutions. Influence of pH on the adsorption of BSA onto ZnO NPs was also investigated. The study suggests that the electrostatic force of attraction favors the adsorption of BSA onto ZnO NPs. The adsorption data fitted well by Freundlich isotherm compared to Langmuir isotherm. The kinetics of adsorption fitted best to pseudo-second-order.

RETRACTED: Synthesis and characterization of silver sulfide nanoparticles for photocatalytic and antimicrobial applications

The study describes a simple and novel method for the synthesis of silver sulfide nanoparticles (Ag2S NPs). The synthesized NPs were characterized by SEM (scanning electron microscope), XRD (X-ray diffraction), particle size analyzer, zeta sizer and EDX (Energy dispersive X-ray). The Ag2S NPs were spherical in shape with an effective diameter size of 30 nm. The synthesized particles possess photocatalytic activity under visible light and exhibited excellent antimicrobial effect. The photocatalytic property of Ag2S NPs was also evaluated by the degradation of methylene blue dye under visible light. NPs degraded 87% of methylene blue with in 1h at pH 8. The NPs of 0.1 μg/mL showed a growth inhibition of more than 75% against S. aureus (ATCC 25923), E. coli (ATCC 13534), and E. coli (ATCC 25922).

Bioremoval of Basic Violet 3 and Acid Blue 93 by Pseudomonas putida and its adsorption isotherms and kinetics.

Basic Violet 3 and Acid Blue 93 are the most important group of synthetic colourants extensively used in textile industries for dyeing cotton, wool, silk and nylon. Release of these dye pollutants in to the environment adversely affects the human health and aquatic organisms. The present study we used Pseudomonas putida MTCC 4910 for the adsorptive removal of Basic Violet 3 and Acid Blue 93 from the aqueous solutions. The pH (4-9) and NaCl concentrations (1mM-1M) did not influence the adsorption process. The equilibrium adsorption process fitted well to Freundlich model than Langmuir model. The kinetics of adsorption fitted well by pseudo-second-order. Thus in the present study an attempt has been made to exploit the dye removal capability of P. putida MTCC 4910, and it was found to be an efficient microbe that could be used for bio removal of dyes from textile effluents.

Highly selective colorimetric detection and estimation of Hg2+ at nano-molar concentration by silver nanoparticles in the presence of glutathione.

The present study investigated the colorimetric detection of mercury (Hg(2+)) ions by using silver nanoparticles (Ag NPs) in the presence of glutathione. The nanoparticles used in the study were synthesized biologically by using Polyalthia longifolia leaf extract. The synthesized nanoparticles were characterized by UV-visible spectrophotometer, transmission electron microscope, X-ray diffraction, particle size analyzer and zeta sizer. The particles were spherical in shape and it possesses the effective diameter of 5 nm. The zeta potential of the particles was determined to be -28.6 mV. Ag NPs-glutathione conjugates were able to detect Hg(2+) in nanomolar level. Ag NPs-glutathione conjugates upon interaction with Hg(2+) changes from yellowish brown to pale yellow and finally colorless. The study may be applied for the qualitative and quantitative estimation of mercury at very low concentration.

Effect of humic acid on photocatalytic activity of ZnO nanoparticles

Zinc oxide nanoparticles (ZnO NPs) are widely used in consumer products including sunscreens, textiles and paints. The indiscriminate use of such materials may leads to its release into the environment. The present study evaluated the photocatalytic effect of ZnO NPs in presence of humic acid (HA), which is an important factor present largely in the environment. ZnO NPs were characterized by using UV-visible spectrophotometer, scanning electron microscopy, particle size analyzer and X-ray diffraction analysis. The mean diameter of the particles was found to be 55±2.1 nm. The XRD patterns exhibited hexagonal structure for ZnO NPs. The photocatalytic activity of ZnO NPs was evaluated based on the change in UV-visible absorption spectra of the methylene blue solution as a function of reaction time under visible light source. The rate of photocatalytic degradation of methylene blue was decreased with increase in HA concentration.

Characterization and optimization of EPS-producing and diesel oil-degrading Ochrobactrum anthropi MP3 isolated from refinery wastewater

Petroleum refinery wastewater (PRW) containing hydrocarbon is highly toxic to the environment and the surrounding ecosystem. Proper treatment of the PRW effluent is necessary to remove the pollutants before discharge. Bioremediation is considered to be a promising approach as it is eco-friendly and efficient. The exopolysaccharide (EPS) produced by the O. anthropi acts as a bioemulsifier and showed the highest emulsification activity of 60% on diesel. An EPS yield of about 0.42 g/L was obtained under optimized conditions. The carbohydrate and protein content of the EPS was found to be 71.1% and 19.7% respectively, showing the glycoprotein nature. The structural properties of EPS were analyzed by FT-IR and 1H NMR. The batch degradation of oil in PRW by O. anthropi was studied gravimetrically, and showed about 53% degradation in 7 days, indicating the strong ability of the isolated strain to degrade the hydrocarbons in PRW.

Diesel biodegradation capacities of indigenous bacterial species isolated from diesel contaminated soil

Petroleum based products are the major source of energy for industries and daily life. Leaks and accidental spills occur regularly during the exploration, production, refining, transport, and storage of petroleum and petroleum products. In the present study we isolated the bacteria from diesel contaminated soil and screened them for diesel biodegradation capacity. One monoculture isolate identified by 16S rRNA gene sequence analysis to be Acinetobacter baumannii was further studied for diesel oil biodegradation. The effects of various culture parameters (pH, temperature, NaCl concentrations, initial hydrocarbon concentration, initial inoculum size, role of chemical surfactant, and role of carbon and nitrogen sources) on biodegradation of diesel oil were evaluated. Optimal diesel oil biodegradation by A. baumanii occurred at initial pH 7, 35°C and initial hydrocarbon concentration at 4%. The biodegradation products under optimal cultural conditions were analyzed by GC-MS. The present study suggests that A. baumannii can be used for effective degradation of diesel oil from industrial effluents contaminated with diesel oil.

Toxic potential of iron oxide, CdS/Ag2S composite, CdS and Ag2S NPs on a fresh water alga Mougeotia sp

Nanoparticles (NPs) are being used in many industries ranging from medical, textile, automobile, consumer products, etc. This may increase the probability of their (NPs) release into the environment and fresh water ecosystems. The present study focuses on testing the potential effect of iron oxide, nanocomposite of cadmium sulfide and silver sulfide, cadmium sulfide and silver sulfide nanoparticles (NPs) on a fresh water alga Mougeotia sp. as the model organism. The alga was treated with different concentrations of NPs (0.1-25 mg/L). The NPs exposure caused lipid peroxidation and ROS production, and suppressed the antioxidant defense system such as catalase, glutathione reductase, and superoxide dismutase. Adsorption of NPs on algal surface and membrane damage were confirmed through microscopic evaluation and increase in protein content in extracellular medium. The present investigation pointed out the ecological implications of NPs. The study warrants the need for regulatory agencies to monitor and regulate the use of NPs.

Equilibrium and kinetic studies on adsorptive removal of malachite green by the citrate-stabilized magnetite nanoparticles

The present study investigated the adsorptive removal of malachite green (MG) from aqueous solution by using the citrate-stabilized magnetite nanoparticles (NPs). Magnetite NPs were synthesized chemically by precipitation method and they were characterized by XRD, TEM, particle size analyzer and zeta potential measurement. The mean diameter and zeta potential of the NPs was determined to be 25 nm and −33.14 mV, respectively. The adsorption of MG on the magnetite NPs was fitted better to Freundlich than Langmuir model. Kinetics of adsorption follows pseudo-second order rather than pseudo-first-order kinetic model. The pH of the interaction medium influenced the adsorption process. The adsorption of MG on the iron oxide NPs was decreased upon the increase of pH values. The rate of adsorption decreased with the increase of NaCl concentration in interaction medium. The present study may be applied for large scale to remove the dye stuffs from industrial effluents.