Environmental Fate of Zinc Oxide Nanoparticles: Risks and Benefits

Zinc oxide nanoparticles (ZnO-NPs) are among nanoscale materials displaying exponentially growing production due to their applications in the field of cosmetology, medicine, as antibacterial agent and catalyst. The ZnO nanomaterials release into the aquatic ecosystems through domestic and industrial wastewaters has the potential to induce pernicious effects on fish and other organisms. Increasing concerns on the environmental hazard to aquatic biota have been highlighted by the toxic potential of some metal-based nanomaterials. Several characteristics of ZnO-NPs (e.g. size, shape, surface charge and agglomeration state) play a central role in biological effects such as genotoxic, mutagenic or cytotoxic effects. Overall, Zn bioaccumulation, histopathological, and hematological changes with oxidative and cellular stress have been reported in ZnO-NPs exposed animals

Studies on metal resistant bacteria in cochin estuary and its response towards antibiotics and silver nanoparticles

The Cochin estuary (CE), which is one of the largest wetland ecosystems, extends from Thanneermukkam bund in the south to Azhikode in the north. It functions as an effluent repository for more than 240 industries, the characteristics of which includes fertilizer, pesticide, radioactive mineral processing, chemical and allied industries, petroleum refining and heavy metal processing industries (Thyagarajan, 2004). Studies in the CE have been mostly on the spatial and temporal variations in the physical, chemical and biological characteristics of the estuary (Balachandran et al., 2006; Madhu et al., 2007; Menon et al., 2000; Qasim 2003;Qasim and Gopinathan 1969) . Although several monitoring programs have been initiated in the CE to understand the level of heavy metal pollution, these were restricted to trace metals distribution (Balachandran et al., 2005) or the influence of anthropogenic inputs on the benthos and phytoplankton (Madhu et al., 2007;Jayaraj, 2006). Recently, few studies were carried out on microbial ecology in the CE(Thottathil et al 2008a and b;Parvathi et al., 2009and 2011; Thomas et al., 2006;Chandran and Hatha, 2003). However, studies on metal - microbe interaction are hitherto not undertaken in this estuary. Hence, a study was undertaken at 3 sites with different level of heavy metal concentration tounderstand the abundance, diversity and mechanisms of resistance in metal resistant bacteria and its impact on the nutrient regeneration. The present work has also focused on the response of heavy metal resistant bacteria towards antibacterial agent’s antibiotics and silver nanoparticlesCochin University of Science and TechnologyCSIR-National Institute of Oceanography Regional Centre Koch

The extinction of antimicrobial resistant pathogens using silver embedded silica nanoparticles and an efflux pump blocker

Control measures against antimicrobial resistant bacterial pathogens are important challenges in our daily life. In this study we discuss the sensitivity and resistance of four bacterial pathogens, Vibrio alginolyticus, Escherichia coli, Staphylococcus aureus and Bacillus subtilis, to silica nanoparticles embedded with silver nanoparticles. Successively, by combining with an efflux pump blocking agent Verapamil, we find that the silver-silica nanoparticle induces complete mortality to even the most resistive S. aureus. The above pathogens are selected from a pool of 100 bacterial strains resistant to silver nitrate. While S. aureus shows increased resistance to the nanoparticles, the cell wall integrity and genetic stability of V. alginolyticus and E. coli are lost in the presence of silver-silica nanoparticles. This study suggests that the antimicrobial properties of the nanoparticles against Gram negative pathogens originates from an increased oxidative stress, which is confirmed by blocking of reactive oxygen species using scavengers such as ascorbic acid and observing DNA damage. The antimicrobial property of the nanoparticle when combined with its nontoxic nature to mammalian cells makes it a promising agent for controlling drug-resistant Gram negative pathogens

Preparation and characterization of green graphene using grape seed extract for bioapplications

The development of functionalized graphene materials concerning health and environmental aspects via green approaches is currently the most recent topic in the field of nanoscience and nanotechnology. Herein, we report the green reduction of graphene oxide (GO) to reduced graphene oxide (RGO) using grape seed extract (GSE). Structural properties of the prepared RGO were investigated using Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, thermogravimetric analysis (TGA), UV-Visible spectroscopy and X-ray diffraction analysis. These all characterization techniques clearly revealed that the RGO has been successfully prepared. Moreover, the average thickness (4.2 nm) of RGO layers was also confirmed by transmission electron microscopy (TEM). Optical properties such as band gap and photoluminescence of the synthesized RGO were evaluated. The band gap of RGO was found to be 3.84 eV and it showed emission in the visible region. Efficient antimicrobial activity against Escherichia coli and Staphylococcus aureus was observed with 4 ?g ml- 1 & 5 ?g ml- 1 of RGO and also the cell wall damage of these strains has been proved by atomic force microscopy (AFM). The in vitro study of RGO (500 ?g) disclosed the effective anti-proliferative activity (88%) against HCT-116 cell lines. 2016 Elsevier B.V. All rights reserved.The authors would like to express their sincere gratitude to University Grants Commission ( 2061010223 ) (UGC), New Delhi, and Department of Science and Technology (DST-Inspire fellowship) , and DST Nano Mission ( SR/NM/NS-54/2009 ), New Delhi, for their financial support. Special thanks to Centre for Advanced Materials (CAM), Qatar University for supporting this work.Scopu

Exploring the optical limiting, photocatalytic and antibacterial properties of the BiFeO3-NaNbO3 nanocomposite system

Thin films of BiFeO3-NaNbO3 composites were fabricated in a PMMA matrix. XRD and HRTEM were used for structural investigations. The grain size and surface morphology of samples were analysed through HRTEM images. The self-cleaning property of any material accelerates its industrial applications. Hence, along with the optical limiting performance, the photocatalytic and antibacterial activity of BiFeO3-NaNbO3 composite samples were also studied. BiFeO3-NaNbO3 films fabricated in the PMMA matrix exhibit strong optical nonlinearity when excited by 5 ns laser pulses at 532 nm. The origin and magnitude of the observed optical nonlinearity were explained on the basis of the weak absorption saturation and strong excited state absorption. The photocatalytic performance of samples was analysed by dye degradation method using Methyl Orange dye. The dye degradation rate in the presence of the catalyst is heeded in a particular time interval, which exhibits the photocatalytic performance of the samples. The destruction of microbial organisms that are in contact with the material was contemplated, which could prove its antibacterial activity. The effect of the particle size on the photocatalytic activity was also investigated.Peer reviewe

Sequential interactions of Silver-silica nanocomposite (Ag-SiO2NC) with cell wall, metabolism and genetic stability of Psedomonas aeruginosa, a multiple antibiotic resistant bacterium

The study was carried out to understand the effect of silver-silica nanocomposite (Ag-SiO2NC) on the cell wall integrity, metabolism and genetic stability of Pseudomonas aeruginosa, a multiple drugresistant bacterium. Bacterial sensitivity towards antibiotics and Ag-SiO2NC was studied using standard disc diffusion and death rate assay, respectively. The effect of Ag-SiO2NC on cell wall integrity was monitored using SDS assay and fatty acid profile analysis while the effect on metabolism and genetic stability was assayed microscopically, using CTC viability staining and comet assay, respectively. P. aeruginosa was found to be resistant to β-lactamase, glycopeptidase, sulfonamide, quinolones, nitrofurantoin and macrolides classes of antibiotics. Complete mortality of the bacterium was achieved with 80 μgml-1 concentration of Ag-SiO2NC. The cell wall integrity reduced with increasing time and reached a plateau of 70 % in 110 min. Changes were also noticed in the proportion of fatty acids after the treatment. Inside the cytoplasm, a complete inhibition of electron transport system was achieved with 100 μgml-1 Ag-SiO2NC, followed by DNA breakage. The study thus demonstrates that Ag-SiO2NC invades the cytoplasm of the multiple drug-resistant P. aeruginosa by impinging upon the cell wall integrity and kills the cells by interfering with electron transport chain and the genetic stabilityCochin University of Science and TechnologyLetters in applied microbiology, vol.56; 2012; 57-6

Parasite reduction ratio one day after initiation of artemisinin-based combination therapies and its relationship with parasite clearance time in acutely malarious children

Abstract Background In acute falciparum malaria, asexual parasite reduction ratio two days post-treatment initiation (PRRD2) ≥ 10 000 per cycle has been used as a measure of the rapid clearance of parasitaemia and efficacy of artemisinin derivatives. However, there is little evaluation of alternative measures; for example, parasite reduction ratio one day after treatment initiation (PRRD1) and its relationship with parasite clearance time (PCT) or PRRD2. This study evaluated the use of PRRD1 as a measure of responsiveness to antimalarial drugs. Methods In acutely malarious children treated with artesunate-amodiaquine (AA), artemether-lumefantrine (AL) or dihydroartemisinin-piperaquine (DHP), the relationships between PRRD1 or PRRD2 and PCT, and between PRRD1 and PRRD2 were evaluated using linear regression. Agreement between estimates of PCT using PRRD1 and PRRD2 linear regression equations was evaluated using the Bland-Altman analysis. Predictors of PRRD1 > 5000 per half cycle and PRRD2 ≥ 10 000 per cycle were evaluated using stepwise multiple logistic regression models. Using the linear regression equation of the relationship between PRRD1 and PCT previously generated in half of the DHP-treated children during the early study phase, PCT estimates were compared in a prospective blinded manner with PCTs determined by microscopy during the later study phase in the remaining half. Results In 919 malarious children, PRRD1 was significantly higher in DHP- and AA-treated compared with AL-treated children (P  15 months, parasitaemia > 10 000/μl and DHP treatment independently predicted PRRD1 > 5000 per half cycle, while age > 30 months, haematocrit ≥31%, body temperature > 37.4 °C, parasitaemia > 100 000/μl, PRRD1 value > 1000 and no gametocytaemia independently predicted PRRD2 ≥ 10 000 per cycle. Using the linear regression equation generated during the early phase in 166 DHP-treated children, PCT estimates and PCTs determined by microscopy in the 155 children in the later phase were similar in the same patients. Conclusions PRRD1 and estimates of PCT using PRRD1 linear regression equation of PRRD1 and PCT can be used in therapeutic efficacy studies. Trial registration Pan African Clinical Trial Registration PACTR201709002064150, 1 March 2017, http://www.pactr.or