Carbon embedded magnetic ferrite materials are highly active, stable and being widely used in catalysis and pollution control. The carbon containing magnetic copper ferrite was synthesised by solvothermal decomposition method using precursor derived from e-waste. The prepared material was characterized by PXRD, FE-SEM, TEM, Raman, FT-IR, XPS, and NH3-TPD. During the solvothermal decomposition of Fe3(OCH3CH3COO)5·2CH3OH and Cu(CH3COO)2 in-situ generated CO2 would act as a reducing agent for M+3 to M+2 ions reduction and can also be used as carbon source. The as-synthesised copper ferrite (C@CF) was calcined at 400 °C was designated as CF. Both the materials were tested for antimicrobial activity against environmental microorganisms B. subtilis (gram positive, rod shaped) and P. aeruginosa (gram negative, rod shaped) at three exposure concentrations 50, 100 and 200 μg/ml. The possible mechanistic aspects of the antimicrobial actions for CF and C@CF was studied by reactive oxygen species generation and cell membrane permeability assays. C@CF nanoparticles consistently showed significantly higher cytotoxic effects against the test species compared to the CF particles, and this was strongly corroborated by the reactive oxygen species generation and the cell membrane damage results. © 2018 Elsevier B.V.

Muthukumar M

Department of Structural and Geotechical Engineering

School of Civil Engineering

Vellore Campus

Amitava Mukherjee

Centre for Nanobiotechnology

Lakshmi D.S

Acharya S.D

Natarajan S

Bajaj H.C.

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

Materials Chemistry and Physics

In view of the increasing usage of anatase and rutile crystalline phases of titania NPs in the consumer products, their entry into the aquatic environment may pose a serious risk to the ecosystem. In the present study, the possible toxic impact of anatase and rutile nanoparticles (individually and in binary mixture) was investigated using freshwater microalgae, Chlorella sp. at low exposure concentrations (0.25, 0.5 and 1. mg/L) in freshwater medium under UV irradiation. Reduction of cell viability as well as a reduction in chlorophyll content were observed due to the presence of NPs. An antagonistic effect was noted at certain concentrations of binary mixture such as (0.25, 0.25), (0.25, 0.5), and (0.5, 0.5) mg/L, and an additive effect for the other combinations, (0.25, 1), (0.5, 0.25), (0.5, 1), (1, 0.25), (1, 0.5), and (1, 1) mg/L. The hydrodynamic size analyses in the test medium revealed that rutile NPs were more stable in lake water than the anatase and binary mixtures [at 6. h, the sizes of anatase (1. mg/L), rutile NPs (1. mg/L), and binary mixture (1, 1. mg/L) were 948.83. ±. 35.01. nm, 555.74. ±. 19.93. nm, and 1620.24. ±. 237.87. nm, respectively]. The generation of oxidative stress was found to be strongly dependent on the crystallinity of the nanoparticles. The transmission electron microscopic images revealed damages in the nucleus and cell membrane of algal cells due to the interaction of anatase NPs, whereas rutile NPs were found to cause chloroplast and internal organelle damages. Mis-shaped chloroplasts, lack of nucleus, and starch-pyrenoid complex were noted in binary-treated cells. The findings from the current study may facilitate the environmental risk assessment of titania NPs in an aquatic ecosystem. © 2015 Elsevier B.V.

Aquatic Toxicology

Combined toxicity of two crystalline phases (anatase and rutile) of Titania nanoparticles towards freshwater microalgae: Chlorella sp

There is a persistent need to assess the effects of TiO2 nanoparticles on the aquatic ecosystem owing to their increasing usage in consumer products and risk of environmental release. The current study is focused on TiO2 nanoparticle-induced acute toxicity at sub-ppm level (≤1ppm) on the three different freshwater sediment bacterial isolates and their consortium under two different irradiation (visible light and dark) conditions. The consortium of the bacterial isolates was found to be less affected by the exposure to the nanoparticles compared to the individual cells. The oxidative stress contributed considerably towards the cytotoxicity under both light and dark conditions. A statistically significant increase in membrane permeability was noted under the dark conditions as compared to the light conditions. The optical and fluorescence microscopic images showed aggregation and chain formation of the bacterial cells, when exposed to the nanoparticles. The electron microscopic (SEM, TEM) observations suggested considerable damage of cells and bio-uptake of nanoparticles. The exopolysaccrides (EPS) production and biofilm formation were noted to increase in the presence of the nanoparticles, and expression of the key genes involved in biofilm formation was studied by RT-PCR. © 2014 Elsevier Inc.

Environmental Research

Cytotoxicity of TiO2 nanoparticles towards freshwater sediment microorganisms at low exposure concentrations

The aim of the present study was to explore the difference in toxicity mechanism of TiO2 nanoparticles (NPs) at low concentrations (≤1 μg mL-1), in a freshwater bacterial isolate, Bacillus licheniformis, under light (UV-illuminated) and dark (non-illuminated) conditions. Standard plate count and MTT assays showed the dose dependent decrease in the bacterial cell viability. The difference in reduction of cell viability under light (20.7%) and dark conditions (21.3%) was statistically non-significant at 1 μg mL-1 concentration and 2 h interaction period. The fluorescence microscopy of the NP interacted cells (1.0 μg mL-1, 2 h) under light and dark conditions showed the mixture of live and dead cells. A significant dose dependent increase in intracellular ROS generation compared to control was noted. The ROS level after 2 h of interaction was significantly higher under light conditions (7.4 ± 0.13%) as compared to dark conditions (4.35 ± 0.12%). The LDH analyses confirmed a statistically significant increase in membrane permeability under dark conditions compared to the light conditions. The NPs were stable against aggregation in sterilized lake water matrix for a period of 24 h, under both light and dark conditions. However, in the presence of bacterial cells an elevated rate of sedimentation was noted under dark conditions. The electron microscopic (SEM, TEM) observations suggested the concentration buildup of NPs near the plasma membrane leading to internalization. The zeta-potential analysis proved that NP attachment was not charge based. The FTIR studies demonstrated the possible involvement of surface functional groups in the attachment. The concentration of dissolved Ti4+ ions was found to be negligible during the test period. The dominant cytotoxicity mechanism under light conditions was found to be ROS generation, whereas, NP attachment to the cell membrane leading to membrane damage significantly contributed in dark conditions. © 2012 The Royal Society of Chemistry.

Toxicology Research

A comparative cytotoxicity study of TiO2 nanoparticles under light and dark conditions at low exposure concentrations

Journal of Water Process Engineering

Fouling behaviours of PVDF-TiO2 mixed-matrix membrane applied to humic acid treatment

The growing need of antimicrobial agent for novel therapies against multi-drug resistant bacteria has drawn researchers to green nanotechnology. Especially, eco-friendly biosynthesis of silver nanoparticles (Ag NPs) has shown its interesting impact against bacterial infection in laboratory research. In this study, a simple method was developed to form Ag NPs at room temperature, bio-reduction of silver ions from silver nitrate salt by leaf extract from Ocimum gratissimum. The Ag NPs appear to be capped with plant proteins, but are otherwise highly crystalline and pure. The Ag NPs have a zeta potential of −15 mV, a hydrodynamic diameter of 31 nm with polydispersity index of 0.65, and dry sizes of 18 ± 3 nm and 16 ± 2 nm, based on scanning and transmission electron microscopy respectively. The minimum inhibitory concentration (MIC) of the Ag NPs against a multi-drug resistant Escherichia coli was 4 μg/mL and the minimum bactericidal concentration (MBC) was 8 μg/mL, while the MIC and MBC against a resistant strain of Staphylococcus aureus were slightly higher at 8 μg/mL and 16 μg/mL respectively. Further, the Ag NPs inhibited biofilm formation by both Escherichia coli and S. aureus at concentrations similar to the MIC for each strain. Treatment of E. coli and S. aureus with Ag NPs resulted in damage to the surface of the cells and the production of reactive oxygen species. Both mechanisms likely contribute to bacterial cell death. In summary, this new method appears promising for green biosynthesis of pure Ag NPs with potent antimicrobial activity. © 2015 The Authors

Fulltext

Arabian Journal of Chemistry

Green synthesized silver nanoparticles destroy multidrug resistant bacteria via reactive oxygen species mediated membrane damage

Solvothermal synthesis of magnetic copper ferrite nano sheet and its antimicrobial studies

Journal	Data powered by TypesetMaterials Chemistry and Physics
Publisher	Data powered by TypesetElsevier BV
ISSN	0254-0584
Open Access	0