Mukesh Singh

Lippia javanica: a cheap natural source for the synthesis of antibacterial silver nanocolloid

AbstractnAqueous silver nanocolloid was synthesized in a single step by a biogenic approach using aqueous leaf extract of Lippia javanica plant which acts as both reducing as well as capping agent. The as-synthesized silver nanoparticles were characterized by UV–visible absorption spectroscopy, high-resolution transmission electron microscopy and Fourier transform infrared spectroscopy (FTIR). The UV–Vis absorption spectra of colloidal silver nanoparticles showed characteristic surface plasmon resonance peak centered at a wavelength of 415xa0nm. The kinetic study showed that the reduction process was complete within 2xa0h of time. The TEM analysis showed that most of the particles were spherical in shape and their average diameter was about 17.5xa0nm. FTIR study confirmed the presence of some organic functional groups in leaf extract and their participation during the reduction as well as stabilization process. In addition, the as-synthesized silver nanoparticles showed antimicrobial activity against clinically isolated pathogenic strain of E. coli and B. subtilis.

Analysis of cytotoxicity and genotoxicity on E. coli, human blood cells and Allium cepa suggests a greater toxic potential of hair dye.

Pharmaceuticals and personal care products (PPCPs) are among the most important emerging environmental contaminants in recent time. PPCPs include wide range of cosmetics, among which hair dyes, are immensely popular in modern society. However, impact of hair dye and its residual discharged to the environment in relation to human health and ecological imbalance have not been widely studied. Based on the result of initial survey among the group of populations of eastern India, three most popular and commonly used permanent hair dyes are selected. Working sample of dye is prepared as recommended on the instructions booklet of the hair dye. The effect of three dyes is studied on Escherichia coli, human red blood cells (RBC), white blood cells (WBC) and Allium cepa bulbs by growth inhibition, hemolysis, 3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide (3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT) assay and A. cepa micronuclei assays respectively. The Lethal dose (LD) demonstrated significant differences among three dyes and the model systems. In vitro hemolytic assays performed on RBC, and MTT assays on WBC show the cytotoxic effects of hair dye. Significant growth inhibition of E. coli has also been noted. In addition, the root tips of A. cepa treated with the dye have shown major chromosomal abnormalities coupled with cell division retardation. Here low mitotic index confirm cell division retardation. Finally, results of in vitro studies of dye-DNA interactions demonstrate electrostatic interaction. Combing all these results it confirms that hair dyes are cytotoxic and may cause mutagenic effect on living cells irrespective of microbes, plant and animal system.

Elucidation of biogenic silver nanoparticles susceptibility towards Escherichia coli: an investigation on the antimicrobial mechanism

Elucidation of the role of silver nanoparticles (AgNPs) in combating bacterial infection is important for the development of new antimicrobial compounds. In this study, several key factors underlying biological effects of biogenic AgNPs were investigated on recombinant Escherichia coli (XL1-Blue) which contains a reporter gene encoding β-galactosidase enzyme. Biogenic AgNPs were prepared from the tea decoction. Cytotoxicity effects were profound on the bacteria tested by the synthesised NPs. The β-galactosidase activity of the released intracellular proteins in the supernatant of E. coli was used as a measure of membrane damage and cellular leakage. Occurrence of a significant amount of β-galactosiadase activity in the supernatant of treated cells clearly demonstrated the formation of holes in the bacterial membrane. Scanning electron microscope pictures visibly indicated destruction of the membrane of the bacteria, which further confirmed membrane damage. The synthesised NPs caused damage of E. coli genomic DNA in a dose dependent manner.

High genotoxicity of shipyard contaminants on Allium cepa and calf thymus DNA

Water pollution is a major environmental problem worldwide. In particular, shipyards are contaminating waters with iron, lead and copper filings, paints, petrochemical products and solvents. There are only a few reports on the genotoxicity of shipyard contaminants. Here, we study genotoxic effects of surface water from five sites of Hooghly River in West Bengal, India, along the banks of which many shipbuilding and scrap industries are located. Genotoxicity was measured by the detection of micronuclei in Allium cepa and other chromosomal aberrations, as well as damage to genomic DNA of calf thymus. Results show that A. cepa roots treated with contaminated water induced morphological distortions, formation of micronuclei and various types of chromosomal aberrations. The mitotic index was lower than 50xa0% in the treated samples. The breakage of calf thymus DNA was time-dependent with acute damage of 100xa0% for overnight incubation as evidenced by agarose gel electrophoresis. We conclude that the workers of local shipbuilding and scrap industries, the residents of nearby areas and the aquatic biodiversity are vulnerable to contaminated waters.

Microbial decolorization and detoxification of emerging environmental pollutant: Cosmetic hair dyes

Since the usage of hair dyes has increased in recent time, the removal of residual dye from environment is also an emerging issue. Hair dye contains mixture of chemicals including genotoxic chemical, p-phenylenediamine (p-PD or PPD). The present study reports bioremediation of hair dye using bacteria isolated from saloon effluent. Sugarcane bagasse powder (SBP) was used as a source of nutrient and surface for bacterial growth. The 16S rDNA sequencing confirmed the isolate as Enterobacter cloacae which was designated as DDB I. The decolourization of dye was studied using UV-vis spectrophotometer. The detoxification study was conducted on microbes isolated from fresh ponds using well diffusion assay. The 1mg/ml of dye was effectively decolourised within 18h of DDB I treatment in the minimal medium containing 30mg/ml of SBP.

Antimicrobial activity of green silver nanoparticles produced using aqueous leaf extract of Hydrocotyle rotundifolia

In the present work, colloidal silver nanoparticles (AgNPs) were synthesized in a single step process by green biosynthetic method using aqueous leaf extracts of an abundantly available medicinal plant Hydrocotyle rotundifolia. The AgNPs synthesized were characterized by UV-Vis spectroscopy, Transmission Electron Microscopy (TEM), Energy-Dispersive X-ray (EDX), Selected Area Electron Diffraction (SAED) and Fourier transform infrared (FTIR) spectroscopy. The UV-Vis absorption spectra of colloidal silver nanoparticles showed characteristic surface plasmon resonance (SPR) peak centred at 410xa0nm. The high resolution TEM images showed the as-synthesized nanoparticles are mostly spherical with and some elliptical in shape having average diameter of about 7.39xa0nm. FTIR analysis clearly revealed that the biomolecules present in the leaf extract of H. rotundifolia could be responsible for reduction of silver ion as well as prolonged stability of nanoparticles. The as-synthesized nanocolloids were stable and no precipitation was observed up to 3-months incubation at room temperature. The synthesized AgNPs were tested for its antimicrobial property against E. coli (DH5α). The MIC value was recorded as 5xa0μg/mL and demonstrated significant growth inhibition on agar plate. This eco-friendly and economical method may be a good option for the large scale preparation of silver nanoparticles for application in pharmaceutical, food, textiles and cosmetic industries.

Leaf extract of cracker plant (Ruellia tuberosa Linn) induces metal chelating activity and DNA strands break: implications for its antioxidant-prooxidant property

Ruellia tuberosa Linn (cracker plant) of Acanthaceae family is a common flowering plant having enormous medicinal importance. It grows often as a weed in the rainy season. It is native of Central America but has spread in many tropical countries including India. The present study investigates the antioxidant property of aqueous leaf extract of this plant. The aqueous leaf extract was subjected to standard analytical methods for analysis of important phytochemicals, antioxidant content, lipid peroxidation and DPPH. (2, 2-diphenyl-1-picryl-hydrazyl-hydrate) generated free radical scavenging properties. Effect of extract on pUC18 plasmid DNA was demonstrated by agarose gel electrophoresis. The metal chelating activity of leaf extract was studied by spectrophotometer. Result indicates presence of important phytochemicals in significant amount. The result highlighted the strong antioxidant activity of aqueous extract attributed to its polyphenolic compounds such as flavonoids. The aqueous extract of leaf protects plasmid DNA from oxidative stress in a dose-dependent manner. Single and double stranded nicks in plasmid DNA occurred when used above optimum concentration. The concentration of extract that protected DNA also demonstrated higher DPPH free radical scavenging activity, which showing strong positive correlation. The metal chelating activity of the same extract was profoundly exhibited. In conclusion, our results indicate that the leaves of the cracker plant contains important bio-actives compounds and are capable of protecting DNA against oxidative damage probably by acting as a strong antioxidant, but can also damage DNA when concentration exceeds the optimum level probably by acting as a strong pro-oxidant.

Microwave-mediated synthesis of zinc oxide nanoparticles: a therapeutic approach against Malassezia species

A successful protocol was developed to aid in the reduction in dandruff-causing fungi, namely Malassezia globasa and Malassezia furfur. Both the species were isolated from volunteers aged between 20 and 22 suffering from dandruff, cultured ex vivo, and tested against the presence of synthesised zinc oxide nanoparticles (ZnNP). Direct microscopy, scanning electron microscopy (SEM), and biochemical assays specific to Malassezia species were conducted to identify dandruff-causing fungal species. Microwave-mediated synthesis of ZnNP was performed and characterised by UV-vis, X-ray diffraction, and SEM. The nanoparticles were tested against both Malassezia species and proved highly effective in inhibiting these fungi, although M. furfur was more susceptible than M. globosa. An optimum amount of 100u2005ppm was found to be sufficient to work as an antifungal agent. Synergistic effects of ZnNP with commercial shampoos were tested, and the result showed enhanced antifungal effects. To mimic the natural biofilm formed by these species on human skin, the formation of fungal biofilm was allowed on polystyrene coverslips. ZnNP was effective in eradication biofilm. Since zinc is an essential mineral for all living organism and is considered as biocompatible, the synthesised nanomaterials can be used in the formulation of antidandruff shampoos.

Removal enactment of organo-phosphorous pesticide using bacteria isolated from domestic sewage

Three bacteria (MS I, II and III) i.e., Pseudomonas aeruginosa (KY781886), Enterobactor ludwigii (KX881423) and Enterobacter cloacae (KX881513) isolated from domestic sewage were identified on the basis of 16S rDNA sequencing and are capable to growth in the presence of organo-phosphorous pesticide (chlorpyrifos). The mega plasmid size >23u202fkb was found in MS I and III. Biosurfactants of the significant amount were produced by three isolates. The ability of the isolates to degrade pesticide over 3u202fdays in the presence of pesticides containing chlorpyrifos as the active component was estimated. Results of UV-visible, FTIR spectroscopy and GC-MS studies confirmed the removal of chlorpyrifos rather than degradation. Pesticide uptake results showed chlorpyrifos in intracellular components and bound to the cell surface in its native state. Removal of pesticide from soil was also recorded by these bacteria. Microbial treated pesticide did not have any effect on Vigna radita seedlings and goat erythrocytes.