Thangavel Shanmugasundaram

A study of the bactericidal, anti-biofouling, cytotoxic and antioxidant properties of actinobacterially synthesised silver nanoparticles.

Actinobacteria- mediated synthesis of silver nanoparticles (AgNPs) is a reliable, eco-friendly and important aspect of nanobiotechnology. In this study, aqueous silver ions, which were exposed to an actinobacterial biomass of Streptomyces naganishii (MA7), were reduced to form stable AgNPs under optimised conditions. The microbially synthesised AgNPs were characterised by UV-Vis spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), selected area electron diffraction (SAED), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), atomic force microscopy (AFM) and high- resolution transmission electron microscopy (HR-TEM). The size (5-50 nm) and shape (spherical) of the AgNPs were determined. The biosynthesised AgNPs exhibited good bactericidal, anti-biofouling, antioxidant and cytotoxic effects with regards to the HeLa cell line. A single protein band with a molecular weight of 44 kDa was obtained after partial purification of the culture filtrate via polyacrylamide gel electrophoresis. The potent actinobacterial strain was identified by its molecular (16s rRNA sequencing), phenotypic and cultural characteristics. The current study demonstrated the potential use of the extremophilic actinobacterial strain of S. naganishii (MA7) as a novel source for AgNPs synthesis with improved biomedical applications.

Biomedical potential of actinobacterially synthesized selenium nanoparticles with special reference to anti-biofilm, anti-oxidant, wound healing, cytotoxic and anti-viral activities.

Currently, there is an ever-increasing need to develop environmentally benign processes in place of synthetic protocols. As a result, researchers in the field of nanoparticle synthesis are focusing their attention on microbes from rare biological ecosystems. One potential actinobacterium, Streptomyces minutiscleroticus M10A62 isolated from a magnesite mine had the ability to synthesize selenium nanoparticles (SeNPs), extracellularly. Actinobacteria mediated SeNP synthesis were characterized by UV-visible, Fourier transform infrared (FT-IR), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX) and high resolution transmission electron microscopy (HR-TEM) analysis. The UV-spectral analysis of SeNPs indicated the maximum absorption at 510nm, FT-IR spectral analysis confirms the presence of capping protein, peptide, amine and amide groups. The selenium signals confirm the presence of SeNPs. All the diffraction peaks in the XRD pattern and HR-TEM confirm the size of SeNPs in the range of 10-250nm. Further, the anti-biofilm and antioxidant activity of the SeNPs increased proportionally with rise in concentration, and the test strains reduced to 75% at concentration of 3.2μg. Selenium showed significant anti-proliferative activity against HeLa and HepG2 cell lines. The wound healing activity of SeNPs reveals that 5% selenium oinment heals the excision wound of Wistar rats up to 85% within 18 days compared to the standard ointment. The biosynthesized SeNPs exhibited good antiviral activity against Dengue virus. The present study concludes that extremophilic actinobacterial strain was a novel source for SeNPs with versatile biomedical applications and larger studies are needed to quantify these observed effects of SeNPs.

In vitro antimicrobial and in vivo wound healing effect of actinobacterially synthesised nanoparticles of silver, gold and their alloy

The therapeutic use of metal and alloy nanoparticles is claimed to have reduced side effects and enhanced curative activity as compared to its ionic counterpart. With this view, the present study focused on the synthesis of silver (Ag), gold (Au) and silver/gold (Ag/Au) nanoparticles (NPs) by using actinobacterial metabolites as a reducing agent for enhanced in vitro antimicrobial and in vivo wound healing activities. Physico-chemical parameters of the synthesised nanoparticles were systematically assessed by using X-ray based spectroscopic, zeta potential, dynamic light scattering (DLS), atomic and electron microscopic analysis. The average sizes of the AgNPs, AuNPs and Ag/AuNPs were found to be 30.5 nm, 14.5 nm and 41.5 nm respectively. The synthesized AgNPs and Ag/AuNPs showed better antibacterial activity on Gram negative bacterial pathogens (Escherichia coli, Pseudomonas aeruginosa and Aeromonas hydrophila) than Gram positive bacterial pathogens. A Minimum Inhibitory Concentration (MIC) value of 6.25 μg ml−1 was observed for E. coli, P. aeruginosa and Candida albicans. AgNP and Ag/AuNP based ointments of about 10% concentration heal (100%) the excision wound within 19 and 21 days in contrast with standard ointment. Further, the complete healing process was evaluated by histopathological analysis, and estimation of tensile strength, inflammatory cytokines (IL-6, TNFα, IL-10) and collagen constituents (hexosamine, hydroxyproline and hyaluronic acid). Metal and alloy nanoparticle use may provide a new and effective therapeutic direction for achieving development of novel antimicrobial drugs and scarless wound healing in clinical practice.

Bio-medically active zinc oxide nanoparticles synthesized by using extremophilic actinobacterium, Streptomyces sp. (MA30) and its characterization

Abstract The present study describes the synthesis of zinc oxide nanoparticles (ZnO-NPs) using an extremophilic actinobacterial cell-free extract, supplied with aqueous zinc acetate solution. Crystalline nature, morphological features, and polydispersed nanoparticles size (15–30 nm) were identified by X-ray diffraction (XRD), atomic force and electron microscopic analysis with dynamic light scattering (DLS) study. The interaction between biomolecules and ZnO-NPs was analyzed using Fourier transform infra-red spectroscopy (FT-IR). Furthermore antibacterial, antioxidant activities, and cell viability test of ZnO-NPs were systematically evaluated. The present study opens a new avenue for the actinobacterial synthesis of oxide nanoparticles.

Production and optimization of biohydrogen from saccharolytic actinobacterium, Streptomyces rubiginosus (SM16), using sugarcane molasses

ABSTRACT The Actinobacteria are known to produce secondary metabolites like antibiotics, enzymes and pigments and also used in bioremediation. Recently the Actinobacteria have also been reported as a source of biofuels too. Here, the hydrogen production was carried out at different concentrations of sugarcane molasses, pH and temperature through dark H2 fermentation using the actinobacterium Streptomyces rubiginosus (SM16) isolated from a sugarcane molasses dumping site. The maximum biohydrogen production rate was found to be 296 ± 0.042 mL/L at 4% sugarcane molasses. At the optimized pH of 7.0, the maximum biohydrogen production rate was 283 ± 0.015mL/L, whereas at the optimized temperature of 30°C, the yield of biohydrogen was 266 ± 0.022 mL/L using the effective inoculum SM16. The maximum hydrogen production (407.33 ± 5.03 mL/L) was recorded in the optimized fermentation medium with sugarcane molasses 4%, pH 7.0 and temperature 30°C. Gas chromatography (GC) and high performance liquid chromatography (HPLC) analysis proved the presence of organic acid (tartaric acid – 35.7%) and other volatile fatty acids along with H2 gas. Hence, the actinobacterium Streptomyces rubiginosus (SM16) is considered a promising source for biohydrogen production.