No abstract

Herein the principles of green chemistry were applied to optimize the method to produce and extract silver nanoparticles during the growth of bacteria.

Nanoparticles fabricated using medicinal plant extract have great potential in the area of nanomedicine. High surfaceto-volume ratio of nanoparticle enhances the local active biomolecules concentration, leading to many fold increase in the medicinal potentials. The silver nanoparticles (AgNPs) fabricated using indigenous medicinal plants of India, Azadirachta indica and Syzygium cumini, have shown a significant effect on the viability of prokaryotic and eukaryotic cells. Biofabrication of AgNP was confirmed using different spectroscopic and microscopic techniques. Extraction and purification of AgNP from nonconjugated plant moieties are done using centrifugation and size exclusion chromatography. The cytotoxic propensity of AgNP formulations was screened against Gram-positive (Bacillus subtilis), Gram-negative (Escherichia coli) bacteria, cancerous (HT1080) and non-cancerous (HEK293) cell lines. The nanoparticle formulations showed a relatively higher cytotoxic propensity against Gram-positive bacteria and cancerous cell lines. In addition, the surface roughness and reactive oxygen species (ROS) measurements indicated that AgNP formulations mediate the cell activity predominantly by ROS-mediated disruptive change in membrane morphology upon direct interaction with the membrane. Hence, the nanoparticle formulations show an enhanced selective cytotoxic propensity towards Gram-positive bacteria and cancerous cell lines. 2 Materials and methods 2.1 Materials Silver nitrate (AgNO 3-209139), Sephadex resin and Alamar blue were purchased from Sigma-Aldrich, USA. 2′,7′-Dichlorodihydrofluorescein diacetate (DCHF-DA) was purchased

Green synthesis approaches for nanoparticle synthesis are considered as nontoxic, eco-friendly and cost-effective approaches than other physical and chemical approaches. Here, we report green synthesis of silver nanoparticle using the bacteria from the habitat of relatively metal-rich coal mine dust. The bacteria showed resistance to significant concentration of anti-microbial Ag(I) ion. The nanoparticle was synthesized at minimum inhibitory concentration (MIC) of Ag(I) using only two isolates. The synthesis of silver nanoparticle was confirmed from the surface plasmon resonance property of the nanoparticle, whereas morphological features were studied using field emission scanning electron microscope. The hydrodynamic size analysis showed the presence of microparticles along with the nanoparticles. Additionally, IR study provided information about the bacterial proteins involved in either reduction of Ag(I) into silver nanoparticle or capping of reduced silver nanocrystal or both. Thus, majority of the bacteria found in the coal mines have the resistance against the antimicrobial metal ion, and the potential to reduce the ion into nano-or micro-particles. Hence, the bacteria can be used as a single cell factory for production of silver nanomaterial.

The last decade has observed a rapid advancement in utilising biological system towards bioremediation of metal ions in the form of respective metal nanostructures or microstructures. The process may also be adopted for respective metal nanoparticle biofabrication. Among different biological methods, bacteria-mediated method is gaining great attention for nanoparticle fabrication due to their eco-friendly and cost-effective process. In the present study, silver nanoparticle (AgNP) was synthesised via continuous biofabrication using , isolated from swamp wetland of Sunderban, West Bengal, India. The biofabricated AgNP was further purified to remove non-conjugated biomolecules using size exclusion chromatography, and the purified AgNPs were characterised using UV-visible spectroscopy, X-ray diffraction, field emission scanning electron microscopy and transmission electron microscopy (TEM). Additionally, the presence of proteins as capping and stabilising agents was confirmed by the amide-I and amide-II peaks in the spectra obtained using attenuated total reflection Fourier transform infrared spectroscopy. The size of biofabricated AgNP was 10-20 nm, as observed using TEM. Additionally, biofabricated AgNP shows significant antibacterial potential against and . Hence, biofabricated AgNP using, which found resistant to a significant concentration of Ag ion, showed enhanced antimicrobial activity compared to commercially available AgNP.