Delicia A. Barretto

Biogenic and chemogenic synthesis of TiO2 NPs via hydrothermal route and their antibacterial activities

Herein, we outline a simple hydrothermal route for the synthesis of titanium dioxide (TiO2) nanoparticles (NPs) using novel biogenic source Piper betel leaf extract and chemogenic source nitric acid as capping and reducing agents. The synthesized TiO2 NPs were subjected to various characterization techniques such as UV-vis spectrophotometry, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS) for their optical, structural, morphological and compositional analysis. The obtained results reveal the following features; XRD analysis confirms the phase formation and presence of nanocrystalline TiO2. FT-IR spectroscopy analysis reveals the presence of Ti–O vibrational bands, O–H bands, plant proteins, tannins, carbohydrates and polyols. TEM analysis shows the NPs were of spherical shape with an average size of about 8 nm and 75 nm for biogenic and chemogenic synthesized TiO2 respectively. EDS analysis confirms the chemical compositions of the NPs having Ti and O elements. Further, these synthesized TiO2 NPs were studied for their antibacterial activity against multi-drug resistant microorganisms like Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative); here we observe that the minimum inhibitory concentration (MIC) values for biogenic and chemogenic are 25 μg mL−1 and 50 μg mL−1 respectively. These results suggest that biogenic synthesized NPs act as a more effective antibacterial agent than chemogenic synthesized NPs.

Green biosynthesis of CuO & Ag–CuO nanoparticles from Malus domestica leaf extract and evaluation of antibacterial, antioxidant and DNA cleavage activities

The reactivity of metallic and bimetallic nanoparticles of copper and silver towards in vitro study has been quantitatively investigated. Here, we report an easy synthesis of nanoparticles by the green method using Malus domestica leaf extract, which acts as a good stabilizing agent. The synthesized CuO and Ag–CuO nanoparticles have shown Surface Plasmon Resonance maxima (SPR) at 335 and 440 nm, respectively. The particles are spherical and crystalline in nature with average sizes between 18 and 20 nm. The Malus domestica leaf-capped nanoparticles have exhibited interesting antibacterial activity with both Gram-positive and Gram-negative bacteria at microgram concentrations. The antioxidant activity of the synthesized nanoparticles has also been measured on the basis of the free radical scavenging activity by the DPPH (1,1-diphenyl 2-picrylhydrazyl) method. Moreover, the DNA cleavage activities of the synthesized nanoparticles have been screened by agarose gel electrophoresis using the E. coli pBR322 plasmid as a target. Hence. owing to the biologically active nature of the synthesized nanoparticles, these greenly synthesized NPs act as a potent therapeutic agent.

Green synthesized multifunctional Ag@Fe2O3 nanocomposites for effective antibacterial, antifungal and anticancer properties

Multifunctional Ag@Fe2O3 nanoparticles were synthesized by employing a green Adathoda vasica leaf extract assisted process. The synthesized nanoparticles were subjected to FTIR, UV-Vis, PXRD and HRTEM measurements for chemical, structural and morphological studies. It is found that vasicine/quinazoline alkaloids present in the extract are responsible for the stability of the nanoparticles. The green synthesized Ag@Fe2O3 nanoparticles showed excellent antibacterial, antifungal and anticancer activity. The green synthesized Ag@Fe2O3 nanoparticles showed better antibacterial activity against Gram positive as well as Gram negative bacteria as compared to previous communications. They have less hazardous effects because of the involvement of the leaf extract in the synthesis of the nanoparticles rather than hazardous chemicals. The present investigation points out that the synthesized nanoparticles are promising in targeted drug delivery systems, bactericides and fungicides, and may be used for magnetic hyperthermia cancer therapy.

Blastobotrys bombycis sp. nov., a d-xylose-fermenting yeast isolated from the gut of the silkworm larva Bombyx mori

The gut of insects harbors a yeast community that is still poorly understood. Here, a novel species of the ascomycetous genus Blastobotrys is proposed based on a yeast strain isolated from the larval gut of the silkworm Bombyx mori (Order Lepidoptera). The novel species is closely related to Blastobotrys aristata and Blastobotrys elegans on the basis of the results of molecular phylogenetic analyses. A preliminary screening revealed that it produces 1.5 g l-1 ethanol by fermenting 5 % d-xylose. The novel species, that represents the first report, to our knowledge, of yeast isolation from silkworms, is described as Blastobotrys bombycis sp. nov. (type strain RAAB001T=CBS 15274T=PYCC 8105T=MCC 1427T; MycoBank accession number MB 825095).