Biofabrication of Anisotropic Gold Nanotriangles Using Extract of Endophytic Aspergillus clavatus as a Dual Functional Reductant and Stabilizer

Biosynthesis of metal and semiconductor nanoparticles using microorganisms has emerged as a more eco-friendly, simpler and reproducible alternative to the chemical synthesis, allowing the generation of rare forms such as nanotriangles and prisms. Here, we report the endophytic fungus Aspergillus clavatus, isolated from surface sterilized stem tissues of Azadirachta indica A. Juss., when incubated with an aqueous solution of chloroaurate ions produces a diverse mixture of intracellular gold nanoparticles (AuNPs), especially nanotriangles (GNT) in the size range from 20 to 35 nm. These structures (GNT) are of special interest since they possess distinct plasmonic features in the visible and IR regions, which equipped them with unique physical and optical properties exploitable in vital applications such as optics, electronics, catalysis and biomedicine. The reaction process was simple and convenient to handle and was monitored using ultraviolet–visible spectroscopy (UV–vis). The morphology and crystalline nature of the GNTs were determined from transmission electron microscopy (TEM), atomic force spectroscopy (AFM) and X-ray diffraction (XRD) spectroscopy. This proposed mechanistic principal might serve as a set of design rule for the synthesis of anisotropic nanostructures with desired architecture and can be amenable for the large scale commercial production and technical applications

Optimization of process variables for the synthesis of silver nanoparticles by Pycnoporus sanguineus using statistical experimental design

Sequential optimization strategy based on statistical experimental design and one-factor-at-a-time (OFAT) method were employed to optimize the process parameters for the enhancement of silver nanoparticles (AgNPs) production through biological synthesis using Pycnoporus sanguineus. Based on the OFAT method, three significant components influencing the size of AgNPs produced were identified as AgNO3 concentration, incubation temperature, and agitation speed. The optimum values of these process parameter for the synthesis of AgNPs were determined using response surface methodology (RSM) based on Box-Behnken design. The validity of the model developed was verified, and the statistical analysis showed that the optimum operating conditions were 0.001 M of AgNO3, 38°C, and 200 rpm with the smallest AgNPs produced at 14.86 nm. The disc diffusion method also suggested that AgNPs produced using optimum conditions have higher antimicrobial activity compared to the unoptimized AgNPs. The present study developed a robust operating condition for the production of AgNPs by P. sanguineus, which was 8.6-fold smaller than that obtained from un-optimized conditions