Biosynthesis and characterization of polysaccharide-capped silver nanoparticles from Acalypha indica L. and evaluation of their biological activities.

Biosynthesized silver nanoparticles (AgNPs) are gaining popularity due to their distinctive biological applications. In this research work, an eco-friendly method of synthesizing AgNPs from the leaf polysaccharide (PS) of Acalypha indica L. ( A. indica) was carried out. Synthesis of polysaccharide-AgNPs (PS-AgNPs) was indicated by visual detection of colour change from pale yellow to light brown. The PS-AgNPs were characterized with different techniques and further evaluated for biological activities. The Ultra violet-visible (UV-Vis.) spectroscopy expressed a sharp absorption peak at 415 nm confirmed the synthesis. Atomic force microscopy (AFM) analysis revealed the size range of particles from 14 nm to 85 nm. Fourier transform infrared (FTIR) analysis detected the presence of various functional groups. The cubic crystalline structure of PS-AgNPs was confirmed by X-ray diffraction (XRD) and the particles were found to be oval to polymorphic shaped through transmission electron microscopy (TEM) with sizes from 7.25 nm to 92.51 nm. Energy dispersive X-ray (EDX) determined the presence of silver in PS-AgNPs. The zeta potential was -28.0 mV, which confirmed the stability and an average particle size of 62.2 nm was calculated through dynamic light scattering (DLS). Lastly, the thermo gravimetric analysis (TGA) showed the PS-AgNPs were resistant to high temperature. The PS-AgNPs exhibited significant free radical scavenging activity with an IC50 value of 112.91 µg/ml. They were highly capable of inhibiting the growth of different bacterial and plant fungal pathogens and also active to reduce the cell viability of prostate cancer (PC-3) cell line. The IC50 value was 101.43 µg/ml. The flow cytometric apoptosis analysis revealed the percentage of viable, apoptotic and necrotic cells of PC-3 cell line. According to this evaluation, it can be concluded that these biosynthesized and environmentally friendly PS-AgNPs are helpful to improve therapeutics because of significant antibacterial, antifungal, antioxidant, and cytotoxic properties to open up new possibilities for euthenics.