Phytochemicals Coated Silver Nanoparticles as Potential Vehicles for the Delivery of Plant Natural Products

Abstract

Most plant extracts used in traditional medicines possess inherent antimicrobial activity, and nanosizing them or incorporating them into nanostructures may further enhance their efficacy. In this study, silver nanoparticles (AgNPs) were synthesized using aqueous extracts of plants used in ayurvedic medicine to treat wounds: Lannea coromandelica (Indian ash tree, hik, Family: Anacardiaceae) and Pothos scandens (climbing aroid, pota wel, Family: Araceae). Stem bark of L. coromandelica, leaves and stems of P. scandens were dried and pulverized. L. coromandelica and P. scandens (10 g) were sonicated (44 kHz, 40 ºC, 30 min) separately, in H2O. Different concentrations of the aqueous extracts (2.5, 5, 7.5 mg/mL) were each individually mixed with aqueous AgNO3 to synthesize LC-AgNPs and PS- AgNPs. Several different conditions i.e., homogenization or magnetic stirring with exposure to UV light/sunlight/dark were employed and yields were optimized based on UV spectral data. The reduction of AgNO3 by the phytochemicals were analyzed using UV−Vis spectra in the range of 200−600 nm. AgNPs were characterized using particle size analyzer and atomic force microscopy (AFM). The observed Z-average particle diameter was 200.2±1.0 nm with a polydispersity index (PDI) of 0.435 for LC-AgNPs with a zeta potential at –20.3±1.2 mV. The PS-AgNPs showed the Z- average particle diameter of 216.8±0.7 nm with PDI of 0.401 and a zeta potential at –20.2±0.7 mV. The Z-average particle diameter, PDI and zeta potential of uncoated silver nanoparticles (U-AgNPs) were 128.8±0.8 nm, 0.474 and – 17.6±1.2 mV respectively. AFM revealed the presence of spherical LC-AgNPs and PS-AgNPs of the size ranges 100– 300 nm and 200–400 nm respectively. The AFM images on U-AgNPs revealed the presence spherical nanoparticles in the 200–400 nm. This study revealed two novel methods of phytochemicals-assisted synthesis of AgNPs.