Greens Synthesis of Antimicrobial Nanosilver using in vitro Cultured Dioscorea bulbifera

Dioscorea bulbifera is a true yam species which is famous for its medicinal values. The plant is reported to possess anti-inflammatory, antidiabetic and antitumor properties. It has also been found that the D. bulbifera tuber extract is effective in synthesizing silver nanoparticles (AgNPs) because of its unique phytochemistry However, the plant is available in the rainy season only hence in this study in vitro system for maintenance of the D. bulbifera was developed using three media combinations namely basal Murashige and Skoog medium (MS), MS medium supplemented with 5 ppm kinetin (AN) and MS medium enriched with CuSO4·5H2O (CU). Aqueous extracts of these in vitro grown plantlets were found to have significant contents of phenolics, flavonoids and starch. These extracts were found to be effective in rapid synthesis of the AgNPs in 5 h with the optimum temperature of 50 °C and salt concentration equal to 5 mM. Fourier transformed infrared spectroscopy (FTIR) analysis revealed that the polyols in these extracts are responsible for bioreduction. AgNPs synthesized from extracts of Dioscorea bulbifera were characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS). AgNPs from plantlets growing on MS medium were found to have the smallest size and thus showed maximum antibacterial and antibiofilm potential towards Pseudomonas aeruginosa and Vibrio harveyi. The AgNPs synthesized from the extracts of plant-lets growing on AN and CU medium were also found to be effective. The results also suggested the presence of variation in the mechanism of biofilm inhibition by AgNPs against these two bacteria as biofilm inhibition was found to be greater in Vibrio harveyi. To best of our knowledge no such study has been done before with the in vitro grown Dioscorea bulbifera.