Green sonochemical synthesis of silver nanoparticles using Bridelia micrantha extract and evaluation of their antibacterial activity

The emergence of drug resistance and multiple drug resistance has necessitated the discovery of novel strategies for development of new generation of antimicrobial agents from natural substances for control of microbial infections. Metal nanoparticles have proven to have antimicrobial properties, but the chemical methods used in their production use hazardous chemicals and nanoparticles produced are unstable. In this study, an alternative feasible environmentally friendly method was used for the synthesis of silver nanoparticles using Bridelia micrantha, a Kenyan medicinal plant as a reducing, stabilizing and capping agent. The reaction was done over ultrasonic bath. Formation of the nanoparticles was monitored by visual observation and also by use of UV-VIS spectrophotometer. The synthesized silver nanoparticles had an absorption peak at λmax 431 nm due to plasmon resonance. Energy dispersive X-ray (EDX) analysis showed the synthesized nanoparticles were pure silver. High resolution transmition electron microscope (HRTEM) analysis showed the nanoparticles had non uniform surface and were spherical with an average size of 16.07±3.192 nm. Scanning area electron diffraction (SAED) showed distinct shiny spots, confirming the crystallinity of the nanoparticles. Fourier transform infrared (FTIR) analysis indicated the presence of biomolecules capping the nanoparticles. The silver nanoparticles inhibited growth of Escherichia coli and Staphylococcus aureus. The data from this study will significantly contribute in designing novel methods geared towards development of drugs to combat pathogens by use of silver nanoparticles synthesized in an environmentally and ecofriendly way. Key words: Antibacterial activity, Bridelia micrantha, energy dispersive X-ray (EDX), scanning area electron diffraction (SAED), high resolution transmition electron microscope (HRTEM), silver nanoparticles (AgNPs).