Silver Nanoparticles and Their Antibacterial Activity Synthesized Using Selected Medicinal Plant Extracts
Kithokoi, Kilonzo Jackson
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Studies have shown that medicinal plants can mediate synthesis of gold, copper, selenium, silver and titanium nanoparticles of various sizes and different morphology. The plants have an advantage over other green synthetic methods as they stabilize and cap the nanoparticles. In this study, silver nanoparticles (AgNPs) were synthesized using Kenyan medicinal plants namely: - Prunus africana (Muiri in Kikuyu), Adansonia digitata (Kiamba in Kamba, Mbuyu in Swahili) Bridelia micrantha (Mukwego in Embu/ Meru) Warburgia ugandensis (Muthiga in Kikuyu) and Urtica dioica (stinging nettle) known for treatment of various ailments. The synthesis was done on stationary and by use of ultrasound bath (sonicator). The formation of silver nanoparticles (AgNPs) was monitored by UV-VIS absorption spectroscopy where surface Plasmon resonance of the AgNPs was observed between 400 to 450 nm. The Selected Area Electron Diffraction (SAED) analysis showed the crystallinity of the silver nanoparticles. High Resolution Transmission Electron Microscope (HRTEM) analysis showed the silver nanoparticles formed were monodispersed, spherical and their size ranged from 13 nm to 45 nm. Energy Dispersive X-ray (EDX) analysis confirmed the synthesized nanoparticles were of pure silver. Fourier Transform Infra-Red (FTIR) was used to show the functional groups of biomolecules present in the plants responsible for reducing, capping and stabilization of the AgNPs. FTIR spectra showed that O-H stretch and –C=C- functional groups were responsible for the reduction and capping the AgNPs. The synthesized AgNPs were found to be toxic against E. coli and S. aureus. AgNPs mediated by P. africana leaves had the best antibacterial activity on E. coli of 19.06±1.00 mm. The lowest inhibition was shown by those synthesized using P. africana bark on stationary method (11.9±0.251 mm). AgNPs synthesized using U. doica showed the highest activity against S. aureus followed by those synthesized using W. ugandensis with inhibition zones of 19.8±0.163 mm and 19.05±0.048 mm respectively. The study contributes towards application and documentation of some local Kenyan medicinal plants in the generation of useful silver nanoparticles in the fight against diseases.