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Silver nanoparticles from biological extracts and their antimicrobial activities.

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The increasing incidence of multi-drug resistant organisms has led to the resurgence in application of Ag-based compounds. Accordingly, increased efforts have been made in the field of nanotechnology to develop silver nanoparticle (AgNP) synthetic strategies that are inexpensive and environmentally friendly without the use of hazardous chemicals. To this end, sunlight irradiation, a relatively new primary source of energy was used instead of heat to drive the synthesis of AgNPs. Biologically-derived capping substrates were independently extracted fromfresh (F) and freeze-dried (FD) leaf samples of the medicinal tree species, Moringa oleifera. Importantly, the extracted substrates advantageously displayed a dual functionality by reducing Ag+ as well as stabilising the resulting AgNPs. Yield analysis indicated a recovery ranging from 0.81 mg and 0.91 mg AgNPs per gram dry mass F and FD leaf tissue, respectively. AgNPs from both sample types were consistent in terms of their spherical shape with average diameters of 9 nm and 11 nm for F and FD samples, respectively. Fourier transform infrared (FTIR) spectroscopic analysis suggested that flavones; terpenoids and polysaccharides predominate and are primarily responsible for the reduction and subsequent capping of AgNPs. Interestingly, bioactivity screening revealed that AgNPs exhibited broad-spectrum antimicrobial activity against both bacterial and fungal strains. The results suggest that AgNPs derived from M. oleifera leaf extracts exhibit potential for application as broad-spectrum antimicrobial agents.


Master of Science in Biochemistry. University of KwaZulu-Natal, Durban, 2017.


Theses - Biochemistry.