Biological silver nanoparticles were successfully synthesized from a simple green and natural route using the extract of Allium cepa (onion) with the use of silver nitrate as precursor and chemically synthesized using silver nitrate and tri sodium citrate. Nanoparticle synthesis was proven under UV-Visible absorption spectroscopy. Toxicity of sliver nanoparticles was tested using ToxTrak test, in which, fresh overnight broths of Bacillus subtilis and resazurin dye were used to calculate percentage inhibition (PI). PI is only a relative measure and since there is toxic substances that increase respiration, to give result to a negative number. The PI of both chemically and biologically synthesized silver nanoparticles was compared in order to evaluate toxic effect value. The toxic effect value, PI of chemically synthesized silver nanoparticles is much greater (85.45%) than the biologically synthesized sliver nanoparticles from onion (51.39%). These observation shows that the bacteria B. subtilis killed by chemically synthesized silver nanoparticles are more as compare to biologically synthesized sliver nanoparticle.
Key words: Silver nanoparticles, Allium cepa, ToxTrak toxicity test, resazurin dye, ultraviolet spectroscopy, Bacillus subtilis and percentage inhibition (PI).
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