Extracellular Biosynthesis of Silver Nanoparticles Using Aspergillus sp. and Evaluation of their Antibacterial and Cytotoxicity

Aim: Silver nanoparticles are extracellular synthesized by biomass filtrate of Aspergillus sp. Proteins in biomass filtrate of fungal isolate act as a reducing and capping agent to converting Ag+ ion to Ag° metal and produce the silver nanoparticles. During this study silver nanoparticles biologically synthesized by Aspergillus sp. and assessed their antibacterial and cytotoxicity effect on cancer cell represented by Caco-2 cell and normal cell represented by Vero cell.

Place and Duration of Study: The study was performed in Botany & Microbiology Department, Faculty of Science, Al-azhar University, Cairo, Egypt, from October 2015 until January 2017.

Materials and Methods: (1) Different fungal strains were isolated from soil sample collected from El-Wahat desert soil, Giza, Egypt. (2) Screening for extracellular biosynthesis of silver nanoparticles by fungal biomass filtrate. (3) The most potent fungal isolate was identified by cultural and morphological characters. (4) Silver nanoparticles were characterized by UV-vis spectroscopy, TEM, XRD, FTIR and Particle size analysis. (5) Study the antibacterial activity for biosynthesized AgNPs against human pathogenic bacteria by agar well diffusion methods and evaluate cytotoxic effect on two type of cell represented by Caco-2 cell and vero cell.

Results: During this study, the UV–Vis absorption spectra showed a maximum surface plasmon resonance peaks at 400 nm which confirmed the biosynthesis of silver nanoparticles by Aspergillus sp., TEM analysis revealed that, the silver nanoparticles were spherical shape with 5–30 nm in size. FTIR showed bands at 1639, 1383, 1115 and 516 cm−1 which corresponding to different functional groups possibly involved in the synthesis and stabilization of AgNPs while XRD revealed intense peaks corresponding to (111), (200), (220) and (311) which indicating the crystalline nature of the AgNPs synthesized by Aspergillus sp. The antibacterial activity of AgNPs against pathogenic bacteria showed, highest activity against Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli respectively according to diameter of inhibition zone around the well filled by different concentration of AgNPs (100, 50, 25, 12.5, 6.25 and 3.125 µg/mL) in each wells. MTT assay method used to assessment cytotoxic effects of biosynthesized AgNPs against human colorectal adenocarcinoma cells (Caco-2) as cancer cell and kidney of African green monkey (normal Vero cells) when exposure to 1000, 500, 250, 125, 62.5, 31.25, 15.62, 7.81, 3.90, 1.95, 0.97 and 0.48 µg/mL of AgNPs. According to results, IC50 for Caco-2 cell and Vero cell were 3.75 µg/ml and 280 µg/mL respectively. This study demonstrates the possible use of biologically synthesized silver nanoparticles in medical field.