Evaluation of antioxidant and antibacterial activity of various aspect ratio gold (Au) nanorods
1Department of Chemical Sciences, Tezpur University, Napaam, Tezpur, Assam 784028, India
2Department of Molecular Biology and Biotechnology, Tezpur University, Napaam, Tezpur, Assam 784028, India
3Department of Physics, Tezpur University, Napaam, Tezpur, Assam 784028, India
Adv. Mater. Lett., 2015, 6 (3), pp 235-241
Publication Date (Web): Feb 22, 2015
Copyright © IAAM-VBRI Press
In the current scenario, metal nanoparticles acquire much attention in terms of their diverse applications because of their extremely small size and large surface to volume ratio. Hence, our present study deals with the investigation of antioxidant and antibacterial activity of gold (Au) nanoparticles. First, anisotropic Au nanorods with various aspect ratios have been synthesized by a standard seeded growth method using CTAB-coated Au seed nanoparticles with size less than 10 nm as nucleation centre. Characterization of synthesized nanorods is made using UV-visible and TEM analysis. The antioxidant and antibacterial activities of Au nanorods have been investigated using 1,1-diphenyl-2-picrylhydrazyl (DPPH) as free radical source and Agar-well diffusion assay. The radical scavenging reaction of nanorods was monitored by a UV-visible spectrophotometer and found that Au nanorods show better antioxidant activity than spherical seeds due to the presence of more number of atoms as well as active sites for interaction with the free radical of DPPH. For a set of nanorods DPPH scavenging percentage is 80-90, while for seeds it is only 30. Again, very less amount (volume) of high aspect ratio nanorods is required for efficient scavenging. A linear relationship is observed between DPPH scavenging percentage and volume of Au nano-dispersions. The synthesized Au nanoparticles also have potent antibacterial activity, the maximum zone of inhibition (20 mm) is observed for longer nanorods, against indicator strains due to the interaction of more number of Au+ cations to the negatively charged bacterial cell wall that causes rupturing of the cell wall and finally death. The minimum inhibitory concentration (MIC) for nanorods is lower when tested against gram negative bacteria viz. Y. enterocolitica (12.5μg/ml), S. enterica typhimurium (15 μg/ml), and K. pneumoniae (10 μg/ml) as compared to gram positive bacteria viz. S. aureus (20 μg/ml), L. monocytogenes AMDK2 (20 μg/ml) and B. cereus AMDK1 (25 μg/ml). From this study, it is concluded that high aspect ratio Au nanorods can act as an effective antioxidant and antibacterial agent and it makes the nanoparticles as an alternative for the development of new biomedical drugs in near future.
Antibacterial, antioxidant, nanocrystal, DPPH.