Biosynthesis, characterization, and evaluation of bioactivities of leaf extract-mediated biocompatible gold nanoparticles from Alternanthera bettzickiana

Abstract

The objective of the study was to synthesize gold nanoparticles (Au NPs) using leaf extract of Alternanthera bettzickiana (A. bettzickiana). The biosynthesized Au NPs were characterized using UV-vis spectroscopy, X-ray Diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), Energy dispersive X-ray analysis (EDX), Zeta potential and Transmission electron microscopy (TEM). Morphologically, the Au NPs showed spherical shaped structures. Size distribution of Au NPs calculated using Scherrer's formula, showed an average size of 80-120 nm. Au NPs were studied for invitro anti-bacterial and cytotoxic activities. Au NPs exhibited significant anti-microbial activity against Bacillu subtilis, Staphylococcus aureus, Salmonella typhi, Pseudomonas aeroginosa, Micrococcus luteus, and Enterobacter aerogenes by agar well diffusion method. The cytotoxic effect of the biogenic synthesized Au NPs against A549 human lung cancer cell lines provided a vigorous evidence of anticancer activity of Au NPs. Further, the toxicity study of the green synthesized Au NPs on Danio rerio (Zebra fish) embryo was evaluated. This study reports that colloidal Au NPs can be synthesized by simple, non-hazardous methods and that bio-synthesized Au NPs have significant therapeutic properties.

Keywords: A. bettzickiana; Antibacterial; Gold nanoparticles; SEM; Zebra fish embryo.

Fig. 1

Visual observation of Au NPs formation (a) Yellow colour of the gold ion solution changed into (b) red during the formation of Au NPs.

Fig. 2

a) UV–vis spectrum of synthesized gold nanoparticles Alternanthera bettzickiana; b) XRD spectrum green synthesized gold nanoparticles; c) EDAX spectrum shows presence elemental gold; d) FTIR spectrum of green synthesized gold nanoparticles.

Fig. 3

a) SEM image of gold nanoparticles; b) TEM image of bioreduced green synthesized gold nanoparticles.

Fig. 4

Antibacterial activity of green synthesized Au NPS against a) B. subtilis; b) S. aureus; c) Salmonella typhi; d) P. aeruginosa; e) M. luteus; f) E. aerogenes.

Fig. 5

Minimum Inhibitory Concentration (MIC) against a) B. subtilis; b) S. aureus; c) Salmonella typhi; d) P. aeruginosa; e) M. luteus; f) E. aerogenes.

Fig. 6

(a) Gold nanoparticles reduces the cell viability; b) AO/EtBr is used in evaluating the nuclear morphology of apoptotic cells.

Fig. 7

Effects of agarose gel showing the effect on internucleosomal DNA fragmentation in A549 cells.

Fig. 8

a) Immunoblotting analysis of protein expression; b) Effect of compound on tumor suppressor signaling pathway; c) Immunoblotting analysis of protein expression on cyclin cell arrest; d) Effect of drugs on the expression of inflammatory markers in A549 cells. (Experiments were performed in triplicates. The results are expressed as mean ± SE. Significant difference between treated and control group given as *(p < 0.05), ** (p < 0.01) and *** (p < 0.001).

Fig. 9

Immunoblotting of gene expression.

Fig. 10

Effect of gold nanoparticles on gene expression in Bax, Bcl-2 and p53. (Experiments were performed in triplicates. The results are expressed as mean ± SE. Significant difference between treated and control group given as *(p < 0.05), ** (p < 0.01) and *** (p < 0.001).

Fig. 11

Heat map summary and hierarchical clustering of gene expression.

Fig. 12

1. a) Normal development of zebra fish embryo at different time interval (A-12 h, B-36 h and 48 h); 2. b) Normal development of zebra fish embryo treated with plant based gold nanoparticles concentrations of 12μM; 3. c) Normal development of zebra fish embryo treated with plant based gold nanoparticles concentrations of 25μM; 4 d) Normal development of zebra fish embryo treated with plant based gold nanoparticles concentrations of 50 μM.