Physico-chemical and antibacterial properties of gold nanoparticles synthesized using Avicennia marina seeds extract

Abstract

This study investigated the synthesis and antibacterial activity of gold nanoparticles (AuNPs), produced using aqueous Avicennia marina seed extract. Reaction of the extract with chloroauric acid led to the reduction of auric chloride and the formation of AuNPs within 10 min at 28 °C. The size, shape and elemental composition of the nanoparticles (NPs) was studied using transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and UV-visible spectroscopy. Furthermore, the biological capping agents of the NPs were identified via Fourier-transform infrared spectroscopy (FT-IR). The seed extract served as an effective bio-reductant for the synthesis of AuNPs. High-resolution TEM images revealed the NPs to be predominantly spherical in shape, with some hexagonal and rod-shaped particles observed. The AuNPs displayed inhibitory activity against a range of human pathogenic bacterial species: Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, Enterococcus faecalis and Pseudomonas aeruginosa. Complete inhibition was observed at 200 µg/mL. However, E. faecalis was resistant to the NPs. The results suggest that AuNPs synthesised using aqueous seed extracts of mangrove species such as A. marina may serve as broad-spectrum antibacterial agents, particularly for antibiotic resistant strains.

Keywords:

• antibacterial
• biosynthesis
• electron microscopy
• gold nanoparticles
• mangroves

ACKNOWLEDGEMENTS

The authors would like to acknowledge Mr Ajay Bissessur (School of Chemistry and Physics, UKZN, Westville Campus, Durban) for assisting with FTIR analysis.

DISCLOSURE STATEMENT

Authors declare no conflict of interests.

CONTRIBUTORY STATEMENT

KSBN performed the experiments, data analysis and prepared the manuscript. NM assisted with data analysis & electron microscopy, Sershen designed the experiments and reviewed the manuscript. KSBN, NM and Sershen edited and revised the manuscript.

ORCID

Krishna Suresh Babu Naidu http://orcid.org/0000-0003-3155-8878