Enhanced Antimicrobial and Anticancer Activity of Silver and Gold Nanoparticles Synthesised Using Sargassum incisifolium Aqueous Extracts

Abstract

A detailed, methodical approach was used to synthesise silver and gold nanoparticles using two differently prepared aqueous extracts of the brown algae Sargassum incisifolium. The efficiency of the extracts in producing nanoparticles were compared to commercially available brown algal fucoidans, a major constituent of brown algal aqueous extracts. The nanoparticles were characterised using TEM, XRD and UV/Vis spectroscopy and zeta potential measurements. The rate of nanoparticle formation was assessed using UV/Vis spectroscopy and related to the size, shape and morphology of the nanoparticles as revealed by TEM. The antioxidant, reducing power and total polyphenolic contents of the aqueous extracts and fucoidans were determined, revealing that the aqueous extracts with the highest contents produced smaller, spherical, more monodisperse nanoparticles at a faster rate. The nanoparticles were assessed against two gram-negative bacteria, two gram-positive bacteria and one yeast strain. In contrast to the literature, the silver nanoparticles produced using the aqueous extracts were particularly toxic to Gram-negative bacteria, while the gold nanoparticles lacked activity. The cytotoxic activity of the nanoparticles was also evaluated against cancerous (HT-29, MCF-7) and non-cancerous (MCF-12a) cell lines. The silver nanoparticles displayed selectivity, since the MCF-12a cell line was found to be resistant to the nanoparticles, while the cancerous HT-29 cell line was found to be sensitive (10% viability). The gold nanoparticles displayed negligible toxicity.

Inhibition of Bacteria Associated with Wound Infection by Biocompatible Green Synthesized Gold Nanoparticles from South African Plant Extracts

“…It is, however, possible that a higher concentration of the extracts can be active against these bacterial strains as demonstrated previously [ 30 ]. The lower antibacterial activity of the extracts compared to the GNPs may be due to the fact that either the bacteria are adopting resistance mechanisms against the free phytochemicals or there is some synergistic activity between the GNPs and the capping phytochemicals [ 65 ]. The higher antibacterial activity of the biogenic GNPs may also be associated with the increase in the concentration of the active phytochemicals capping the GNPs.…”

Synthesis of Biogenic Gold Nanoparticles from Terminalia mantaly Extracts and the Evaluation of Their In Vitro Cytotoxic Effects in Cancer Cells

“…The viability of the MCF 7, Caco-2, HePG2 and KMST-6 cells treated with TM crude extracts and AuNPs was evaluated using the MTT assay as described previously with some modifications [ 71 ]. The cells were maintained in DMEM containing 10% fetal bovine serum and 1% penicillin–streptomycin cocktail in a 37 °C humidified incubator with 5% CO 2 saturation.…”

Attachment efficiency of gold nanoparticles by Gram-positive and Gram-negative bacterial strains governed by surface charges

“…However, the surface charge measured as a ζ-potential (zeta potential) depends on the bacterial strain and its particular surface characteristics (Kłodzińska et al 2010;Khelissa et al 2017). The electrochemical behavior of bacterial cell surfaces is particularly important for the application of nanoparticles (NPs) as antimicrobial agents (Ramasamy et al 2016;Mmola et al 2016), in the detection of viruses, bacteria, and spores (Sajjanar et al 2015;Donmez et al 2017) or even for the production of NPs inside the microorganism (Nangia et al 2009;Durán et al 2011;Deplanche et al 2012;Srivastava et al 2013;Jung et al 2018).…”