Broad Spectrum Anti-Bacterial Activity and Non-Selective Toxicity of Gum Arabic Silver Nanoparticles

Abstract

Silver nanoparticles (AgNPs) are the most commercialized nanomaterials and presumed to be biocompatible based on the biological effects of the bulk material. However, their physico-chemical properties differ significantly to the bulk materials and are associated with unique biological properties. The study investigated the antimicrobial and cytotoxicity effects of AgNPs synthesized using gum arabic (GA), sodium borohydride (NaBH4), and their combination as reducing agents. The AgNPs were characterized using ultraviolet-visible spectrophotometry (UV-Vis), dynamic light scattering (DLS), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FT-IR). The anti-bacterial activity was assessed using agar well diffusion and microdilution assays, and the cytotoxicity effects on Caco-2, HT-29 and KMST-6 cells using MTT assay. The GA-synthesized AgNPs (GA-AgNPs) demonstrated higher bactericidal activity against all bacteria, and non-selective cytotoxicity towards normal and cancer cells. AgNPs reduced by NaBH4 (C-AgNPs) and the combination of GA and NaBH4 (GAC-AgNPs) had insignificant anti-bacterial activity and cytotoxicity at ≥50 µg/mL. The study showed that despite the notion that AgNPs are safe and biocompatible, their toxicity cannot be overruled and that their toxicity can be channeled by using biocompatible polymers, thereby providing a therapeutic window at concentrations that are least harmful to mammalian cells but toxic to bacteria.

Biomedical Applications of Plant Extract-Synthesized Silver Nanoparticles

“…Several studies have demonstrated the potential anti-cancer activity of AgNPs, including AgNPs synthesized from various plant extracts [ 23 ]. Table 5 highlights some of the plant-synthesized AgNPs and their anti-cancer effects on multiple cancer cell lines, namely breast (MCF-7) [ 110 ], lung (A549) [ 111 ], cervical (HeLa) [ 112 ], colon (HT-29, Caco-2) [ 113 ], prostate (PC-3) [ 26 ], and VCaP [ 114 ] cancer cell lines. The half-maximal inhibitory concentration (IC 50 ) of AgNPs was comparable to that of standard anti-cancer drugs [ 23 ] and a validation that AgNPs could be useful as anti-cancer agents.…”

“…Although the biogenic AgNPs are considered to have a reduced risk of toxicity compared with cAgNPs, they are also non-selective. The toxicity of biogenic AgNPs is also influenced by a number of parameters, among others being the size [ 113 ].…”

Highly active antiretroviral therapy-silver nanoparticle conjugate interacts with neuronal and glial cells and alleviates anxiety-like behaviour in streptozotocin-induced diabetic rats

“…Thus, conjugation of AgNPs to HAART may exert significant benefits, such as reducing the dosage of HAART needed for therapy and inhibiting some pathophysiological mechanisms mediated by HAART in contribution to diabetes ( Lawal et al, 2021 , Olojede et al, 2022 ). Although, the issues related to the toxicity profile of AgNPs on the biological tissues have been raised ( Fadaka et al, 2022 ). Conversely, studies have reported that the toxicity profile of AgNPs depends on several factors such as nanoparticles size, shape, morphology, dimension, and capping agent ( Alkaladi et al, 2014 , Fadaka et al, 2022 ).…”

“…Although, the issues related to the toxicity profile of AgNPs on the biological tissues have been raised ( Fadaka et al, 2022 ). Conversely, studies have reported that the toxicity profile of AgNPs depends on several factors such as nanoparticles size, shape, morphology, dimension, and capping agent ( Alkaladi et al, 2014 , Fadaka et al, 2022 ).…”

Frontiers in Antimicrobial Biomaterials

“…Gum arabic was deemed to be the most effective reducing agent in improving the bactericidal efficiency of the synthesized silver nanoparticles. However, the authors concluded that the nanoparticle toxicity could not be completely overcome, even by using a greener synthesis methodology, which is required in order to establish ranges of effectiveness for human safety [ 9 ]. Novel aminothiazoles with superior antiviral, antioxidant, and antibacterial activities were also synthesized by Minickaitė et al They demonstrated that, by using substitutes in the thiazole ring, optimized antimicrobial structures could be generated with target specificity [ 10 ].…”