Biocompatible Copolymerized Gold Nanoclusters: Anti-TNF-α siRNA Binding, Cellular Uptake, Cytotoxicity, Oxidative Stress and Cell Cycle Effects In Vitro

Small interfering RNAs (siRNAs) have emerged as a powerful tool in the treatment of aggressive cancers. By exploiting and mimicking the natural gene regulation mechanism of RNA interference (RNAi), they allow for sequence-specific silencing of aberrant genes. siRNA-mediated knockdown of the inflammatory cytokine tumour necrosis factor-alpha (TNF-α) presents a novel therapy for triple-negative breast cancer (TNBC). This study investigated the potential of novel biomimetic glutathione-synthesised gold nanoclusters (AuNCs) as siRNA delivery vehicles. AuNCs were functionalized with biocompatible chitosan and polyethene glycol, and their interactions with siRNAs were investigated through binding studies. In vitro cytotoxicity and cellular uptake were conducted in the human breast cancer (MCF-7), TNBC (MDA-MB-231), and embryonic kidney (HEK293) cells, while the effect of anti-<i>TNF-α</i> siRNA nanocomplexes on biological processes, such as oxidative stress, apoptosis, and cell cycle distribution, was investigated using flow cytometry. UV-visible and Fourier transform infrared spectroscopy, as well as transmission electron microscopy, confirmed the synthesis and functionalization of the AuNCs. Functionalized AuNCs (FAuNC) effectively bound and condensed siRNA and protected against nuclease degradation. AuNCs facilitated efficient cellular uptake and were well-tolerated in vitro. Anti-<i>TNF-α</i> siRNA treatment of the MDA-MB-231 cells increased apoptosis and oxidative stress levels, and affected cell cycle distribution. Although the overall knockdown was low, these FAuNCs exhibited favorable physicochemical characteristics, low cytotoxicity and good cellular uptake in vitro, warranting further optimisation for improved delivery of therapeutic siRNAs.