Gold and silver nanoparticles for safe and effective biomedical applications

Metallic gold and silver nanoparticles have been extensively studied as nanoscale technologies for targeted gene and drug delivery agents. This narrative review incorporates the latest advances in the therapeutic and diagnostic potential of gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs) while also critically investigating their toxicity, safety concerns, and clinical translation. The therapeutic applications include antibacterial, antiviral, anti-inflammatory, anticancer, and dermatological applications. This review also provides a critical comparison between AuNPs and AgNPs in terms of their therapeutic potential and toxicological concerns. Epigenetic effects and clinical translation barriers are also compared. More importantly, AuNPs and AgNPs differ significantly in terms of their readiness to be translated clinically. As compared to AgNPs, greater biocompatibility and higher physicochemical stability are exhibited by AuNPs. On the other hand, AgNPs have been known to demonstrate higher cytotoxicity and antimicrobial potential but are at a higher risk of causing systemic toxicity and oxidative degradation. These therapeutic and diagnostic potentials are mainly due to surface plasmonic resonance, oxidative stress-associated cytotoxicity, surface functionalization, photothermal conversion, and nanoparticle-mediated cellular signaling pathway modulation. However, clinical translation of these metallic nanoparticles is still limited owing to toxicological concerns, biodistribution, and epigenetic or multigenerational issues. Therefore, incorporation of these metallic nanoparticles in clinical settings requires addressing systemic toxicity, controlled biodistribution, chronic toxicity, and standardization issues.