Hot injection synthesis of metal-doped Ag2S nanocrystals: A novel multifunctional approach for cancer therapy, antibacterial strategies, and antioxidant defense

This pioneering study presents the synthesis and comprehensive evaluation of bare and metal-doped Ag₂S nanocrystals (NCs) as multifunctional agents with potential applications in antibacterial, antioxidant, and anticancer therapies. The incorporation of manganese, nickel, cobalt, and zinc into Ag₂S NCs resulted in a notable enhancement of their bioactivity, representing a novel approach in nanomaterial design. The antibacterial assessments revealed that Mn:Ag₂S NCs were the most potent candidate, exhibiting exceptional activity against S. aureus and E. coli, with the lowest MIC values recorded at 1.28 mg/mL and 1.08 mg/mL, respectively. The antioxidant studies demonstrated that the Mn:Ag₂S NCs exhibited remarkable free radical scavenging and ferric reducing capacities, with the lowest IC50 values (22.69 µg/mL for DPPH and 61.31 µg/mL for FRAP) underscoring their potential to mitigate oxidative stress. Importantly, cytotoxicity assays revealed that Ni:Ag₂S and Mn:Ag₂S nanocrystals selectively inhibited the proliferation of human colon cancer cells (HT-29), achieving IC50 values of 61.51 µg/mL and 90.12 µg/mL, respectively. Furthermore, these NCs demonstrate reduced toxicity towards mouse fibroblast cells (L929). This selective cytotoxicity indicates the potential of these agents in targeted cancer therapies, thereby reducing damage to healthy tissues. To the best of our knowledge, this is the first study to systematically explore the synergistic effects of metal doping on the multifunctional properties of Ag₂S NCs. These findings provide a robust basis for further in vivo studies and offer new avenues for the development of safe and effective nanomaterials in biomedical applications, particularly as antimicrobial, antioxidant, and anticancer agents.