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In recent years, due to the potential application of metal nanomaterials in the field of medical sectors, the biological preparation of silver nanoparticles is attracting people's interest. Melanin is a natural biological dye, has a variety of biological functions, and has been widely used in the preparation of composites. In this study, melanin-nanometer silver (Mel-AgNPs) composites were prepared by one-step biological method using silver nitrate as raw material and melanin as reducing agent and coating agent. The ultraviolet - visible spectrum of MEL-AgNPS composites showed the maximum absorption wavelength at 403 nm, which proved nano silver formation. The FTIR confirmed the carboxyl group in melanin to reduce the Ag+ reduction as AgNPs, which promoted melanin covered in nano-silver surface. The SEM analysis showed that the morphology of Mel-AgNPs showed a spherical, and the particle diameter was about 30 nm. The element silver in the synthesized Mel-AgNPs was confirmed using EDX to exist silver in the synthetic Mel-AgNPS, and the crystal structure was characterized by XRD. The antibacterial activity experiments showed that Mel-AgNPs composites had inhibitory effect both on Escherichia coli and Staphylococcus aureus, and the inhibitory effects on E.coli is greater than Staphylococcus. In vitro antioxidant experiments showed that Mel-AgNPs composites had strong Fe3+ reduction ability and scavenging activity of DPPH and ABTS radical. The cytotoxicity experiments showed that Mel-AgNPs composite had weak toxicity to normal mouse fibroblast L929 and had inhibitory effect on human breast cancer cell line MCF-7, and Mel-AgNPs composites could down-regulate the level of BCl-2 gene in MCF-7 cells. This indicated that the material could inhibit the growth of cancer cells by regulating the pathways involved in the process of apoptosis and had certain anti-tumor activity. The anti-tumor experiments showed that Mel-AgNPs composites have strong antiviral capabilities to the H3N2 of the influenza virus, which can be used as a promising potential antiviral agent.

In this study, BM-Fe (black sesame melanin iron complex) was prepared and characterized; The results showed that the carboxyl hydroxyl group of BSM (black sesame melanin) participated in the chelation...