Green synthesis of nisin-loaded pectin based silver nanoparticles and their antimicrobial and biosafety assessment

Antibacterial ability and biosafety of silver nanoparticles (AgNPs) is attracting more and more attention. In this work, nisin was loaded on the surface of pectin-based AgNPs (P-AgNPs), and NP-AgNPs was synthesized by using a one-pot method. The nanomaterials were characterized by using the following methods, TEM showed that the average diameters were changed from 21.79 to 25.35 nm, FT-IR indicated that Ag⁺ was reduced by electrostatic interaction, XPS showed that nisin was conjugated on the surface of AgNPs, and Zeta potential assays showed the changes of surface potential. It was worth noting that NP-AgNPs had excellent antibacterial capacity, the minimum inhibitory concentration (MICs) reached 16.7 and 33.3 µg/mL against E. coli and S. aureus, respectively, which were 32 and 16 times lower than those of P-AgNPs. The experimental results indicated that the loading of nisin increased the zeta potential of NP-AgNPs, which made it easier to bind to the bacterial cells. Antibacterial mechanism indicated that NP-AgNPs caused cell membrane and cell wall damage, and produced more ROS, which resulted in bacterial lysis and leakage. Furthermore, NP-AgNPs showed higher hemocompatibility, lower cytotoxicity, and higher inhibitory effects on tumour cells. Overall, NP-AgNPs have the potential to be used in pharmaceutical and food industry.