Antibacterial performance effects of Ag NPs in situ loaded in MOFs nano-supports prepared by post-synthesis exchange method

The preparation of metal nanoparticles (NPs) on metal-organic frameworks (MOFs) has aroused great interest in the field of bacteriostasis. However, MOFs as nano-supports to form uniformly dispersed NPs loadings has still been in the exploratory stage. The use of Agx/Cu-BTC as nano-supports was investigated for the preparation of silver nanoparticles and their antibacterial activity. The post-synthetic exchange method was used to achieve the in situ loading of Ag NPs on copper(II) benzene-1,3,5-tricarboxylate (Cu-BTC) nano-supports and the Agx/Cu-BTC (x = 7, 14, 21% molar ratio) were successful synthesized. The crystal structure characteristics and the physicochemical properties of the prepared materials were analyzed by SEM, EDS, FT-IR, XRD, XPS, TG, and BET. Using Bacillus subtilis as the experimental strain and Cu-BTC as the antibacterial activity standard, the antibacterial performance of Agx/Cu-BTC was evaluated using the minimum inhibitory concentration test and the Kirby-Bauer test. According to the reaction mechanism of related antibacterial materials, a reasonable mechanism explanation was given for the antibacterial effect of Ag NPs. All characterization results demonstrated that the preparation of Ag NPs using Cu-BTC as nano-supports did not destroy the structure of Cu-BTC. Agx/Cu-BTC still maintained the ortho-octahedral structure, which demonstrated the in situ preparation of Ag NPs was achieved. With the ratio of Ag NPs increased, the specific surface area became smaller, the average pore size became larger, and the thermal stability was enhanced. Agx/Cu-BTC showed significantly stronger antibacterial activity than Cu-BTC. Among the synthesized materials, Ag21/Cu-BTC showed the strongest antibacterial activity, which was due to the more adsorption of Ag NPs onto the cell wall, causing irregular pits and damaging the cell wall and cell membrane. As a result, the cell membrane permeability was altered, allowing more nutrients to flow out of the cell. Ag NPs entered the cell causing a significant increase in the level of reactive oxygen species (ROS), leading to cell damage or death. The higher the concentration of Ag NPs, the more Ag+ was released and the stronger the antibacterial activity. Overall, the in situ preparation of Ag NPs by MOFs nano-supports has the potential to enhance the antibacterial performance of Ag NPs, making them more effective in applications.