Lignin micro-nanospheres loaded with silver nanoparticles for excellent antibacterial activity

Silver nanoparticles (AgNPs) have been widely studied for their tunable structural properties and broad-spectrum antibacterial properties. However, AgNPs are easy to accumulate and unstable. Herein, lignin micro-nanospheres (LMNs) loaded with silver nanoparticles were prepared by chemical reduction method. The AgNPs/LMNs composite manifested good stability and dispersibility to AgNPs. The total release content of Ag/Ag⁺ was only 0.13 % within 12 h and only 2.25 % within 24 h due to the self-antibacterial properties and high surface activity of LMNs. The AgNPs/LMNs showed excellent inhibition and killing effects on both Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) within 24 h, with the minimum bactericidal concentrations (MBC) of 5 and 2.5 μg/mL, respectively. After collaborative photothermal-assisted treatment, the MBC was reduced to 2.5 and 1.25 μg/mL, respectively. Compared to the same type of AgNPs composite, the concentration of antibacterial components required using the method was reduced by >90 %. The AgNPs in the AgNPs/LMNs caused direct damage to the bacterial cell membrane by generating reactive oxygen species and releasing silver ions, thus achieving an antibacterial effect. This provides an effective strategy for the development of new antibacterial materials.