Choline-amino acid-based polyionic liquids and ionogels for antimicrobial infections

Microbial infections pose a serious threat to human health. Although antibiotics from various sources continue to be discovered, antibiotics often induce resistance in microorganisms. Therefore, the development of novel antimicrobial agents or materials based on new mechanisms remains an urgent need. Herein, a series of choline-amino acid polyionic liquids ([Cho][AA] PILs) and the corresponding composite ionogels (BC/PILs) made from [Cho][AA] PILs and bacterial cellulose (BC) were prepared by ex situ method. The antimicrobial properties of PILs and BC/PIL ionogels, as well as the mechanical, conductive and biocompatible properties of BC/PIL ionogels were investigated. The resultant PILs and BC/PIL ionogels exhibited efficient antimicrobial activity against Gram-positive bacteria, Gram-negative bacteria and fungi. Moreover, the concentration, chirality, hydrophilic and hydrophobic properties of [Cho][AA] PILs have a significant impact on the antimicrobial performance of these materials. Among them, D-type phenylalanine-based PILs (D-P[Cho][Phe]) and BC/PIL ionogels based on the highest concentration of D-type PILs (D-BC/PIL-1.6 ionogels) showed the strongest antimicrobial properties against microorganisms. The MIC and MBC of D-P[Cho][Phe] could be as low as 32±1.6 mmol L-1 and 64±3.2 mmol L-1. Morover, D-P[Cho][Phe] displayed the fastest bactericidal rate and killed bacteria within 2 h. In addition, BC/PIL ionogels with excellent mechanical and conductive properties could be achieved by controlling the concentration and type of [Cho][AA] PILs. Serine-based ionogels (BC/P[Cho][Ser]) possessed the highest mechanical strength. BC/PIL-1.6 ionogels showed the highest conductivity. More significantly, [Cho][AA] PILs and BC/PIL ionogels exhibited good biocompatibility. These results provided novel ideas and a practical basis for the development of new antimicrobial materials and suggested the promising application potential of [Cho][AA] PILs and their corresponding BC/PIL ionogels in the biomedical field.