Synthesis of “Offensive and Defensive Integrated” Cyclodextrin-Grafted N⁺-borneol Esters Antibacterial Polymer via RAFT

Bacterial infection of surface-damaged fruit is one of the troubling issues in daily life. To address this issue, the β-cyclodextrin (CD) grafting N⁺-borneol ester antibacterial polymer (CD-NBO<i>_x</i>), containing borneol with active groups and quaternary ammonium compounds (QACs) positive charges, was successfully synthesized using RAFT and characterized by NMR, Fourier-transform infrared, and gel permeation chromatography. Its antibacterial activity and biofilm inhibition were evaluated against <i>Escherichia coli</i> and <i>Staphylococcus aureus</i>, and the adhesion resistance was measured by crystal violet (CV) staining experiments. It indicated that the antibacterial rate of CD-NBO_<i>x</i> reached 99.9 and 87.3% and the biofilm inhibition rates were up to 97.5% against <i>E. coli</i>. Interesting, there was no spoilage of the fruit and only 20% weight loss in the 15-day fruit preservation experiment. CD-NBO<i>_x</i> possesses excellent antibacterial and adhesion resistance due to the synergy between cyclodextrin for biocompatibility and N cation for antibacterial and borneol stereochemistry. In summary, CD-NBO<i>_x</i> as a constructing "offensive and defensive integrated" is validated as a viable antibacterial material while also expanding potential life applications of N⁺-borneol ester polymers in fruit preservation in the future.