Zirconium-Coated β-Cyclodextrin Nanomaterials for Biofilm Eradication

Under alkaline treatment, zirconyl chloride (ZrOCl₂.8H₂O) became a zirconia gel and formed a stable complex with beta-cyclodextrin (βCD). This complex was highly active in reactive oxygen species (ROS) formation via H₂O₂ decomposition. Its surface with numerous hydroxyl groups acts as an ionic sponge to capture the charged reaction intermediates, including superoxide (O₂^-•) and the hydroxyl radical (^•OH). ROS, especially ^•OH radicals, are harmful to living microorganisms because of their kinetic instability, high oxidation potential, and chemical nonselectivity. Therefore, ^•OH radicals can engage in fast reactions with virtually any adjacent biomolecule. With H₂O₂, the complex with cationic and hydrophobic moieties interacted with the anionic bacterial membrane of two Gram-positive (Staphylococcus aureus and S. epidermidis) and two Gram-negative (Escherichia coli and Klebsiella pneumoniae) strains. The Zr-βCD-H₂O₂ also eradicated more than 99% of the biofilm of these four pathogens. Considering the difficult acquisition of resistance to the oxidation of ^•OH, the results suggested that this βCD-based nanomaterial might be a promising agent to target both drug-resistant pathogens with no cytotoxicity and exceptional antimicrobial activity.