Characterization and antibacterial activity of ruthenium-based shikimate cross-linked chitosan composites

The unsustainable antibacterial activity of ruthenium antibacterial agents is an important factor limiting their applications. This present work attempts to prepare ruthenium (Ru) coordination polymer composites with chitosan quaternary ammonium polymers (CQ) and shikimic acid (SA) through the interaction of ionic bonds and covalent bonds by microwave-assisted high-pressure homogenization methods. The prepared CQ@Ru-SA was characterized by size distribution, zeta potential, TEM, UV-vis, FTIR, XPS and XRD analyses. The coordination structure and morphology of Bridge-CQ-NH-Ru-SA were verified. The CQ@Ru-SA was well-dispersed in both the aqueous or anhydrous states. MIC and MBC, time-killing curves, biofilm formation inhibition assay, mature biofilm disruption assay, SEM, Ca²⁺ mobilization assay and Ca²⁺-Mg²⁺-ATPase activity studies revealed that CQ@Ru-SA had a stronger inhibitory effect against S. aureus than CQ and showed sustained antibacterial properties in the dynamic time-killing curves. Meanwhile, CQ@Ru-SA had good antibacterial effects against S. aureus and inhibited their biofilm forming ability in a dose-dependent manner. Further studies on antibacterial mechanisms revealed that CQ@Ru-SA influenced cell membrane integrity, Ca²⁺-Mg²⁺-ATPase activity on the cell membrane and intracellular Ca²⁺ levels of S. aureus. This study will provide the necessary data for the further design and development of ruthenium-based photosensitive antibacterial agents.