From staples to biodegradable solutions: AZ31 magnesium alloy sutures with dual-layer PAA-chitosan coating for...

Postoperative complications such as suture-related infections and rapid corrosion of biodegradable materials remain critical challenges in gastrointestinal surgeries. This study investigates a novel dual-layer coating of polyacrylic acid (PAA) and chitosan applied to AZ31 magnesium (Mg) alloy wires. The AZ31 Mg wires were coated through layer-by-layer (LbL) deposition, with polyethylene imine used as a primer to facilitate attachment. The coated sutures were characterized using Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), tensile testing, hydrogen evolution, stability studies, electrochemical corrosion, antibacterial assays, hemolysis, MTT assay, and in vivo evaluation. FTIR analysis confirmed the successful deposition of PAA and chitosan, revealing functional groups indicative of anticorrosive and antibacterial activity. The tensile strength of coated wires increased significantly from 252 N to 420 N. Hydrogen evolution was reduced by >80 %. Electrochemical corrosion demonstrated a significant reduction in corrosion current density (Icorr), from 8.805 × 10^-8 A/cm² for uncoated samples to 1.807 × 10^-10 A/cm² for the PAA-Ch coated samples, with the corrosion potential (Ecorr) shifting from -1.393 V to -2.935 V. Antibacterial assays revealed broad-spectrum efficacy against S. aureus, E. faecalis, E. coli, and K. pneumoniae. Hemolysis percentages remained below 2 %, and the MTT assay indicated excellent cytocompatibility, with cell viability >85 %. Under simulated physiological conditions, coated sutures exhibited an average weight loss reduction of approximately 50 %. In vivo studies further demonstrated minimal inflammatory response and favorable tissue integration. These findings highlight that the PAA-Chitosan dual-layer coating significantly enhances the corrosion resistance, antibacterial properties, and biocompatibility of AZ31 Mg sutures.