Nanosilica-reinforced carboxymethyl cellulose/polyacrylamide hydrogel composites for sustained lidocaine release

Despite the widespread clinical use of lidocaine, conventional delivery systems (e.g., injections, patches) suffer from rapid drug release (<24 h duration). To address this limitation, this study developed a nanosilica-reinforced carboxymethyl cellulose/polyacrylamide (CMC/PAM/SiO₂) hydrogel for sustained lidocaine delivery. A sol-gel method combined with free radical polymerization constructed a three-dimensional network, where nano-SiO₂ (0-1.00 g loading) served as multifunctional crosslinkers to enhance mechanical strength (117 kPa tensile strength, 588% increase vs. pure PAM) and pore density (400% equilibrium swelling ratio). Characterizations of CMC/PAM/SiO₂ confirmed homogeneous SiO₂ dispersion and hydrogen bonding between Si-OH and polymer groups (-COO^-/-CONH₂). In vitro drug release experiments demonstrated that the drug loading of lidocaine in the composite hydrogel achieved a cumulative release rate of 91.48% within 72 h, which conformed to the Ritger-Peppas kinetic model, indicating a synergistic effect of diffusion and swelling mechanisms. Nano-SiO₂ doping at 1.00 g optimized antibacterial performance (2.16-fold enhancement against E. coli vs. PAM) while maintaining high water retention (67% after 24 h). This mechanically robust platform provides slow release of lidocaine with integrated antibacterial functionality, demonstrating significant potential for extended-duration local anesthesia.