Chlorine dioxide-loaded poly(acrylic acid) gels for prolonged antimicrobial effect.

Chlorine dioxide, the so-called "ideal biocide", can be successfully applied as an antiseptic agent based on its rapid and safe antimicrobial property. One of the significant limitations of its topical or oral use is that the chlorine dioxide residence time in aqueous solution is very short due to the volatility of the gas. Therefore, the primary purpose of the present study was to increase the duration of chlorine dioxide effect by creating a system capable of loading the gas for a prolonged time and gradually releasing it at the site of action. Poly(acrylic acid) gels of various chlorine dioxide and polymer concentrations were formulated to achieve this goal. A two-factor, three-level face-centred central composite design was applied for the formulation. The microstructure of the gels was tracked by positron annihilation lifetime spectroscopy based on the ortho-positronium (o-Ps) lifetime distributions with the residual chlorine concentrations, determined by iodometric titration and their antibacterial effects. The results indicate that the polymer possesses two functions. On the one hand, as a diffusion barrier inhibits the fugacity of the gaseous chlorine dioxide but on the other side, the polymer chains form an arranged supramolecular structure with the hydrated forms of chlorine dioxide thus resulting in its sustained fugacity. The latter showed optimum as a function of the polymer concentration in the investigated range (0.1-0.3% w/w). The o-Ps lifetime distributions confirmed the microstructural changes of the formulations and were in good agreement with the analytical and microbiological evaluation. The application of chlorine dioxide-loaded bioadhesive gels could be a promising alternative for the effective and safe treatment of topical infections.