One-Pot Hydrothermal Synthesis of Benzalkonium-Templated Mesostructured Silica Antibacterial Agents

Novel mesostructured silica microparticles are synthesized, characterized, and investigated as a drug delivery system (DDS) for antimicrobial applications. The materials exhibit a relatively high density (0.56 g per 1 g SiO₂) of benzalkonium chloride (BAC), pore channels of 18 Å in width, and a high surface area (1500 m²/g). Comparison of the small-angle X-ray diffraction (SAXRD) pattern with Barrett-Joyner-Halenda (BJH) pore size distribution data suggests that the 18 Å pores exhibit short-range ordering and a wall thickness of ca. 12 Å. Drug release studies demonstrate pH-responsive controlled release of BAC without additional surface modification of the materials. Prolonged drug release data were analyzed using a power law (Korsmeyer-Peppas) model and indicate substantial differences in release mechanism in acidic (pH 4.0, 5.0, 6.5) versus neutral (pH 7.4) solutions. Microbiological assays demonstrate a significant time-dependent reduction in Staphylococcus aureus and Salmonella enterica viability above 10 and 130 mg L^-1 of the synthesized materials, respectively. The viability of cells is reduced over time compared to control samples. The findings will help in widening the use of BAC as a disinfectant and bactericidal agent, especially in pharmaceutical and food industries where Gram-positive and Gram-negative bacterial contamination is common.