Simple Approach for the Preparation of Carboxylatopillar[5]arene‐Modified Silver Nanoparticles as Carriers for Antimicrobial Benzalkonium Chloride

Recent advancements have highlighted the remarkable potential of silver nanoparticles (AgNPs), which are celebrated for their unique properties and effective antimicrobial performance. This study investigates the dual‐function potential of carboxylatopillar[5]arene (CP5) as both a reducing and stabilizing agent in the synthesis of AgNPs (CP5‐AgNPs). A straightforward synthesis method was developed, demonstrating the effective reduction of silver ions to form stable CP5‐AgNPs without the need for additional energy sources. Characterization techniques were utilized to confirm the successful synthesis of CP5‐AgNPs, highlighting the simplicity of the preparation method and the ability to control particle size. The incorporation of benzalkonium chloride (BC) onto the surface of CP5‐AgNPs through host‐guest interactions facilitated the formation of CP5‐AgNPs‐BC composites, which significantly enhanced their antimicrobial properties. Antibacterial assays demonstrated that CP5‐AgNPs‐BC exhibited potent synergistic antimicrobial activity against Staphylococcus aureus (ATCC 29213, a common Gram‐positive bacterium), with an inhibition zone of ∼1.75 cm and a minimum inhibitory concentration (MIC) of 1.59×10 −3  mM (based on BC), but showed no inhibitory effect on Escherichia coli (ATCC 25922, a common Gram‐negative bacterium). The results indicated that the novel CP5‐AgNPs‐BC composites not only exhibited potent antimicrobial activity against Gram‐positive bacteria but also offered a promising platform for the development of advanced drug delivery systems targeting Gram‐positive bacterial infections in medical fields.