pH triggered polycarvacrol-based antibacterial microspheres: Integrated offensive and defensive platform

Abstract

The natural plant essential oil carvacrol exhibits substantial antimicrobial properties. However, its efficacy is significantly compromised following functionalization, thereby limiting its optimal application in polymer science. In this study, a quaternary ammonium carvacrol ester ionic liquid monomer was synthesized utilizing the ionic liquid technique. Subsequently, a series of cyclodextrin-grafted poly(quaternary ammonium carvacrol ester) polymer nanospheres were prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization. The controllability offered by RAFT polymerization enables precise loading of carvacrol small molecules, representing a significant breakthrough for the incorporation of carvacrol into polymers. Particularly noteworthy is the CD-DM_x formulation, which demonstrates exceptional antibacterial efficacy against both E. coli and S. aureus. This is attributed to the synergistic interaction between carvacrol and cationic components, resulting in a 100% antibacterial ratio. Additionally, the labile nature of the betaine ester bonds with carvacrol and cations facilitates the controlled release of carvacrol from the CD-DM_x matrix while preventing its deactivation during functionalization. This property facilitates the transition of CD-DM_x from exhibiting antibacterial properties (offense mode) to demonstrating anti-protein adhesion properties (defense mode). Furthermore, cytotoxicity assessments and electrospinning studies have demonstrated the biocompatibility and potential applications of CD-DM_x in medical protective equipment. In summary, we have not only proposed a strategy for the efficient utilization of natural carvacrol essential oil but has also developed a green, environmentally friendly cationic essential oil-based antibacterial agent that is well-suited for medical applications.