Thyme oil-loaded chitosan microparticles: an antibacterial approach against pathogenic bacteria

Thyme oil was encapsulated effectively in chitosan microparticles (CTT-MPs) through ionic gelation with a maximum entrapment efficiency of 73.42%. The optimal encapsulation was achieved using 15 mg/ml of chitosan and 7 mg/ml of tripolyphosphate. The CTT-MPs exhibited considerably higher antimicrobial activity than free thyme oil and blank chitosan microparticles. In particular, the CTT-MPs had lower minimum inhibitory concentrations (MICs) against Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Staphylococcus aureus. In addition, CTT-MPs successfully suppressed biofilm formation, with over 99% inhibition of biofilm formation. The CTT-MPs had excellent antioxidant activity, with a DPPH radical scavenging ability of 87.67%, which is much greater compared to the 57.77% for blank microparticles. Particle-size analysis showed that the CTT-MPs had a particle diameter of 1.6 µm. The zeta potential of the CTT-MPs was found to be 38 mV, reflecting good colloidal stability. These results underscore the potential of CTT-MPs as a new therapeutic platform that possesses antibacterial, antibiofilm, and antioxidant activities with a novel application for thyme oil delivery.