LAUSR

Antibiotic-loaded in situ forming gels are particularly attractive for periodontitis treatment. They are in a sol form and gradually alter to a solid-like depot after administration into a periodontal pocket to deliver and maintain the effective high level of drug in the gingival crevicular fluid. Solvent-inducing in situ forming gel mostly exhibits the burst drug release owing to rapid diffusion of solvent. This study incorporated peppermint oil to modulate the drug release and the gel characteristics of doxycycline hyclate-loaded Eudragit RS in situ forming gel systems. Peppermint oil increased the viscosity and syringeability of the Eudragit RS solution comprising NMP as solvent and retarded the water penetration. Therefore the diminishment of burst liberation and the prolongation of drug release with an addition of peppermint oil were attained with concentration dependence mainly following Fickian diffusion mechanism. The drug release from the membrane-less diffusion method was apparently slower than that from the dialysis method because the rapid phase separation into solid-like matrix through a direct contact with dissolution medium generated a hard surrounding shell. These solvent exchange-inducing in situ forming gels comprising peppermint oil effectively inhibited Staphylococcus aureus, Escherichia coli, Streptococcus mutans and Porphyrommonas gingivalis; therefore, they exhibited the potential use as localized delivery systems for periodontitis treatment.Graphical Abstract