Fluid properties and phase transition of antimicrobial eudragit RS/clove oil in situ forming depot

In situ forming depot (ISD) is a liquid drug delivery formulation generating solid depot after injection via a syringe into the body. The 5% w/w doxycycline hyclate (DH)-incorporated poly (ethyl acrylate, methyl methacrylate, trimethylammonioethyl methacrylate chloride) (Eudragit RS) ISD systems comprising clove oil (CO) dissolved in N-methyl pyrrolidone (NMP) were prepared and evaluated for their fluid properties (density, viscosity, injectability and thermal properties) and phase transition (depot formation, mechanical properties). The higher weight percentage of Eudragit RS and CO apparently enhanced the viscosity of the prepared ISDs. The rapid in vitro depot formation owing to solvent exchange was evident for ISD containing higher NMP amount whereas higher CO amount retarded the phase transition. The easier injectability and more efficient antimicrobial activities corresponded with lower viscosity of ISD comprising higher content of NMP and vice versa for CO content. ISDs exhibited a plastic deformation with rather low F_remaining/F_{max deformation} ratio and efficiently inhibited the test bacteria and fungi. Thus, DH-loaded Eudragit RS /CO ISD shows as a potential local delivery system for periodontitis treatment.