Physical properties and bioactivity of clove oil-loaded solvent exchange-induced in situ forming gel

Abstract

Clove oil (CO) has been claimed for its efficient antimicrobial activities against many microbes especially in oral cavity and it is interesting for using as active component in the lauric acid-based solvent exchange-induced in situ forming gel (IFG). The present study investigated the physicochemical properties of lauric acid-based solvent exchange-induced IFG loading different amounts of CO dissolved in N-methyl pyrrolidone (NMP). The increasing amount of CO enhanced the density as well as viscosity, contact angle and surface tension. When administered into PBS pH 6.8 by injection, phase separation of lauric acid was evident with time. By comparison, the system containing the higher amount of CO demonstrated the slower phase separation, indicating that the increased viscosity hindered solvent exchange and subsequent phase separation. Similarly, the observation under stereoscope revealed more rapid gel formation of IFG containing lesser amount of CO. All systems showed the increased gel formation and decreased diffusion rate with time whereas the slower matrix formation and diffusion rate was evident in systems containing the higher amount of CO. Although the system with high viscosity led to increase in the force and work of injectability, all of the prepared IFGs showed the compressed force that was lower than 10 N, indicating ease of administration by injection. All of the prepared IFGs containing CO exhibited the inhibition zone against test microbes. Due to the antimicrobial activity of CO, the system containing the higher amount of CO contributed to the larger inhibition zone especially against C. albicans. It was noticed that the most sensitive system for tested microbes was those containing 20% CO (3:2:5 LCN). Thus, the system comprising 20% CO (3:2:5 LCN) could be offered as the potential use for the treatment of oropharyngeal candidiasis.