Mixed Solvent-Lauric Acid Solvent-Exchange Induced <i>In Situ</i> Forming Gel

Abstract

Designing lauric acid (L) solvent-exchange induced in situ forming gel (ISG) was conducted in this study by using mixed solvents (N-methyl pyrrolidone (NMP), 2-pyrrolidone (PYR) and dimethyl sulfoxide (DMSO) at different ratios. The pH, density, viscosity, matrix formation, contact angle/surface tension and antimicrobial activities of 50% w/w L in mixed solvents were determined. The pH and density of solvent decreased apparently with L addition. More amount of PYR in the solvent mixture increased the density and viscosity. High viscous manner of PYR resulted in the high surface tension and contact angle. The solvent mixture of NMP/PYR promoted a higher contact angle than the other mixed solvent systems. L in DMSO, PYR or solvent mixture with high ratio of DMSO or PYR transformed into matrix-like rapidly while those in NMP or high ratio of NMP had slower matrix formation after exposure to aqueous fluid. NMP and PYR showed antimicrobial activities effectively against all test microbes while L matrix retarded their activities. The mixed solvent concept is interesting to use for designing ISG comprising L as matrix former to prolong the drug release.