In recent years, the world has faced the issue of antibiotic resistance. Methicillin-resistant Staphylococcus aureus (MRSA) is a significant problem in various treatments and control of infections. Biocompatible materials with saturated fatty acids of different chain lengths (C8–C18) were studied as matrix formers of localized injectable vancomycin HCl (VCM)-loaded antisolvent-induced in situ forming matrices. The series of fatty acid-based in situ forming matrices showed a low viscosity (5.47–13.97 cPs) and pH value in the range of 5.16–6.78, with high injectability through a 27-G needle (1.55–3.12 N). The preparations exhibited low tolerance to high concentrations of KH2PO4 solution (1.88–5.42% v/v) and depicted an electrical potential change during phase transformation. Their phase transition and matrix formation at the microscopic and macroscopic levels depended on the chain length of fatty acids and solvent characteristics. The VCM release pattern depended on the nucleation/crystallization and solvent exchange behaviors of the delivery system. The 35% w/v of C12–C16 fatty acid-based in situ forming matrix prolonged the VCM release over seven days in which C12, C14, C16 –based formulation reached 56, 84, and 85% cumulative drug release at 7th day. The release data fitted well with Higuchi’s model. The developed formulations presented efficient antimicrobial activities against standard S. aureus, MRSA, Escherichia coli, and Candida albicans. Hence, VCM-loaded antisolvent-induced fatty acid-based in situ forming matrix is a potential local delivery system for the treatment of local Gram-positive infection sites, such as joints, eyes, dermis of surgery sites, etc., in the future.

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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.

Alpha-mangostin (aMG) phase inversion induced in situ forming gel (ISG) was prepared by dissolving matrix formers including palmitic acid (P) and lauric acid (L) in dimethyl sulfoxide (DMSO) and N-methyl pyrrolidone (NMP). The pH and density values were in range of 4.42-6.22 and 0.9731-1.0943 g.cm-3, respectively. The prepared formulas have low viscosity and high injectability which were suitable for injection. The gel formation behavior was affected by type of fatty acid and solvent. P dissolved in DMSO showed a rapid transformation into matrix at initial time. The extended release of aMG was attained in P-based ISG. aMG phase inversion induced ISG improved microbial inhibition.