Chitosan/gelatin/copaiba oil emulsion formulation and its potential on controlling the growth of pathogenic bacteria

This work report the development of an emulsion formulation combining chitosan and copaiba oil. The antimicrobial activity and cytotoxic effect of three different copaiba oils (CO-A, CO-B and CO-C), chitosan/gelatin gel (CG), and chitosan/gelatin/copaiba oil (CGCO) emulsions against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa were evaluated. Susceptibility tests were performed by the minimum inhibitory concentration (MIC) using the micro-broth dilution technique. The cytotoxicity effect of compounds on Vero cell line was also evaluated using the MTT assay. CG inhibited S. aureus, E. coli, and P. aeruginosa growth, showing MIC of 31.2, 62.5, and 31.2 μg mL−1, respectively. Copaiba oils inhibited S. aureus with MIC of 2.0 × 103 μg mL−1 for CO-A, 500 μg mL−1 for CO-B, and 62.5 μg mL−1 for CO-C. The results observed for CGCO-C emulsion against S. aureus suggest synergism. The CO-C and CG gel demonstrate bacteriostatic and bactericidal activity against S. aureus, respectively, whereas CGCO-C emulsion was bactericidal at a lower concentration and at short time interval than the individual compounds. CO-A and CO-B showed toxicity to Vero cells whereas, for CO-C, CG gel and all the emulsions, no cytotoxic effect was observed. The results of this study demonstrated that emulsions formulated by the combination of chitosan/gelatin/copaiba oils have potential as a new selective agent to control S. aureus.