Ciprofloxacin loaded o/w microemulsion against Staphylococcus aureus. Analytical and biological studies for topical and intranasal administration

Abstract An o/w microemulsion was designed and successfully loaded with the antibiotic ciprofloxacin for potential topical and intranasal use against Staphylococcus aureus. Based up on a physicochemical study an optimal system composed of 2.50% of isopropyl myristate, 42% of polysorbate 80: ethyl alcohol (2:1), and 55% of water was selected and then loaded with 0.30% of ciprofloxacin. The formulation presented a polydispersity index of (0.259 ± 0.021) and a particle size of (13.44 ± 0.24) nm. The pH value (5.32) was optimal for both topical and intranasal uses. Besides, the formulation presented adequate osmolarity for instillation (341.9 mOsm L−1). The microemulsion stability over time and under different conditions was demonstrated. The permeation constant was 2.73 × 10−4 cm h−1, a higher value compared with that of free ciprofloxacin (8.25 × 10−5 cm h−1). The antibacterial and antibiofilm activities were evaluated using the S. aureus Newman and MW2 strains in a murine model for testing the in vivo efficacy of the o/w formulation. It exhibited a minimal inhibition concentration of 375 μg mL-1 and disrupted by 54% the previously formed biofilms. In conclusion, the new proposed ciprofloxacin formulation caused a significant reduction of S. aureus nasal colonization and skin infection.