Investigation of Colloidal Structure and Biopharmaceutical Properties of New Antibacterial Composition of Gramicidin S

Introduction. Gramicidin S has been conventionally manufactured as buccal tablets. However, in the past decade, the interest in the development of spray formulations has been growing. Those formulations contain excipients that enhance the solubility of the antibiotic in water solutions. However, the real structure of gramicidin S containing sprays remains unrevealed.Aim. Investigation of colloidal structure and biopharmaceutical properties of new gramicidin S antibacterial composition.Materials and methods. The composition sample was obtained using gramicidin S dihydrochloride, propylene glycol, polysorbate-80, ethanol and purified water. Raman spectroscopy has been performed to determine the composition of the phases. Dynamic light scattering analysis was performed to characterize the composition particles. Release of gramicidin S was performed by dialysis method and the concentration was determined by HPLC. The antimicrobial properties were investigated in accordance with the requirements of the XIV edition of the Russian pharmacopoeia.Results and discussion. Dynamic light scattering analysis results show gramicidin S formulation particles having an average size in solution 5–50 nm and ζ-potential (–1.1: +7.9 mV). Based on the obtained data on the composition properties and formulation parameters it was classified as colloidal solution. The kinetic stability evaluation was performed. We compared the solubility in water and release parameters of the active pharmaceutical ingredient in the native state and in the micelles. The enhancement of the antimicrobial activity of the peptide in the colloidal solution was confirmed and ascribed to the synergic effect gramicidin S – surfactant.Conclusion. We reported the colloidal type of the composition, that aggregate gramicidin S at a concentration of 8 mg/mL. We found that gramicidin S inclusion into the colloidal solution led to significant efficiency increase, which reveals the potential to reduce the drug dose and side effects level.