Дослідження впливу мікроструктури сумісних агрегатів неіонної пар і цетостеарилового спирту на реологічні властивості гідрофільних кремових основ та вивільнення діючих речовин в дослідах in vitro

The aim. To study the effect of the microstructure of mixed aggregates and adsorption layers of non-ionic surfactant and cetostearyl alcohol (CSA) on the rheological characteristics of hydrophilic cream bases and the release of certain active substances in experiments in vitro. Materials and methods. Cream bases with a dispersion medium of water and propylene glycol (9:1) were studied. The ratio of surfactant to CSA was varied within the base formulations. The rheological properties of the bases were analysed using rotational viscometry, and the microstructure of the aggregates was examined by the spin probe method employing four probes based on fatty acids. The release of active substances from the bases and solutions was tested in vitro; the content of active substances in the dialysate was determined by liquid chromatography. Results. The apparent viscosity of the bases was observed to reach its maximum at certain ratios of surfactant to CSA, when coagulation structures were formed. The structural arrangement of mixed aggregates of surfactant and CSA was dependent on their ratio. It was demonstrated that a higher specific fraction of CSA in aggregates/adsorption layers contributed to lateral phase separation at the interface with the dispersion medium. This process led to the formation of solid CSA domains and liquid surfactant domains. The mixed aggregates of surfactant and CSA possessed a non-spherical configuration. The hydration of aggregates was ensured by non-ionic surfactant domains. These factors contributed to the formation of coagulation structures at certain concentrations of surfactant and CSA. An increase in the specific fraction of surfactant led to a tendency towards a homogeneous distribution of surfactant and CSA in their aggregates. This was accompanied by a decrease in the apparent viscosity of dispersed systems and a transition from creams to liquids. A decrease in the surfactant fraction resulted in a decline in the hydration of aggregates/adsorption layers, consequently leading to a decrease in the apparent viscosity of the bases. The release of ofloxacin or dexpanthenol was significantly retarded from the bases where coagulation structures were formed. Conclusions. The rheological characteristics of hydrophilic cream bases are contingent on the microstructure of mixed aggregates or adsorption layers formed by nonionic surfactant and CSA. These properties can be modified by adjusting the mass ratios between these emulsifiers. In the case of cream bases, where a coagulation structure has formed, the release of active ingredients is found to be significantly retarded.