RHEOLOGICAL AND PHYSICOCHEMICAL CHARACTERIZATION OF HYDROGEL SYSTEMS FOR TOPICAL PROBIOTIC AND POSTBIOTIC PREPARATIONS

Introduction. The increasing prevalence of antibiotic-resistant wound infections highlights the need for alternative topical delivery systems. Hydrogels are promising matrices for wound applications because of their hydrophilicity, biocompatibility, and ability to maintain a moist environment. Combined polymer systems may provide rheological and structural properties suitable for the subsequent incorporation of probiotic and postbiotic components. Objective. To develop and comparatively evaluate the physicochemical and rheological properties of model hydrogel bases composed of different combinations of hydrophilic polymers for the subsequent development of topical probiotic and postbiotic systems based on Lactobacillus spp. and bacterial lysates. Materials and Methods. Eight model hydrogel formulations based on hydroxypropyl methylcellulose (HPMC), sodium alginate, Carbopol 980, sodium carboxymethylcellulose (Na-CMC), and polyvinylpyrrolidone (PVP) were prepared. Glycerol and EDTA-2Na were used as auxiliary components. Organoleptic characteristics, pH, and rheological properties were evaluated. Rheological measurements were performed using a Brookfield HBDV-II+ rotational viscometer with spindle No. 6 at 20, 50, and 100 rpm in three replicates. Flow behavior was characterized using the Ostwald–de Waele power-law model. Results. The developed hydrogel systems had pH values ranging from 4.94 to 5.45. All formulations demonstrated pseudoplastic shear-thinning behavior, with flow behavior indices (n) ranging from 0.037 to 0.290. Combined polymer formulations generally showed more balanced viscosity profiles and structural characteristics than single-polymer systems. Formulations A2, K2, and H2 were identified as the most promising, combining homogeneous structure, suitable pH, favorable spreadability, and stable viscosity profiles during cyclic changes in shear. Carbopol-containing formulations showed lower viscosity and signs of reduced structural homogeneity. Discussion. The results suggest that combining hydrophilic polymers may provide hydrogel matrices with a more balanced relationship between viscosity, spreadability, and structural stability, which is advantageous for topical formulations. However, the total polymer concentrations differed between single- and multi-polymer formulations; therefore, the observed differences cannot be attributed exclusively to synergistic polymer–polymer interactions. In addition, long-term stability, swelling capacity, exudate absorption, moisture retention, vapor permeability, adhesion, mechanical strength, biocompatibility, and the viability and antimicrobial activity of incorporated probiotic microorganisms were not assessed in the present study. These parameters require further experimental validation. Conclusion. The A2, H2, and K2 formulations demonstrated the most favorable combination of physicochemical and rheological characteristics and may be considered promising model matrices for the subsequent development of topical probiotic and postbiotic preparations. Further studies should include incorporation of Lactobacillus spp. and postbiotic components, assessment of their stability and biological activity, and comprehensive evaluation of wound-relevant technological and safety characteristics.