Rheological, mechanical, and bioadhesive behavior of hydrogels to optimize skin delivery systems

Background: Hydrogels are widely used for cutaneous formulations; thereby comparing the bioadhesive properties of polymers with a view to prolong the residence time of topical drugs on the skin would be very useful to design novel topical drug delivery systems. Aim: The objective of this study was to correlate data from rheological studies and texture profile analysis, with bioadhesion on the skin. Methods: Polyacrylic acid polymers used were carbomer homopolymer type A (C971) and type B (C974), and polycarbophil (PP) dispersed in water at various concentrations (0.1, 0.5, 1.0, 1.5, 2.0, 3.0, 5.0%, w/v). Rheological, texture, and bioadhesive properties were determined to compare the hydrogels. Results: Rheological analysis showed that all samples exhibited pseudoplastic behavior with thixotropy. Texture profile analysis showed that compressibility, hardness, and adhesiveness of the hydrogels were dependent on the polymer concentration, and the cohesion values were high. Bioadhesion of C974 and PP at 0.5 and 2% was of the same magnitude, while all samples of C971 had lower values. The bioadhesion of 5% C974 was the highest, while that 5% PP was lower, possibly because PP showed the greatest hardness and this rigidity may decrease the interaction of the polymer with the skin. Conclusion: A comprehensive comparative rheological and textural analyses of several polymers for topical systems were undertaken in terms of their bioadhesion. Therefore, it is possible to conclude that these polymers can be used for optimization of drug delivery systems on the skin.