Development and evaluation of alginate-based gastroretentive raft-forming systems enabling sustained release of propolis in gastric ulcer treatment

This study aimed to develop alginate-based raft-forming systems incorporating propolis–whey protein isolate (5%) nanocomplexes to alleviate reflux symptoms and enable the sustained, gastric-specific delivery of propolis for ulcer management. Propolis–protein complexes were prepared at four ratios (2.5:100, 5:100, 7.5:100, and 10:100 w/v) by heating at 85 °C for 5 h at pH 2, producing nanofibrils characterized by thioflavin T fluorescence, intrinsic fluorescence, encapsulation efficiency (up to 78%), and antioxidant activity. The optimal complex was incorporated into alginate rafts at 5%, 10%, and 15% (w/v). Rafts exhibited prolonged floatability (>8 h), increased thickness (from 3.2 ± 0.4 mm to 4.7 ± 0.3 mm with higher propolis loading), enhanced mechanical strength (up to 1.6-fold improvement), and improved reflux resistance. SEM imaging revealed a more compact and uniform porous structure, while FT-IR confirmed molecular interactions between alginate and the propolis–protein complex. In vitro release studies in simulated gastric fluid showed suppression of initial burst release, with sustained propolis release over 6–8 h. Overall, alginate rafts containing propolis–protein nanocomplexes demonstrated enhanced structural performance, controlled release behavior, and promising potential for targeted gastric delivery in the management of gastric ulcers.