BACKGROUND To improve the environmental resistance of probiotics, and particularly their survival in the gastrointestinal environment, a fish gelatin (FG) / sodium alginate (SA) double network gelation (FSDN) was developed to encapsulate them. Thermal treatment and calcium ion inducement were adopted to fabricate fish gelatin and sodium alginate gels. It was feasible to scale up this process. The effects of FG concentration (0–60 g/L) on FSDN properties, including morphology, water‐holding capacity, and encapsulation efficiency were evaluated. RESULTS The results indicated that the addition of FG could improve the transparency, rehydration, and water‐holding capacity of FSDN. Scanning electronic microscope (SEM) images revealed that FSDN had a denser and more complete structure than SA. Encapsulation efficiency improved from 15.85% to 91.91% as the FG concentration ranged from 0 to 50 g/L. Bifidobacterium longum embedded by FSDN showed better thermal stability than when it was free. Compared with bare probiotics (1.7%), the encapsulated ones exhibited higher viability (above 15%) in simulated gastric fluid. CONCLUSION In conclusion, interpenetrating FSDN is an effective barrier constituent and could achieve the targeted delivery of probiotics. It is a potential new delivery carrier for the oral administration of probiotics. © 2021 Society of Chemical Industry

We developed the interpenetrating double network composite hydrogel based on poly (vinyl alcohol) (PVA) and fish gelatin (FG) via thermal treatment and repeated freeze-thawing. A function of salicylic acid was incorporated into the hydrogel to improve its antibacterial properties. The color values, water contents, water evaporation rate, and swelling behavior were investigated. The drug-loading performance of the composite hydrogel was demonstrated by loading salicylic acid in various hydrogel systems. Moreover, the cumulative dissolution percentage of salicylic acid and the antibacterial activity of composite hydrogel were carried out. The results revealed that as FG concentration increased from 0% to 3.75% (w/v), gels changed from white to slight yellow and the swelling ratio increased from 54% to 83% (within 8 h). The presence of FG decreased the water content of gels which ranged from 86% to 89% and also decreased water evaporation rate. All gels presented the swelling index within 0.5–1.0, indicating a non-Fickian diffusion mechanism. The drug sustained dissolution behavior of pure PVA and composite hydrogel showed the same trend. Besides, the presence of the obvious bacteriostatic zones means that drug-loaded composite hydrogels have an effective antibacterial property. These results demonstrated that PVA/FG-based interpenetrating hydrogel is an appropriate biomaterial for drug-carrying wound dressing application.