The Hong Kong Polytechnic University (PolyU) has developed an acid-resistant "ultra-stable mucus-inspired hydrogel" (UMIH), marking a breakthrough in the field of gastrointestinal medicine. Traditional hydrogels—gelatin-like materials that absorb and retain water—are widely used to aid wound healing and extend drug release. However, they usually break down in acidic environments like the stomach. Inspired by the natural properties of gastric mucus, a PolyU research team has developed UMIH, a hydrogel that adheres 15 times more strongly than conventional gastric mucosal protectants, showing considerable potential for wound repair and targeted drug delivery and promising large‑scale commercialisation.
The research was carried out by the PolyU team in collaboration with researchers and clinicians from Sichuan University. The research showed that UMIH significantly improved gastrointestinal wound healing in animals and outperformed a clinically approved mucosal protectant used to protect the stomach lining. The study, "Mucus-inspired hydrogels with protonation-driven adhesion for extreme acidic conditions," has been published in Cell Reports Physical Science.
Prof. WANG Zuankai, Associate Vice President (Research), Dean of the Graduate School, Kuok Group Professor in Nature-Inspired Engineering and Chair Professor of the Department of Mechanical Engineering, Director of Research Center for Nature-Inspired Science and Engineering at PolyU, who led the study, said, "UMIH shows promise in treating gastroesophageal reflux and gastric ulcers, and in protecting post-surgical wounds. It can also be combined with endoscopic drug delivery for minimally invasive therapy. This research establishes UMIH as a transformative, extremely acid-tolerant platform, with immediate applications in gastrointestinal repair and targeted drug delivery, while also opening avenues for next-generation implantable devices to accelerate translation to the clinic."
Prof. Wang explained that aluminium phosphate gel (APG)—a clinically approved mucosal protectant and antacid—has long been used to treat gastric ulcers and gastro‑oesophageal reflux. The experimental data show that, under simulated gastric conditions (pH 2), UMIH achieved a wet adhesion strength of 64.7 kilopascals (kPa), 15-fold higher than APG; APG fully degraded after three days, whereas UMIH retained about 50% of its structural integrity after seven days. In vitro tests on cultured gastrointestinal cells found no signs of toxicity, while UMIH also inhibited the growth of Escherichia coli and Staphylococcus aureus, indicating antibacterial potential.
Like conventional hydrogels, UMIH consists of a meshwork of polymers that absorb water to create a strong but jelly-like consistency. To enhance its acid resistance, the research team integrated three key molecular components into UMIH's structure: ELR-IK24, a protein that binds hydrogen ions under acidic conditions to reduce local acidity; tannic acid, which boosts adhesion of hydrogel; and HDI, a molecule that stabilises the hydrogel's structure under acidic conditions.
"Our hydrogel is a synergistic combination of three essential molecular components. This multi-crosslinking architecture keeps UMIH firmly intact in strong acid while maintaining softness and injectability—qualities well suited to clinical use," said Ms Yeung Yeung CHAU, a Research Associate of the PolyU Department of Mechanical Engineering and a member of the research team.
"We tested UMIH in pig and rat models of esophageal injury. Compared with control animals and APG‑treated animals, UMIH adhered more firmly to wound faces and improved healing. UMIH reduced tissue damage and inflammation and promoted the growth of new blood vessels, which is essential for healing," explained Dr Xiao YANG, a Postdoctoral Fellow of the PolyU Department of Mechanical Engineering and a member of the research team.
While clinical trials will be needed to validate UMIH's safety and efficacy in humans, it holds strong potential for commercialisation. It is low-cost, easy to mass-produce and developed from components with established safety profiles. The material is ready to use both in operating room and on the production line. Looking ahead, the research team plans to integrate UMIH with drug release systems and implantable flexible electronics to create smart gastrointestinal devices capable of real-time treatment and monitoring.
