Density-Driven One-Step Assembly of Janus Hydrogels for Gastric Perforation Sealing

The development of Janus hydrogels with asymmetric adhesion and high interfacial integrity remains a challenge in polymer engineering. Herein, we report an ingenious one-step sequential casting strategy to construct an all-biobased Janus hydrogel, named PA-G-X/Y/Z, by leveraging the density mismatch and gravitational stability between N -acryloyl aspartic acid (AASP) and methacrylated gelatin (GelMA) precursors. By systematic optimization of methacrylation degree (X), polymer concentrations (Y), and casting volume ratios (Z), a seamless interface was achieved through molecular diffusion and subsequent UV-induced covalent cross-linking with excellent mechanical properties of a tensile strain of 1529.7% and a tensile stress of 18 kPa. The incorporation of Laponite nanodiscs further reinforced the polymer network, resulting in a significant enhancement of a burst pressure up to 135 mmHg and a peeling strength of 216.3 ± 3.2 N/m. It remains stable after prolonged immersion in PBS or simulated gastric fluid (SGF), which is crucial for sealing pressurized organs like the stomach. The Janus material exhibits functional asymmetry: a highly swelling PA layer serving as an “swelling-assisted conformal sealing”, a highly hydrated G layer for antipostoperative adhesion, and the graded degradation of two layers aligns with the wound healing period. In vivo evaluations in a rat gastric perforation model confirmed that this exogenous metal-ion-immersion-free polymer system prevents excessive inflammation and supports orderly mucosal repair. This work provides a versatile physical-strategy-driven blueprint for the rapid manufacturing of advanced asymmetric surgical sealants.