In Situ 4D Printing of Polyelectrolyte/Magnetic Composites for Sutureless Gastric Perforation Sealing.

In situ bioprinting has emerged as one of the most promising techniques for the sutureless tissue sealing of internal organs. However, most existing in situ bioprinting methods are limited by the complex and confined printing space inside the organs, harsh curing conditions for printable bioinks, and poor ability to suturelessly seal injured parts. The combination of in situ bioprinting and 4D printing is a promising technique for tissue repair. Herein, the in situ 4D printing of polyelectrolyte/magnetic composites by gastroscopy for sutureless internal tissue sealing is reported. Using gastric perforation as an example, a gelatin/sodium alginate/magnetic bioink is developed, which can be precisely located by a gastroscope with the assistance of an external magnetic field, solidified in gastric fluid, and firmly adhered to tissue surfaces. The solidified bioink along the defect can be attracted by an external magnetic field, resulting in sutureless sealing. A demonstration using a porcine stomach with an artificial perforation confirms the feasibility of sutureless sealing using 4D printing. Moreover, an in vivo investigation on gastric perforation in a rat model identifies the biocompatibility by H&E and CD68+ staining. This study provides a new orientation and concept for functionality-modified in situ 4D bioprinting.