Myocardial infarction (MI) is a disease of the coronary arteries that causes a dramatic reduction or interruption of blood flow within the artery, followed by severe and prolonged acute myocardial ischemia, leading to myocardial ischemic necrosis. Myocardial regenerative capacity after infarct is limited.
Although modern medicine has developed many treatments, clinical effects are not ideal. In recent years, with the development of regenerative medicine, two different strategies of injectable hydrogel and cardiac patches have been widely used to reconstruct post-infarction myocardial function. The team of Prof. Liu Wenguang and Associate Prof. Wang Wei of Tianjin University designed a series of functional injectable gel systems for the reconstruction of myocardial function in response to the characteristics of myocardial beat rhythm（Biomaterials 2018, 160:69-81；Biomaterials 2017, 122: 63-71.）.
For cardiac patches, current research focuses on suturing or ultraviolet light (laser) irradiation to attach the patch to the heart. These methods can cause new damage to the fragile myocardium, cause immune reactions or Grade oxidative stress, thereby affecting myocardial function. Therefore, a more suitable clinical application strategy needs to be explored. Recently, the team designed a suture-free conductive hydrogel patch that has excellent adhesion under a dynamic moist environment in the body, which can be quickly and easily applied to the myocardium and successfully explored a new approach to repair an infarcted myocardium. First dopamine and pyrrole groups are introduced into the hyperbranched polymer; then Fe3+ is used as a multifunctional initiator to simultaneously polymerize the pyrrole and dopamine groups in the hyperbranched structure, thereby giving the gel excellent electrical conductivity and wet adhesion to obtain a suture-free smearable conductive patch. The experimental results showed that the polymerization of non-free pyrrolyl groups succeeded in solving the problem that polypyrrole (Ppy) is insoluble and difficult to uniformly disperse into the gel network, and the in-situ formed conductive Ppy nanoparticles act as cross-linking sites. It promotes the stability of the system and long-term stable conductivity. Based on the unique properties of the gel, ie, the initial stage of gelation, the gel is soft and viscous, so it can be applied to curved surfaces in a gel state without leakage. At the beginning of the gel formation, the catechol groups in the gel produce excellent interfacial binding capacity with the amino and sulfhydryl groups on the surface of the tissue. After the gel rapidly adheres to the tissue, due to the covalent cross-linking between pyrrole polymerization and dopamine, the adhesive strength is converted into cohesive strength, and the increase in modulus eventually results in the fixed shape of the application. The results of animal experiments show that the conductive hydrogel patch can effectively improve the function of the infarcted myocardium, and promote electrical impulse signal transduction and angiogenesis in the infarct area. The suture-free cardiac patch designed by the team has a clear clinical application prospect.
Schematic diagram of sutureless conductive hydrogel applied to myocardium
The results were published online in the magazine (Adv. Mater. 2018, 1704235) on April 24, 2018. The first author of the research paper was Liang Shuang, a masters student, and Dr. Zhang Yinyu co-first author. The animal experiment part of the research was strongly assisted by Prof. Fan Guanwei and Prof. Cui Yuanlu of Tianjin University of Traditional Chinese Medicine. This work was supported by the National Natural Science Foundation of China (51473117, 31771030), the National Outstanding Youth Fund (51325305), the Tianjin Natural Science Foundation (15JCQNJC03300), and the National Key Research Development Plan (No. 2016YFC1101301).
By: School of Materials Science and Engineering
Editors: Qin Mian and Christopher Peter Clarke
