In the field of tissue engineering, conductive hydrogels have been the most effective biomaterials to mimic the biological and electrical properties of tissues in the human body. The main advantages of conductive hydrogel include not only its physical properties, but also its adequate electrical properties, thus providing electrical signals to cells efficiently. However, when introducing a conductive material into a non-conductive hydrogel, a conflicting relationship between the electrical and mechanical properties may develop. This review examines the strengths and weaknesses of the generation of conductive hydrogels using various conductive materials and introduces the use of these conductive hydrogels in tissue engineering applications.

Polyglycolic acid (PGA) is a promising polymer in the packaging field owing to excellent hydrolysis, heat resistance and gas barrier properties, but there are limited in application due to poor toughness. For this reason, a covalently bonded chain extender is introduced to increase compatibility with flexible polymers. However, covalent bonds are unfavorable for application to degradable plastics because of require a lot of energy for reverse reactions. Therefore, it is intended to effectively control the ductility of blending plastics by using a novel ionic chain extender having a relatively weaker non-covalent bond than the existing covalent bond. Polycaprolactone (PCL), which has biodegradability and flexibility, was selected as a blending polymer. For comparison, a covalently reactive chain extender (G-CE) and a non-covalently ionic chain extender (D-CE) were synthesized and compounded to blending plastics. Each chain extenders were improved the compatibility between PGA and PCL, and the ductility of the PGA/PCL blending plastics were greatly enhanced with non-covalently bonding D-CE than with covalently bonding G-CE. At this time, the ductility of PGA/PCL blending plastic without CE is 7.2%, the ductility of 10D with D-CE is 26.6%, and the ductility of 10G with G-CE is 18.45%. Therefore, it was confirmed that the novel ionic chain extender inducing non-covalent bonds improves the compatibility between PGA and PCL and is more advantageous in enhancing ductility through a reversible reaction.