Disclosed is a composition for forming an injectable hydrogel. The composition includes 1% by weight or less of a graphene-based material and 5% by weight or more of a triblock copolymer. The triblock copolymer may be a copolymer represented by Formula 1:wherein n is an integer from 8 to 540, m is an integer from 16 to 70, and R is H or a vinylcarbonyl group (CH2═CHCO—). When R in Formula 1 is a vinylcarbonyl group, the triblock copolymer may be crosslinked through the vinylcarbonyl group to form a nanogel. The composition can be prepared by a simple mixing process. In addition, the composition is substantially free from in vitro and in vivo stability problems encountered with conventional hydrogel compositions. Furthermore, the composition has high biocompatibility as well as excellent mechanical properties such as high storage modulus.
