The invention provides a preparation method of a completely new gel form, namely a critical gel, wherein with carboxymethyl
chitin as a
raw material and natural and non-toxic
amino acid, namely
lysine, as a modifying substance, the critical gel is prepared under the catalytic action of a
coupling reagent, namely 4-(4,6-dimethoxytriazin-2-yl)-4-methyl
morpholine hydrochloride (DMTMM). The gel has the main characteristic that the gel can constantly keep
viscous modulus and elasticity modulus equal, which is to say the gel possesses two properties, namely high
viscosity and high elasticity. The modified gel, which is under a 'critical state', can achieve
terminal sterilization, prolong an
in vivo residue time and achieve single-
dose injection; with the application of the non-toxic
amino acid modifying substance, the intrinsic
biocompatibility and bio-activity of the carboxymethyl
chitin are reserved, and all potential risks are avoided; since the
viscous modulus and the elasticity modulus are simultaneously increased and are constantly kept equal, the
viscoelasticity of the carboxymethyl
chitin is enhanced; and meanwhile, the original
liquid state of the carboxymethyl chitin is kept, so that pain in injection can be relieved easily.