Stimuli-sensitive hydrogels have attracted considerable attention as intelligent materials in the fields of biochemistry and biomedicine due to their ability to detect environmental changes and undergo structural changes by themselves such as solubility and swelling ratio. Among the developed stimuli-sensitive materials, polymers showing a sol-to-gel transition with changing temperature have been proposed for use as injectable drug delivery systems. These hydrogels, however, have several unresolved drawbacks that limit their potential as injectable drug delivery systems. When temperature-sensitive hydrogels are injected into the body via syringe, the warmth of the body tends to cause gels to form within the needle, to inject into the body. Also, after injection, the hydrogels tend to undergo the rapid degradation of the block copolymer, resulting in the formation of an acidic monomer such as lactic or glycolic acid. It decreases the pH of the hydrogel. Consequently, the low pH environment associated with the hydrogel is known to be deleterious to some proteins and nucleic acids, such that the pH change that occurs within these biodegradable hydrogels is an important consideration. We designed the novel block copolymers composed of the temperature-sensitive block and pH sensitive block to fabricate thermo and pH sensitive injectable hydrogel. As shown in Figure 1, their sol-gel transition behavior was controllable depending on the introduced chargeable block. In our laboratory, sulfonamide and poly(β-amino ester) were considered as pH-sensitive block using their anionic and cationic property, respectively. We are trying to use as these injectable hydrogels for protein delivery and tissue engineering.