N-Isopropylacrylamide/acrylamide copolymer hydrogels were prepared with crosslinking agent by free radical polymerization. Swelllng/shrinking ratio, amount of water uptake, transmittance, and the change of phase transition temperature of copolymer hydrogel were studied. Invertase, sucrose hydrolase, was immobilized within N-Isopropylacrylamide/acrylamide copolymer hydrogels with different content of acrylamide and its enzymatic activities as a function of temperature were also studied. As the acrylamide content increased, swelling/shrinking ratio, amount of water uptake, and the phase transition temperature were increased. Swelling/shrinklng ratios of copolymer hydrogel were increased up to 7, 20, 80% when the temperatures were 20, 30 and 40℃, respectively. Amounts of water uptake by copolymer hydrogel at 30℃, were increased as much as 11, 19, 22 and 44% when the contents of acrylamide was 3, 5, 7 and 10%, respectively. Phase transition temperature of N-isopropylacrylamide hydrogel is 32∼34℃. As the content of acrylamide increased, phase transition temperature of copolymer hydrogel was increased up to 53℃. Enzymatic activities of invertase immobilized within copolymer hydrogels with different content of acrylamide were switched on and off by the change of reaction temperature below and above their respective phase transition temperature of copolymer hydrogel.

N-Isopropylacrylamide와 친수성 공단량체인 acrylamide에 가교제를 사용하여 자유 라디칼 중합반응에 의한 공중합수화겔을 제조하고, 이 공중합수화겔의 온도변화에 따른 팽윤/수축비, 함수율, 투광도 및 상전이온도의 변화를 조사하였다. 그리고, N-Isopropylacrylamide/acrylamide 공중합수화겔에 sucrose 분해효소인 invertase를 고정화하여 온도변화에 대한 효소활성의 특성에 대하여 연구하였다. Acrylamide의 함량이 증가할수록 공중합수와겔의 팽윤/수축비, 함수율 및 상전이온도는 증가하였다. 공중합수화겔의 팽윤/수축비는 온도가 20, 30, 40℃ 일때 7, 20, 80%까지 각각 증가하였고, 30℃에서의 함수율은 공단량체의 함량이 3, 5, 7, 10%잎때 11, 19, 22, 44%씩 각각 증가하였다. N-Isopropylacrylamide의 상전이온도는 32∼34℃이지만 공단량체의 함량이 증가할수록 공중합수화겔의 상전이온도는 증가하여 53℃까지 이르게 된다. 공중합수화겔에 고정화된 invertase의 환성은 공중합수화겔의 각각의 상전이온도에 따라 효소활성의 "switch on-off"현상을 나타내고 있다.

Keywords: Thermoresponsive; hydrogel; enzyme immobilization