BIOCHEMICALLY CONTROLLED THERMAL PHASE-TRANSITION OF GELS

Recognition of biochemical reaction and subsequent conversion directly into mechanical work has long been a technological dream. Physical systems that respond specifically to a particular kind of molecule have similar capabilities to biological transducers, sensors, and actuators, in which molecular signals trigger biological activities. A gel is designed and synthesized that undergoes a discontinuous swelling-shrinking phase transition at a specific temperature when enzyme reaction takes place. The gel consists of a network of poly(N-isopropylacrylamide) in which liver esterase is immobilized. The enzyme hydrolyzes ethyl butyrate into ethanol and butyric acid. A change in substrate-product composition triggers the phase transition. A theoretical analysis of the phenomena is given.