Biochemo-mechanical function of urease-loaded gels.

A gel system is developed that undergoes a reversible volume phase transition in response to a small amount of urea. An N-isopropylacrylamide gel in which urease is immobilized by entrapping changes its equilibrium volume discontinuously when urea molecules are hydrolyzed by urease causing a change in pH that alters the osmotic balance of the gel triggering the phase transition. The system demonstrates a method of mechano-biochemical transformation where molecular recognition and biochemical reaction are achieved by an enzyme and the macroscopic amplification of the reaction is carried out by a gel capable of a volume phase transition. The work presented here is dedicated to Professor Allan S. Hoffman to honor his 60th birthday and his pioneering contribution to the science and technology of polymer gels, both as a scientist and as an educator.