Improving Thermal Stability of Enzymatic Micromotors by a Temperature-Sensitive Smart Polymeric Shell

Enzyme-powered micromotors using biocompatible substances as fuel are promising candidates in biomedical applications due to their potential autonomous movement in biological fluid and supreme biocompatibility. However, the inherent fragility of enzymes in complex environment hinders their application in practice. Herein, the smart temperature-responsive poly(N-isopropylacrylamide) (PNIPAM) is introduced to SiO₂@urease micromotors to increase the stability of the enzyme engine by the confinement effect derived from shrinkage of PNIPAM at temperatures above its lower critical solution temperature (LCST). As a result, the structure transformation and subunit dissociation of the enzyme are suppressed, leading to improved thermal stability of the urease engine. A systematic comparison of PNIPAM protected and bare SiO₂@urease micromotors after thermal treatments at identical temperatures for various time intervals has clearly revealed the enhancement of stability against thermal deformation by PNIPAM integration. This work, paving a way to the development of thermally stable enzyme-powered micromotors, can greatly raise the prospect of the intelligent micromachines toward practical biomedical applications.