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 temperatureresponsive poly(N-isopropylacrylamide) (PNIPAM) is introduced to SiO 2 @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 SiO 2 @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.
It is widely accepted that live vaccines elicit higher immune protection than inactivated vaccines. However, the mechanisms are largely unknown. Here, an array with 64 recombinant outer membrane proteins of Vibrio parahemolyticus was developed to explore antibody responses of live and inactivated V. parahemolyticus post immunization of the 8th, 12th, 16th and 20th day. Among the 64 outer membrane proteins, 28 elicited antibody generation. They were all detected in live vaccine-induced immunity but only 15 antibodies were found in inactivated vaccine-induced immunity. Passive immunization showed that higher percent survival was detected in live than inactivated vaccine-induced immunities. Active immunization indicated that out of 19 randomly selected outer membrane proteins, 5 stimulated immune protection against V. parahemolyticus infection. Among them, antibodies to VP2309 and VPA0526 were shared in mice immunized by live or inactivated vaccines, whereas antibodies to VPA0548, VPA1745, and VP1667 were only found in mice immunized by live vaccine. In addition, live V. parahemolyticus stimulated earlier antibody response than inactivated bacteria. These results indicate that not all of the outer membrane proteins elicited antibody responses when they work together in the form of live or inactivated bacteria; live vaccine elicits more protective antibodies, which contribute to higher immune protection in live vaccine than inactivated vaccine. Notably, the recombinant proteins might be different from those separated from live bacteria, and they might be different in their immunogenic potencies.
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