Fabrication,Characterization And Application Of Self-Propelled Enzymatic Catalysis System

Micro-/nanomotors(MNMs)are tiny apparatuses that can convert energy from local chemical reactions or external physical fields into mechanical energy and exhibit autonomous motion.The active movement of MNMs can accelerate mass transfer on the microscale and increase the opportunity of contacts between the active site on their surface and the surroundings,facilitating chemical/physical processes.Using MNMs as a carrier,the resultant self-propelled enzyme-immobilized particles(EIPs)are able to relieve the limited diffusion and enzymatic performance of immobilized enzymes.Hence,it is of great significance to study the interplay between enzymatic reactions and motion behavior of self-propelled EIPs and explore novel MNMs-based EIPs.This work was first designed to fabricate different EIPs with asymmetrical(AHP-CRL)and symmetrical(SMHP-CRL)enzyme distributions and to investigate the interplay between enzymatic reactions and their motion behavior.It was found that all the EIPs displayed substrate-concentration-dependent enhanced diffusions,but Janus enzyme-immobilized particles(AHP-CRL)exhibited the maximum enhancement(60%)of diffusion coefficient as well as superior specific activity increments(> 2 times).The results indicated that the asymmetrical enzyme distribution on Janus particles enhanced the favorable mutual promotion between the self-propelled movement and enzymatic reactions,leading to improved diffusional and enzymatic performance.Then,multilight-responsive micromotors were fabricated by in situ precipitation of photothermal Fe3O4 nanoparticles(NPs)onto polymeric microparticles.The composites exhibited phototactic swarming movement by irradiation at 320-550 nm,which can be reversibly and remotely manipulated by irradiation position,“on/off”switch,and light intensity.The micromotor made of Fe3O4@poly(glycidyl methacrylate)/polystyrene(Fe3O4@PGS)presented a propulsion speed as high as 270μm/s under ultraviolet irradiation.Using an array of experimental methods and numerical simulations,a thermal convection mechanism was proposed for the propulsion.Namely,under light irradiation,the photogenerated heat on Fe3O4 NPs decreased the density of the irradiated spot,leading to the swarming motion of the composite particles propelled by a “hydrodynamic drag” toward the light spot.It was found that the propulsion increases the catalytic efficiency of Fe3O4 NPs for rhodamine B degradation by over 10 times under sunlight.Moreover,it was proved to accelerate the enzymatic reactions of lipase on Fe3O4@PGS in both aqueous and organic systems by more than 50%.By coupling His-modified ultra-small Fe3O4 NPs(HSFe3O4)with cholesterol oxidase(Ch Ox),we prepared HSFe3O4@Ch Ox nanomotors.The HSFe3O4@Ch Ox nanomotors exhibited dual propulsion modes.Namely,HSFe3O4@Ch Ox can be powered by an enzymatic reaction in a substrate-concentration-dependent manner or by a self-thermophoretic force in a NIR-intensity-dependent manner.The propulsion of HSFe3O4@Ch Ox significantly enhanced the catalytic efficiency of immobilized Ch Ox.Moreover,HSFe3O4 exhibited superior peroxidase-like activity,which enables it as the alternate of HRP for detecting H2O2.Combing the catalytic activities of Ch Ox and HSFe3O4,HSFe3O4@Ch Ox nanomotors were used to quantificationally detect cholesterol.Furthermore,the autonomous movement of HSFe3O4@Ch Ox was able to shorten the detecting time by 1/3.The research designed and prepared an enzyme-powered micromotor,a multilight-responsive micromotor and a dual enzymatic/light-powered nanomotor to explore the interplay between motion behavior and enzymatic of self-propelled EIPs and prove the motion-accelerated enzymatic reaction.The findings provided new theoretical bases and technical support for the design of novel EIPs and MNMs.