Study On The Biocompatibility,Motion Control And Chemical Communication Of Micro/Nanomotors

Artificial micro/nanomotors?MNMs?are the key components of micro/nanomachines.They can perform specific tasks in liquid media due to their autonomous motion capabilities,including active drug delivery,cell separation,and accelerate environmental remediation.To achieve these goals,MNMs need to have excellent biocompatibility,high degree of motion control and intelligence.However,most self-propelled MNMs require toxic or corrosive fuels,restricts their applications in biological field.On the other hand,due to the inherent asymmetry of the MNMs,their motion direction is often severely disturbed by Brownian motion and local liquid flow.Therefore,in most cases,self-propelled MNMs can only perform random motion,the precise manipulation of self-propelled MNMs is still a challenge.In addition,the smart behaviors of MNMS are yet to be developed.It is expected that they will be able to respond to the surrounding environment to achieve autonomous navigation or mutual cooperation.Therefore,in this doctoral dissertation,we focusing on several key issues of MNMs such as improving their biocompatibility,motion controllability,and developing their smart behavior.First of all,considering the self-propelled MNMs require toxic fuels and their poor biocompatibility,we have developed biocompatible magnesium-based Janus micromotors that directily use water or human body fluid?such as plasma?as fuel.First,we use sodium bicarbonate to quickly remove the magnesium hydroxide passivation layer on the surface of the magnesium-based motor,and developed Mg/Pt Janus micromotors.Secondly,the residue of the micro/nanomotors may cause undesired results to organisms,to slove this issue,we have developed fully degradable magnesium-based motors.Thirdly,we developed Mg/Pt-PNIPAM Janus micromotor that can directly propel in simulated body fluids or human plasma,and demonstrated their temperature-controlled drug release ability.The research of this series of magnesium-based motors lays the foundation for the practical application of micro-motors in vivo and environmental treatment.Afterwards,in view of the current difficulty to control the moving direction of the micro/nanomotor,we realized this problem is mainly caused by their small size and asymmetrical structure,which leads to the constant gesture changing in moving environment.We have developed bioinspired isotropic phototactic semiconductor micromotors.Owing to the limited penetration depth of light in the semiconductor material,under light irradiation,an asymmetric chemical reaction is eatablished on the surface of the isotropic spherical motors,thus fix the moving direction of these micromotors regardless of Brownian rotation of the particels.We then extended the phototaxis behavior to positive and negative phototaxis.By using semiconductor materials with different band gaps,we can also use visible light to accurately navigate the micromotor.Subsequently,we showed the concept of guiding the motion of micromotors by using chemical gradients in moving environment.We use artificial nanoparticles to modify natural sperm cells and use the chemoattractant secreted by the egg cell to regulate the moving direction of the sperm motor.We have further studied the chemotaxis behaviors,movement patterns,and speed control mechanisms of these spermatozoa micromotors.By carrying the Fe2O3@DOX payload,we tested their potential application in cancer treatment and demonstrated their ability to kill human ovarian cancer cells?SKOV-3 cells?in vitro.Finally,in the future applications,it is necessary to use the cooperation between the micro/nanomotors to accomplish the designed task.To achieve this goal,we show the concept that two different artificial nanomotors can perform bioinspired chemical communication and change their motion behavior based on the information transferred in the communication.To demonstrate this concept,we first prepared an activation motor PS/Ni/Au/Ag containing a surface metal silver component that was eroded in hydrogen peroxide to release silver ions.When the activation motor approaches the activated motor?SiO2/Pt?,the silver ion signal released will be detected by the SiO2/Pt motor and will redeposit on its surface in the form of elemental metallic silver.Since the SiO₂/Pt motor after communication has a Pt-Ag bimetallic alloy surface,it has a higher hydrogen peroxide catalytic decomposition rate under the synergistic effect of an electronic and geometrical effect,and thus has a higher propulsion rate.