The Preparation And Application Of The Polydopamine Based Self-propelled Micromotors

Micro/nanomotors are some devices with micrometer or nanometer dimensions.They can self-propel by changing chemical or external energy(heat,electricity,light,etc.)into mechanical energy in different environments.Micromotors based on polymers(such as polypyrole,polyaniline,and polyamino acids),metals(such as Mg,Au,and Pt),and some inorganic oxides(such as SiO2,TiO2,and ZnO)have been widely fabricated and used in various fields in recent years.In addition,different shapes of micro/nanomotors are also designed,such as tubular,rod,spherical,etc.Otherwise,various modes of self-proplusion are invented,such as light-driven,ultrasound-driven,magnetic field-driven,enzyme-driven,etc.Nowadays,the micro/nanomotors have been applied in environmental remediation,drug delivery,biosensing,and micro/nanoscale surgery.However,the lack of different types and quantities of side-chain functional groups also made them difficult to load enough kinds and numbers of payloads on their surface,which limits their application especially in drug delivery and environmental remediation,etc.Polydopamine(PDA)is a biodegradable material with good biocompatibility,adhesion capability,photothermal transfer efficiency,and drug binding capacity.In this thesis,we used PDA as the material of micromotors and constructed two types of micromotors and explored their applications in drug delivery.The work is carried out from the following two aspects:1.The fabrication of a polydopamine tubular micromotor and its drug delivery studyBortezomib(BTZ)is the dipeptide boric acid analogue with antitumor activity,it is a specific,effective and reversible proteasome inhibitor for the treatment of multiple myeloma and gastric cancer.The boronic acid bond of BTZ can be combined with various materials to form drug delivery systems.It can be used individually or with other anticancer drugs to increase the anti cancer properties.Since the boronic acid bond on BTZ can bind to the catechol group of PDA to constitute a pH-sensitive boronic ester bond,the drug-delivery system with PDA was constructed.The PDA tubular micromotors were prepared by the template electrodeposition method,then Fe and Zn was deposited in to the tubular,respectively.Zn can react in an acidic environment and generate bubbles to drive the micromotors,Fe can not only control the direction of the micromotors by the magnet,but also further provide the power when Zn was consumed.The drug delivery system of PDA/Fe/Zn tubular micromotors can be prepared by combining BTZ with PDA through boronic ester bond.The release of BTZ was measured in different pH environments.Experimental results showed that the PDA tubular micromotors can effectively load certain concentration of BTZ.The drug release rate was higher in an acidic environment than in a neutral environment.Toxicological experiments in mice showed that after 24 h of oral administration of the PDA/Fe/Zn micromotors,the mice were in good health and had no toxic reaction.Therefore,these micromotors have the advantages of good biocompatibility and low toxicity,and are expected to be applied in drug delivery.2.Study on the drug-loaded Mg-based Janus microsphere motor constructed with polydopamineThe driving methods of micro/nanomotors has been a major focus of researchers.H2O2 is always used as fuel to propel micro/nanomotors in previous studies.However,the corrosiveness and toxicity of H2O2 limits the usage of micro/nanomotors especially in biological fields.Otherwise,magnesium can generate hydrogen bubbles in water and in acidic environment,thereby the magnesium microsphere can be used to construct the self-propelled micromotors.On the basis of the previous works,we constructed a Janus microsphere motor with Mg spheres as the matrix,Eudragit(S-100)as the middle layer and self-polymerised PDA nanoparicles as the outer layer.The outer layer of PDA can be combined with the anticancer drugs adriamycin(DOX)and curcumin(CUR)through π-π interactions and hydrogen bonding to form the DOX/PDA/Eudragit/Mg microsphere motors and the CUR/PDA/Eudragit/Mg microsphere motors.The drugs can be released more quickly in a weakly acidic environment than in a neutral environment.The movement speed and lifetime of PDA/Eudragit/Mg microsphere motors in several kinds of pH environments(pH=2,5,8)are studied.In the blood compatibility test,the PDA/Eudragit/Mg microsphere motors showed excellent biocompatibility,so it is expected to further expand its drug delivery application in blood.