Fabrication Of Tubular Micromotor With Tunable Surface Charge And Its Application For Nucleic Acid Isolation

The detection of nucleic acids has received considerable attention over the past few decades for the biomedicine,food safety,and environmental monitoring.To improve the sensitivity and specificity of the detection,it is crucial to extract nucleic acids from clinical samples with high efficiency and purity.In recent years,a variety of nucleic acid extraction methods have been emerging.Among them,the microfluidic technology-based nucleic acid extraction methods can lead to substantial reduction of workload and valuable sample or reagent volumes.However,they need to design complexly structured chips and to be operated by sophisticated instrumentations such as the pressure-driven pump system and/or external vibration motor.Therefore,it is still urgent to develop new technology to improve the microchip-based nucleic acid extraction methods.Compared to static micro/nanomaterials,the tubular micromotors with the continuous movement are capable of stirring and moving independently in the chip without the aid of external devices.The recently developed nucleic acid isolation method based on tubular micromotors can only capture the single-strand nucleic acid with specific sequence;however,the captured nucleic acid cannot be released,which is unsuitable for practical applications.In this thesis,we combine polyethyleneimine?PEI?with tunable surface charge and tubular micromotors to develop a platform for the isolation of nucleic acids.Firstly,we prepared the single-conical multi-layer PPy-COOH/PPy/Ni/Pt tubular micromotor by the template-assisted electrodeposition method.In the meanwhile,we investigated the effects of deposition voltage and the concentration of pyrrole on morphology of motors,the influence of fuel concentration on motion speed and the motion control by altering the external magnetic field.The results showed that the optimal condition for electrochemical deposition of PPy layer was electropolymerized at+0.806 V for a charge of 0.5 C from a plating solution containing 74 mmol/L pyrrole.The speed of tubular micromotors can be greatly improved by increasing the concentration of fuel.The average speed of the tubular micromotors was increased to485±38?m/s when the concentration of H₂O₂ was increased to 4%.In addition,by incorporating a magnetic layer of Ni into the body of tubular micromotor,the movement direction of tubular micromotor can be controlled by an external magnetic field,which provides the possibility to realize the directional transportation of micromotors.In this work,the tubular micromotors can be further surface functionalized,and it is expected to be used in the biomedical field as a cheap functional device.Secondly,on the basis of the above-mentioned study of tubular micromotors and the charge tuneable PEI,we first prepared the polyethyleneimine?PEI?-modified PPy-COOH/PPy/Ni/Pt tubular micromotors.Then we investigated the effects of initial concentration of H2O2,pH value,reaction time and the amount of motors on the capture of nuclei acid,and also the effect of pH on the recovery of nucleic acid.In the meanwhile,we studied the recycling performance,the capture efficiency in solution containing protein and nucleic acids,and the movement in microfluidic chips.The results indicated that the as-prepared micromotors can isolate nucleic acids with arbitrary base sequences efficiently in a liquid environment?pH 4.0?.The optimal reaction time and amount of motors were 50 min and 8?g,respectively.When the tubular micromotors were transferred to a basic medium,the captured nucleic acids can be released from their surface,and the recovery efficiency of the nucleic acids was reached to 80%at pH 11.0.In the stimulated sample,the influence of BSA on isolation can be eliminated by controlling the pH value of capture solution.In addition,PEI-modified micromotors showed great reusability during the capture and recovery of nucleic acids,and good motility in microchannel chips under the guidance of magnetic field.Since holding a considerable promise for simplifying the process of nucleic acid isolation,the as-prepared PEI-modified micromotors can promote the future development of molecular diagnostics.This dissertation not only provides a new way of nucleic acid separation,but also provides new ideas for the development and application of micro/nanomotors.