Research On Comb Electrode Microfluidic Chip For Detecting Myocardial Infarction Markers

Acute myocardial infarction(AMI)is the most common cardiovascular disease in clinic.Cardiac troponin I(cTnI)is an important marker for the diagnosis and differential diagnosis of AMI.Therefore,the development of cTnI detector with high sensitivity,fast response,low cost and miniaturization is of great significance for the early diagnosis of AMI.Microfluidic electrochemical detection technology has many advantages,such as high sensitivity,low cost,easy compatibility with micro-processing technology,and has broad application prospects in the real-time detection of major disease markers.Comb electrodes are an important part of microfluidic electrochemical detectors.The optimization of their structure and size is of great significance to improve the detection sensitivity.However,the structure optimization of comb electrode and its application in the detection of cTnI still need to be further studied.In view of the above problems,the following studies are carried out in this paper:(1)The influence of the structure size of comb electrode array on the current and the thickness of diffusion layer was analyzed,and the geometric structure of comb electrode array was optimized.A numerical model of the diffusion layer of comb-shaped electrode array was established,and the basic theory of the influence of the structure parameters of the electrode on the diffusion current was studied.A two-dimensional model of the comb-shaped electrode array was established by using COMSOL finite element software.The geometrical structure of the electrode array was optimized by comparing the current response and concentration diffusion overlap of the comb-shaped electrode array with different sizes.(2)A microfluidic chip integrated with comb electrode array for electrochemical detection of cTnI was designed and fabricated.The overall structure of the chip was designed.The chip consists of a glass substrate with an integrated comb electrode array and a PDMS cover with a microchannel.The comb electrode array was fabricated by sputtering and wet etching,and its morphology was tested by tool microscopy.The PDMS cover was fabricated by casting method,and the bonding between glass substrate and PDMS cover was realized by oxygen plasma bonding.The bonding performance of the chip was tested with red biodye.(3)The electrochemical performance and repeatability of microfluidic chip with integrated comb electrode array were studied.Firstly,the cyclic voltammetry of potassium ferrocyanide at different sweeping speeds was carried out in potassium ferrocyanide solution.The linear fitting coefficients between the peak current of potassium ferrocyanide oxidation and the square root of sweeping speed were 0.998 and 0.994,respectively,which indicated that the chip had good electrochemical performance.The relative standard deviations of peak potential and peak current of potassium ferrocyanide oxidation were 1.36% and 1.94% respectively,which indicated that the chip had good repeatability.(4)The microfluidic immunoelectrochemical chip with comb electrode array was tested using cTnI antigen as a sample.Firstly,the surface of PDMS microchannel was modified.The modified microchannel and comb electrode arrays together constitute an electrochemical immunoassay system.The effectiveness of the system was verified by cyclic voltammetry.Then,cyclic voltammetry was performed in the range of 1ng/mL-10μg/mL of cTnI antigen concentration.The linear correlation coefficient between current and logarithm of cTnI antigen concentration was 0.972.The results show that the detection limit is 0.63 ng/mL,and the detection time is 10 minutes.