Preparation Of Electrochemical Sensor Enhanced By Electric Field Force And Its Application In Gut-on-a-chip

Colorectal cancer is the third most common cancer and the second most deadly cancer in the world.Diagnostic staging playing a crucial role in determining patient prognosis,survival,and treatment of patients.Fortunately,early prognosis of the colorectal cancer can lead to a 5-year survival rate of over 90%.Currently,electrochemical sensors are utilized for early colorectal cancer screening by detecting biomarkers such as micro RNA-21 and interleukin-6 in human body fluids like blood,urine,and sweat.These biomarkers concentrations change with the occurrence and development of colorectal cancer.However,in the early stage of colorectal cancer,the biomarkers concentration such as micro RNA-21 is extremely low,often at the f M level.To effectively screen for early colorectal cancer,it is necessary to develop an electrochemical sensor with high sensitivity and low detection limits.This paper explored the use of ordered arrangements of one-dimensional nanomaterials,as well as the modification of nanomaterials such as carbon nanotubes and gold nanoparticles,and the fabrication of microelectrode arrays to amplify current signals in biosensors.These techniques improved sensor sensitivity and reduce detection limits.The following experiments were conducted:1)To increase the active sites of the electrode,the electric field force was used to rotate and rearrange random multi-walled carbon nanotubes（MWCNTs）at the microscale to improve the active sites of the electrode.The free-standing-MWCNTs were densely and high-orderly embedded into the MWCNT-PDMS bare electrode along the direction of the electric field.Compared to the bare electrode,the cyclic voltammetric peak current response of the freestanding-MWCNT electrode improved by 150 times.2)A nano-genosensor based on the free-standing-MWCNT electrode was developed for measuring colorectal cancer biomarker micro RNA-21.The nano-genosensor showed a wide linear range from 0.01 × 10^-15 to 100 × 10^-12 M,and a low detection limit of 1.2 × 10^-18 M.The present nano-genosensor showed superior performance for micro RNA-21 in human serum samples and demonstrated a potential application for the diagnosis of early-stage colorectal cancer.3)A free-standing-Ag NWs/Au NPs based electrochemical sensor was fabricated under the action of electric field and integrated into the gut-on-a-chip for real-time detection of interleukin-6 secreted by colorectal cancer cells（Caco-2 cells）.The cyclic voltammetric oxidation peak current of the free-standing-Ag NWs/Au NPs electrode was 500 times of MWCNT-PDMS bare electrode.Au NPs not only solve the problem of rapid oxidation of Ag NWs at extremely low potential（<70 m V）,but also improve the electrochemical response of Ag NWs electrodes.This biosensor showed a wide linear range from 0.001 ng ml^-1 to 100 ng ml^-1 and a low detection limit of 0.53 pg ml^-1.During the 10-day culture period,the concentration of interleukin-6secreted by Caco-2 cells on the gut-on-a-chip reached 7.8 pg ml^-1.This indicated that the sensor can achieve real-time detection of colorectal cancer markers on the gut-on-a-chip.In addition,an electrochemical sensor based 36 channels microelectrode array was further developed and applied to the detection of carcinoembryonic antigen and interleukin-6.Microelectrode arrays with hemispherical diffusion patterns exhibited larger diffusion-controlled Faradaic currents than large electrodes with linear diffusion patterns.This increases the current density,improves the signal-to-noise ratio,reaches steady state quickly（independent of convection）,and has a faster mass transfer rate.The simultaneous detection of carcinoembryonic antigen and interleukin-6 can also reduce false positives/negatives.