Study Of The Construction And Properties Of Indium Oxide Thin Film Field Effect Transistor Biosensor

Field-effect transistor（FET）biosensors convert biological signals to electrical signals and have an important role in bioscience research,medical diagnosis,and environmental monitoring because of their high integration,good stability,and real-time detection.FET biosensors consist of FET part and bioprobe molecule part.Currently,researchers modulate the FET part or the bioprobe molecule part alone,and the performance of FET biosensors still has much potential for improvement.Therefore,the development of novel detection strategies for the synergistic modulation of the FET part and the bioprobe molecule part of FET biosensors is the key to build high-performance FET biosensors.This thesis provides a new idea for the development of high-performance FET biosensors by synergistically modulating the indium oxide FET part and the bioprobe molecule part to enhance the detection performance of indium oxide FET biosensors.The main research of the thesis is as follows.1.To construct a highly sensitive FET biosensor targeting the ovarian cancer marker CA125,we shorten the distance from the bioprobe molecule to the surface of the indium oxide FET channel by modulating the modification site of the antibody probe molecule.Centimeter-scale,ultrathin indium oxide films（6 nm）are prepared by the solution spin-coating method,and indium oxide FET devices with high switching ratio（10⁵）and mobility(7.2 cm² V^-1 s^-1)performance are constructed.The antibody molecule biofunctionalization method has been used to covalently attach the CA125 antibody probe molecule on the surface of the indium oxide FET,and the N-terminal modification method has been used to bring the probe molecule close to the surface of the indium oxide FET channel to enhance the interaction between the probe molecule and the indium oxide FET channel.The indium oxide FET biosensor has a high sensitivity for the detection of CA125,achieves a low detection limit（100 n U/m L）and has a wide linear response range（100 n U/m L 1 U/m L）,which shows a promising application in the field of low concentration disease marker detection and analysis.2.The FET biosensor detection performance is further enhanced by precisely adjusting the Debye length（λ_D）to synergistically regulate the effective charge of the sensor probe molecule and the indium oxide FET channel carriers.By controlling the passivation layer thickness and buffer concentration to precisely regulate λ_D close to min(R_P,R_P+T)(R_P is the height of the probe molecule before binding to the target,R_P+Tis the height of the probe molecule after binding to the target),the change in effective charge concentration of the bioprobe molecule is maximized,and thus the change in conductive charge concentration of the indium oxide thin-film FET channel is maximized,which improves current response and the detection performance of the indium oxide thin-film FET biosensor.By modulatingλ_D close to min(R_P,R_P+T),the detection limit of serotonin can be as low as 5 fM and the linear range can reach 10 fM to 1 n M,which further extends to the detection of dopamine and glucose,verifying the universality of λ_D modulated indium oxide thin-film FET biosensor and providing a new theoretical and technical support for the development of highly sensitive FET biosensors.3.The mechanism of the interaction between the bioprobe molecule and the indium oxide FET channel on its detection performance was fully revealed by regulating the gate voltage of the indium oxide FET biosensor.A telomerase primer single-stranded DNA（ssDNA）was immobilized as a probe molecule on the surface of the indium oxide FET trench to develop a gate voltage regulated telomerase biosensor.The gate voltage of the indium oxide FET biosensor can control the height of the ssDNA probe,the number of ssDNA effective charges and the number of indium oxide FET carriers synergistically and achieve the regulation of the interaction between the probe molecule and the indium oxide FET channel,effectively improving the sensitivity of the FET biosensor for telomerase detection,achieving a very low detection limit（13 cells）and a wide linear range（100 5000 cells）.The reliability and universality of the gate voltage strategy of the indium oxide FET biosensor are confirmed in the results of telomerase activity detection in cancer cells（Hep G2,He La,MCF-7）and normal cells（HLF）,which is an important reference value and significance for the development of highly sensitive FET biosensors required for clinical diagnosis of cancer markers.