Method and sensor for detecting L-cystine

A method for detecting L-cystine, comprising steps:

• step (1):
• implanting a p-well in an N-type substrate, wherein the N-type substrate is arranged on a Si substrate layer of a field effect transistor (FET), constructing a source electrode and a drain electrode at the p-well by thermal evaporation and magnetron sputtering techniques to obtain a processed Si substrate layer, wherein the processed Si substrate layer is provided with the p-well in the N-type substrate, the source electrode and the source electrode, constructing a SiO2 layer on the processed Si substrate layer, plating an Al—Cu alloy layer, a Cr—Pd alloy layer and an Au membrane layer sequentially on a substrate layer of a polysilicon gate electrode by the thermal evaporation and magnetron sputtering techniques, finally constructing a silicon nitride layer on the substrate layer of the polysilicon gate electrode and the SiO2 layer, and extending the polysilicon gate electrode by 0.1-500 mm to obtain an extended gate FET (EGFET) with a gold-gate electrode (GGE);
• step (2):
• preparing an ethanol solution of sodium 3,3′-dithiodipropane sulfonate (SPS), immersing a cleaned GGE of the EGFET in the ethanol solution of the SPS, allowing to stand still at 25° C. to obtain an immersed GGE, and then washing the immersed GGE to obtain an SPS membrane-modified GGE/SPS;
• and
• step (3):
• connecting a reference electrode and the SPS membrane-modified GGE/SPS to an electrode connector of the EGFET to form a differential amplifier circuit with two high-impedance ends;
• inserting the reference electrode and the SPS membrane-modified GGE/SPS into a phosphate-buffered solution (PBS);
• connecting power connectors of the EGFET to a positive electrode and a negative electrode of a regulated power supply respectively, and connecting a signal output connector of the EGFET to a test port of a multimeter to form a sensing loop;
• wherein a potential change of the sensing loop is sensitively detected based on an FET in-situ signal amplification;
• a potential of the SPS membrane-modified GGE/SPS in the PBS tends to stabilize gradually with time, and the SPS membrane-modified GGE/SPS is used as a working electrode;
• when the potential of the SPS membrane-modified GGE/SPS is stable, adding test samples containing different concentrations of the L-cystine to obtain corresponding potential response data to achieve detection of the L-cystine in the test samples.