Detection of Prostate Specific Antigen by Coulometric Immunosensor Based on Functional Graphite Nano Sheets

Using graphite as raw material and 1-pyrene butyric acid (PBA) as surfactant, non covalently functionalized graphite nano sheets loaded with PBA (PBA@GNSs) were synthesized by ultrasonic stripping method, and characterized by scanning electron microscope(SEM). Then PBA@GNSs were sprinkled on the surface of brushed screen-printed carbon electrodes (SPCEs) to achieve batch modification of electrodes. Then the carboxyl group of PBA was activated by N-hydroxysuccinimide and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (NHS-EDC), bovine serum albumin (BSA) was used as the blocking agent, and antibody (Ab₁) was fixed with PBA@GNSs to construct Ab₁/PBA@GNSs/SPCEs immunosensor. Cyclic voltammetry and electrochemical impedance spectroscopy were used to study the construction process of the above sensor, and coulometry was used to quantify the prostate specific antigen (PSA). As shown by the results, the linear range of this immunosensor was 10-3 000 ng · L^-1, with detection limit of 3.3 ng · L^-1. Five parallel determinations were conducted on the samples, with RSDs of the determined values less than 2.0%. The recovery of the spiked samples was in the range of 96.1%-101%. It was shown by the selectivity and stability tests that the immunosensor had good selectivity for PSA, and after being stored at 4 ℃ for 18 d, the Coulomb response signal only decaied to 92.0% of the initial signal.