Highly Sensitive and Selective Photoelectrochemical Aptasensor for Cancer Biomarker CA125 Based on AuNPs/GaN Schottky Junction

A gold nanoparticle (AuNPs)/gallium nitride (GaN) Schottky junction was fabricated by growing AuNPs in situ on the surface of GaN and then etched by H2O2 to appropriate diameter. The photogenerated electrons of GaN can be captured and transferred by the AuNPs to increase the migration efficiency, and the electron–hole pairs were separated, which results in the enhancement of the photoelectric performance of the system. The Fermi energy level of AuNPs and the charge transfer efficiency of the AuNPs/GaN can be adjusted by controlling the size of the AuNPs. Then the AuNPs/GaN Schottky photoelectrode had been applied to develop a novel photoelectrochemical (PEC) aptasensor for the epithelial ovarian cancer marker-CA125 detection. The DNA aptamer of CA125 was modified on the surface of the AuNPs via Au–S bonds. The aptamer can bind with the target with high selectivity, and the photoelectron transfer process of the system can be blocked by the protein, which results in the decrease of the photocurrent of the system. The ratio of photocurrent before and after incubation with CA125 (I1/I0) has a linear with the concentration of CA125 in the range of 1–100 U/mL with a detection limit of 0.3 U/mL. The standard addition recovery rates were between 86.01% and 90.09%. This method showed good sensitivity, selectivity, and reliability in detecting CA125 in serum.