Photoelectrochemical Aptasensor of α-Fetoprotein Using Ag NPs/Ba 3 (PO 4 ) 2 /TiO 2 Nanorod Arrays

Abstract α-Fetoprotein (AFP) is a crucial biomarker for the early diagnosis of hepatocellular carcinoma, making its sensitive and reliable detection of considerable clinical importance. Herein, this study reports the construction of a photoelectrochemical (PEC) aptasensor based on an Ag nanoparticle (Ag NP)-decorated Ba3(PO4)2/TiO2 nanorod array (NRA) for highly sensitive AFP detection. Briefly, vertically aligned TiO2 NRA was grown in situ on fluorine-doped tin oxide (FTO) substrates and subsequently modified via solvothermal deposition of short rod-like Ba3(PO4)2 to construct a heterojunction, followed by chemical reduction decoration of Ag NPs onto the electrode surface. The resulting Ag NPs/Ba3(PO4)2/TiO2 NRA photoelectrode combines the large surface area and efficient electron transport of TiO2 NRA with heterojunction-enhanced charge separation and the surface plasmon resonance (SPR) effect of Ag NPs, leading to significantly improved photocurrent response and charge-transfer efficiency. An AFP-specific aptamer was subsequently immobilized on the photoelectrode to construct the PEC aptasensor, enabling the selective AFP recognition. Under optimized conditions, the PEC aptasensor exhibited a wide linear detection range from 0.001 to 500 ng/mL, with a low detection limit of 0.41 ng/mL (S/N = 3). The PEC aptasensor also demonstrated excellent selectivity, stability, and reproducibility, and was successfully applied to the AFP determination in spiked human serum samples. Overall, this work presents a sensitive and reliable PEC sensing platform for AFP detection and provides a promising strategy for the development of high-performance PEC biosensors for clinical diagnostics.