Self-powered photoelectrochemical immunosensor using MIL-88A-derived NiFe LDH double-shell nanocages/TiO2/P-doped graphitic carbon nitride heterostructure for hCG detection in urine samples of pregnant and non-pregnant women

Abstract

Human chorionic gonadotropin (hCG) is an essential biomarker for pregnancy and seminal system disorders, with elevated levels linked to tumor progression. Early and accurate detection of hCG is critical for disease diagnosis, necessitating the development of highly sensitive and selective assays. Self-powered photoelectrochemical (PEC) biosensors, which function without an external power source at zero bias voltage, offer superior anti-interference properties and have emerged as a promising approach for biomarker detection. This study presents the synthesis of MIL-88A-derived NiFe LDH double-shell nanocages integrated with titanium dioxide (TiO₂) and phosphorus-doped graphitic carbon nitride (PCN). The resulting Ni-Fe LDH DSNCs/TiO₂/PCN heterostructure was immobilized on a fluorine-doped tin oxide (FTO) substrate for efficient hCG detection under zero-bias conditions (0 V vs. Ag/AgCl). Ascorbic acid (AA) acts as an electron donor to scavenge photogenerated holes, thereby improving the sensitivity of the PEC immunosensor. Compared to bare FTO, the Ni-Fe LDH DSNCs/TiO₂/PCN heterostructure exhibited a significantly higher PEC signal, attributed to its enhanced photoelectric conversion efficiency, lower charge recombination, and effective charge separation. The PEC immunosensor shows a linear response to hCG (0.0001–100 ng/mL) with a detection limit of 0.087 pg/mL. The superior performance of the Ni-Fe LDH DSNCs/TiO₂/PCN-based PEC immunosensor can be attributed to its optimized bandgap, efficient charge transport, broad visible-light absorption, and large surface area. Furthermore, the PEC sensor exhibited excellent stability, selectivity, and reproducibility, with high recovery rates in real urine sample analysis, demonstrating its potential for reliable hCG detection.