A three-dimensional gold nanoparticles spherical signal array - enhanced dual-mode aptasensor for facile and sensitive detection of ochratoxin A.

Ochratoxin A (OTA), a highly carcinogenic mycotoxin contaminating agricultural products, presents critical challenges to food safety and human health. Existing biosensors are predominantly limited to single-signal detection modes, which necessitates the development of more efficient and reliable dual-mode sensors to enhance anti-interference capabilities. Herein, a three-dimensional(3D) gold nanoparticles spherical signal array (AuNPs-SSA)-enabled dual-mode aptasensor that synergistically integrates fluorescence (FL) and surface-enhanced Raman scattering (SERS) detection was established. The aptasensor architecture employs polystyrene microparticles (PS) as scaffolds to organize 5-carboxyfluorescein (FAM)-ssDNA and 4-mercaptobenzoic acid (MBA)-functionalized AuNPs into a spatially optimized 3D spherical array with controlled interparticle distances. This aptasensor achieves structural stability through tunable interparticle AuNPs spacing, simultaneously a FL signal was amplified via maximized FAM-ssDNA loading, and SERS activity was enhanced via utilizing Raman "hot spots" generated by leveraging precisely engineered nanogaps. Through competitive binding between OTA and the AuNPs-SSA probe with aptamer-modified magnetic nanoparticles (MNPs-H0), the aptasensor enables simultaneous FL and SERS enhancement responses. Demonstrating superior sensitivity, the dual-mode system achieves linear detection across 102-107 fg/mL with ultralow limits of detection (21.87 fg/mL for FL and 17.06 fg/mL for SERS). Validation using spiked samples (peanuts, rice and beer) yielded recoveries of 90.44-108.11 % (FL) and 95.88-108.27 % (SERS), confirming practical reliability.