Electrostatic-FRET coupled dual-mode aptasensor for sensitive and visual detection of bisphenol A

Bisphenol A (BPA) is a common monomer in polycarbonate plastics and epoxy resins that can migrate into food and water under extreme conditions, posing significant health risks including endocrine disruption, infertility, and metabolic disorders. Conventional detection techniques such as HPLC, HPLC-MS, and ELISA offer high sensitivity but suffer from costly instrumentation, complex pretreatment, and limited field applicability. Aptamer-based biosensors provide an attractive alternative due to their high specificity, low cost, and ease of use. Dual-mode platforms integrating colorimetric and fluorescent signals can overcome the limitations of single-mode detection.

Here, we developed an electrostatic-FRET coupled dual-mode aptasensor for BPA detection using cysteamine-modified gold nanoparticles (CS-AuNPs) and a FAM-labeled aptamer. In the absence of BPA, FAM-aptamer adsorbed onto CS-AuNPs, leading to fluorescence quenching and colloidal stability. Upon BPA binding, aptamer conformational change suppressed electrostatic adsorption, resulting in fluorescence recovery and nanoparticle aggregation with a visible color shift. Under optimized conditions, the fluorescence mode displayed a linear response from 10 to 1000 nM with a detection limit of 1.19 nM, while the colorimetric mode showed a range of 25-1000 nM with a detection limit of 2.22 nM. The dual-mode system demonstrated high selectivity against BPA analogues and reliable recoveries (92.7-109.2 %) in spiked tap water, confirming its accuracy and robustness in real sample analysis.

This study presents a cost-effective and visually responsive aptasensor that integrates electrostatic adsorption and FRET for sensitive BPA detection. By combining fluorescence and colorimetric modes, the platform achieves complementary readouts, reducing false positives and enhancing detection reliability. The work highlights the potential of positively charged AuNPs in multimodal biosensing, offering a promising tool for environmental monitoring and food safety assessment.