Aptamers selected and identified as a colorimetric dual-mode sensing platform for selective and sensitive detection of capsaicin

Capsaicin (CAP), a prominent indicator, has been identified for detecting the gutter oil in adulterated edible oils. In view of the limited availability of efficient and reliable methods for detecting gutter oil, the present study employed the Capture-SELEX technology, which utilizes a high-throughput sequencing (HTS) platform, to facilitate the precise tracking of screening rounds and facilitate the isolation of aptamers with specific affinity for CAP. Isothermal titration calorimetry (ITC) determined the highest affinity and K_d value of 15.5 ± 4.69 nM for aptamer Cap-1. A colorimetric dual-mode aptasensor was designed for CAP detection based on graphene oxide (GO)@gold nanoparticles (AuNPs) composite. A high-sensitivity assay can be achieved using a Synergy™ H1 multimode zymography instrument and a smartphone. Under optimal conditions, the colorimetric dual-mode aptasensor has a detection range of 0.5 ∼ 120 ng mL⁻¹ and a low limit of detection (LOD) of 0.14 ng mL⁻¹. The quantitative recovery of the sensor for CAP in edible oil was 86.25∼98.12 %. Compared with the conventional single-mode aptasensor, the dual-mode aptasensor has independent signal conversion, which provides suitable detection solutions for different scenarios and improves detection accuracy and reliability.