In-depth interpretation of aptamer-based sensing on electrode: Dual-mode electrochemical-photoelectrochemical sensor for the ratiometric detection of patulin

Electrochemical aptasensors have been extensively used to quantify food contaminants (e.g., mycotoxin) by using high-affinity aptamer for target recognition. Yet, analytical performance of aptasensors using different aptamers can be varied for the same target. Here, four aptamers with different sequences (i.e., A22, A34, A42, and A45) of patulin (PAT) were selected to estimate sensing behaviors at electrodes with electrochemical (EC) and photoelectrochemical (PEC) assays. Synergistic effect of steric hindrance and electron transfer distance was found to significantly affect EC and PEC response for PAT at aptasensors fabricated with A22, A34, A42, or A45. Eventually, A22 emerged to be the optimal aptamer for aptasensing, despite the highest affinity of A42 to PAT. The A22-based EC-PEC dual-mode ratiometric aptasensor offered a linear range of 50 fg mL-1 - 500 ng mL-1 with a detection limit of 30 fg mL-1 for PAT, and it was applied to apple product (i.e., juice, puree) analysis.

Automated summary

Electrochemical aptasensors using high-affinity aptamers have been widely used for quantifying food contaminants. However, the analytical performance can vary for different aptamers targeting the same contaminant. In this study, four aptamers with different sequences were compared for detecting patulin. The aptasensor with A22 exhibited the best performance, despite A42 having the highest affinity. The A22-based EC-PEC dual-mode ratiometric aptasensor showed a linear range of 50 fg mL-1 - 500 ng mL-1 and a detection limit of 30 fg mL-1 for patulin.