Biosensors for Detection of Organophosphate Exposure by New Diethyl Thiophosphate-Specific Aptamer

Abstract

Objective An aptamer specifically binding to diethyl thiophosphate (DETP) was constructed and incorporated in an optical sensor and electrochemical impedance spectroscopy (EIS) to enable the specific measurement of DETP as a metabolite and a biomarker of exposure to organophosphates. Results DETP-bound aptamer was selected from the library using capillary electrophoresis-systematic evolution of ligands by exponential enrichment (CE-SELEX). A colorimetric method revealed the aptamer had the highest affinity to DETP with a mean Kd value (± SD) of 0.103 ± 0.014 µM. Changes in resistance using EIS showed selectivity of the aptamer for DETP higher than for dithiophosphate (DEDTP) and diethyl phosphate (DEP) which have similar structure and are metabolites of some of the same organophosphates. The mean (± SD) of percentage of altered resistance of DETP was calculated at 47.5 ± 8.8% which was significantly higher than of DEDTP at 14.3 ± 1.5% and of DEP at 7.0 ± 1.4%. Conclusions The current method showed a great promise in using the DETP-specific aptamer to detect the exposure history to organophosphates, by measuring their metabolite, although degradation of organophosphate parent compounds might occur.