Rapid detection of cocaine using aptamer-based biosensor on an evanescent wave fibre platform.

The rapid detection of cocaine has received considerable attention because of the instantaneous and adverse effects of cocaine overdose on human health. Aptamer-based biosensors for cocaine detection have been well established for research and application. However, reducing the analytic duration without deteriorating the sensitivity still remains as a challenge. Here, we proposed an aptamer-based evanescent wave fibre (EWF) biosensor to rapidly detect cocaine in a wide working range. At first, the aptamers were conjugated to complementary DNA with fluorescence tag and such conjugants were then immobilized on magnetic beads. After cocaine was introduced to compete against the aptamer-DNA conjugants, the released DNA in supernatant was detected on the EWF platform. The dynamic curves of EWF signals could be interpreted by the first-order kinetics and saturation model. The semi-log calibration curve covered a working range of 10-5000 µM of cocaine, and the limit of detection was approximately 10.5 µM. The duration of the full procedure was 990 s (16.5 min), and the detection interval was 390 s (6.5 min). The specified detection of cocaine was confirmed from four typical pharmaceutic agents. The analysis was repeated for 50 cycles without significant loss of sensitivity. Therefore, the aptamer-based EWF biosensor is a feasible solution to rapidly detect cocaine.