A sensitive tapered-fiber optic biosensor for the label-free detection of organophosphate pesticides

A new optical biosensor for the detection of organophosphate compounds is reported. The transducing element is a non-adiabatic tapered fiber operates based on interference of propagation modes. By measuring the spectral shift of interferometric pattern, the proposed sensor shows a sensitivity as high as 2100 nm RIU∧1 to bulk refractive index. By chemically activating the fiber surface with a bi-functional cross-linker, the enzyme acetylcholinesterase is immobilized on the optical probe with a kinetic rate of 0.0355 min∧1. The label free detection of methyl-parathion (MPT), as an organophosphate pesticide, is achieved through online monitoring of its binding to the enzyme. Limit of detection of the biosensor is found to be as low as 2.4 í 10∧10 M (S/N = 3) for a concentration range of 10∧10 M to 5 í 10∧5 M for methyl-parathion. The tapered fiber biosensor shows highly reproducible response to pesticide and reactivating agent with the relative standard deviation (RSD) of 2.36% and 2.44% (n = 6), respectively. The proposed sensor suggests a new tool for rapid, sensitive, cost-effective, and real-time screening of organophosphate pesticides.