Development of QCM based biosensor for the selective and sensitive detection of paraoxon

In this study, a quartz crystal microbalance (QCM) based sensor was developed that selectively recognizes and binds the paraoxon molecule. For this purpose, poly (styrene-maleic anhydride) (PSMA) polymer was synthesized to obtain nanofiber. A 30% (wt/wt) PSMA/DMSO solution was prepared for use in the electrospinning process, with operating conditions of 5 kV potential and 1 mL/h flow rate. After obtaining the nanofibers, AChE enzyme was immobilized to nanofiber. The QCM gold electrode surface was coated with AChE immobilized nanofiber. For this purpose, the QCM electrode was first functionalized with 4-aminothiophenol. The quartz electrode coated with the recognition layer was sequentially studied with aqueous solutions containing 50% (v/v) methanol, ranging from 0.1 ppm to 10 ppm of paraoxon. When the electrode interacts with paraoxon, the frequency value decreases. The obtained data were converted to graphs and a calibration graph was obtained. The LOD value was found to be 4.57 × 10^-8 and the LOQ value was found to be 1.52 × 10^-7 M. These results show us that the developed method can analyze very small quantities of paraoxon samples. The Langmuir adsorption equation was used to study the interaction of the bond between the electrode surface and the paraoxon. For the calculation of the coupling constant Ka, Δm/C (g/M) versus Δm (g) was plotted on the graph. The Ka binding constant of the obtained graphic was found to be 5 × 10⁷ M^-1.