Preparation of Disposable Saliva α-Amylase Biosensor
Abstract A disposable α-amylase biosensor based on ferrocene as an electron transfer mediator has been developed by the screen-printing technique. The PVC plate was coated with the sliver ink as the conductive track. Aside from the two end of the PVC plate, the PVC ink was deposited onto the conductive track as the insulating layer. The one end of the plate uncoated with PVC ink was an electrical contact site, while the other end was printed with the carbon ink as the working electrode (ϕ 3 mm). Glucose oxidase and alpha-glucosidase were immobilized on the screen-printed electrode modified with the ferrocene and Nafion. The gelatin solution was dipped onto the electrode and dried in air. The electrode was soaked into glutaraldehyde solution for 2 min at last. Thus, enzymes were immobilized on the electrode by the indirect cross-linking method. The proposed biosensor presented good repeatability, stability, and accuracy allowing alpha-amylase quantification at levels down to 17.0 U l−1. Moreover, the biosensor showed a wide linear response range (from 60 to 840 U l−1 for alpha-amylase). The biosensor response time was very short, reaching 95% of the steady-state current in less than 30 s. The dependence on the biosensor response was investigated in terms of the pH, the buffer solution, temperature, and the other interferences. The biosensor could be used to detect the saliva α-amylase activities to identify people's stressful condition conveniently and accurately.