IMPEDANCE BASED SENSING OF THE SPECIFIC BINDING REACTION BETWEEN STAPHYLOCOCCUS ENTEROTOXIN-B AND ITS ANTIBODY ON AN ULTRA-THIN PLATINUM FILM

Immunobiosensing techniques to measure specific antigen-antibody binding reactions are important in the development of biosensor applications in biotechnology, in vitro diagnosis, medicine and food technology. An immunobiosensor was constructed to measure the specific binding reaction between Staphylococcus enterotoxin B (SEE) and anti-SEE antibodies. The biosensor comprised an anti-SEE bioactive layer covalently immobilized on an ultra-thin platinum (Pt) film sputtered onto a 100 nm thick silicon dioxide layer on a silicon chip. The Pt film was discontinuous with a normal thickness of 25 Angstrom. The impedance of the Pt film decreased during the binding of the anti-SEE to SEE in phosphate buffered saline (PBS) at room temperature. The impedance decreases were irreversible in PBS before saturation of the specific binding sites. When saturated, the impedance at 100 Hz was 14% of the value obtained for the fresh anti-SEE layer in PES. The magnitude of the impedance (/Z/) decrease followed a simple relationship with SEE concentration in the range between 0.389 and 10.70 ng/ml SEE. The specificity of the biosensor was demonstrated by showing that no irreversible impedance decreases occurred when the sensor was exposed to 100 ng/ml kappa-casein, alpha-casein, or alpha-lactalbumin, in PBS.