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 bindi ng reactions are important in the development of biosensor application s in biotechnology, in vitro diagnosis, medicine and food technology. An immunobiosensor was constructed to measure the specific binding rea ction between Staphylococcus enterotoxin B (SEE) and anti-SEE antibodi es. The biosensor comprised an anti-SEE bioactive layer covalently imm obilized on an ultra-thin platinum (Pt) film sputtered onto a 100 nm t hick silicon dioxide layer on a silicon chip. The Pt film was disconti nuous 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 wer e 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 b iosensor was demonstrated by showing that no irreversible impedance de creases occurred when the sensor was exposed to 100 ng/ml kappa-casein , alpha-casein, or alpha-lactalbumin, in PBS.