CMOS integrated biosensor for the detection of biomarkers

In this contribution we report on results of a micromechanical sensor intended for the detection of allergens and biomarkers, which has been developed within the framework of the Euregio funded project "UniHealth". This project aims at the development of a cost effective label free biosensor system that is intended for point of care applications concerning the detection of large range of allergens e.g. the papain enzyme, gluten and peanuts and the detection of biomarkers e.g. cholera toxine B on GM1 saccharide. The typical mass of allergens and biomarkers is in the range of 20 kDa and 80 kDa. For the label free detection of allergens and biomarkers a mass sensor with micro and nanostructures is a promising detection principle. In this work we report on electrical measurements of membrane structures that have been realized with CMOS compatible pressure sensor technology. The adopted sensor principle relies on electrostatically driven resonating micromechanical membrane structures with a functionalized surface that allows the selective binding of allergens and biomarkers, as shown in Figure 1. The analyte binding causes an increase of the effective mass of the membrane and therefore induces a decrease of the mechanical resonance frequency. The performed measurements of the electrical spectra show nonlinear behaviour, which is explained by a nonlinear oscillator model. As shown in Figure 2, the calculation of the derivation of a sharp transition has the advantage of a sharp peak, i.e. high frequency resolution, where the position of the peak can be easily determined. The sensor element consists essentially of a free standing membrane, which is electrostatically actuated to an oscillation with a resonance frequency of about 4 MHz and a mass sensitivity in the picogram range. We report on experiments with streptavidin on biotin as it is shown in Figure 3, with cholera toxin subunit B biomarkers onto GM1 functionalized sensors with a diameter of 60 µm.