Experimental characterization of proteins immobilized on Si-based materials

We studied the possibility to use techniques that are traditionally employed in microelectronics to detect biological molecules immobilized on and into Si-based materials having, as final goal, the structural characterization of a glucose biosensor. The inorganic immobilization surfaces used were both bulk and porous silicon dioxide and the biological molecule to monitor was the enzyme glucose oxidase, widely used as a sensing element in glucose biosensors. Bulk SiO2 was used to optimize the immobilization protocol and the step-by-step characterization was mainly carried out by Atomic Force Microscopy measurements. Once optimized, the same protocol was used to anchor the enzyme in a porous Si dioxide matrix. Traditional measurement techniques may fail in biological molecule detection since C, basic element of such biological molecules, is present in Si as a contaminant, or introduced during sample preparation, e.g. for TEM cross section analysis.The enzyme monitoring was carried out by electron diffraction X-ray measurements coupled with scanning electron microscopy and to be sure of the protein presence, it was previously labelled with gold nano particles. We believe that this last measurement technique could be implemented for quantitative direct measurements of the biological molecules concentration in complex matrixes.