Development and functionalisation of Sb doped SnO2 thin films for DNA biochip applications

In view of developing DNA biochips based on electric detection, well controlled DNA functionalisation of conductive substrate electrode is a challenging process. In this study, the whole process of functionalisation onto home made conductive films with controlled properties has been performed. The latter were Sb doped SnO2 thin films with increasing thickness deposited on oxidized Si using aerosol pyrolysis technique. Their surface morphology shows a roughness increasing with the thickness in association with the polycrystalline microstructure. The silanization process of the as-deposited films was particularly controlled using a combination of different techniques such as wettability and spectroscopic techniques, i.e. X-ray-reflectometry and X-ray photoelectron spectroscopy. The different results confirmed the presence of the silane on the films. The DNA grafting and hybridization to complementary DNA target labelled with fluorescent markers were clearly demonstrated using fluorescence microscopy. The influence of the Sb doped SnO2 film thickness in close relation with the SiO2 thickness on the fluorescence intensity was emphasized. This study has proved the feasibility of a high quality DNA functionalisation of conductive SnO2 films with controlled properties. Moreover, this validates the use of such films as potential substrate electrode for biochips based on the electric detection of DNA hybridization.