Silicon nanostructures for DNA biochip applications

Although most DNA microarrays present good quality, accuracy and reliability properties, they are often made on a planar surface structure with its inherent drawbacks: poor accessibility of the targets to the probes and low loading capacity of the solid support. We propose to build up a pseudo-three-dimensional structure based on CVD process adopted for the growth of rough polycrystalline silicon. These nanostructures are covered with a silicon oxide layer, obtained by oxidation and then submitted to various chemical steps in order to introduce a large number of reactive functions for covalent bindings with biomolecules. The influence of the density of nanostructures on the emitted fluorescence was emphasized. This paper presents an experimental characterisation of the fluorescence intensity and the optimisation of the density of silicon grains that composed the substrate used for DNA microarrays. The performances of these silanised supports are investigated by means of hybridization experiments using complementary fluorescent-labeled oligonucleotides targets. Our results indicate that these novel surfaces provide an increase of the density of biomolecules and a higher accessibility of the targets to the probes, which will increase the sensitivity of the fluorescence signal in comparison to the results obtained with a planar surface structure.