An Advanced, Silicon-Based Substrate for Sensitive Nucleic Acids Detection.

Surface substrate and chemical functionalization are crucial aspects for the fabrication of the sensitive biosensor based on microarray technology. In this paper, an advanced, silicon-based substrate (A-MA) allowing enhancement of optical signal for microarray application is described. The substrate consists in a multilayer of Si/Al/SiO₂ layers. The optical signal enhancement is reached by a combination of the mirror effect of Al film and the SiO₂ thickness around 830 nm, which is able to reach the maximum of interference for the emission wavelength of the Cy5 fluorescent label. Moreover, SiO₂ layer is suitable for the immobilization of single-strand DNA through standard silane chemistry, and probe densities of about 2000 F/um² are reached. The microarray is investigated in the detection of HBV (Hepatitis B Virus) pathogen with analytical samples, resulting in a dynamic linear range of 0.05⁻0.5 nM, a sensitivity of about 18000 a.u. nM-1, and a Limit of Detection in the range of 0.031⁻0.043 Nm as a function of the capture probe sequence.