Detection of sequence-specific DNA with morpholino-functionalized silicon chip

In this work, an efficient method for the sequence-specific detection of DNA based on a morpholino-functionalized silicon chip platform has been proposed. Briefly, morpholino was firstly immobilized to the surface of silicon chip by using 3-Aminopropyltriethoxysilane (APTES) as the silane coupling agent and 1, 4-Phenylenediisothiocyanate (PDITC) as the cross linker, and then hybridized with DNA in the ensuing step. The fluorescence label was introduced by strongly binding rhodamine B, which contains a terminal carboxylic group, with DNA by means of phosphate-zirconium-carboxylate coordination reaction. X-ray photoelectron spectroscopy (XPS) was used to characterize the silicon surface. Under the optimal conditions, morpholino-functionalized silicon chip presented a great linear relationship between the fluorescence intensity and logarithm of target DNA concentrations in the range from 1 pM to 1 nM with a detection limit of 4.52 pM. Furthermore, fully complementary versus single-base mismatched, three-base mismatched and non-complementary DNA could be effectively identified. The chip showed excellent stability for that it could be reused for another hybridization experiment after denaturing morpholino-complementary DNA duplex. In addition, the chip rendered satisfactory analytical performance for detection of DNA in serum samples, thus exhibiting practical significance. Morpholino-functionalized silicon chips display good sensitivity and selectivity for detection of DNA, and promising applications in single nucleotide polymorphisms (SNPs).