Detection of sequence-specific DNA with a 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 first immobilized on the surface of a silicon chip 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 optimal conditions, the morpholino-functionalized silicon chip presented a great linear relationship between the fluorescence intensity and the 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 because it could be reused for another hybridization experiment after denaturing the morpholino-complementary DNA duplex. In addition, the chip rendered satisfactory analytical performance for the detection of DNA in serum samples, thus exhibiting practical significance. Morpholino-functionalized silicon chips display good sensitivity and selectivity for the detection of DNA and promising applications in single-nucleotide polymorphisms (SNPs).