Indicator free DNA hybridization detection via EIS based on self-assembled gold nanoparticles and bilayer two-dimensional 3-mercaptopropyltrimethoxysilane onto a gold substrate

A novel indicator free DNA biosensors fabricated by self-assembling of bilayer two-dimensional 3-mercaptopropyltrimethoxysilane (B2dMPTS), gold nanoparticles and oligonucleotide has been studied on gold substrate. The thiol groups of 3-mercaptopropyltrimethoxysilane (MPTS) serve as binding sites for the covalent attachment of MPTS to gold electrode surface. After hydrolysation and condensation, the polymerized monolayer, one-dimensional network of MPTS (1dMPTS) was combined together into a two-dimensional sol-gel network (2dMPTS). The second silane layer (B2dMPTS) was formed by immersing electrodes back into the MPTS solution overnight, and then the gold nanoparticles were chemisorbed onto the thiol groups of the second silane layer. Finally, the mercapto oligonucleotide was self-assembled onto the surface via the gold nanoparticles. Electrochemical impedance spectroscopy (EIS) was used to characterize the modified process. And we used the impedance spectroscopy as a platform for reagentless DNA sensing assay. The performance and factors influencing the performance of the resulting biosensor were studied in detail. The linear range of the biosensor was from 1.0 × 10−8 to 1.0 × 10−6 M with a detection limit of 5.0 × 10−9 M at 3σ. In addition, the experiment results indicate that oligonucleotide immobilized on this way exhibits a good sensitivity, selectivity, stability and a long-term maintenance of bioactivity.