Impedance based DNA chip for direct Tm measurement

Si/SiO2 chips were used to detect the hybridization of immobilized Oligo d(T)20 through impedance measurement. The immobilization procedure involved an aminopropyl silane grafted silicon oxide surface activated by glutaraldehyde and subsequently modified by an aminolinker supporting oligonucleotides. The immobilization procedure was optimized and, in the best conditions, the hybridization of the immobilized oligonucleotide was able to generate a 50 Ω impedance change at an applied dc potential of −300 mV. The optimized DNA sensor was then used to directly determine the immobilized oligonucleotide Tm via impedance measurement in a continuous temperature control flow system. A reproducible and specific 65 Ω impedance change was observed at 32 °C with a step duration as low as 15 min. This value compared well with the 31.4 °C theoretical value calculated from the sequence base pair composition and length.