Direct deoxyribonucleic acid detection using ion-sensitive field-effect transistors based on peptide nucleic acid

We have investigated an ion-sensitive field-effect transistor (IS-FET)-based biosensor to directly monitor the hybridization of deoxyribonucleic acid (DNA) using peptide nucleic acid (PNA) as a probe. The PNA was immobilized on a Ta2O5 gate surface using aminosilane via glutaraldehyde as a bifunctional crosslinker. Variations in surface charge density in the gate region of the IS-FET were monitored as shifts in threshold voltage after DNA hybridization. Large positive shifts in threshold voltage, as high as 170 mV, were observed during ID-VG measurements. The changes in threshold voltage observed for neutral PNA-immobilized IS-FETs were more than 5 times greater than those for negatively charged DNA-immobilized IS-FETs. Thus, this approach demonstrates that the PNA-modified IS-FET-based biosensor works more effectively as a signal transducer of genetic information. We expect potential applications in medical diagnostics and molecular biology.