3. Bio-Electronics Integration
3.1 Polypeptide based carbon nanotube biosensor for universal detection of DNA
Although DNA recognition has been achieved using numerous biosensors with various sensing probes, the utilization of bio-interaction between DNA and biomolecules has seldom been reported in universal DNA detection. Peptides as natural molecules have the unique ability to bind to universal DNA and excellent selectivity for DNA after being functionalized with specific groups. In this work, we report a peptide based carbon nanotube (CNT) thin-film-transistor (TFT) biosensor, which can achieve sensitive sequence-independent DNA detection. In the presence of DNA, a significant increase of DIon could be observed within 5 minutes, which was considered to be due to the electrostatic adsorption between the DNA and peptide of opposite zeta potential. With the gradual increase of the concentration of DNA, the DIon signals agree with the Hill–Langmuir model, indicating a negatively cooperative interaction between the peptide and DNA (the Hill coefficient n < 1). Compared with the former reported universal DNA bio-detector and NanoDrop (a spectrometer from Thermo Scientific), this unique peptide based CNT-DNA sensor demonstrated a broader sensing range from nearly 1.6 10-4 to 5 mmol /L and a much lower detection limit of approximately 0.88 mg L1 . For the quantification of cDNA from T47D cancer cells, this unique peptide based CNT sensor could achieve efficient cDNA detection. To the best of our knowledge, this is the first report on the utilization of a peptide as a sensing element in the design of CNT based DNA biosensors, which enables highly efficient universal DNA detection.