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Label-Free Protein Biosensor Based on Aptamer-Modified Carbon Nanotube Field-Effect Transistors Kenzo Maehashi, Taiji Katsura, Kagan Kerman, Yuzuru Takamura, Kazuhiko Matsumoto, and Eiichi Tamiya Anal. Chem. 2007, 79, 782-787. Jui-Ming (Ryan) Yang. Outline. Background CNT applications
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Label-Free Protein Biosensor Based on Aptamer-Modified Carbon Nanotube Field-Effect TransistorsKenzo Maehashi, Taiji Katsura, Kagan Kerman, Yuzuru Takamura, Kazuhiko Matsumoto, and Eiichi TamiyaAnal. Chem. 2007, 79, 782-787 Jui-Ming (Ryan) Yang
Outline • Background • CNT applications • CNT biosensor : detection of Immunoglobulin E • Experimental Setup • Result • Conclusion / Consideration
Background • CNT – FET • CNT – Gas Sensor • CNT – Biosensor • Protein Sensor • DNA Sensor Lin, Y.-M., et al., IEEE Electron Device Lett. (2005) 26, 823 A Modi et al. (2003) Nature 424 171 S Meng, et al. Nano Letter (2007) 7 1 45-50
Background • Goal: Detection of Immunoglobulin E (IgE) • Aptamer (synthetic oligonucleotides) • Monoclonal Antibody against IgE (IgE-mAb) • Debye Length: distance required for screening the surplus charge by mobile carriers present in the material
Experimental Setup • CNT-FET • p+ type substrate / 100nm SiO2 • source – drain contact: Ti/Au • ethanol thermal CVD growth CNT • Custom-Synthesized DNA Aptamer • Immobilized Aptamer onto CNT • 1-pyrenebutanoic acid succinimidyl ester with dry dimethylformamide solutions • expose to aptamer in PBS overnight • deactivate and block the excess reactive groups via ethanolamine D17.4ext: 5’-NH2-GCG CGG GGC ACG TTT ATC CGT CCC TCC TAG TGG CGT GCC CCG CGC-3’
Result • p-type characteristics in blank PBS • The current increased after the IgE-aptamer modification (at the source-drain bias of 0.2 V ) • Stability test • Selectivity test Brovie serum albumin (BSA) binding event
Result • Sharp decrease in the source-drain current after introducing IgE, then saturation at lower values • Non-specific binding of IgE can be suppressed • Comparison to IgE-mAb modified CNT-FET
Conclusion • Aptamer modified CNT detects the immunoglobulin E with a good dynamic range, from 250pM to 20 nM • Promising candidate for the development of an integrated, high-throughput, real-time biosensor • Consideration • Experimental setup scheme: gate reference • Signal target detection limitation • Questions…