Kim Jun Pyo, Lee Byung Yang, Hong Seunghun, Sim Sang Jun
Department of Chemical Engineering, Sungkyunkwan University, Changan-gu, Suwon 440-746, South Korea.
Anal Biochem. 2008 Oct 15;381(2):193-8. doi: 10.1016/j.ab.2008.06.040. Epub 2008 Jul 9.
We report a method to build ultrasensitive carbon nanotube-based biosensors using immune binding reaction. Here carbon nanotube-field effect transistors (CNT-FETs) were functionalized with antibody-binding fragments as a receptor, and the binding event of target immunoglobulin G (IgG) onto the fragments was detected by monitoring the gating effect caused by the charges of the target IgG. Because the biosensors were used in buffer solution, it was crucial to use small-size receptors so that the charged target IgG could approach the CNT surface within the Debye length distance to give a large gating effect. The results show that CNT-FET biosensors using whole antibody had very low sensitivity (detection limit approximately 1000 ng/ml), whereas those based on small Fab fragments could detect 1 pg/ml (approximately 7 fM level). Moreover, our Fab-modified CNT-FET could successfully block the nontarget proteins and could selectively detect the target protein in an environment similar to that of human serum electrolyte. Significantly, this strategy can be applied to general antibody-based detection schemes, and it should enable the production of label-free ultrasensitive electronic biosensors to detect clinically important biomarkers for disease diagnosis.
我们报道了一种利用免疫结合反应构建基于碳纳米管的超灵敏生物传感器的方法。在此，碳纳米管场效应晶体管（CNT-FET）用抗体结合片段作为受体进行功能化，通过监测目标免疫球蛋白G（IgG）电荷引起的门控效应来检测目标IgG与片段的结合事件。由于生物传感器用于缓冲溶液中，使用小尺寸受体至关重要，这样带电荷的目标IgG能够在德拜长度距离内接近碳纳米管表面，从而产生较大的门控效应。结果表明，使用完整抗体的CNT-FET生物传感器灵敏度非常低（检测限约为1000 ng/ml），而基于小Fab片段的生物传感器能够检测到1 pg/ml（约7 fM水平）。此外，我们的Fab修饰的CNT-FET能够成功阻断非目标蛋白，并能够在类似于人血清电解质的环境中选择性地检测目标蛋白。值得注意的是，这种策略可应用于基于抗体的一般检测方案，并且应该能够生产出用于检测疾病诊断中临床重要生物标志物的无标记超灵敏电子生物传感器。
