This paper presents a simple and sensitive method for the real-time detection of a prostate cancer marker (PSA-ACT complex) through label-free protein biosensors based on a carbon nanotube field effect transistor (CNT-FET). Herein, the CNT-FET was functionalized with a solution containing various linker-to-spacer ratios, the binding event of the target PSA-ACT complex onto the receptor detected by monitoring the gating effect caused by charges in the target PSA-ACT complex. Since the biosensors were used in a buffer solution, it was crucial to control the distance between the receptors through introduction of linkers and spacers so that the charged target PSA-ACT complex could easily approach the CNT surface within the Debye length to give a large gating effect. The results show that CNT-FET biosensors modified with only linkers could not detect target proteins unless a very high concentration of the PSA-ACT complex solution (∼500 ng/ml) was injected, while those modified with a 1:3 ratio of linker-to-spacer could detect 1.0 ng/ml without any pretreatment. Moreover, our linker and spacer-modified CNT-FET could successfully block non-target proteins and selectively detect the target protein in human serum. Significantly, this strategy can be applied to general antibody-based detection schemes and enables production of very simple and sensitive electronic biosensors to detect clinically important biomarkers for disease diagnosis.
Bibliographical noteFunding Information:
This work was supported by the grant (No. 10017190) from Next Generation New Technology Development Program from the Ministry of Commerce, Industry and Energy (MOCIE) and National Research Laboratory (NRL) Program grant funded by the Korea government (MEST) (grant no. R0A-2008-000-20078-0) of the Republic of Korea. SH acknowledges the support from the NRL program (no. R0A-2004-000-10438-0).
- Carbon nanotube
- Field effect transistor
- Prostate cancer
- Surface modification
ASJC Scopus subject areas
- Biomedical Engineering