A fully microfabricated carbon nanotube three-electrode system on glass substrate for miniaturized electrochemical biosensors

Abstract

We present an integration process to fabricate single-walled carbon nanotube (SWCNT) three-electrode systems on glass substrate for electrochemical biosensors. Key issues involve optimization of the SWCNT working electrode to achieve high sensitivity, developing an optimal Ag/AgCl reference electrode with good stability, and process development to integrate these electrodes. Multiple spray coatings of the SWCNT film on glass substrate enabled easier integration of the SWCNT film into an electrochemical three-electrode system. O₂ plasma etching and subsequent activation of spray-coated SWCNT films were needed to pattern and functionalize the SWCNT working electrode films without serious damage to the SWCNTs, and to remove organic residues. The microfabricated three-electrode systems were characterized by microscopic and spectroscopic techniques, and the electrochemical properties were investigated using cyclic voltammetry and chrono-amperometry. The fully-integrated CNT three-electrode system showed an effective working electrode area about three times larger than its geometric surface area and an improved electrochemical activity for hydrogen peroxide decomposition. Finally, the effectiveness of miniaturized pf-SWCNT electrodes as biointerfaces was examined by applying them to immunosensors to detect Legionella(L) pneumophila, based on a direct sandwich enzyme-linked immunosorbent assay (ELISA) format with 3,3',5,5'-tetramethylbenzidine dihydrochloride/hydrogen peroxide(TMB/H₂O₂) as the substrate/mediator system. The lower detection limit of the pf-SWCNT-based immunosensors to L. pneumophila is about 1500 times lower than that of the standard ELISA assay.

Emerging nanotechnological research for future pathways of biomedicine

“…For what about the use of carbon nanotubes in biosensors for cancer diagnostics, Kim et al (2009) present a simple and sensitive method for the real-time detection of a prostate cancer marker through label-free protein biosensors based on a carbon nanotube field effect transistor (see and cf. Kim et al, 2012). Instead, Bareket et al (2010) report the development of an electrochemical biosensor based on carbon nanotubes for detection of formaldehyde released from a cancer cell line treated with formaldehyde-releasing anticancer prodrugs [see Yang et al (2012) for pancreatic cancer].…”