Efficient Fluorescence Based Protein Chip using Pseudo 3D Single-Walled Carbon Nanotube Film

摘要

We have achieved two types of biomolecular sensors, colorimetric protein chips and label-free electrical sensors using high yield of single- walled carbon nanotubes (SWNTs). First, pseudo 3-dimensional SWNT films coated with carbonyldiimidazole-Tween20 (CDI-Tween20) surfactant demonstrated as a facile platform for fluorescence based protein chip. Highly selective protein bindings of biotin-BSA+SA (streptavidin) and SpA (protein A)+IgG (Immunoglobulin G) pairs, as well as those of small molecules such as FLAG peptide+anti-FLAG and biotin-SA. In this system, the geometry of pseudo 3- dimensional high yield of SWNTs preserves protein shapes intact, therefore increases the efficiencies of specific bindings. Furthermore, CDI-Tween20 mediates effective immobilization of probe proteins through covalent linkage, as well as prohibition of nonspecific bindings. By avoiding bovine serum albumin (BSA) which has been generally used as a biomolecular blocking agent during the protein chip manufacturing, it has been possible to reduce process steps, quenching of interaction signals from small molecules, and background noise. We also have fabricated ultrahigh sensitive electrical protein sensors using single-walled carbon nanotube-field effect transistors (SWNT-FETs) which contain increased Schottky contact area. A simple fabrication technique utilizing thin shadow mask and thermal evaporation at tilted angles allowed metal to penetrate underneath of the mask efficiently. Hence, thin and wide metal to SWNT contact regions are obtained, which could accommodate more proteins comparing to the typically fabricated SWNT-FET devices by photolithography. Direct protein adsorption of SpA and specific binding of hCG+anti Beta-hCG pairs on SWNT-FET changed more than 1% of conductance change at 1 pM concentration without NSB. These new SWNT-FET devices have increased the detection limit about four orders of magnitude compared to the previous devices.