Streptavidin as CNTs and DNA Linker for the Specific Electronic and Optical Detection of DNA Hybridization

Streptavidin was used as an interlinker between single-wall carbon nanotubes (SWNTs) and oligonucleotides for the electronic and optical detection of DNA hybridization. The aim of using streptavidin as a linker was to prevent nonspecific adsorption of biomolecules onto carbon nanotubes (CNTs) and also to prevent the aggregation of DNA strands or other contaminants to the source and drain electrodes that can modify the Schottky barrier. The electronic detection was performed by using arrays of CNTs field effect transistors (CNTFETs) and statistically significant changes in the threshold voltage and ION current were inferred. For the optical approach, a complementary DNA strand labeled with a dye was used, and the hybridization was detected by fluorescence microscopy. Streptavidin was noncovalently bonded to SWCNTs. Afterward, single-strand DNA modified with biotin was attached to the streptavidin, followed by DNA hybridization with the complementary DNA strand. Direct addition of the complementary DNA strand to the SWNTs covered with streptavidin was also performed to rule out any false hybridization positives due to nonspecific adsorption, and neither electrical nor optical responses were recorded. The results indicated that streptavidin efficiently prevents nonspecific adsorption of high-affinity molecules such as DNA onto CNTs. The wrapping of SWNTs with streptavidin allows both electrical and fluorescence detection of DNA hybridization.