Electrochemical characterization of oligonucleotide-carbon nanotube functionalized using different strategies

Carbon nanotubes (CNTs) were functionalized with a single-strand deoxyoligonucleotide oligomer (DNO) using two different methods and characterized using different electrochemical techniques to finally evaluate their ability of the DNO to hybridize. The DNO immobilization methods were: direct adsorption (CNT-DNOADS) and covalent attachment (CNT-DNOCOV). The electrochemical behavior of both systems was characterized using cyclic voltammetry, differential pulse voltammetry and scanning electrochemical microscopy. These systems were compared using a bare glassy carbon (GC) electrode and an electrode containing oxidized CNTs without DNO (CNTCOOH). Our results indicate that the direct physical adsorption of DNO improves the dispersion of CNTs in aqueous media and therefore, the film generated over the electrode is more homogeneous than the films created with CNTCOOH and CNT-DNOCOV. The results demonstrated the existence of two different spatial conformations of the oligonucleotide on the CNT depending on the type of functionalization. The modified electrodes to hybridization studies were tested using the well-known DNA intercalation agent methylene blue. Thus, both conformations allowed for the detection of the hybridization process between DNO and its complementary strand; however, using CNT-DNOADS yielded a higher response.