Applications Of Carbon Nanotubes In Visual Analysis Of DNA And Catalytic Analysis Of Pharmaceuticals

Owing to the unique structure, electronics, machanical and chemical properties, carbon nanotubes (CNTs) have been wildly used in the fields of composite materials, modification of electrodes, sensors and biology since their discovery in 1991. This article puts forward new analytical methods for DNA hybridization and organic small molecules based on the multi-wall carbon nanotubes (MWNTs) which have very strong light scattering signals and have the catalysis to the redox reaction. The main content is as follows:(1) A visual sensor for DNA hybridization with DNA probe-modified MPs and MWNTs respectively. DNA probe-modified MWNTs could be dispersed in aqueous medium and have strong light scattering signals under the excitation of a light beam in the UV-Vis region. DNA probe-modified MWNTs could connect with DNA probe-modified MPs together in the presence of perfectly complementary target DNA and form a sandwich structure. In a magnetic field, the formed MP-MWNT species can easily be removed from the solution, resulting in a decrease of light scattering signals. Thus, by measuring the light scattering signals with DNA-modified MWNTs as recognition elements, this sensor could be used in DNA hybridization and PCR products analysis. And this sensor could be reused at least 17 times and was stable for more than 6 months.(2) It was found that MWNTs could catalyze the redox reaction between hydrochlorauric acid (HAuCl₄) and reductive drugs such as tetracycline hydrochloride (TC), producing gold nanoparticles (Au NPs). Au NPs have the intense plasmon absorption and light scattering signals, and the light scattering signals are more sensitive than the absorption signals. By measuring the plasmon resonance light scattering (PRLS) signals of the resulted Au NPs, tetracycline hydrochloride can be detected simply and rapidly with a linear range of 4²6μmol/L, a correlated coefficient (r) of 0.9955, and a limit of detection (3a) of 6.0 nmol/L. This method has been successfully applied to the detection of tetracycline hydrochloride tablets in clinic with the recovery of 101.9% and that of fresh urine samples with the recovery of 98.3—102.0%.(3) MWNTs could catalyze the redox reaction between hydrochlorauric acid and dopamine. By controlling the concentration of dopamine, we can synthesize gold nanoparticles or gold nanoflowers of large size. The gold nanoflowers have the same light scattering spectrum as gold nanoparticles, but their characteristic absorbtion peak is different. Gold nanoparticles could be synthesized when dopamine concentration is lower with a new absorption peak nearby 560 nm, on the other hand, gold nanoflowers could be synthexized when dopamine concentration increased to 5.0×10^-4 mol/L, and a new absorption peak could be presented nearby 470 nm.