Carbon Nanotube - Conducting Polymer Modified Biological Electrode

In this study single walled carbon nanotubes (SWNTs) and Poly (3,4-ethylenedioxythiophene) (PEDOT) nano-composite electrodes were prepared through three methods of paste, alignment and codeposition. Dexamethasone sodium phosphate was incorporated in the composite via electropolymerization and released in PBS using cyclic voltammetry (CV). The resultant composite electrodes possessed the merits of high specific surface area, high conductivity, biocompatibility, and mechanical modulus gradient. The composite electrodes are promising in the application of in-situ, real time and in vivo therapy through controlled drug delivery.SWNTs was purified and shortened to about 1μm in a concentrated nitric and sulfuric acid mixture(1:3 ration v/v) firstly. The composite electrodes, constructed by different concentrations of dopants and various amount of SWNTs, were studied by CV to characterize their capacitances, electron diffusion behavior and stability. The contact angle demonstrated hydrophile of the SWNTs, PEDOT film on the gold surface. The introduction of Cysteamine (Cys) was analyzed by X-ray photoelectron spectrometry (XPS). The successful loading of SWNTs on gold surface was investigated by Raman and CV. Field emission scanning electron microcopy (FESEM) images of the composite electrode revealed that the surface of electrode had fussy and porous structures when pasting method was applied in preparation, a large cascading structure and large surface area when aligning, and a well-proportioned nano-fungus with size around 1OOnm for codeposition method.Dexamethasone sodium phosphate was incorporated in PEDOT and PEDOT-SWNTs composite respectively, and then released by CV stimulation. FTIR analysis of the surface showed the presence of Dsp on the coated electrode. More than 1.62mg/cm2 Dsp released for per 5th CV cycles and more than 10.27 mg/cm2 in total after 30th CV cycles. The amount of drug release increased with doping SWNTs-COOH. FESEM suggested that there was a loss of PEDOT on the gold during the period of drug released which indicated that PEDOT was unstable at high potential.