Fabrication and evaluation of [Co(phen)_21]~(3+)-modified DNA-MWCNT andSDS-MWCNT electrodes for electrochemical detection of 6-mercaptopurine

摘要

A multiple sweep voltammetry is effectively applied to the electrochemical assembly of polypyridylcobalt(111) complexes [Co(phen)_2(tatp)]~(3+)and[Co(phen)_3]~(3+)(where phen 1,10-phenanthroline andtatp = 1,4,8,9-tetra-aza-triphenylene) on a glassy carbon electrode modified with DNA or sodium dodecylsulfate (SDS)-dispersed multi-walled carbon nanotubes (MWCNTs). The DNA-MWCNTs and SDS-MWCNTs are found to impact redox reactions of [Co(phen)2L]~(3+)(L=phen or tatp) adsorbed on the elec-trode surfaces. The anionic surfactant (SDS) facilitates the adsorption of [Co(phen)_2L]~(3+)on the MWCNTsurfaces via a fully-packed π—π stacking mode. An excess amount of DNA as the dispersant attached tothe surface of MWCNTs interferes with the π-π stacking between MWCNTs and 1Co(phen)_2L]~(3+), repre-senting a DNA-bridged binding mode. Moreover, the DNA-MWCNT or SDS-MWCNT modified electrodesare suitable for the detection of 6-mercaptopurine (6-MP) using [Co(phen)_2(tatp)]~(3+)as voltammetricprobes. The proposed sensor exhibits a high selectivity to 6-MP (detection limit=0.05 μM) and a goodlinear response in the range from 0.2 Al to 0.2 mM.