Accumulation and trace measurements of phenothiazine drugs at DNA-modified electrodes

The DNA-phenothiazine intercalative association is utilized for designing a highly sensitive electrochemical biosensor for phenothiazine drugs. The DNA-modified carbon paste electrode permits convenient measurements of nanomolar concentrations of various phenothiazines following short accumulation times. The extent and rate of the accumulation depend upon the structure of the drug. The chronopotentiometric response is evaluated with respect to the preconcentration potential and time, concentration dependence, detection limits, reproducibility and other variables. Detection limits of 5 nM promethazine, 7 nM chlorpromazine and 12 nM phenothiazine are obtained after 10 min accumulation. Similar results are reported for DNA-coated microfabricated thick-film electrodes. The profound structural effect upon the response holds a great promise for using DNA-modified electrodes for studying drug-DNA interactions.