Disposable DNA electrochemical biosensors for environmental monitoring

Two disposable electrochemical biosensors are described; the first one is useful for the detection of the hybridization of DNA and the second one is able to detect low-molecular weight compounds (toxins, pollutants, drugs) with affinity for nucleic acids. Synthetic single-stranded oligonucleotides have been immobilized onto graphite screen-printed electrodes using adsorption at a controlled potential. The probes were hybridized with different concentrations of the complementary sequences. The hybrids formed on the electrode surface were evaluated by chronopotentiometric stripping analysis using daunomycin hydrochloride as an indicator of the hybridization reaction. The DNA sensor was able to detect 0.2 mg 1(-1) of a 21-base target sequence. The determination of low-molecular weight compounds with affinity for DNA was measured by their effect on the oxidation signal of the guanine peak of calf thymus immobilized on the electrode sensor and investigated by chronopotentiometric analysis. The DNA biosensor is able to detect known intercalating and groove binding compounds. Detection limits of 0.3, 0.2 and 10 mg 1(-1) were obtained for daunomycin, polychlororinated biphenyls (PCBs) and aflatoxin BI, respectively. Applicability to river water samples was demonstrated. (C) 1999 Elsevier Science B.V. All rights reserved.