Disposable DNA electrochemical biosensors for environmental monitoring

Two disposable electrochemical biosensors are described; the first one is u seful for the detection of the hybridization of DNA and the second one is a ble to detect low-molecular weight compounds (toxins, pollutants, drugs) wi th affinity for nucleic acids. Synthetic single-stranded oligonucleotides h ave been immobilized onto graphite screen-printed electrodes using adsorpti on at a controlled potential. The probes were hybridized with different con centrations of the complementary sequences. The hybrids formed on the elect rode surface were evaluated by chronopotentiometric stripping analysis usin g daunomycin hydrochloride as an indicator of the hybridization reaction. T he 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 chrono potentiometric analysis. The DNA biosensor is able to detect known intercal ating 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 demons trated. (C) 1999 Elsevier Science B.V. All rights reserved.