Electrochemical DNA biosensor for polycyclic aromatic hydrocarbon detection

Four DNA electrochemical biosensors using four types of DNA (calf thymus ssDNA, calf thymus dsDNA, salmon testis ssDNA and salmon testis dsDNA) were constructed using graphite screen printed electrodes. These biosensors were exploited as analytical tool to detect polycyclic aromatic hydrocarbons-DNA interactions using benzo(a)anthracene and phenantrene as model analytes, the guanine oxidation peak variation being the signal revealing the interaction between PAHs and immobilized DNA. The salmon testis ssDNA biosensor resulted as the most promising device and was further evaluated for benzo(a)anthracene, fluorene, indeno(1,2,3-cd)pyrene, anthracene, and phenanthrene in 5-40 ng mL(-1) solutions, and for benzo(a)pyrene (5-50 ng mL(-1)). A concentration dependent variation of the DNA guanine oxidation peak was observed for all compounds. The effect of benzo(a)pyrene ultraviolet (UV) activation on the benzo(a)pyrene (BaP)-DNA interaction was evaluated at concentration levels of 20 and 50 ng mL(-1), and a 3.5- and 2.7-fold increases of the guanine oxidation peak was measured respectively. The salmon testis ssDNA biosensor was examined with PAHs contaminated samples of Mytilus galloprovincialis. Upon UV irradiation of three sample extracts exceeding the BaP maximum level, a positive variation of the DNA guanine oxidation was obtained. An average 2.4-fold increase of the guanine oxidation peak was detected demonstrating that the sensor can be used to detect toxic degradation products of PAHs.[...]