Determination of polycyclic aromatic hydrocarbons in water using an electrochemical DNA biosensor

Polycyclic aromatic hydrocarbons (PAHs) are widespread environmental contaminants in aquatic environments. These contaminants are generated through oil spills, manufactory processes, and industrial wastes or naturally through the incomplete combustion of coal, oil, gas, and wood waste. Most of these compounds are noted as carcinogenic and mutagenic. Therefore, detection of these pollutants by a sensitive and inexpensive method is very important. In this study, an electrochemical DNA biosensor was used to detect PAHs due to its sensitivity, ability, and high response rate. For this purpose, the bovine thymus double-stranded DNA was fixed on a screen-printed electrode. Then, the electrodes electrochemical behavior was investigated. This electrochemical DNA biosensor works upon the difference between the electrochemical response of guanine bases in DNA structure in the presence and absence of PAH compounds. To evaluate the biosensors performance, the response of biosensor to real samples was compared with conventional pollutant determination methods like liquid-liquid chromatography. Optimum conditions were examined for biosensor response including effect of activation potential and time on electrode pretreatment, applied potential for DNA immobilization, and detection potential. Under optimal conditions, the pretreatment of the electrode obtained in 1.6 V for 350s, then the DNA was immobilized on the electrode surface by applying a potential of -0.5 V to detect different PAHs in real samples in the range of micro molar. Electrochemical DNA biosensors are capable of detecting the sum of PAHs in water samples with high accuracy, sensitivity, and low cost compared with chromatographic methods.