Identification of mammalian species using genosensors

This work reports the development of DNA biosensors for the identification of mammalian species in real samples based on specific oligonucleotide probes. The oligonucleotide sequences (the probes) of each species studied were selected starting from the sequence of satellites DNA. Two inosine-modified (guanine-free) DNA sequences of 21 and 25 bases have been immobilised on screen printed electrodes (SPEs) as capturing agent and the detection of the duplex formation, via guanine oxidation of the target, was examined and optimised. The duplex formation was detected using the square-wave voltammetry. The developed sensors were applied on bovine and porcine DNA extract samples without polymerase chain reaction (PCR), after a restriction enzyme digestion to avoid steric hindrance. Using standard solutions the hybridisation event was identified when 3 microg/mL of complementary oligonucleotide were presented in solution with a coefficient of variation (CV) of 15%. Using total genomic DNA extracts a clear discrimination of the species with a detection limit of less than 30 microg/ml of total genomic bovine DNA was obtained (CV < 20%). The sensors were able to discriminate among the species indicating that the approach is suitable for the identification of mammalian species.