Biosensor array based on ligand binding proteins for narcotics and explosives detection

The detection and identification of dangerous substances including narcotics or explosives remain a major challenge for customs agencies. In this context, a range of natural and modified Ligand Binding Proteins (LBPs) belonging to the families of Odorant Binding Proteins (OBPs) and Major Urinary Proteins (MUPs) were selected and integrated on to nanodiamond coated surface acoustic wave (SAW) transducers. An array of sensors was created, targeting the detection of explosives and illegal drugs with high sensitivity and selectivity, based on the ligand binding affinities of these compounds to the protein binding pockets. The affinity constant of 14 LBPs toward 19 chemical targets was initially assessed in aqueous solution by competitive binding assay using fluorescence probe N-phenylnaphthalen-1-amine (1-NPN) for insect OBPs and MUPs and 1-aminoanthracene (1-AMA) for porcine OBPs. The sensing performances of SAW transducers grafted with selected proteins were then investigated in the vapor phase and their sensitivities compared to the ligand binding behavior of the LBPs in liquid. A linear response in the concentration range from ppb to low ppm values was observed for all sensors. Some correlation between sensitivities in the vapor phase and affinity constants was observed for most proteins. The sensor array was able to discriminate between a range of explosives and narcotic compounds as demonstrated by Principal Component Analysis (PCA). These results hold promise for the use of bioelectronics noses in such security applications.