Location-specific immunodetection of cocaine on banknotes

A novel in-gel bioanalytical immunodetection method has been developed to determine both the presence and the location of cocaine on the surface of banknotes. The cocaine was ‘fixed’ to the surface of the banknote via a coating of a polyacrylamide gel matrix. Immunostaining of the immobilised cocaine on the banknote surface was performed using an anti-cocaine primary antibody, either pre-labelled with horse radish peroxidase (HRP) or in conjunction with a HRP-labelled secondary antibody. Visualisation of the location of the cocaine was achieved through chemiluminescence imaging of the banknote following application of a chemiluminescent substrate. The novel method was applied to the detection of cocaine on partial and whole banknote samples obtained from general circulation. Newly minted banknotes, with or without spiked cocaine, were used as positive and negative controls, respectively. The results obtained, for the first time, demonstrate the successful location-specific immunostaining of cocaine on banknotes. A preliminary analysis of six UK banknotes, obtained from general circulation, suggests that cocaine can be present at variable locations across the whole of the banknote.