The immunodetection of cocaine for forensic applications

• Main Author: Van Der Heide, Susan
• Published: University of East Anglia 2014
• Subjects: 540
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614614

Cocaine on banknotes can be indicative of drug trade; analytical methods which can distinguish ‘drug money’ from contaminated banknotes in general circulation are crucial in providing incriminating evidence. The development and application of two analytical methods for the detection of cocaine on banknotes are presented in this thesis. A competitive enzyme immunoassay (cEIA) was developed and used to quantify cocaine in extracts taken from both banknotes and latent fingerprints. The limit of detection (LOD) of 0.162 ng mL-1 achieved with the assay was comparable to that of conventional chromatography-mass spectroscopy techniques. When compared to LC-MS for the analysis of ten UK banknote samples, the two approaches produced results with statistically significant similarity. The immunoassay presents a simple and cost-effective alternative to the current techniques for the quantitation of cocaine at forensically significant concentrations. Secondly, a novel immunodetection method was developed for the location-specific staining of cocaine on banknotes. The method was based on the application of an acrylamide gel matrix for maintaining the position of the cocaine during subsequent immunostaining. The performance of the method was determined using newly-minted UK banknotes as true negative sample matrices, resulting in staining which could be readily distinguished from that on newly-minted notes spiked with cocaine. The method was successfully applied for the detection of cocaine on the surface of six UK banknotes from general circulation. The developed method, for the first time, demonstrates the location-specific immunostaining for the visualisation of cocaine on banknotes. Finally, a comparison of four different techniques for the functionalisation of cocaine-binding antibody-gold nanoparticles via protein or ligand intermediates is also described. The addition of antibody onto the AuNP surface was facilitated by a polyethylene glycol (PEG) linker with a –COOH terminal functional group, an aminated PEG ligand and an SPDP-Protein A/G intermediate. The study showed that the cocaine binding efficacy was the greatest for AuNP functionalised with the Protein A/G intermediate.