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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - NARCOREADER (Novel electrochemical strategies for rapid, on-site multiscreening of illicit drugs)

Teaser

Summary

\"The project aims at developing fast and accurate methods for the detection of illicit drugs in-the-field, based on electrochemcistry, to address the negative effects of drug trafficking and abuse on human health and worldwide economy. European customs services in the harbours and national airports are important points of entry of drugs to the european markets and thus are keen to monitor passing cargo, luggage and people for the presence of illicit drugs. Currently, colour tests are mostly used for on-site screening of drugs. However they produce only qualitative results (yes/no) and give a high number of false positive and false negative results. In this light, there is a need for better testing systems able to quickly and accurately detect illicit drugs at borders. A sensing strategy based on electrochemistry would overcome the issues related to colour tests, as it would reveal the unique \"\"fingerprint\"\" of each illicit drug as a voltammetric response, allowing at the same time its quantification. It would allow to quickly and accurately detect illicit drugs at borders (to allow imediate action to stop drugs entering the european markets) and in biological samples, such as saliva (to verify drug use by drivers of vehicles, employees at workplaces or to initiate drug screening programs in medical labs for the general public). This will lead to a better overall management of the issues related to illicit drugs use.\"

Work performed

Given the sometimes complex composition of drugs street samples and biological samples (such as saliva from drugs users) strategies have been developed to accurately detect illicit drugs in such samples. These strategies involved changing the experimental conditions (such as pH of the solution), modifying the sensor surface or developing biomimetic materials that capture only the target drug close to the sensor surface, thus leading to an improved performance of the sensor. Computational design was used to model the interaction between the target illicit drug and the compounds (monomers) used to prepare biomimetic materials. Computational modeling helped to produce biomimetic materials with recognition cavities that bind specifically to the illicit drugs, and exclude other compounds present in the sample. The sensitive and selective detection detection of illicit drugs was achieved by electrochemical methods, by applying a potential at the working electrode (sensor) and measuring the current that results from the oxidation of the illicit drug. Cocaine, heroin, amphetamine, methamphetamine, MDMA and cannabinoids were selected as target drugs.
Electrochemical fingerprinting of illicit drugs was done on unmodified and modified electrodes (with nano- and biomimetic-materials). In terms of designing biomimetic materials with specific recognition cavities two strategies have been followed (i) designing biomimetic receptors (molecularly imprinted polymers-MIPs) in form of nanoparticles (nanoMIPs) followed by integration onto electrodes and (ii) direct electrosynthesis onto electrodes in form of thin MIP-layers. The first strategy was developed based on a novel solid-phase synthesis procedure within the Biotechnology group of University of Leicester, during a secondment and served for developing nanoMIPs for cocaine, morphine and tetrahydrocannabinol. The synthesis of MIPs in the form of thin layers directly onto electrodes was efficient for the selective detection of cocaine, heroin and MDMA. Another strategy for electrodeposition of MIPs in the form of nanoparticles was developed based on multipulse amperometry and successfully applied for heroin and MDMA detection. Amphetamine is a primary amine and does not show an electrochemical signal in the potential window of the single use electrodes. A novel strategy was developed to make possible the electrochemical detection of amphetamine.
Illicit drugs and some of their metabolites have been detected in standard (buffer) solution by square wave voltammetry. The unique electrochemical fingerprint of the target drugs and some of their metabolites has been established. Quantification has been achieved for illicit drugs on bare and (imprinted) polymers/nanomaterials modified graphite electrodes. The sensorsâ€™ performance for illicit drugs in terms of the lowest concentration detectable (detection limit), the range of concentrations that can be determined (linear range) and reproducibility (relative standard deviation) was established. Detection limits between 5 and 125 ÂµM were obtained, and the relative standard deviation varied amongst drugs from 0.7-15.8%.
The developed electrochemical strategies were applied on the analysis of drug street samples seized in Belgium, both in the lab and on-site using a portable, miniaturized potentiostat (at the National Institute of Criminalistics and Criminology and Port of Antwerp). The electrochemical screening allowed the accurate detection of illicit drugs in complex street samples, in the presence of most adulterants/cutting agents. The polymer based sensor for cocaine was applied further to detect cocaine in spiked saliva samples and river water.

Final results

Currently presumptive tests such as color tests and spectroscopic devices are used for on-site detection of drugs. However they suffer from low accuracy â€“ high number of false results- or high costs. An electrochemical device able to detect illicit drugs in complex samples such as street samples has never been developed before. Moreover, there is a lack of specific attention on adulterants and cutting agents and their effects on the signals of illicit drugs in literature regarding electrochemical detection of illicit drugs. Narcoreader investigated electrochemical behavior of illicit drugs in the presence of adulterants and cutting agents (in real samples) and revealed the influences/interferences. By investigating the redox pathways of several of illicit drugs and most common adulterants/cutting agents, new knowledge was created. The further integration of biomimetic receptors tackled selectivity issues allowing specific detection. Biomimetic receptors were developed herein as a good alternative to natural receptors, which suffer from lack of stability, high costs and the need of very controlled operational conditions for testing, make biomolecules unsuitable for the development of multi-sensors for remote applications. Biomimetic receptors are known for their robustness and stability and this, together with their molecular recognition abilities, make them ideal for sensor development.
The project has a positive impact on public health and on security. Drug abuse inflicts immeasurable harm on the health of the citizens, on their families and on communities. Beyond direct public health issues, drug abuse also poses major safety risk to people (e.g. driving under influence). The fast and cost-efficient nature of the technology allows border control to perform more scans with the same resources, increasing the chances of drugs being detected at this early stage and being kept out of circulation. The fast detection of illicit drugs and precursors at borders is a major unmet need for border authorities, now hindering them in taking immediate action to protect the safety of citizens and combat drug-related crimes. The project comes in support of customs for better targeting risky consignments, equipping customs with efficient, affordable systems to identify and mitigate the risks related with illicit drugs.