Study On Immunosensing Technology For The Detection Of Regulated And Prohibited Drugs

The prohibited drugs are those narcotic and/or psychotropic drugs which oncecured thousands of peoples but are forbidden to be kept on due to their seriousside-effects such as to induce the dependence and addiction for many peoples.Regulated drugs also belong to narcotic and/or psychotropic drugs that still keep on butthe dosage and medication are controlled within limits in clinical. The abuse of thoseprohibited/regulated drugs will cause severely impair for human health even socialcivilization. Presently, the most seriously abused prohibited/regulated drugs around theworld mainly include ketamine, heroin, morphine, methamphetamine and so on. Therequirement of rapid detection of those prohibited/regulated drugs is urgent for moreand more occasions as field drug-seizing in confines of the country, raiding policing inentertainment place, drugs screening of traffic accident or the customs inspection ofdrugs and so on. As a forensic toxicological analyst with many years of experience, thecandidate knows deeply the necessity of rapid and accurate detection method of thesedrugs and the embarrassment without rapid and simple detection technology in practicalwork. Immunoassay, Spectroscopy, GC, GC-MS, LC and LC-MS etc are all reported forthese drugs detection, but are hard to realize the rapid and accurate on-site test. Wedevote the research to develop the sensing technology for on-site usage of these drugsexpediently just as the on-site test of alcohol.N. Alizadeh et al published an article in Journal of Pharmaceutical and BiomedicalAnalysis, they used a PVC membranous ionic elective electrode (ISE) to determine theketamine hydrochloride but unexactly comprehended the response mechanism asentirely ion-exchange based in their research. We also studied the response ofso-developed membranous ISE and discussed its real response mechanism. Throughexperiment research and theoretical ratiocination, we concluded that the response of the potential sensitive membrane was induced from infiltration in addition to ion-exchange.In most cases, the infiltration was predominated than ion-exchange. Thus we explainedthe causation of why its selectivity was very poor and then restored its realpotentiometric response characteristics.Since the response of the previous PVC ISE toward ketamine was not very idealand selectivity was also not so perfect, we tried to take on the research via the approachof electrochemical immunosensing technology to determine the ketamine for moresensitive and selective. The mice monoclonal antibody of ketamine was immobilized onthe self-assembly modified (SAM) and activated gold electrode. It was thencharacterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy(EIS) and atomic force microscope (AFM). The experiment conditions for preparingand utilizing of the sensor were both optimized. This electrochemical immunosensorwas then used for the determination of ketamine with EIS as sensing signal. The resultsshow that the sensitivity of this immunosensor approached to0.41×10-12mol/L. It coulddirectly detect the ketamine in serum samples after diluted for2000folds withoutinterference from the blood substrates. This method can save a lot of time required insample preparation such as GC-MS etc. With the merits as rapid detection and highsensitivity, the developed immunosensor is expected to be made into a small device,used in on-site rapid test of ketamine coupled with a pocket instrument in drugsmuggling seizing, recognition of driving after drugs abusing, emergency medical aimsand so on.Based on the development of ketamine electrochemical immunosensor, themorphine and methamphetamine electrochemical immunosensor were prepared as thesame way. The results showed that the morphine electrochemical immunosensor hashigh sensitivity, reached to0.266×10-6pg/L. Part of the development work ofmethamphetamine immunosensor has been completed. In view of time, the work ofregeneration of immunosensor and determination of practical samples are in progress.Electrochemical quartz crystal microbalance (EQCM) could be combined withimmunosensing technology to improve the detection sensitivity due to its ultra-highmass-sensitivity. Up to now, the researches about the quartz crystal mass sensing technology of ketamine, morphine or methamphetamine are hardly reported. To carry onthe research in this area, some important modification on a CHI-400A QCM was madeto meet the required analytical performance. After to analyze and discuss the influencefactors for frequency stability and the noise of QCM in liquid/solid surface, somepractical measures were put forward to solve the problems. Those new technicalmeasures resulted in the great improvement in seismic stability, electromagneticinterference resistance and the frequency fluctuation that was induced from the tensileforce of liquid/solid interface. Based on this, the researches about the immuno-QCMsensing technique for these drugs are carried on in progress.