Study On The Novel Methods For Detecting Saxitoxin And Cocaine

Saxitoxin is one of paralytic shellfish toxins,which can cause death with minimum dose.Cocaine is harmful to human digestive system and immune system.In addition,it can produce excitatory effects on the central nervous,and such has been abused by human.The precise detection of saxitoxin and on-site detection of cocaine is one of the most effective methods for preventing the harm of saxitoxin and the cocaine abuse.The main aim of this paper is to develop a novel method for the sensitive detection of saxitoxin by using capillary electrophoresis-inductively coupled plasma mass spectrometry(CE-ICP-MS)together with metal labeling,and a rapid method for the on-site detection of cocaine based on exonuclease ? and cocaine-specific aptamer.The main contents include:(1),A novel sensitive method for the quantification of trace saxitoxin based on Eu3+-diethylenetriamine-N,N,N',N",N"-pentaacetic acid(DTPA)labeling and CE-ICP-MS was developed.The saxitoxin was firstly labeled with Eu3+ by chelating it with Eu3+ and DTPAA,and the europium-tagged saxitoxin were effectively separated by capillary electrophoresis and were sensitively determined by ICP-MS.The proposed method has a extremely low detection limit of 3.4×10-10 mol/L(100 nL of sample injection),and a linear range of 5×10-9-6×10-8mol/L.With the help of the proposed method,we have successfully detect trace saxitoxin in real shellfish sample with a recovery of 96%-110%and a relative standard deviation(RSD,n=4)<6%.The success of the present method provides a new potential for the sensitive detection of shellfish toxins in sea food.(2),We discovered that the exonuclease ?(Exo ?)can preferentially digests the unbound cocaine-specific aptamer,whereas,the cocaine-aptamer complexes can not effectively be digested by Exo ?.Based on above discovery,a novel label-free fluorescence assay was developed for the sensitive,specific and rapid detection of trace cocaine by using pre-folded cocaine-specific aptamer 38-GT as recognition probe and SYBR green I as signal.The developed method has excellent specificity and high sensitivity.The proposed method has a linear range of 1-100 ?M,a detection limit of 1?M and a RSD<6%.The detection limit of 1?M is five-fold lower than that of previous exonuclease ?-assisted fluorescence assay.More importantly,the proposed assay has better specificity in comparison with previous assays,which based on target-displacement strategy.The successful development of this method is expected to provide a more sensitive and reliable method for the rapid screening of cocaine.