Research On Several Alkaloid Molecularly Imprinted Electrochemical Sensors

Molecularly imprinted electrochemical sensors(MIECS)combine molecular imprinting technology(MIT)with electrochemical method and it is an ideal tool for trace component analysis which can achieve rapid detection of intended target with high selectivity,high sensitivity and low cost.There have been lots of reports about MIECS but few of them are about anticancer active alkaloids such as camptothecin(CPT),hydroxycamptothecine(HCPT),aconitine(ACO).In this paper,four kinds of molecularly imprinted electrochemical sensors were constructed with different preparation methods and used in the analysis of the actual samples for the detection of camptothecin,hydroxycamptothecin and aconitine.Also,the characteristics of those sensor were suited.Specific work is as follows:1.A simple and rapid method for the determination of hydroxycamptotheine(HCPT)in complex samples was established.The classical Hummers method was applied to prepare the good conductive graphene(G),which was modified on the surface of the glassy carbon electrode(GCE)as a sensitized material.The HCPT-MIM/G/GCE was obtained by in situ polymerization of the molecular imprinted membrane on the surface of the graphene modified electrode(G/GCE)with acrylamide(AM)as functional monomer,HCPT as template molecule,ethylene glycol dimethacrylate(EGDMA)as crosslinking agent at the mole ratio of HCPT,AM and EGDMA as 1:4:40.The morphology,structure and properties of modified electrode were characterized by scanning electron microscopy,infrared spectroscopy and cyclic voltammetry.Under the optimal condition,the HCPT-MIM/G/GCE showed a good linearity for HCPT detection in the range of 1.0?212.0 ?mol/L with the detection limit(S/N=3)0.2606 ?mol/L,which was based on the differential pulse method.The recoveries of HCPT detection were between 96.00%and 103.0%,and the RSD was within 4.4%.The sensor was used for the detection of HCPT in camptothecin leaves and serum samples with the recoveries in the range of 96.0%?103.0%and the RSD<4.4%.2.A novel molecular imprinting electrochemical sensor(CPT-MIP/G/GCE)for camptothecin(CPT)determination was constructed by using chitosan to immobilize camptothecin molecular imprinted polymer(MIP)on a graphene modified electrode.Camptothecin MIP were prepared by sacrificial silica gel using CPT as template molecule,acrylamide(AM)as functional monomer,ethylene glycol dimethacrylate(EGDMA)as crosslinking agent.The mole ratio of CPT/AM/EGDMA was optimized as 1:4:40.The sensor named as CPT-MIP/G/GCE could simultaneous test CPT and HCPT through the differential pulse method using K3Fe(CN)6 as a probe and showed good selective and high stability.The good linearity for CPT and HCPT detection was obtained in the range of 0.12-46.88 ?mol/L and 0.12?40.88 ?mol/L,respectively.And the detection limit(S/N=3)was 36.01 nmol/L and 58.70 nmol/L,respectively.The sensor had been successfully used to detect CPT and HCPT in serum samples with the recoveries in the range of 97.7%?103.3%and the RSD below 4.2%.Finally,HCPT-MIM/G/GCE and CPT-MIP/G/GCE were used in combination to achieve the detection of camptothecin in camptothecin leaves with the recoveries below 97.7%and the RSD<5.4%.3.In order to realize the simple and rapid analysis of aconitine,two kinds of molecular imprinted electrochemical sensors were synthesized through indirect construction and direct construction.Firstly,molecularly imprinted polymer(MIP)were synthesized by precipitation polymerization under the optimum conditions such as functional monomer,molar ratio of template,monomer and cross-linking agent.The ACO-MIP/CNTs/CPE was synthesized by modifying carbon nanotubes(CNTs)and MIP in the carbon paste electrodes.The electrochemical performance of the modified electrode was characterized by cyclic voltammetry and chronoamperometry.The results showed the modified electrode exhibited good stability,reproducibility and easy to update.The calibration graph for the detection of ACO by the sensor was linear in the range of 5.0?265.0 ?mol/L with the detection limit(S/N = 3)0.9755 ?mol/L.And it was applied to the detection of ACO in urine samples,and the recoveries were between 99.4%and 102.2%with the RSD<3.5%.4.In order to obtain better performance of electrochemical sensors,another molecularly imprinted electrochemical sensor(ACO-MIM/GCE)was constructed by in situ polymerization of the molecular imprinted membrane(MIM)on the surface of glassy carbon electrode(GCE)Under the optimal polymerization conditions.,methacrylic acid was selected as functional monomer and the mole ratio of ACO,MAA and crosslinking agent(EGDMA)was optimized as 1:4:40.The morphology,structure and properties of modified electrode were characterized by scanning electron microscopy,infrared spectroscopy and cyclic voltammetry.Based on he differential pulse voltammetry methode,the sensor not only showed a better linear rang of 0.07?0.97 ?mol/L for the detection of ACO with the lower detection limit(S/N=3)30.20 nmol/L,but also had good selective,high stability and reproducibility.The sensor was successfully used for the ACO analysis in urine and serum samples with the recoveries ranging from 99.1%to 103.8%and the RSD<3.8%.