Study And Application Of Molecularly Imprinted Electrochemical Sensor Based On Novel Nanomaterials

It is of great importance to develop fast,selective and sensitive methods for detection of pharmaceuticals.Among the various analytical methods,sensors have been used extensively due to their admirable features.In recent years,molecularly imprinted polymer has gained increasing attention as recognition elements in sensor development due to its high affinity to template molecules,excellent chemical and mechanical stability.In this paper,three novel electrochemical sensors based on molecularly imprinted polymer were developed for estrone 3-sulfate sodium salt,metronidazole and dopamine determination.The main content consists of the following three parts:(1)An ultrasensitive and selective electrochemical sensor for determination of estrone 3-sulfate sodium salt based on molecularly imprinted polymer modified carbon paste electrodeA highly sensitive and selective electrochemical sensor based on carbon paste electrode(CPE)modified with molecularly imprinted polymers(MIPs)has been developed for determination of estrone 3-sulfate sodium salt(ESS).MIPs were prepared in polar medium via bulk polymerization and characterized by scanning electron microscopy and infrared spectroscopy.CPE was prepared in a traditional way by hand-mixing graphite powder and paraffin oil at a ratio of in an agate mortar.The resulting uniform paste was then packed into an empty cartridge and electrical contact was made by placing a copper wire through the other end.Experimental conditions in preparation of MIP/CPE including the molar ratio of template molecule(T)to functional monomer(M),reaction solvents and eluant were optimized.Cyclic voltammetry was performed to study preparation process and the binding behavior of the MIP-modified CPE(MIP/CPE)toward ESS.The conditions for preparing MIPs and MIP/CPE,as well as ESS detection were optimized.Under the optimal experimental conditions,the detection linear range for ESS is 4×10-12 M to 6×10-9 M with a limit of detection of 1.2×10-12 M(S/N=3).In addition,the sensor exhibits high binding affinity towards ESS over its structural analogues with excellent repeatability and stability.The fabricated MIP/CPE was then successfully employed to detect ESS in pregnant mare urine(PMU)without any pretreatment.High performance liquid chromatography was adopted as a reference to validate the established approach in detecting ESS and their results showed good agreement.The as-prepared sensor has high potential to be a decent tool for on-site determination of ESS in complicated matrix in a fast and convenient manner.(2)Molecularly imprinted polymer functionalized nanoporous Au-Ag alloy microrod: Novel supportless electrochemical platform for ultrasensitive sensing of metronidazoleWe describe here an ultrasensitive electrochemical detection of metronidazole(MNZ)by using a freestanding Au-Ag alloy microrod(AMR)as working electrode.Nanoporous Au-Ag AMR(NPAMR)was facilely prepared by dealloying of smooth AMR and further modified with electropolymerized molecularly imprinted polymer(MIP),which affords simultaneous identification and quantification of the target molecules.A series of parameters are investigated and optimized during sensor preparation.Scanning electron microscopy and energy dispersive spectroscopy were used to characterize the morphology and elemental analysis of MNZ-MIP/NPAMR respectively.Chronocoulometry was employed to estimate the electrode surface area before and after dealloying.The results indicate that the effective surface area of the electrode gets increased significantly(about 20 times)after dealloying,which is very helpful in signal amplification and sensitivity enhancement.The electrochemical behavior of the MIP/NPAMR was explored by CV with [Fe(CN)6]3-/4-as the redox probe.The MIP-decorated NPAMR showed a remarkably low detection limit of 2.7×10-14 M(S/N=3)and a wide determination range from 8.0×10-14 to 1.0×10-6 M for MNZ.The developed sensor has been successfully applied in detection of MNZ in real samples(fish tissues and drug tablet),and admirable specificity and anti-interference capability were achieved.This protocol offers great promise for cost-effective and precisely quantitative analysis of trace biological and chemical substances without assistance of any extra working electrode.(3)Supportless electrochemical sensor based on molecularly imprinted polymer modified nanoporous microrod for determination of dopamine at trace levelIn this work,the preparation method of nanoporous Au-Ag alloy microrod is the same as that of(2)and further modifying with electro-polymerized molecularly imprinted polymer(MIP).Influencing factors during electro-polymerization process including pH value and molar ratio of monomer to template molecule were optimized.Under the optimal conditions,Scanning electron microscopy were used to characterize the morphology of MIP/NPAMR.The elemental composition of NPAMR and DA-MIP/NPAMR were analyzed by energy spectrum analysis.The electrochemical behavior of the DA-MIP/NPAMR was explored by cyclic voltammetry and electrochemical impedance spectroscopy.A linear range from 2×10-13 to 2×10-8 M for measuring DA was obtained with an ultralow detection limit of 7.63×10-14 M(S/N=3).In addition,the MIP-modified electrode was successfully employed to detect DA in rabbit serum and rat brain tissue samples.