Study Of Molecularly Imprinted Electrochemical Sensor For Biogenic Amine Detection Based On Conducting Polymers

Biogenic amines were nitrogenous compounds of low molecular weight found a smallamount in plants and animals. Biogenic amines were commonly found in foods. Biogenicamines in food were formed mainly by the decarboxylation of amino acids. It is well knownthat if the amount of biogenic amines is high in human body, it will cause a various range ofdiseases. The content of biogenic amines can be used as an indicator of the freshness of food,and control of biogenic amines in food production was particularly important. In this work, aseries of molecularly imprinted electrochemical sensors based on nanomaterials andconducting polymers for the detection of tyramine, histamine, β-phenylethylamine andtryptamine were fabricated. The proposed sensor showed good selectivity, wide linear rangeand low detection limit. It has been successfully used in real samples.The main contents of our work were as follows:1、A novel sensitive molecularly imprinted electrochemical sensor has been developedfor selective detection of tyramine by combination of multiwalled carbon nanotubes-goldnanoparticles （MWCNTs-AuNPs） composites and chitosan. MWCNTs-AuNPs compositeswere introduced for the enhancement of electronic transmission and sensitivity. Chitosanacted as a bridge for the imprinted layer and the MWCNTs-AuNPs composites. Themolecularly imprinted polymer （MIP） was synthesized using tyramine as the templatemolecule, silicic acid tetracthyl ester and triethoxyphenylsilane as the functional monomers.The molecularly imprinted film displayed excellent selectivity towards tyramine. Under theoptimum conditions, the current response had a linear relationship with the concentration oftyramine in the range of1.08×10^-7to1×10^-5mol/L, with a limit of detection5.7×10^-8mol/L.The proposed sensor exhibited excellent repeatability, which was better than the result fromprevious literature. The relative standard deviation （RSD） of the repeated experiments fortyramine （5mmol/L） was7.0%. Determination of tyramine in real samples showed goodrecovery.2、 A novel sensitive electrochemical sensor for the selective detection of histamine wasfabricated built based on the molecularly imprinted technology which was combined tomultiwalled carbon nanotubes （MWCNTs） and horseradish peroxidase （HRP）-enzymatic amplifier. The molecularly imprinted polymer （MIP） was synthesized using histamine as thetemplate molecule and2-aminophenol as the functional monomer. The MWCNTs used had agood conductivity and they enhanced the electronic transmission and sensitivity of thedeveloped sensor. Due to the competition reaction between the histamine and theHRP-histamine, HRP was also used to improve the sensitivity of the developed sensor. Underthe optimum conditions, the proposed sensor exhibited a linear range of histamine detectionbetween8.7×10^-10mol/L and1.0×10^-6mol/L, with a limit of detection was8.7×10^-10mol/L.The relative standard deviation （RSD） for histamine (3.0×10^-7mol/L, n=5) was4.1%. Theproposed sensor was successfully applied to the determination of histamine in real samples.3、A novel selective electrochemical sensor was proposed for the determination ofβ-phenylethylamine （PEA）, using molecularly imprinted polymers （MIPs） as the recognitionelement and combining with polypyrrole and multiwalled carbon nanotubes-cobaltphthalocyanine-gold nanoparticle-silk fibroin （MWCNTs-CoPc-AuNPs-SF） composites film.MIPs film was synthesized by electropolymerization using PEA as the template,2-aminophenol as the monomer. The surface feature of the modified electrode wascharacterized by cyclic voltammetry （CV） and electrochemical impedance spectroscopy （EIS）.The proposed sensor was tested by chronoamperometry. Some parameters, known to affectthe response behaviors of the sensor, were investigated and optimized. The experimentalresults showed that the MWCNTs-CoPc-AuNPs-SF composites film could enhance thecurrent response evidently. This sensor displayed excellent selectivity towards PEA whencompared with structurally similar molecules. Under optimum conditions, PEA atconcentrations of3.0×10^-7mol/L to9.0×10^-5mol/L could be determined with a detection limitof2.2×10^-7mol/L （S/N=3）. The relative standard deviation （RSD） for PEA (3.0×10^-6mol/L,n=5) was5.5%. Determination of PEA in practical samples showed good recovery.4、An imprinted electrochemical sensor based on polypyrrole-sulfonated graphene（PPy-SG）/hyaluronic acid-multiwalled carbon nanotubes （HA-MWCNTs） for sensitivedetection of tryptamine was presented. Molecularly imprinted polymers （MIPs） weresynthesized by electropolymerization using tryptamine as the template, andpara-aminobenzoic acid （pABA） as the monomer. The surface feature of the modifiedelectrode was characterized by cyclic voltammetry （CV）. The proposed sensor was tested by chronoamperometry. Several important parameters controlling the performance of themolecularly imprinted sensor were investigated and optimized. The results showed that thePPy-SG composites films showed improved conductivity and electrochemical performances.HA-MWCNTs bionanocomposites could enhance the current response evidently. The goodselectivity of the sensor allowed three discriminations of tryptamine from interferents, whichinclude tyramine, dopamine and tryptophan. Under the optimal conditions, a linear rangingfrom9.0×10^-8mol/L to7.0×10^-5mol/L for the detection of tryptamine was observed with thedetection limit of7.4×10^-8mol/L （S/N=3）. This imprinted electrochemical sensor wassuccessfully employed to detect tryptamine in real samples.