Interface Building Of Phenylalanine Dipeptide-graphene Composite And Its Application As An Electrochemical Biosensor

Interface building is the core of the electrochemical sensor,and is also one of the effective ways to improve electrochemical sensor sensitivity and selectivity.Looking for the new features of structural materials that can be used for electrochemical sensor and designing new way to build electrochemical sensor has been a hot research.This paper takes phenylalanine dipeptide?FF?-graphene?rGO?complexes as the object,to prepare of the different microstructure of composite interface using self-assembly,pulse potential and Langmuir-Blodgett?LB?film methods.On this basis,bovine hemoglobin?Hb?,glucose oxidase?GOD?,cytochrome c?Cyt.c?and alcohol soluble protein antibody?Anti-gliadin?was selected,a series of electrochemical biosensors with high sensitivity and high selectivity was presented.These detailed works are as follows: 1.Synthesis,characterization of Phenylalanine dipeptide and its derivativesA series of FF derivatives including FAF,FAAAF,FFA,FFAAA and ferrocenecarboxylic acid-FF?Fc-FF?were synthesized by Fmoc Solid-phase Strategy.The peptides were analyzed and purified by reversed phase high-performance liquid chromatography?RP-HPLC?and were characterized by electrospray ionization mass spectrometry?EI-MS?.2.Self-assembled dipeptide-graphene nanostructures and its application in electrochemical biosensorSelf-assembled nanowires of diphenylalanine and graphene?FF-G?nanocomposites have been prepared in aqueous solution by a simple one-step method.Hemoglobin?Hb?as a model molecule is further immobilized on the FF-G nanocomposites in order to construct a mediate H₂O₂ amperometric biosensor.According to UV–vis spectroscopy,the immobilized Hb,overall retains its original structure and the bioactivity.Systematic electrochemical tests demonstrate that the Hb/FF-G modified glassy carbon electrode shows high electrocatalytic activity to H₂O₂.The biosensor exhibits a wide linear response in the range from 5.0 × 10-7 to 5.0 × 10-4 mol L-1,with a low detection limit of 1.0 × 10-7 mol L-1.Our results indicate that the nanowires of FF-G nanocomposites obtained in a facile method are promising for application in electrochemical biosensors due to its excellent biocompatibility and good charge-transfer ability.3.Pulse potential method to construct phenylalanine dipeptide-graphene composite membrane and its application in electrochemical sensorWe presented first to build the electrochemical reduction graphene?ErGO?and phenylalanine dipeptide-electrochemical reduction graphene?FF-ErGO?interface using pulse potential method in a graphene oxide or phenylalanine dipeptide-graphene?FF-GO?solution.Levodopa?L-dopa?was studied on electrochemical behavior in ErGO modified electrodes.Related electrochemical parameters were calculated using various electrochemical methods.Under optimized conditions,a simple,rapid and sensitive way to detected L-dopa in the presence of uric acid?UA?and ascorbic acid?AA?was proposed.In addition,the Hb as a model molecule is further immobilized on the FF-ErGO interface to construct electrochemical biosensor.Direct electrochemical behavior of Hb on the biointerface and its electrochemical catalytic characteristics to CH₃NO₂ were studied.Besides,we presented an easy and fast way to fabricate the glucose oxidase-diphenylalanine-reduced graphene oxide?GOx-FF-rGO?film by using pulsed potentiostatic method in a graphene oxide mixture solution.Electrochemical characterizations of the GOx-FF-rGO film modified GCE and its subsequent application in glucose determination are described.Our results indicate that the easy and fast electrochemical approach used for the preparation of graphene-based composite film may open up new horizons in the production of highly sensitive and stable electrochemical biosensors.4.Based on peptide?FFAAA?-graphene LB film to build electrochemical biosensorsPeptide?FFAAA?-rGO as material,we discuss the performance of FFAAA-rGO LB film.By atomic force microscopy?AFM?and electrochemical methods,LB film morphology and electrochemical properties were characterized.On the basis,a simple and convenient method is put forward to directly embedded cytochrome c?Cyt.c?into LB films of FFAAA-rGO composite.UV-vis spectrum proved that the Cyt.c in LB films of FFAAA-rGO composite can keep the original structure conformation.Electrochemical experiment shows LB films of FFAAA-rGO composite can effectively promote direct electron transfer between Cyt.c and the electrode surface.In addition,the modified electrodes with smaller apparent michaelis constant?app MK?,indicate that LB films of FFAAA-rGO composite can build good environment,thus to H₂O₂ with high catalytic activity and higher affinity.In addition,LB film of FFAAA-rGO composite interface as platform,antibody to gliadin?Anti-gliadin?was fixed using condensation reaction.Because LB films of FFAAA-rGO composite have the characteristics of specific surface area and good conductive performance,loads can significantly increase,so as to improve the sensitivity of the biosensor.Under the optimal conditions,the electrochemical biosensor for detecting gliadin linear range as follows: 5.0 80.0 ng mL-1,the detection limit of 1.0 ng mL-1.The method was used in the detection of gliadin in actual samples with the satisfactory result.