The Assembly Of Multilayer Films And The Construction Of Novel Sulf-compound Electrochemical Biosensors

The assembly multilayer film through LBL technology can effectively retain its stability.When the assembly multilayer film is applied into electrochemical biosensor, the multilayer electrode can selected different materials as the modified components based on the demands of electrochemical sensing and electrocatalysis,and can make use of the reaction of substrate and enzyme to achieve the efficient and sensitive determination,and can simply adjust the thickness to change the amount of the immobilized enzyme and control the catalysis ability of multilayer film.The construction of assembly multilayer film and its application in electrochemical biosensor have taken on the significance.This paper constructed a disperse system of carboxylated carbon nanotubes(CNTs) in barbiturate solutions and researched the characterization of soluble CNT material and the electrochemical property of the assembly multilayer film.The novel sulf-compound electrochemical biosensor based on multilayer film was constructed and achieved the fast and sensitive determination for sulfides and thiols.The paper explored the analytical application of the sulf-compound electrochemical biosensor in environmental and biological samples.The fast detection method for sulf-compounds in practical system was constructed.Based on the biospecific affinity of concanavalin A(Con A) and glycoprotein horseradish peroxidase(HRP),(Con A/HRP)_n was prepared and developed to a thiol electrochemical biosensor.The atomic force microscopy(AFM) and electrochemical impendence spectra(EIS) both indicated the homogeneous and uniform properties of the Con A/HRP multilayer film.Under the optimal conditions,a series of reduced thiols were detected by this inhibition biosensor and oxidized thiols showed no effect on the current response of the biosensor.The multilayer biosensor exhibited good selectivity.The homogeneous and stable dispersion of CNTs in barbiturate solutions was obtained.Based on the soluble CNT material,the sulfide electrochemical biosensor was constructed.Scanning electron microscopy(SEM) and Raman spectra indicated that the degrees of purification and order of carboxylated CNTs increased.The dispersion of CNTs can be remain stably for one year.UV-vis spectra revealed the barbital had no effect on the intrinsic property of CNTs.of MWNTs in 0.4 mol L^-1 barbital buffers was researched.The soluble multiwall carbon nanotubes(MWNTs) was used to constructed MWNTs/HRP multilayer film.AFM and SEM monitored the uniform assembly process of MWNTs/HRP multilayer film and UV-vis indicated the linear relationship of the HRP activity and the number of bilayer.The electrochemical property of the MWNTs/HRP multilayer biosensor was researched and the results revealed MWNTs on the electrode improved the electron transfer.The MWNTs/HRP multilayer biosensor can be successfully applied to detect sulfide,which presented a linear response from 0.4 to 16.6μmol L^-1 with a detection limit of 0.08μmol L^-1.The electrochemical biosensor exhibited high sensitivity,good reproducibility and stability.The polycation poly(allylamine hydrochloride)(PAH) was introduced into the soluble MWNTs to obtain the water-soluble PAH-MWNTs material,and the novel thiol electrochemical biosensor was constructed.Transmission electron microscope(TEM) and UV-vis spectra revealed MWNTs were wrapped with PAH and retained pristine feature.The PAH-MWNTs/HRP multilayer film was fabricated on the Au electrode.The cyclic voltammogram(CV) indicated the cooperation of the polyelectrolyte and nano-material led to increasing the amount of immobilized enzyme and improving the electron transfer.The reduced thiols were detected by the PAH-MWNTs/HRP multilayer biosensor and the oxidized thiols showed no effect on the detection.The electrochemical biosensor exhibited good reproducibility and stability.The multilayer electrochemical biosensors for sulf-compounds were developed to practical application.The common cations and anions from environmental matrix components showed no interference on Con A/HRP multilayer biosensor for determination of sulfide,which revealed the high selectivity of the biosensor.Different types of waste water sample were analyzed by Con A/HRP multilayer biosensor.The results were consistent with that of standard spectrophotometric method.The potential interfering agents in biological fluids did not effect the detection of PAH-MWNTs/HRP multilayer electrochemical biosensor for cysteine(CSH).The biosensor was used to analysis the CSH content of blood serum sample.The recoveries of CSH in different serums were obtained and ranged from 98.4 to 106%.The above results revealed the developed multilayer electrochemical biosensor possesses the application potential and could be applied into the practical analysis.