| OBJECTIVE: Dopamine(DA),epinephrine(E)and norepinephrine(NE)were used to study the activation of carbon fiber microelectrodes(CFME)contaminated with serotonin(5-HT),NADH,and histamine.On the basis of anti-pollution research,quantitative detection of serotonin was achieved by current correction method;The CFME treated by potentiostatic electrochemical method or modified with nano-material was developed to improve the sensitivity of catecholamine neurotransmitters,and the above method was applied to the highly sensitive detection of biological samples.METHODS:(1)Deteriorated carbon fiber microelectrodes were regenerated by graphene oxide using electrodeposition method,and the electrochemical behavior of dopamine(DA)solution on the regenerated electrode was investigated by cyclic voltammetry(CV)and differential pulse voltammetry(DPV).The electrodepositing time and voltage of graphene oxide were also optimized.(2)The prepared CFME was placed in 1.0×10-4mol/L 5-hydroxytryptamine(5-HT)solution by cyclic voltammetry for ten cycles,then the electrochemical behaviors of the electrode in ferricyanide and dopamine(DA)were investigated.The experimental results showed that the surface of carbon fiber ultramicroelectrode has been passivated by the oxidation products of hydroxytryptamine.The deteriorated ultramicroelectrodes was burned in the faint flame to activate the surface,and the peak current ratio of the activated electrode and the bare electrode at 1.0×10-3mol/L ferricyanide solution as the current correction factor,the active area of the electrode was corrected by dividing the correction factor.(3)The carbon fiber electrode which has been poisoned by serotonin(5-HT)was regenerated and activated in pure water by current-time curve method.The surface structure and morphology of the electrode were characterized by scanning electron microscopy(SEM)and X-ray energy dispersive spectroscopy(EDS).The mechanism of activation carbon fiber electrode by this method is discussed.(4)The carbon fiber microelectrode(CFME)was modified with oxygen-containing groups(RO)in pure water by potentiostaticelectrodeposition in ultrapure water.,Then the RO/PDDA-AuNPs/CFME modified electrode was prepared by electrodeposition the gold nanoparticles(AuNPs),prepared by using polydiene dimethylammonium chloride(PDDA)as protective agent onto the surface of the electrode by potentiostat method.The surface morphology of CFME before and after modification was characterized by scanning electron microscope(SEM).The electrochemical behavior of modified electrode in DA solution was investigated by cyclic voltammetry and differential pulse voltammetry.(5)The carbon fiber microelectrode modified with nano-gold had good electrocatalytic activity to aloe polysaccharide,and the modified electrode was inserted into the aloe gel liquor in vivo.The dynamic monitoring of aloe polysaccharides in aloe plants under different growth conditions was carried out to evaluate the changes of the content of aloe polysaccharides to the stress environment of the plants.RESULTS:(1)The experimental results showed that the regenerated electrode modified with graphene oxide had a good electrochemical response to dopamine and norepinephrine in 20mmol/L Tris-HCl buffer solution.Under the optimized conditions,the oxidation peak current of DA was linear with its concentration in range of 0.1~100 ?mol/L by DPV,and the detection limit was 0.1 ? mol/L.(2)The experimental results show that there is a good linear relationship between the corrected peak current of serotonin oxidation and its concentration in the range of 1.0×10-6~ 2.0×10-4mol/L.The linear regression equation was I(nA)=0.2073 C(?mol/L)+0.3074,and the correlation coefficient was R2= 0.9962.The method was used to determine the concentration of serotonin.The recovery was 98.0% ~ 102.4%.The method is simple and reproducible.It is expected to be used for the determination of serotonin in biological samples.(3)The experimental results show that the insulating film on CFME surface can be removed by potentiostatic electrodeposition.The initial voltage of 1.5V was applied to CFME in pure water by current-time curve method,and the redox peak current of CFME treated by electroactivation increased significantly in neurotransmitters.The results show that the electrode activation is attributed to electrochemical oxidation etching to remove the insulating layer on the electrode surface.In addition,oxygen functionalgroups(such as hydroxyl,carboxyl,carbonyl,lactone)are formed on the electrode surface during electrochemical treatment.The surface wettability and hydrophilicity of carbon fiber electrode was improved,and dopamine accumulation on the electrode surface was promoted.The oxidation peak current of DA was linear with the concentration of 1.0×10-7-1.0×10-4mol/L,and the detection limit was 3.1×10-8mol/L.Regenerated CFME is very stable with excellent sensitivity and selectivity and can be used to monitor neurotransmitters in complex biological microenvironments.(4)The experimental results show that the composite modified membrane RO/AuNPs-PDDA has remarkable electrocatalytic activity towards the oxidation of DA in 20 mmol/L pH7.0 Tris-HCl buffer solution.Under the optimized conditions,the dopamine was analyzed quantitatively by differential pulse voltammetry.The experimental results show that the oxidation peak current of DA has a good linear relationship with its concentration in the range of 1×10-7~1×10-4mol/L.The linear correlation coefficient R2 was 0.9912 and the detection limit was 3.3×10-8mol/L(S/N=3).In brief,the RO/AuNPs-PDDA/CFME has the advantage of simple preparation,good reproducibility and high stability.It can be widely used in the highly sensitive analysis of DA in biological samples.(5)The electrocatalytic activity of Aloe polysaccharide in Aloe hydrogel tissue was enhanced by CFME and gold electrode modified with gold nanoparticles.The dynamic changes of aloe polysaccharides in aloe plants under different growing environments have significant statistical differences and can be used to measure the photosynthesis intensity of aloe. |
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