Carbon Nanotube Sensitized Enzyme Electrode Sensor And Its Application For Detection Of Diabetic Kidney Disease

Enzyme electrode sensor is fabricated by immobilizing the enzyme on the electrode surface by physical or chemical methods.The electrical signals are obtained by measuring electron transfer,which was generated by the redox reaction of enzymes and assays.Enzyme electrode sensor has received extensive attention from researchers in the field of medical detection.In addition,carbon nanotubes(CNTs)have been widely used in the field of sensors because of their excellent electrical and mechanical characteristics.With the improvement of living standards,people gradually pay attention to personal health.Diabetic kidney disease(DKD),as a complication of diabetes,seriously affects the life of patients.The high prevalence also places a huge burden on society and country.Early diagnosis of the disease and daily monitoring are very important for DKD patients.With medical testing,the information of DKD can be obtained,which was crucial for the treatment.In this paper,we aimed to design the enzyme electrode sensors with excellent performance.First,the composite sensitive materials were prepared.Then,the detection performance of the enzyme electrode sensors were investigated for the detection of DKD.The main research contents are as follows:(1)The CNTs/tetrathiafulvalene(TTF)sensitive materials and CNTs/gold nanoparticles(AuNPs)sensitive materials were prepared by combining TTF or AuNPs,respectively,with CNTs.Electrochemical analyses of the composite sensitive materials are completed,which could demonstrate excellent electrical conductivity and promotion of the reactions occurring on the enzyme electrode.The CNTs/TTF sensitive materials can also accelerate the electron transfer between the active center of enzyme and the electrode surface.Additionally,the CNTs/AuNPs sensitive materials not only have a small electrochemical impedance,but also can catalyze chemical reactions on enzyme electrodes.Therefore,the composite sensitive materials can be used as supports for enzymes immobilization.On the one hand,it can achieve highly efficient enzyme immobilization on the electrode.On the other hand,chemical reactions and electron transfer,occurring on the enzyme electrode,can also be promoted by the composite sensitive materials.(2)The CNTs/TTF/horseradish peroxidase(HRP)electrode was fabricated by immobilizing HRP on the electrode with the CNTs/TTF sensitive materials as supports for the detection of hydrogen peroxide(H2O2)and reduced nicotinamide adenine dinucleotide(NADH).The CNTs/TTF sensitive materials could facilitate the electron transfer between the enzyme and the electrode.The detection performance of the enzyme electrode sensor was analyzed by electrochemical workstation.The detection of H2O2 can be performed at a low working potential of-0.3 V with linear response ranging from 1×102 μM to 3.5×105 μM and a detection limit of 10 μM.Subsequently,since the NADH could be oxidized by methylene blue(MB)to release H2O2,the sensor enabled to detect the NADH in the MB buffer at low operating potential(-0.3 V).The linear response ranged from 10 μM to 790 μM,with a sensitivity of 4.76 μA/mM and a detection limit of 1.53 μM were obtained under the optimum conditions.The low working potential made the biosensor avoid the interference from other electroactive substances.And,the biosensor has good application potential for the detection of DKD.(3)The CNTs/AuNPs/glucose oxidase(GOx)electrode was constructed by immobilizing GOx on the electrode with the CNTs/AuNPs sensitive material as supports for the detection of urinary glucose.In order to design a self powered sensor,a hexagonal electrode arranged enzyme electrode sensor was fabricated based on the reaction principle of enzymatic biofuel cell(EBFC).The CNTs/AuNPs sensitive materials can improve the electrical conductivity of the enzyme electrode and catalyze the reaction of the bioanode.For the anode,the CNTs/AuNPs/GOx was used as catalyst,and the CNTs/manganese dioxide(MnO2)was used as cathode catalyst.After the addition of 5 mM glucose fuel,the prepared sensor was able to generate a maximum power density of 220 μW/cm2,and an open circuit voltage of 0.6 V.In addition,the self powered sensor device consistrd of an enzyme electrode sensor,a power management module,and an indicator of light emitting diode(LED).The power management module could collect the energy produced by the enzyme electrode,and control the lighting of the LED.The LED would blink with different frequencies depending on the concentration of glucose fuel.After adding glucose fuel,the blinking of LED could be clearly observed.There was also a good linear relationship between the blinking frequency of the LED and the glucose concentratio,in the range of 1 mM to 5 mM.The concentration of fuel can be calculated according to the blinking frequency.Finally,the device was integrated with the diaper and simulated experiments on urinary glucose detection were tested,which demonstrated its promising application in the field of urinary glucose detection,and could be used in the clinical detection of DKD.