Properties And Applications Of Hydrogel-Magnetic Nanoparticles Immobilized Enzyme Complexes

Glucose and cholesterol are essential substances in the human body,they are also important parameters for diagnosis and treatment of human diseases,such as diabetes and cardiovascular disease.So it is of great significance to detect the blood glucose and cholesterol concentration in human body rapidly and sensitively.The fiber optic sensors have been studied extensively in biomedical field because they have many advantages such as strong ability to resist disturbance,high sensitivity,possibility of on-line detection and so on.Enzymes immobilized on the magnetic nanoparticles composite not only have the advantages of general immobilized enzyme,butalsohavetheadvantageoffastseparation.If poly(N-isopropylacrylamide-co-acrylamide)(P(NIPAAm-co-AAm))is used to form a complex with magnetic immobilized enzyme,the hydrogel will shrink at the temperature higher than its LCST and the enzyme is isolated from the substrate,which will cause the enzymatic catalysis reaction to stop.On the other hand,when the temperature is lower than its LCST,the hydrogel will swell,which allow the enzyme to come into contact with the substrate and cause enzymatic catalysis reaction to take place.Therefore,by controlling the temperature the enzyme performance can be controlled.In this thesis,this kind of complex materials were prepared and were used as the sensing materials for the fiber optic biosensor to perform temperature controllable detection of glucose.A fiber optic cholesterol sensor based on magnetic nanoparticles composite immobilized COD was studied.The above work can lay the foundation for the investigation of fiber optic multi parameters biosensor.The main research results of this thesis are shown as follows:(1)Poly(NIPAAm-co-AAm)was prepared.The effects of AAm addition on the properties of hydrogels were investigated.Magnetic nanocomposite particles with mesoporous structure were prepared and glucose oxidase was immobilized on these particles.Hydrogel-magnetic immobilized GOD complex(PMIGC)was prepared and the properties of these samples were studied and analyzed.The"on-off"effect of enzymatic catalysis of PMIGC was studied.(2)A temperature controllable optical fiber glucose biosensor based on PMIGC was constructed and the optimal detection conditions for this biosensor were achieved with pH6.5,35°C and 12 mg of GOD amount.At 25°C,a good linear relationship between?,the phase delay change of the sensor head,and the glucose concentration in the range of 50-700 mg/dL(2.78-38.89 mmol/L)was observed.This linear graph can be defined by the equation of y=0.01463+0.0003313x,R~2=0.9914.The detection limit was 8.33 mg/dL(0.46 mmol/L)(S/N=3).The biosensor has the characteristics of good repeatability and selectivity,and can be used for the glucose detection in practical samples.(3)COD was immobilized on magnetic nanoparticles.An optical fiber cholesterol biosensor was constructed based on this immobilized COD.The optimal detection conditions for this biosensor were achieved with pH7.0,40°C and 10 mg of COD amount.At 40°C,a good linear relationship between?,the phase delay change of the sensor head,and the cholesterol concentration in the range of 25-250 mg/dL(0.65-6.47 mmol/L)was observed.This linear graph can be defined by the equation of y=0.01962+0.0025x,R~2=0.987.The biosensor has the characteristics of good repeatability and selectivity,and can be used for the cholesterol detection in practical samples.