Study On Dispersing And Modifying Of Nano-diamond Applied To Immobilization Of Glucose Oxidase

In recent years,the application of nano-diamond has been extended to biomedicine because of its biocompatibility,low toxicity,fluorescence effect and chemical inertness.Also the mature making technology and mass production of nano-diamond provide a condition of its widespread use.Glucose oxidase can composite a system with catalase to release gluconic acid.Free enzyme can't be recovered and has a large limitation of reaction condition.By immobilizing GOD with nano-diamond,it can improve the stability of reaction process and retrievability.The representation and selection of Nano-diamond,surface modification,surface activation,the immobilization of Nano-diamond,the perpormance of immobilized enzyme and the biocompatibility of Nano-diamond have been researched respectively.The experiment results show that:1.Samples synthesized by detonating and crushing are tested by ICP,XRD,TEM and laser particle size detection.Then we choose nano-crystalline diamond prepared by crushing method to be the experimental material by the requirement of immobilization technology,whose metal content is below 0.006% and have none impurity of graphite.The median size and minimum size of samples are 5.25?m and 0.7?m,composed by fine nano-diamond of(5-20)nm.2.The applications of the ultrasound,the high temperature process in air condition and in N2 condition are carried out for dispersing nano-diamond.The experiment results show that,ultrasound treatment can improve the dispersity to some extent,but it has a long period and poor efficiency.By the means of heat process in air condition at 425?,5h,it shows that the median size of samples are 1.538?m and has a well-dispersed performance,because of the removal of electrostatic attraction and absorbed water among particles.As for heat treatment in N2 condition,it brings an improvement of dispersion without impurity by the high temperature.But the particle size in water shows a wider distribution and an easier aggregation.3.Through liquid phase reactions of mixed acid of H2SO4/HNO3,we modify thecarboxyl groups on the particles' surface.By the treatment of Fenton reagent,the hydroxy groups appeared on the surface.Both of the treatment bring carboxide groups.4.The immobilization efficiency of nano-diamond functionalized with carboxyl groups and hydroxy groups are 21.3% and 20.9%.It indicates that both of the modified nano-diamond can immobilize the glucose oxidase.The test of HPLC shows that the enzyme activity of them are 105.81 and 108.37.The enzyme activity after washing by phosphate buffer five times are 58.94% and 60.37% respectively.