Growth Mechanism Of Hierarchical Protein Hybrid Nanoflowers Based On Nanofiber Membrane

Protein is the basic organic matter to constitute cell and the main undertake of the life activities. The biochemical property and activity of the protein will be transferred to the substrate surface once the protein being immobilized onto the substrate. It can expand the application in the field of biosenor, bioreactor, biochip, biomacromolecular separation and so on.As the large specific surface area, the superior biocompatibility and the high adsorption of the nanofiber, the PVA-co-PE nanofiber membrane was used to immobilized the protein. The membrane was first activated with cyanuric chloride by solid-phase synthesis technology, subsequently the iminodiacetic acid was grafted on the membrane and then the Cu2+ was absorbed by the IDA-Cu2+ chelation. Finally, the protein was immobilized as nanoflower-like structure by the interaction of Cu2+ and protein and PO43-.The structure and performance of the nanofiber membrane in different reaction periods were analyzed by the SEM, FTIR-ATR and water contact angle measurements. The effect of interface on the immobilization of the protein-inorganic hybrid nanoflowers was analyzed by contrasting to the PVA-co-PE common membrane and the cellulose filter. On this basis, the protein-inorganic hybrid nanoflowers were prepared by the same principle and the structure of immobilized nanoflowers and free nanoflowers were investigated by SEM, TEM and XRD. The result showed that the structure of the immobilized nanoflowers were same to the free nanoflowers. Due to possessing of high specific surface areas, the compact and integrated protein-inorganic hybrid nanoflowers were constructed on the surface of nanofiber membrane.In order to study the formation mechanism of nanoflowers, the influence of the protein concentration, reaction time, p H and ionic strength on nanoflowers morphological was analyzed. The result showed that the Cu2+ and PO43- were indispensable to the formation of protein hybrid nanoflowers. The morphology size, compactness and number of nanoflowers would be changed by the protein concentration, reaction time, p H and ionic strength. As the growth of the multidimensional nanoflowers conformed to the Ostwald ripening mechanism and the growth mechanism of the orientation, the crystal plate germinated around and the crystal nucleus formed on nanofiber as a centre.In addition, the HRP-Cu₃（PO₄）₂·3H₂O hybrid nanoflowers immobilized PVA-co-PE nanofiber membrane was prepared to analyzed its the activity, durability and stability by measuring the absorption peak caused by oxidation reaction of guaiacol by H₂O2. The result showed that the 0.5 g/L HRP immobilized nanofiber membrane had the best activity during the concentration of 0.1 g/L, 0.5 g/L, 1 g/L. After 90 days, the relative activity of HRP-Cu₃（PO₄）₂·3H₂O hybrid nanoflowers is 80%, which was much higher than the free HRP of 5%. The HRP-Cu₃（PO₄）₂·3H₂O hybrid nanoflowers could maintain higher relative activity from p H 5 to p H 7. However, the free HRP could only be used at p H 7.