Preparation Of Polyacrylonitrile-based Membranes And Enzyme Immobilization

Polymer membranes for enzyme immobilization have attracted much attention in recent years, especially in the fields of bioreactor and biosensor. The morphology and chemical structure of membranes play a significant role in the performance of enzyme-immobilized membranes. Considering these, in this thesis, novel strategies were explored to tailor the membrane structures for improving the properties of enzyme-immobilized membranes. Furthermore, the intercorrelation between enzymes and the supports were studied.First, immersion precipitation phase inversion and electrospining were used to fabricate polyacrylonitrile-based asymmetric and fibrous membranes, respectively. The morphologies of the membranes were characterized by field emission electron microscopy (FESEM). Pure water flux and BSA rejection experiment were applied to study the properties of the asymmetric membranes. It was found that the nonsolvent additive, water, could obviously improve the permeation performance of the asymmetric membranes, while retaining the BSA rejection. The mixtures of water with PEG or glycerol show cooperative effect on the permeation performance and morphology of the membranes. For the fibrous membrane, on the other hand, the concentration and composition of spinning solution also have a significant impact on the diameter and morphology of the fibers.Second, fibrous membranes were selected for enzyme immobilization. Influences of pre-modified through Multiwalled Carbon Nanotubes (MWCNTs) filling or protein-involved biomimetic tethering were explored. The membranes were characterized by FESEM, transmission electron microscopy, confocal laser scanning microscopy and UV-vis spectra. It was found that the both modifications increase the activities of the immobilized enzymes. In addition, MWCNTs filling improves the storage stabilities and biomimetic tethering enhances the operational stabilities. However, different proteins tethering have distinct effects on the thermal and storage stabilities of the enzymes. The enzyme-support interactions were studied by AFM, water contact angle measurement, circular dichroism, fluorescence and UV-vis spectra. The results indicate that the interactions largely decide the conformations and active sites of the enzymes, which affect their performance in turn. Subsequently, the enzyme-immobilized fibrous membranes were applied in glucose sensor and chronoamperometry was used to study the parameters of the biosensor. It was found that MWCNTs filling improves the current and sensitivity.To sum up, this thesis has established several effective methods to tailor the morphological and chemical properties of the membranes for enzyme immobilization. It has also explored a foundation for the application of fibrous membranes in biosensor. Furthermore, the study of the enzyme-support interactions will promote the design of supports for enzyme immobilization.