Nanofibrous membranes with an average diameter of 100 and 180nm were fabricated from poly(acrylonitrile-co-maleic acid) (PANCMA) by the electrospinning process. These nanofibrous membranes contain reactive groups which can be used to covalently immobilize biomacromolecules. Two natural macromolecules, chitosan and gelatin, were tethered on these nanofibrous membranes to fabricate dual-layer biomimetic supports for enzyme immobilization in the presence of 1-ethyl-3-(dimethyl-aminopropyl) carbodiimide hydrochloride (EDC)/N-hydroxyl succinimide (NHS). Lipase from Candida rugosa was then immobilized on these dual-layer biomimetic supports using glutaraldehyde (GA), and on the nascent PANCMA fibrous membrane using EDC/NHS as coupling agent, respectively. The properties of the immobilized lipases were assayed. It was found that there is an increase of the activity retention of the immobilized lipase on the chitosan-modified nanofibrous membrane (45.671.8%) and on the gelatin-modified one (49.771.8%), compared to that on the nascent one (37.671.8%). The kinetic parameters of the free and immobilized lipases, Km and Vmax, were also assayed. In comparison with the immobilized lipase on the nascent nanofibrous membrane, there is an increase of the Vmax value for the immobilized lipases on the chitosan- and gelatin-modified nanofibrous membranes. Results also indicate that the pH and thermal stabilities of lipases increase upon immobilization. The residual activities of the immobilized lipases are 55% on the chitosan-modified nanofibrous membrane and 60% on the gelatin-modified one, after 10 uses.

Increasingly, carbohydrate-protein interactions are viewed as important mechanisms for many biological processes such as blood coagulation, immune response, viral infection, inflammation, embryogenesis, and cellular signal transfer. However, the weak affinity of the interactions and the structural complexity of carbohydrates have hindered efforts to develop a comprehensive understanding of carbohydrate functions. Fortunately, synthetic polyvalent glycoligands give us a chance to reveal the nature of these biological processes. In this work a sugar-containing monomer (R-D-allyl glucoside (AG)) was grafted onto polypropylene microporous membrane (PPMM) by UV-induced graft polymerization to generate a glycosylated porous surface for the first time. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy were employed to confirm the glycosylation. Water contact angle measurement was used to evaluate the hydrophilicity change of the surfaces before and after the graft polymerization of AG. It was found that the grafting density increased reasonably with the increase of AG monomer concentration, and then this increase slowed when the AG concentration exceeded 80 g/L. At the same time a 20-25 min UV irradiation was enough for the grafting polymerization. The photoinitiator concentration also influenced the grafting density obviously, and there was an optimal concentration of the photoinitiator for the grafting process. The water contact angle of the polyAG-tethered membrane surface decreased from 149° to 80° with the increase of grafting density from 0 to 187.76 íg/cm2, which indicated a hydrophilic variation of the membrane surface by the grafting of AG. Results also indicated that the surface-grafted polyAG chains showed weak interaction with Con A when the grafting density was low. However, when the sugar density exceeded 90 íg/cm2, the binding affinity increased dramatically which was the due to the “glycoside cluster effect”.

Carbohydrate residues are found on the extracellular side of the cell membrane. They form a protective coating on the outer surface of the cell and are involved in intercellular recognition. Synthetic carbohydrate-based polymers, so-called glycopolymers, are emerging as important well-defined tools for investigating carbohydrate-based biological processes and for simulating various functions of carbohydrates. In this work, the surface of a polypropylene microporous membrane (PPMM) was modified with comb-like glycopolymer brushes by a combination of UV-induced graft polymerization and surface-initiated atom-transfer radical polymerization (ATRP). 2-Hydroxyethyl methacrylate(HEMA) was first grafted to thePPMMsurface underUVirradiation in the presence of benzophenone and ferric chloride. ATRP initiator was then coupled to the hydroxyl groups of poly(HEMA) brushes. Surface-initiated ATRP of a glycomonomer, D-gluconamidoethyl methacrylate, was followed at ambient temperature in aqueous solvent. Water had a significant acceleration effect on the ATRP process; however, loss of control over the polymerization process was also observed. The addition of CuBr2 to the ATRP system largely increased the controllability at the cost of the polymerization rate. The grafting of HEMA, the coupling of ATRP initiator to the hydroxyl groups, and the surface-initiated ATRP were confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy.