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”.

Nanofibrous membranes that possess reactive groups are fabricated by the electrospinning process from PANCAA solutions that contain MWCNTs. Field emission scanning electron microscopy is used to evaluate the morphology and diameter of the nanofibers. Potentials for applying these nanofibrous membranes to immobilize redox enzymes by covalent bonding are explored. It is envisaged that the electrospun nanofibrous membranes could provide a large specific area and the MWCNTs could donate/accept electrons for the immobilized redox enzymes. Results indicate that, after blending with MWCNTs, the diameter of the PANCAA nanofiber increases slightly. The PANCAA/ MWCNT nanofibrous membranes immobilize more enzymes than that without MWCNTs. Moreover, as the concentration of the MWCNTs increases, the activity of the immobilized catalase is enhanced by about 42%, which is mainly attributed to the promoted electron transfer through charge-transfer complexes and the p system of MWCNTs.

Novel nanofibrous membranes containing reactive carboxyl groups were fabricated from poly- (acrylonitrile-co-maleic acid) (PANCMA) by the electrospinning process. The morphology and fiber diameter were analyzed with field emission scanning electron microscopy. It was found that the fiber diameter could be varied from 100 to 600 nm by changing the solution concentration. Lipase from Candida rugosa was covalently immobilized onto the membrane surface via the activation of carboxyl groups in the presence of 1-ethyl-3- ((dimethylamino)propyl)carbodiimide hydrochloride/N-hydroxylsuccinimide. The properties of the immobilized lipases on the nanofibrous and hollow fiber PANCMA membranes were measured. It was found that, compared with the hollow fiber membrane, the enzyme loading and the activity retention of the immobilized lipase on the nanofibrous membrane increase from 2.36 ( 0.06 to 21.2 ( 0.7 mg/g and from 33.9 to 37.6%, respectively. The kinetic constants of the free and immobilized lipases, Km and Vmax, were assayed. Results indicate that the Vmax values are similar for both immobilized enzymes, while the Km value of the immobilized enzyme decreases from 1.36 on the hollow fiber membrane to 0.98 on the nanofibrous membrane. The studied lipase-immobilized nanofibers can be used as biocatalysts for polyester synthesis and/or in situ formation of nanofiber reinforcement composites.