Polyetherimide: a new membrane-forming polymer for biomedical applications

High functional hollow fiber membrane modified with phospholipid polymers for a liver assist bioreactor

For practical application of a liver assist system with a tissue-conjugated hollow fiber membrane (HFM) bioreactor used in an extracorporeal therapy, it would require a highly sophisticated HFM which has both hemocompatibility on one side and cytocompatibility on the other side. In this study, we present a cellulose acetate (CA) HFM modified with 2-methacryloyloxyethyl phosphorylcholine (MPC) copolymers (PMB30 (MPC-co-n-butyl methacrylate) and PMA30 (MPC-co-methacrylic acid) for preparing a novel liver assist HFM bioreactor. A CA/PMB-PMA30 HFM modified asymmetrically on the inner and outer surface with the PMB30 and PMA30 was prepared successfully. Analysis with an X-ray photoelectron spectroscope showed that the intensity of the phosphorus atom attributed to the MPC units on the outer surface of the modified HFM was stronger than that of the inner surface. The PMA30 was immobilized on the outer surface of the CA/PMB30 blend HFM by a chemical condensation reaction. The CA/PMB-PMA30 HFM showed good water and solute permeability in comparison with the CA HFM. The morphologies of the adherent hepatocytes were round in shape in comparison with the cells that adhered on CA HFM. Furthermore, hepatocytes cultured on the inner surface of the CA/PMB-PMA30 HFM showed higher functional expression in terms of urea synthesis and albumin synthesis than that of the CA HFM.

Design of functional hollow fiber membranes modified with phospholipid polymers for application in total hemopurification system

In this study, we prepared cellulose acetate (CA) hollow fiber membranes (HFMs) modified with poly (2-methacryloyloxyethyl phosphorylcholine (MPC)-co-n-butyl methacrylate)(PMB30 and PMB80) by the dry-jet wet spinning process. The physical and chemical structures of the HFMs were controlled in order to design highly functional HFMs that had suitable performance to each targeting HFM device used in a total hemopurification system. The CA HFMs modified with the MPC polymer, such as CA/PMB30, CA/PMB80, and CA/PMB30-80 HFMs, were successfully prepared by controlling the spinning conditions. The modified HFMs showed an improved performance in solute and water permeability, due to the modification by the hydrophilic MPC polymers. The CA/PMB30 and CA/PMB80 showed a high potential in an application for a high performance hemocompatible plasmapheresis and hemofilter device. Furthermore, CA/PMB30-80 HFM, modified asymmetrically with PMB30 and PMB80, showed a potential for application in an advanced total hemopurification system as a highly functional scaffold for a biohybrid renal tubule, or a liver assist bioreactor device, because of their enhanced permeability, hemocompatibility, and cytocompatibility.

Membranes for biohybrid liver support systems--investigations on hepatocyte attachment, morphology and growth

The biological properties of four different membranes were studied regarding their possible application in biohybrid liver support systems. Two of them, one made of polyetherimide (PEI), and a second based on polyacrylonitrile-N-vinylpyrollidone co-polymer (P(AN-NVP)), were recently developed in our lab and studied for the first time. Together with pure polyacrylonitrile (PAN) membranes, the three preparations were characterised as ultra-filtration membranes. Their ability to support cell attachment, morphology, proliferation and function of human hepatoblastoma C3A cells was studied. The role of surface morphology for the interaction with hepatocytes was highlighted using a commercial, moderately wettable polyvinylidendifluoride (PVDF) membrane with micro-filtration properties. Comparative investigations showed strongest interaction of C3A cells with PAN membranes, as the focal adhesion contacts were more expressed and cell growth was also high. However, the functional activity in terms of albumin synthesis was reduced. Very similar results were obtained with the most hydrophobic PEI membrane. In contrast, the most hydrophilic membrane P(AN-NVP) was found to provoke stronger homotypic adhesion (E-cadherin expression) of C3A cells and less substratum attachment (focal adhesions), but enhanced albumin secretion. However, proliferation of C3A cells was lowered. Micro-porous PVDF membrane showed very good initial attachment, but the resulting cell material and cell-cell interaction were relatively poor developed. Among four membranes tested, PEI seems to be the most attractive membrane for biohybrid liver devices, as it provides good surface properties for hepatocytes interaction, but in addition it is highly thermostable, which would permit steam sterilisation. No simple relationship, however, between the wettability of the membranes and their ability to support hepatocyte adhesion and function was found in this study.