4-(4-Fluorophenyl)-1-methoxymethyl-2-phenyl-1H-imidazole

In the crystal structure of the title compound, C₁₇H₁₅FN₂O, the mol­ecules form a three-dimensional network stabilized by π–π inter­actions between two imidazole rings related by a centre of symmetry. The distance between the centroids is 3.5488 (8) Å. The imidazole ring makes dihedral angles of 14.30 (7) and 33.39 (7)° with the 4-fluoro­phenyl ring and the phenyl ring, respectively.

Influence of p38MAPK inhibition on IL-1beta-stimulated human chondrocytes: a microarray approach

Articular chondrocytes respond to extracellular influences by activating signaling pathways which change gene expression. One key signal transduction pathway of inflammatory joint disease is mediated by the p38MAPK which is known to be activated by the pro-inflammatory cytokine IL-1beta. We used the p38MAPK inhibitor SB203580 and a whole human genome microarray in an in vitro inflammation model to identify genes regulated by this pathway in human chondrocytes. We found that 1,141 genes were regulated by IL-1beta, and 646 genes were regulated by the inhibitor whereas 116 genes were co-regulated by both substances. To elucidate the overall effect of SB203580, a GoMiner pathway analysis was performed which revealed involvement of versatile biological processes. Predominantly affected terms were 'response to stimulus', 'oxygen metabolism' and 'ligase activity'. We discuss herein the relevance and function of affected fields including the involved genes and unexpected effects of p38MAPK inhibition as it relates to the context of cartilage. Our results do not predict a pro-apoptotic or cancer promoting effect and markedly extend the knowledge on p38MAPK inhibition in chondrocytes beyond primary target genes.

Hemocompatibility of poly(ether imide) membranes functionalized with carboxylic groups

Materials for blood-contacting applications have to meet high requirements in terms to prevent thrombotic complications after the medical treatment. Surface induced thrombosis, e.g., after application of cardiovascular devices, is linked clearly to the activation of coagulation system and platelet adhesion and activation. The flat sheet poly(ether imide) membrane (PEI) was modified by binding of iminodiacetic acid (IDA) for different periods of time to obtain surfaces with carboxylic (-COOH) groups, namely PEI-1 (modified for 1 min) and PEI-2 (modified for 30 min). The successful binding of the ligands was monitored by thionin acetate assay. The physico-chemical characteristics of the materials were analyzed by SEM, AFM, water contact angle, and Zeta potential measurements. Hemocompatibility of the polymer materials was studied by analyzing the activation of coagulation system (plasma kallikrein-like activity) and platelet adhesion/activation by using immunofluorescence technique. The blood response to PEI membranes was compared to that of a commercial poly(ethylene terephthalate) (PET) membrane. Our results showed that the increase of the negative charges on the modified PEI membrane surfaces (number of -COOH groups) caused a higher contact activation of the coagulation system and a higher rate of platelet adhesion and activation compared to non-modified PEI. However, overall the hemocompatibility of all PEI membranes was higher than that of PET.

In vitrometabolite identification of ML3403, a 4-pyridinylimidazole-type p38 MAP kinase inhibitor by LC-Qq-TOF-MS and LC-SPE-cryo-NMR/MS

Prediction of the metabolic profile of a potential new drug is recommended at an early stage in industrial drug discovery process to determine whether or not any potentially reactive or toxic metabolites are formed. In the present study, we investigated the in vitro metabolism of ML3403 ({4- [5-(4-Fluorophenyl)-2-methylsulfanyl-3H-imidazol-4-yl]-pyridin-2-yl -(1-phenylethyl)-amine), a potent and selective p38 MAP kinase inhibitor using mouse liver microsomes. The combination of LC-ESI-Qq-TOF (tandem quadrupole time-of-flight)-MS (mass spectrometer) and LC-SPE (solid phase extraction)-cryo-NMR (nuclear magnetic resonance)/MS at 600 MHz has been applied for comprehensive and straightforward structural elucidation of ML3403 metabolites. It was possible to determine the metabolic profile of ML3403, revealing eight different metabolites formed by N-desalkylation, S-mono- and di-oxidation, aliphatic hydroxylation and pyridine-N-oxidation. The ESI-Qq-TOF-MS data yielded elemental compositions of all metabolites and their fragments by evaluation of the accurate mass and isotopic pattern information using the sigma-fit algorithm. Evaluation of 2D NMR spectra obtained from pure ML3403 an its major metabolite ML3603 allowed the unequivocal assignment of the resonances in 1D NMR spectra obtained directly from the microsomal incubation by LC-SPE-cryo-NMR/MS. The presented method significantly decreases the time required for a complete structural assignment of metabolites from microsomal in vitro assays.

IL-1beta regulates FHL2 and other cytoskeleton-related genes in human chondrocytes

In osteoarthritis (OA), cartilage destruction is associated not only with an imbalance of anabolic and catabolic processes but also with alterations of the cytoskeletal organization in chondrocytes, although their pathogenetic origin is largely unknown so far. Therefore, we have studied possible effects of the proinflammatory cytokine IL-1beta on components of the cytoskeleton in OA chondrocytes on gene expression level. Using a whole genome array, we found that IL-1beta is involved in the regulation of many cytoskeleton-related genes. Apart from well-known cytoskeletal components, the expression and regulation of four genes coding for LIM proteins were shown. These four genes were previously undescribed in the chondrocyte context. Quantitative PCR analysis confirmed significant downregulation of Fhl1, Fhl2, Lasp1, and Pdlim1 as well as Tubb and Vim by IL-1beta. Inhibition of p38 mitogen-activated protein kinase (MAPK) by SB203580 counteracted the influence of IL-1beta on Fhl2 and Tubb expression, indicating partial involvement of this signaling pathway. Downregulation of the LIM-only protein FHL2 was confirmed additionally on the protein level. In agreement with these results, IL-1beta induced changes in the morphology of chondrocytes, the organization of the cytoskeleton, and the cellular distribution of FHL2. We conclude that L-1beta is involved in the regulation of various cytoskeletal components in human chondrocytes including the multifunctional protein FHL2. This might be relevant for the pathogenesis of OA.

Pharmacokinetics of ML3403 ({4-[5-(4-Fluorophenyl)-2-methylsulfanyl-3H-imidazol-4-yl]-pyridin-2-yl}-(1-phenylethyl)-amine), a 4-Pyridinylimidazole-Type p38 Mitogen-Activated Protein Kinase Inhibitor

The p38 mitogen-activated protein kinase (MAPK) is a key mediator in cytokine-induced signaling events that are activated in response to a variety of extracellular stimuli such as stress factors, apoptosis, and proliferation. Therefore, the MAPK family plays an integral role in disease states including oncogenesis, autoimmune diseases, and inflammatory processes. Inhibition of these protein kinases represents an attractive strategy for therapeutic intervention. In particular, one class of p38 MAP kinase inhibitors, the pyridinyl imidazole derivatives, is intensely investigated by several industrial groups, but so far no studies concerning the metabolism of these structurally related substances seem to be available. The objective of our examinations was the preclinical characterization of ML3403, {4-[5-(4-fluorophenyl)-2-methylsulfanyl-3H-imidazol-4-yl]-pyridin-2-yl}-(1-phenylethyl)-amine, a potent inhibitor of p38 MAP kinase, comprising the basic pyridinyl imidazole structure. In human hepatic microsomal incubations, the sulfoxidation to ML3603 ({4-[5-(4-fluorophenyl)-2-methylsulfinyl-3H-imidazol-4-yl]-pyridin-2-yl}-(1-phenylethyl)-amine) and M-sulfone ({4-[5-(4-fluorophenyl)-2-methylsulfonyl-3H-imidazol-4-yl]-pyridin-2-yl}-(1-phenylethyl)-amine) was found to be the predominant metabolic transformation. In addition, oxidative removal of the phenylethyl moiety, pyridine N-oxidation, and hydroxylation reactions were observed. Incubations were carried out with hepatic microsomes from various species and with recombinant human cytochrome P450 isoenzymes, showing that CYP1A2, CYP2C19, CYP2D6, and CYP3A4 are the prominent enzymes in the metabolism of ML3403. Michaelis-Menten kinetics of ML3603 formation by these recombinant isoenzymes showed that CYP3A4 plays a pivotal role in the sulfoxidation reaction. In addition, pharmacokinetics of ML3403 were evaluated in male and female Wistar rats after oral gavage, showing a fast and high conversion to its active sulfoxide metabolite ML3603. A remarkable gender-specific difference in the systemic exposure to ML3403 and ML3603 was found in rats. No gender-specific difference was detected in incubations with human liver microsomes.

Identification and confirmation of increased fibrinopeptide a serum protein levels in gastric cancer sera by magnet bead assisted MALDI-TOF mass spectrometry

Gastric cancer is the second most common malignancy and prognosis remains dismal. The reasons for the poor prognosis are the lack of sensitive serum markers for early detection and screening of high-risk individuals as well as the limited treatment options in advanced cancer stages. Using MALDI-TOF mass spectrometry after prefractionation of sera with magnet hydrophobic C8 coated beads sera from 14 patients with gastric cancer and 14 healthy controls mass spectra were generated. A peptide fragment was found to be highly elevated in cancer sera and was identified as fibrinopeptide A. To confirm proteome analysis of gastric cancer sera, we then screened a larger series of patients with gastric cancer (n = 99), high-risk individuals (n = 13) and normal controls (n = 111) for fibrinopeptide A serum levels. Interestingly, the mean logarithmic concentrations of serum fibrinopeptide A levels were significantly higher in cancer patients (mean 3.636 +/- 0.3738; p < 0.0001) and high-risk individuals (mean 3.569 +/- 0.4722; p < 0.05) compared to normal controls (mean 3.303 +/- 0.4012). In contrast, we observed no association of fibrinopeptide A levels with tumor stage, tumor location, presence of regional or distant metastasis, and Lauren type of gastric cancer. In conclusion, MALDI-TOF mass spectrometry of prefractionated gastric cancer sera allows the identification of potential biomarkers that may lead to the development of serum based tests for screening of high-risk individuals.

Poly(ether imide) Membranes Modified with Poly(ethylene imine) as Potential Carriers for Epidermal Substitutes

Poly(ether imide) (PEI) membranes were modified with a linear low-molecular weight (PETIM_0.6) and a branched high-molecular weight poly(ethylene imine) (PETIM_60). The membrane surfaces became more hydrophilic and the zeta potentials were shifted from negative to positive zeta values after immobilisation of both PETIM. These measurements also indicated the presence of a swollen surface layer in the case of PETIM_60, while a regular structuring of the surface was observed with scanning force microscopy for PETIM_0.6. A human keratinocyte cell line HaCaT was cultured on the different membranes. It was found that HaCaT cell growth was stimulated by PETIM_0.6. Cells reached earlier confluence on this substratum, while their growth was inhibited on a PEI membrane modified with PETIM_60, which makes PEI membranes modified with PETIM_0.6 a promising material for in vitro culture of epidermal transplants.

The viability and function of primary rat hepatocytes cultured on polymeric membranes developed for hybrid artificial liver devices

Bioartificial liver devices require membranes to support the function and viability of hepatocytes because they are anchorage-dependent cells. This study investigated the ability of several polymeric membranes to support the functions of primary hepatocyte cultures. Tailor-made membranes were sought by synthesizing acrylonitrile copolymers with different comonomers resulting in ionic, hydrophilic, or reactive functional groups on the polymer surface. Hepatocyte morphology and viability were assessed by confocal microscopy, and function by the content and activities of cytochrome P450, and the expression of glutathione S-transferases. Hydrophilic membranes (polyacrylonitrile and acrylonitrile copolymerized with 2-acrylamino-2-methyl-propane sulfonic acid) were more biocompatible than hydrophobic membranes such as polysulfone. The chemistry of the hydrophilic group was important; amine groups had a deleterious effect on maintenance of the primary hepatocytes. The biocompatibility of hydrophobic membranes was improved by collagen coating. Improving the chemistry of membranes for artificial liver devices will enhance the phenotypic stability of the cells, enabling us to prolong treatment times for patients.

Synthesis and biological testing of purine derivatives as potential ATP-competitive kinase inhibitors

On the basis of ATP adenine, a series of adenine and purine derivatives was prepared and tested for their ability to inhibit a spectrum of disease-related kinases. There has been scant research investigating the potential of cosubstrate derived kinase inhibitors for other kinases than CDKs. Our inhibitor design combined the purine system from the original cosubstrate ATP and phenyl moieties in order to explore possible interactions with the different regions of the ATP binding site in several disease-related protein kinases. There have been a number of hits for the assayed substances, which led us to conclude that the spectrum of compounds may prove to be a valuable tool kit for the evaluation of bonding and selectivity patterns for a wide variety of kinases.

The influence of the chemical composition of cell culture material on the growth and antibody production of hybridoma cells

The multiplication and antibody production of murine hybridoma cells cultured on five different polymer membranes were tested and compared with conventional tissue culture polystyrene (TCPS). Membranes were prepared from polyacrylonitrile (PAN) and acrylonitrile copolymerized with N-vinylpyrrolidone (NVP20, NVP30), Na-methallylsulfonate (NaMAS) and N-(3-amino-propyl-methacrylamide-hydrochloride) (APMA). Cell number and antibody concentration were quantified as criteria for viability and productivity. Adhesion of hybridoma cells was characterized by vital and scanning electron microscopy. The results suggest that a strong adhesion of cells, observed on APMA and TCPS, increased cell growth but reduced monoclonal antibody production. In contrast membranes with lowered adhesivity such as NVP20 provided favourable conditions for monoclonal antibody production. In addition it was shown that this membrane also possessed a minor fouling as indicated by the low decrease of water flux across the membrane after protein adsorption. It was concluded that NVP20 could be a suitable material for the development of hollow fibre membranes for bioreactors.

Development of polymer membranes with improved haemocompatibility for biohybrid organ technology

Biomedical technology has opened up possibilities of treating the failure of internal organs like kidney and liver by artificial organ therapy. Most of these techniques are based on polymer membranes, which allow the removal of excess of water, salts and toxins from the circulation. However, haemodialysis for the replacement of kidney function results in an increased morbidity and mortality of patients after long-term application. Conventional therapy, such as haemofiltration for the treatment of acute liver failure does not improve significantly the survival rate of patients. Biohybrid organ support as a combination of the artificial organ therapy with the functional activity of immobilised cells seems to be a solution of the problem. Membranes applied in these devices have to face both tissue cells and blood. Organ cells in biohybrid organs have to make intimate contact with the surface of membrane but must also develop close cell-cell-connections as a prerequisite for their survival and high functional activity. Blood to be detoxified will contact the other side of membrane and may not become activated by the synthetic material. New polymer membranes based on acrylonitrile were developed to address these requirements by tailoring the composition of copolymers and to be applied in a specific hollow fibre bioreactor with an outer fibre for blood contact, and an inner fibre for tissue contact or vice versa.

Change over Time in the Thermal Conductivity of Ten-Year-Old PUR Rigid Foam Boards with Diffusion-Open Facings

To estimate the long-term change in thermal conductivity of PUR rigid foam, various accelerated ageing processes (e.g. 70 °C ageing procedure) are used. Results of ageing processes are safety increments to cover a lifetime in practice of between 25 and 50 years.

To compare estimated increments with the change over time in thermal conductivity of real boards, a research project was started. The research project was sponsored by the German Polyurethane Producers’ Association (IVPU) and funds of the German Minister of Economics over the AIF (Association of Industrial Research Institutes).

The tables and diagrams show the thermal conductivity of PUR boards in full thickness and the cell gas composition over a period of ten years.

The shape of the curves and the measured values are compared with the typical diffusion coefficients and thermal conductivity of cell gases.

The development of the curves shows that the fixed increments in the European PUR standard EN 13165, 2001–10 for pentane blown PUR foams are correctly calculated. These fixed increments provide assurance for the users of PUR rigid foam boards over very long periods (e.g. 25 years) and give confidence to the builders and the building supervisory authorities.

Influence of polymer membrane porosity on C3A hepatoblastoma cell adhesive interaction and function

The effect of the porosity of acrylonitrile-N-vinylpyrrolidone copolymer membranes on human C3A hepatoblastoma cell adhesive interaction and functioning is investigated on four membranes with an average pore size ranging between 6 and 12 nm. Adhesion of C3A cells was quantified and characterized by studying overall cell morphology and focal adhesion formation. Cell-cell interactions were characterized by E-cadherin expression and organization. Cell growth, fibronectin synthesis and cytochrome P450 activity were estimated as criteria of functional cell activity. The results suggest that membrane porosity influences the initial cell-surface interactions since an increasing pore size augmented cell adhesion and aggregate formation. Cell growth after 7 d was diminished on membranes with an average pore size of 12 nm. The activity of P450 measured by 7-ethoxycoumarin conversion at day 7 was influenced by membrane topography representing a clear optimum in the range of 7-10 nm pore size. These results indicate that membrane porosity is a determinant for the function of hepatocytes in extracorporal liver assist devices.

Randomized Phase II trial assessing estramustine and vinblastine combination chemotherapy vs estramustine alone in patients with progressive hormone-escaped metastatic prostate cancer

Based on the results of combined data from three North American Phase II studies, a randomised Phase II study in the same patient population was performed, using combination chemotherapy with estramustine phosphate (EMP) and vinblastine (VBL) in hormone refractory prostate cancer patients. In all, 92 patients were randomised into a Phase II study of oral EMP (10 mg kg day continuously) or oral EMP in combination with intravenous VBL (4 mg m² week for 6 weeks, followed by 2 weeks rest). The end points were toxicity and PSA response in both groups, with the option to continue the trial as a Phase III study with time to progression and survival as end points, if sufficient responses were observed. Toxicity was unexpectedly high in both treatment arms and led to treatment withdrawal or refusal in 49% of all patients, predominantly already during the first treatment cycle. The mean treatment duration was 10 and 14 weeks, median time to PSA progression was 27.2 and 30.8 weeks, median survival time was 44 and 50.9 weeks, and PSA response rate was only 24.6 and 28.9% in the EMP/VBL and EMP arms, respectively. There was no correlation between PSA response and survival. While the PSA response in the patients tested was less than half that recorded in the North American studies, the toxicity of EMP monotherapy or in combination with VBL was much higher than expected. Further research on more effective and less toxic treatment strategies for hormone refractory prostate cancer is mandatory.

Novel substituted pyridinyl imidazoles as potent anticytokine agents with low activity against hepatic cytochrome P450 enzymes

A series of polysubstituted pyridin-4-yl imidazole inhibitors of p38 MAP (mitogen-activated protein) kinase was prepared as small molecular anticytokine agents and drug candidates for the treatment of chronic inflammatory diseases. The contribution of substituents at the pyridinyl and imidazole moiety to selective inhibition of p38 without concomitant cytochrome P450 interaction was evaluated. Placement of a 1-phenylethyl (7e, p38: IC(50) 0.38 microM) or acetyl substituent at the exocyclic nitrogen of several 2-aminopyridine imidazoles led to the identification of potent p38 inhibitors which exceeded the starting lead ML 3375 (p38: IC(50) 0.63 microM) in potency. A preliminary modeling study related the enhanced bioactivity of 7e to a novel interaction between its 1-phenylethylamino side chain and a hydrophobic pocket close to the linker region of p38. The most active p38 inhibitors in this series maintained their efficacy in functional PBMC (peripheral blood mononuclear cells) and whole blood assays. Moreover, cytochrome P450 interaction, which has been linked to the liver toxicity observed for model p38 inhibitors, was very efficiently reduced through introduction of a tetramethylpiperidine substituent at the 1 position of the imidazole nucleus. Combination of both structural features provided 14c (p38: 0.34 microM, inhibition of CYP1A2 0%, 2C9 2.6%, 2C19 7.6% at 10 microM), which was selected for further development.

Fibrinogen adsorption and platelet interactions on polymer membranes

The hemocompatibility of four different wettable polymer membranes, namely Cuprophan (CE), polyether-polycarbonate (PC-PE), polysulfone (PSU), and polyetherimide (PEI), was investigated with respect to fibrinogen (Fng) adsorption and platelet adhesion/activation. In order to estimate the polar and dispersion components of the surface free energy, contact angles using water/vapor and water/n-hexadecane systems were measured. Adsorption of fibrinogen was studied using fluorescence-labeled protein. The adsorption isotherms showed that the amount and the affinity of adsorbed Fng increased with decreasing surface wettability of the membranes, which correlates with the dispersion and polar components of the surface free energy. The conformational changes of adsorbed Fng were detected by measuring the difference between monoclonal antibody binding to the conformation-sensitive epitope in the D-domain and the binding of polyclonal anti-Fng antibody. The anticipated conformational/orientational changes were greater for PEI and PSU membranes (the least wettable membranes) and negligible for the more wettable PC-PE and CE membranes. In addition, a possible relationship with the degree of platelet activation was found, showing negligible platelet adhesion on PC-PE and CE, but high platelet adhesion on PEI and PSU. Furthermore, platelets were spread to a large extent on PEI, while the formation of aggregates was observed on PSU. This may correspond to the anticipated differences in the conformational state of Fng on both membranes.

Combined scintigraphic and pharmacokinetic investigation of enteric-coated mesalazine micropellets in healthy subjects

BACKGROUND

There is a growing clinical trend to increase the daily dose of mesalazine, which leads to significant compliance issues associated with multiple dosings of current preparations.

AIM

To examine the gastrointestinal performance and systemic exposure of a 1.5 g sachet (micropellets) mesalazine formulation, compared with three enteric-coated tablets (500 mg each, Claversal).

METHODS

A randomized, two-way, cross-over pharmacoscintigraphic (scintigraphy plus pharmacokinetics) study and a two-way, cross-over, pharmacokinetic-only study were performed in 24 healthy volunteers (12 subjects per investigation).

RESULTS

The relative bioavailability of mesalazine was 92% comparing micropellets with Claversal tablets, and the cumulative urine excretion was c. 26% for both preparations, suggesting comparable systemic exposure for the two types of preparation. In the majority of subjects, drug release from the micropellet formulation occurred predominantly in the terminal ileum and ascending colon. The Claversal tablets disintegrated in comparable intestinal sites, albeit at slightly later time points than the micropellets, principally due to slower gastric emptying for the single-unit formulation.

CONCLUSION

The 1.5 g micropellet formulation offers comparable delivery properties to the marketed tablets, but with greater convenience of dosing.

Morphological studies on the culture of kidney epithelial cells in a fiber-in-fiber bioreactor design with hollow fiber membranes

A hollow fiber-in-fiber-based bioreactor system was tested for the applicability to host kidney epithelial cells as a model system for a bioartificial kidney. Hollow fibers were prepared from polyacrylonitrile (PAN), polysulfone-polyvinylpyrollidinone (PVP) blend (PSU) and poly(acrylonitrile-N-vinylpyrollidinone) copolymer P(AN-NVP). Hollow fibers with smaller and larger diameters were prepared so that the smaller fitted into the larger, with a distance of 50-100 microm in between. The following material combinations as outer and inner fiber were applied: PAN-PAN; PSU-PSU, PSU-P(AN-NVP). Madin-Darby kidney epithelial cells (MDCK) were seeded in the interfiber space and cultured for a period up to 14 days. Light, scanning, and transmission electron microscopy were used to follow the adhesion and growth of cells, and to characterize their morphology. As a result, we found that MDCK cells were able to grow in the interfiber space in mono- and multilayers without signs of systemic degeneration. Comparison of the different materials showed that PAN and P(AN-NVP) provided the best growth conditions, indicated by a tight attachment of cells on hollow fiber membrane, and subsequent proliferation and development of structural elements of normal epithelia, such as tight junctions and microvilli. In conclusion, the fiber-in-fiber design seems to be an interesting system for the construction of a bioartificial kidney.

Interaction of human skin fibroblasts with moderate wettable polyacrylonitrile--copolymer membranes

The development of a bioartificial skin is a step toward the treatment of patients with deep burns or nonhealing skin ulcers. One possible approach is based on growing dermal cells on membranes to obtain appropriate living cellular stroma (sheets) to cover the wound. New membrane-forming copolymers were synthesized, based on acrylonitrile (AN) copolymerization with hydrophilic N-vinylpyrrolidone (NVP) monomer, in different percentage ratios, such as 5, 20, and 30% w/w, and with two other relatively high polar comonomers--namely, sodium 2-methyl-2-propene-1-sulfonic acid (NaMAS) and aminoethylmethacrylate (AeMA). All these copolymers were characterized for their bulk composition and number average molecular weight, and used to prepare ultrafiltration membranes. Water contact angles and water uptake were estimated to characterize the wettability and scanning force microscopy to visualize the morphology of the resulting polymer surface. Cytotoxicity was estimated according to the international standard regulations, and the materials were found to be nontoxic. The interaction of the membranes with human skin fibroblasts was investigated considering that these cells are among the first to colonize membranes upon implantation or with prolonged external contact. The overall cell morphology, formation of focal adhesion contacts, and cell proliferation were estimated to characterize the cell material interactions. It was found that the pure polyacrylonitrile homopolymer (PAN) membrane provides excellent conditions for seeding with fibroblasts, comparable only to a copolymer containing AeMA. In contrast, the presence of NaMAS with acidic ionic groups decreased both the attachment and proliferation of fibroblasts. Low content of NVP in the copolymer, up to about 5%, still enabled good attachment and spreading of cells, as well as subsequent proliferation of fibroblasts, but higher ratios of 20 and 30% resulted in a significant decrease of these cellular activities.

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.