Interactions of cells with polymer-based biomaterials are influenced by properties of the substrate. Polymers, which are able to induce cell specific effects, gain increasing importance for biotechnology and regenerative therapies. A test system was developed, which allows studying primary human keratinocytes and fibroblasts in mono- and cocultures to analyze and operate the effect of polymer properties. This system offers to identify polymers for keratinocyte cultivation or wound dressings, since adherence, viability and functionality can be analyzed. Especially the coculture system enables the characterization of potential cell specific effects of polymer-based biomaterials. To establish a coculture test system, it is challenging to find a suitable culture medium, to identify initial seeding densities for comparable cell growth and to develop methods to distinguish and characterize both cell types. Poly(n-butyl acrylate) networks (cPnBAs) as model biomaterials were used to demonstrate the applicability of our newly developed coculture screening system for differential cell growth. The apparent Young's modulus of the cPnBAs differentially regulated fibroblasts and keratinocytes. Particularly, cPnBA73 with an apparent Young's modulus of 930±140 kPa measured in phosphate buffered saline (PBS) solution at ambient temperature seemed to have favoring properties for keratinocyte adhesion, while fibroblast adhesion was not affected. For keratinocytes the concentration of some pro-inflammatory cytokines was lower on cPnBA73 and a decreased deposition of collagen, elastin and fibronectin was observed in the coculture.

Acrylonitrile-based polymer systems (PAN) are comprehensively explored as versatile biomaterials having various potential biomedical applications, such as membranes for extra corporal devices or matrixes for guided skin reconstruction. The surface properties (e.g. hydrophilicity or charges) of such materials can be tailored over a wide range by variation of molecular parameters such as different co-monomers or their sequence structure. Some of these materials show interesting biofunctionalities such as capability for selective cell cultivation. So far, the majority of AN-based copolymers, which were investigated in physiological environments, were processed from the solution (e.g. membranes), as these materials are thermo-sensitive and might degrade when heated.In this work we aimed at the synthesis of hydrophobic, melt-processable AN-based copolymers with adjustable elastic properties for preparation of model scaffolds with controlled pore geometry and size. For this purpose a series of copolymers from acrylonitrile and n-butyl acrylate (nBA) was synthesized via free radical copolymerisation technique. The content of nBA in the copolymer varied from 45 wt% to 70 wt%, which was confirmed by 1 H-NMR spectroscopy. The glass transition temperatures (T g ) of the P(AN-co-nBA) copolymers determined by differential scanning calorimetry (DSC) decreased from 58 • C to 20 • C with increasing nBA-content, which was in excellent agreement with the prediction of the Gordon-Taylor equation based on the T g s of the homopolymers. The Young's modulus obtained in tensile tests was found to decrease significantly with rising nBAcontent from 1062 MPa to 1.2 MPa. All copolymers could be successfully processed from the melt with processing temperatures ranging from 50 • C to 170 • C, whereby thermally induced decomposition was only observed at temperatures higher than 320 • C in thermal gravimetric analysis (TGA). Finally, the melt processed P(AN-co-nBA) biomaterials were sterilized with ethylene oxide and tested for cytotoxicity in direct contact tests with L929 cells according to the EN DIN ISO standard 10993-5. All tested samples exhibited non-toxic effects on the functional integrity of the cell membrane and the mitochondrial activity. However, the morphology of the cells on the samples was different from that observed on polystyrene as control, indicating slightly cytotoxic effects according to the evaluation guide of the US Pharmacopeial Convention. Thus, the melt-processable, hydrophobic P(ANco-nBA) copolymers with adjustable mechanical properties are promising candidates for in vitro investigations of tissue growth kinetics.

of the original manuscript: Scharnagl, N.; Hiebl, B.; Trescher, K.; Zierke, M.; Behl, M.; Kratz, K.; Jung, F.; Lendlein, A.: ABSTRACTThe chemical composition of a substrate can influence the adhesion, viability and proliferation of cells seeded on the substrate. The aim of this work was to investigate the influence of different cationic or anionic moieties in acrylonitrile based copolymers on the interaction with fibroblasts. A series of ten different types of acrylonitrile based copolymers with a random sequence structure was prepared using a water born synthesis process to exclude potential residues of organic solvents. As charged comonomers cationic methacrylic acid-2-aminoethylester hydrochloride (AEMA), N-3-amino-propyl-methacrylamidehydrochloride (APMA) and anionic 2-methyl-2-propene-1-sulfonic acid sodium salt (NaMAS) were utilized. By application of a specific sintering procedure the copolymer materials were processed into transparent disks for conducting cell tests in direct contact. The copolymers were analyzed with respect to their composition and surface properties.Cytotoxicity tests of the polymer extracts, as well as of the disks were performed with L929 mouse fibroblasts. All copolymers showed no cytotoxic effects Furthermore for higher molar ratios of AEMA and NaMAS (> 4.4 and 9.9 mol-%) a reduction in cell growth could be observed, which might be a hint that higher charge densities are unfavorable for the proliferation of L929 cells.

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Purpose: The cyclin-dependent kinase (Cdk) inhibitor p27Kip1 may be involved in regulating re-entry of residual hepatocytes into the cell cycle upon loss of liver tissue by partial hepatectomy (PH). As yet, changes in Kip1 expression during the initial period following PH are not well-characterized. We investigated immediate changes in Kip1 mRNA and protein levels as well as changes in Kip1 phosphorylation in liver tissue within the relevant time window between surgery and the onset of DNA synthesis at 10–12 h.Methods: We used real-time PCR, quantitative Western blotting, and immune histochemistry on tissue samples of adult rats obtained during or between 2 and 10 h after surgical removal of two thirds of the liver to analyze Kip1 mRNA or protein levels, respectively, or to quantify nuclear expression of Kip1.Results: Kip1 mRNA was down-regulated within 4 h after PH by 60% and remained unchanged thereafter up to 10 h. With a lag phase of 2–3 h, Kip1-protein was down-regulated to a level of 40% of the control. The level of Thr187-phosphorylated Kip1 started to increase at 4 h and reached a maximum level at 8–10 h after PH. Kip1 immunoreactivity was observed in 30% of the hepatocytes before PH. Within 6–8 h after PH, more than half of the hepatocytes lost nuclear Kip1 signals. Kip1-specific micro-RNAs (miRNA221, miRNA222) were not changed upon PH.Conclusions: A portion of hepatocytes in adult rats constitutively express Kip1 and down-regulate Kip1 immediately upon PH. This response involves transcriptional processes (loss of Kip1 mRNA) as well as accelerated degradation of existing protein (increase in pThr187-phosphorylation mediating polyubiquitinylation and proteasomal degradation of Kip1). Kip1 down-regulation occurs precisely within the intervall between surgery and onset of DNA synthesis which supports the hypothesis that it mediates activation of G0/0S-phase Cdk/cyclin-complexes and re-entry of hepatocytes into the cell cycle.