TY  - JOUR
A1  - Sauter, Tilman
A1  - Lützow, Karola
A1  - Schossig, Michael
A1  - Kosmella, Hans
A1  - Weigel, Thomas
A1  - Kratz, Karl
A1  - Lendlein, Andreas
T1  - Shape-memory properties of polyetherurethane foams prepared by thermally induced phase separation
JF  - Advanced engineering materials
N2  - In this study, we report the preparation of two structurally different shape-memory polymer foams by thermally induced phase separation (TIPS) from amorphous polyetherurethanes. Foams with either a homogeneous, monomodal, or with a hierarchically structured, bimodal, pore size distribution are obtained by adoption of the cooling protocol. The shape-memory properties have been investigated for both foam structures by cyclic, thermomechanical experiments, while the morphological changes on the micro scale (pore level) have been compared to the macro scale by an in situ micro compression device experiment. The results show that the hierarchically structured foam achieves higher shape-recovery rates and a higher total recovery as compared to the homogeneous foam, which is due to an increased energy storage capability by micro scale bending of the hierarchically structured foam compared to pure compression of the homogeneous foam.
Y1  - 2012
U6  - https://doi.org/10.1002/adem.201200127
SN  - 1438-1656
VL  - 14
IS  - 9
SP  - 818
EP  - 824
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Schneider, Tobias
A1  - Kohl, Benjamin
A1  - Sauter, Tilman
A1  - Kratz, Karl
A1  - Lendlein, Andreas
A1  - Ertel, Wolfgang
A1  - Schulze-Tanzil, Gundula
T1  - Influence of fiber orientation in electrospun polymer scaffolds on viability, adhesion and differentiation of articular chondrocytes
JF  - Clinical hemorheology and microcirculation : blood flow and vessels
N2  - Degradable polymers with a tailorable degradation rate might be promising candidate materials for biomaterial-based cartilage repair. In view of the poor intrinsic healing capability of cartilage, implantation of autologous chondrocytes seeded on a biocompatible slow degrading polymer might be an encouraging approach to improve cartilage repair in the future. This study was undertaken to test if the fiber orientation (random versus aligned) of two different degradable polymers and a polymer intended for long term applications could influence primary articular chondrocytes growth and ultrastructure.
 A degradable copoly(ether) esterurethane (PDC) was synthesized via co-condensation of poly(p-dioxanone) diol and poly(epsilon-caprolactone) diol using an aliphatic diisocyanate as linker. Poly(p-dioxanone) (PPDO) was applied as commercially available degradable polymer, while polyetherimide (PEI) was chosen as biomaterial enabling surface functionalization. The fibrous scaffolds of PDC and PPDO were obtained by electrospinning using 1,1,1,3,3,3 hexafluoro-2-propanol (HFP), while for PEI dimethyl acetamide (DMAc) was applied as solvent. Primary porcine articular chondrocytes were seeded at different cell densities on the fibrous polymer scaffolds and analyzed for viability (fluorescein diacetate/ethidiumbromide staining), for type II collagen synthesis (immunolabelling), ultrastructure and orientation on the fibers (SEM: scanning electron microscopy).
 Vital chondrocytes adhered on all electrospun scaffolds irrespective of random and aligned topologies. In addition, the chondrocytes produced the cartilage-specific type II collagen on all tested polymer topologies suggesting their differentiated functions. SEM revealed an almost flattened chondrocytes shape on scaffolds with random fiber orientation: whereby chondrocytes growth remained mainly restricted to the scaffold surface. On aligned fibers the chondrocytes exhibited a more spindle-shaped morphology with rougher cell surfaces but only a minority of the cells aligned according to the fibers. As a next step the reduction of the fiber diameter of electrospun scaffolds should be addressed as an important parameter to mimic cartilage ECM structure.
KW  - Chondrocytes
KW  - electrospinning
KW  - scaffold
KW  - differentiation
KW  - multiblock copolymer
Y1  - 2012
U6  - https://doi.org/10.3233/CH-2012-1608
SN  - 1386-0291
VL  - 52
IS  - 2-4
SP  - 325
EP  - 336
PB  - IOS Press
CY  - Amsterdam
ER  -