Kommareddy K.P.,Max Planck Institute of Colloids and Interfaces |
Lange C.,Max Planck Institute of Colloids and Interfaces |
Rumpler M.,Ludwig Boltzmann Research Institute |
Dunlop J.W.C.,Max Planck Institute of Colloids and Interfaces |
And 5 more authors.
Biointerphases | Year: 2010
Bone regeneration is controlled by a variety of biochemical, biomechanical, cellular, and hormonal mechanisms. In particular, physical properties of the substrate such as stiffness and architecture highly influence the proliferation and differentiation of cells. The aim of this work is to understand the influence of scaffold stiffness and cell seeding densities on the formation of tissue by osteoblast cells within polyether urethane scaffolds containing pores of different sizes. MC3T3-E1 preosteoblast cells were seeded on the scaffold, and the amount of tissue formed within the pores was analyzed for culture times up to 49 days by phase contrast microscopy. The authors show that the kinetics of three-dimensional tissue growth in these scaffolds follows two stages and can be described by a universal growth law. The first stage is dominated by cell-material interactions with cell adherence and differentiation being strongly dependent on the polymer material. After a delay time of a few weeks, cells begin to grow within their own matrix, the delay being strongly dependent on substrate stiffness and seeding protocols. In this later stage of growth, three-dimensional tissue amplification is controlled rather by the pore geometry than the scaffold material properties. This emphasizes how geometric constraints may guide tissue formation in vitro and shows that optimizing scaffold architectures may improve tissue formation independent of the scaffold material used. © 2010 American Vacuum Society.
Cui J.,Research Center Geesthacht GmbH and Berlin Brandenburg Center for Regenerative Therapies |
Kratz K.,Research Center Geesthacht GmbH and Berlin Brandenburg Center for Regenerative Therapies |
Heuchel M.,Research Center Geesthacht GmbH and Berlin Brandenburg Center for Regenerative Therapies |
Hiebl B.,Research Center Geesthacht GmbH and Berlin Brandenburg Center for Regenerative Therapies |
Lendlein A.,Research Center Geesthacht GmbH and Berlin Brandenburg Center for Regenerative Therapies
Polymers for Advanced Technologies | Year: 2011
The formation of functional tissue is strongly dependent on biochemical as well as physical signals. A common approach in tissue engineering is the application of passive scaffold systems with fixed morphology and stiffness. In this paper, we explored whether mechanically active scaffolds, exhibiting self-sufficient shape changes under physiological conditions, can be prepared from radio-opaque shape-memory polymer composites (SMPCs). The influence of different thermomechanical treatments on the kinetics of the shape change was studied. Radio-opaque SMPCs were obtained by incorporation of barium sulfate (BaSO4) microparticles (up to 40 wt%) into an amorphous polyether urethane (PEU) via co-extrusion technique. The shape-memory properties of the composites were investigated by cyclic, thermomechanical tensile tests consisting of a specific shape-memory creation procedure (SMCP), in which the programming temperature (Tprog) was varied, followed by recovery under stress-free condition, enabling the determination of the switching temperature (Tsw). An almost complete recovery with shape recovery rate (Rr) values ranging from 88% to 98% was realized within a small temperature interval of ΔTrec = 30°C for all composites, while Tsw was found to be close to the applied Tprog. The feasibility of actively moving scaffolds was demonstrated using model scaffolds, where originally square-shaped pores were temporarily fixed in an expanded circular shape at different Tprog. We found that the kinetics of the shape change obtained under physiological conditions could be adjusted by variation of Tprog between 1 and 6 hr. Such radio-opaque scaffolds could serve as model scaffolds for investigating the active mechanical stimulation of cells in vitro or in vivo. © 2010 John Wiley & Sons, Ltd.