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Hiebl B.,Geesthacht GmbH and Berlin Brandenburg Center for Regenerative Therapies | Mrowietz C.,Geesthacht GmbH and Berlin Brandenburg Center for Regenerative Therapies | Ploetze K.,TU Dresden | Matschke K.,TU Dresden | And 2 more authors.
Microvascular Research | Year: 2010

In cardiac surgery the substitution of lost blood volume by plasma substitutes is a common therapeutical approach. None of the currently available blood substitutes has a sufficient oxygen transport capacity. This can limit the functional integrity of the myocardium known as highly oxygen consumptive. The study was aimed to get information about the minimal hematocrit, also known as critical hematocrit (cHct), which guarantees a stable and adequate oxygen partial pressure in the myocardium (pO2). In adult female pigs (n = 7) the hematocrit was reduced by isovolemic blood dilution with an intravenous infusion of isotonic 4% gelatine polysuccinate solution, The substituted blood volume ranged between 3000. ml and 7780. ml (mean: 5254 ± 1672. ml). In all animals the pO2 of the myocardium of the beating heart and of the resting skeletal muscle increased until blood dilution resulted in a Hct decrease down to 15%. Further blood dilution resulted in a decrease of the pO2. Only after the Hct was < 10% the pO2 was lower than before blood dilution and accompanied by a lethal ischemia of the myocardium. These data indicate a cHct of about 10% in the pig animal model. © 2010 Elsevier Inc.


Cui J.,Geesthacht GmbH and Berlin Brandenburg Center for Regenerative Therapies | Kratz K.,Geesthacht GmbH and Berlin Brandenburg Center for Regenerative Therapies | Hiebl B.,Geesthacht GmbH and Berlin Brandenburg Center for Regenerative Therapies | Jung F.,Geesthacht GmbH and Berlin Brandenburg Center for Regenerative Therapies | Lendlein A.,Geesthacht GmbH and Berlin Brandenburg Center for Regenerative Therapies
Polymers for Advanced Technologies | Year: 2011

Mechanical conditioning can serve as a potent tool to influence mechano-responsive cells, which plays a prominent role during formation and regeneration of functional tissue. Recently, the differentiation of mesenchymal stem cells could be influenced by the local stiffness of hydrogels used as 2D substrates. However, the mechanical properties and the swellability of hydrogels in physiological liquids are difficult to control precisely as their properties strongly depend on physical parameters like ionic strength or pH value. Here, we explored amorphous, hydrophobic poly(n-butyl acrylate) networks (cPnBA) as soft substrates for cell culture system with adjustable mechanical properties. cPnBAs were synthesized via bulk radical polymerization from n-butyl acrylate (nBA) and poly(propylene glycol) dimethacrylate (PPGDMA) as crosslinker. The Young's modulus for cPnBAs determined by tensile tests could be systematically adjusted from 100 kPa to 10 MPa by increasing the PPGDMA-content at ambient temperature, while the glass transition temperature (Tg) was found to increase from -46 to -22°C. All cPnBAs exhibited similar surface properties with a surface roughness (Rq) in the range from 1.4 to 0.4 μm and advancing contact angles from 115° to 100°, which remained constant after ethylene oxide sterilization. The extracts of sterilized materials were tested for cytotoxic effects with L929 cells. All tested samples were non-cytotoxic. The functional integrity of cell membranes and mitochondrial activity stayed unaffected. The investigated polymer networks are promising candidates as soft substrates for passive mechanical stimulation of cells in vitro in cell culture devices or in vivo as implant coatings. © 2010 John Wiley & Sons, Ltd.

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