Hydroxyapatite-coated polyurethane for auricular cartilage replacement: an in vitro study.

Auricular reconstruction remains a major challenge facing reconstructive surgeons owing to the complexity of autogenous transplants. In this study, the development of a three-dimensional custom-made polyurethane (PU) auricular implant with hydroxyapatite (HA) coating is described. The PU implant was produced by computerized tomography (CT) scanning and indirect rapid prototyping. To improve the physiological response of the implant, the PU prototype was coated with a microrough, homogenous layer of HA by a novel solvent-compression coating method. Bioactivity of the HA coated PU substrates was confirmed by apatite formation on the HA coating after 9 days in revised simulated body fluid (pH 7.4). Adhesion strength of the HA coating to the PU surface using the tensile pull-off test revealed partial failure of the coating with an average tensile strength of 1.6 MPa. As an initial stage indication of cytocompatibility for a soft tissue application, in vitro cell culturing on the HA-coated PU substrates using Graham 293 fibroblast cells was performed. After 24 and 72 h, the HA coated surfaces displayed significantly higher cell numbers and metabolically active cells compared with the virgin uncoated PU surfaces. This indicates that HA coated PU surfaces are cytocompatible towards fibroblasts and could potentially be applied to auricular cartilage tissue replacement.

An in vitro and in vivo study on the properties of hollow polycaprolactone cell-delivery particles.

The field of dermal fillers is evolving rapidly and numerous products are currently on the market. Biodegradable polymers such as polycaprolactone (PCL) have been found to be compatible with several body tissues, and this makes them an ideal material for dermal filling purposes. Hollow PCL spheres were developed by the Council for Scientific and Industrial Research (CSIR) to serve both as an anchor point and a "tissue harbour" for cells. Particles were tested for cytotoxicity and cell adherence using mouse embryo fibroblasts (MEF). MEFs adhered to the particles and no significant toxic effects were observed based on morphology, cell growth, cell viability and cell cycle analysis, suggesting that the particles are suitable candidates for cell delivery systems in an in vivo setting. The objective of providing a "tissue harbour" was however not realized, as cells did not preferentially migrate into the ported particles. In vivo studies were conducted in BALB/c mice into whom particles were introduced at the level of the hypodermis. Mice injected with PCL particles (ported and non-ported; with or without MEFs) showed evidence of local inflammation and increased adipogenesis at the site of injection, as well as a systemic inflammatory response. These effects were also observed in mice that received apparently inert (polystyrene) particles. Ported PCL particles can therefore act as a cell delivery system and through their ability to induce adipogenesis, may also serve as a dermal bulking agent.

Hepatocyte function in a radial-flow bioreactor using a perfluorocarbon oxygen carrier.

UNLABELLED: The aims of this study were, first, to indicate the metabolic activity of hepatocytes in a radial-flow polyurethane foam matrix bioreactor relative to monocultures, and second, to evaluate the effect on the hepatocytes of including a synthetic perfluorocarbon (PFC) oxygen carrier to the recirculating medium. The efficient O2-carrying ability of PFCs may be beneficial to bioreactors employed in stressed cellular environments. Thus, they may also be useful in the treatment of an acute liver failure patient with a bioartificial liver support system (BALSS). Data on the function of three-dimensional (3-D) hepatocyte cultures exposed to emulsified PFCs are lacking. RESULTS: the metabolic functions of the 3-D hepatocyte cultures were improved relative to monocultures. Three-dimensional cultures with and without PFC behaved similarly, and no adverse effects could be detected when PFC was included in the recirculating medium. The addition of PFC significantly improved lidocaine clearance possibly due to the presence of higher O2 tension in the medium. Imaging indicated that large aggregates formed and that seeding had followed flow through the matrix. Simulations indicated first, that the cell numbers used in this study had been insufficient to challenge the bioreactor O2 supply explaining the similarity in performance of the 3-D cultures, and second, that the benefit of adding PFC would be more pronounced at the cell densities likely to be used in a BALSS bioreactor.