No abstract

Several publications have shown approaches for the optimization of tissue engineering constructs by magnetic resonance imaging (MRI). However, the technology is still scarcely used, probably because of the poor spatial resolution of clinical scanners and their temporally limited availability for many researchers. The new benchtop- MRI (BT-MRI) equipment used in the present study is much more affordable, for example, because of the low static magnetic field strength of 0.5 T and the absence of a helium cooling system. In this study, the method of BT-MRI was evaluated for the characterization of a tissue engineering scaffold. Hollow cylinder scaffolds were made of hydroxyapatite (HA), collagen, and chitosan and wrapped in a polyglycolic acid mesh. Mass transport between construct and surrounding medium was investigated by dynamic contrast agent-enhanced MRI with gadolinium(III)-diethylaminepentaacetic acid. The results demonstrate that BT-MRI permits detailed, space-resolved insights into diffusion processes within the three-dimensional matrices, enabling a comparison of the mass transport inside different scaffold types. Inhomogeneities of the HA distribution in scaffolds caused by the fabrication were also visible in MR images. The fate of cells, labeled with superparamagnetic iron oxide nanoparticles and seeded on the scaffold surface, was monitored. For the first time, it was shown that mass transport, inhomogeneities of the HA distribution, and localization of superparamagnetic iron oxide nanoparticle-labeled cells are accessible in a tissue engineering scaffold by BT-MRI. Hence, it is demonstrated that BT-MRI is a powerful analytic method for the noninvasive evaluation of tissue engineering constructs.

For successful bone tissue engineering, scaffolds with tailored properties are a basic requirement. The combination of different available materials not only appears to be desirable but also very challenging. In this study, a composite material consisting of hydroxyapatite and collagen was produced by a biomimetic precipitation method and characterized by X-ray diffraction (XRD) and thermogravimetry (TGA). Subsequently, a suspension-quick-freezing and lyophilization method was used to incorporate the hydroxyapatite into a polymeric matrix consisting of collagen and chitosan. Before physicochemical characterization, the highly porous scaffolds were consolidated by a dehydrothermal treatment (DHT). The main attention was focused on the particle size of hydroxyapatite, which should be in the nanometer range. This is relevant to achieve a homogeneous resorption of the material by osteoclasts. Small-angle X-ray scattering (SAXS), atomic force microscopy (AFM), and environmental scanning electron microscopy (ESEM) were used to evaluate the outcome. The results suggest a successful polymeric embedding of nanoscaled hydroxyapatite particles into the matrix of the spongy construct. (c) 2010 Wiley Periodicals, Inc. J Biomed Mater Res, 2010.