Characterization of Scaffolds for Tissue Engineering by Benchtop-Magnetic Resonance Imaging

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.

Imaging challenges in biomaterials and tissue engineering

“…6B) [96,102,104,106,108,109] and to noninvasively monitor their presence in engineered tissues in vitro [98,103]. MRI has also been used to track localization of SPION labeled cells to damaged tissues [64,97,105] or areas of inflammation [107] following intravascular injection in small animal models.…”

Application of Benchtop-magnetic resonance imaging in a nude mouse tumor model

“…The lower quality of the NMR images is expected due to the low field strength and decreased magnet homogeneity. However, very recently we could show that BT-MRI is able to characterize floating mono- or bilayer tablets, osmotic controlled push-pull tablets [1-4] or scaffolds for tissue engineering in vitro [5]. A broad, important and increasing range of MRI applications are linked with preclinical studies on small rodents such as mice or rats [6-8].…”

Monitoring Cartilage Tissue Engineering Using Magnetic Resonance Spectroscopy, Imaging, and Elastography

“…A bench-top MRI scanner developed by the Mä der group for characterization of scaffolds is one such example. 31 In the clinical setting, gadolinium-enhanced MRI could prove to be useful; therefore, the correlation of proteoglycan with a fixed charged density derived from gadolinium-enhanced MRI for cartilage tissue-engineering constructs is encouraging. 36 In addition, as sodium MRI becomes more feasible (with the advent of more high field clinical MR scanners), it may be possible to derive fixed charge density information without the use of a contrast agent.…”

“…MRS and imaging are wellestablished techniques that have been used to probe the structure and dynamics of biochemical changes in engineered tissues. [28][29][30][31][32][33][34][35][36][37][38][39][40][41][42] MR elastography, while relatively new, is rapidly being employed to assess the mechanical properties of engineered tissues. 30,43 Using MR spectroscopy, imaging, and elastography together, it is possible to create three-dimensional (3D) maps of chemical shifts, relaxation times, diffusion coefficient, spectral couplings, and tissue stiffness.…”