Collagen density significantly affects the functional properties of an engineered provisional scaffold

Department of Orthopaedic Surgery, Children's Hospital of Boston, Boston, MA 02115, USA.
Journal of Biomedical Materials Research Part A (Impact Factor: 3.37). 01/2009; 93(1):150-7. DOI: 10.1002/jbm.a.32508
Source: PubMed


The formation of a provisional scaffold is essential in wound healing. However, for tissues inside of joints, this process is impeded by the synovial fluid environment and wound healing is significantly impaired as a result. Therefore, development of substitute provisional scaffolds which are effective in the intra-articular environment is of great interest. Collagen-platelet hydrogels have recently been found useful as substitute provisional scaffolding materials. In this study, our hypothesis was that increasing the collagen density in the hydrogel would result in physiologic changes that would be likely to affect their function as provisional scaffold substitutes. The primary functional outcome measures were modulus of the hydrogel, platelet activation, fibroblast proliferation, and scaffold retraction. Increased collagen density resulted in collagen-platelet hydrogels with a higher storage modulus. Platelet activation was not found to be dependent on the collagen density within the range tested. Increasing the collagen density had a suppressive effect on both fibroblast proliferation and scaffold retraction. These studies suggest that the collagen density may be able to significantly influence the function of collagen-platelet hydrogels used as substitute provisional scaffolds.

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    • "Collagen type I hydrogels are known to be good scaffolds and are often used for the growth of collagen related tissue such as cartilage or dermis [4] [5]. For assessing the hydrogel properties, more researchers are currently finding their way to various types of microscopy, such as confocal fluorescence or reflectance microscopy and label-free second harmonic generation (SHG) microscopy, which is particularly useful in the case of collagen scaffolds [6] [7]. "
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    ABSTRACT: Successful engineering of bio-mimetic tissue relies on an accurate quantification of the mechanical properties of the selected scaffold. To improve this quantification, typical bulk rheological measurements are often complemented with microscopic techniques, including label-free second harmonic generation (SHG) imaging. Image correlation spectroscopy (ICS) has been applied to obtain quantitative information from SHG images of fibrous scaffolds. However, the typical polarization SHG (P-SHG) effect, which partly defines the shape of the autocorrelation function (ACF), has never been taken into account. Here we propose a new and flexible model to reliably apply ICS to P-SHG images of fibrous structures. By starting from a limited number of straightforward assumptions and by taking into account the P-SHG effect, we are able to cope with the typically observed ACF particularities. Using simulated datasets, the resulting model is thoroughly evaluated and compared with models previously described in literature. We show that our new model has no restrictions concerning the fibre length for the density retrieval. For certain length ranges, the model can additionally be used to obtain the average fibre length and the P-SHG related non-zero susceptibility tensor element ratios. From experimental data on collagen type I hydrogels, values of SHG tensor element ratios and fibre thickness are determined which match values reported in the literature, thereby underpinning the validity and applicability of our new model.
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