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Bioengineering researchers in Rice University in Texas have made a major step forward in the field of craniofacial reconstruction with the development of a modified hydrogel that is liquid at room temperature but solidifies into a gel at body temperature. The researchers have published their results in a ‘Just Accepted’ manuscript in the American Chemical Society journal Biomacromolecules. The hydrogel can ‘fit’ into irregular three-dimensional spaces, relevant in the case of craniofacial reconstruction following illness or injury, and in a preliminary encapsulation assay was shown to be capable of delivering mesenchymal stem cells (MSC). This would be highly relevant in tissue engineering to encourage delivery of growth factors and cell proliferation to ultimately direct new bone formation.

The study builds on other research considering the applicability of thermosensitive technologies as an alternative to prefabricated scaffolds in craniofacial reconstruction. The researchers introduced chemical modifications to a polymer called poly(N-isopropylacrylamide) ( PNiPAAm) which improved its properties in terms of biodegradability and hydrogel shrinkage. Inadequate biodegradability causes physical barriers to tissue repair and leaves the patient prone to inflammation while shrinkage has a negative effect on nutrient diffusion and on tissue integration. In addition, they carried out in vitro cytocompatibility assays on rat fibroblast cells using their modified hydrogel and were able to demonstrate cytocompatibility of the hydrogel degradation products. Importantly in terms of the potential of this hydrogel for cell delivery applications in tissue engineering projects such as craniofacial reconstruction, MSC encapsulation studies were carried out. MSCs in serum-containing media were successfully encapsulated in the hydrogel, with live cells being supported for up to 7 days. This did not affect hydrogel cross-linking.

The potential of this is enormous as the macromolecule can be injected, be converted to a gel at body temperature and support bone tissue growth and then be readily removed by being converted back into a liquid form. The authors of the study are continuing their research and the lead investigator, Antonius Mikos is hopeful that development of this thermosensitive hydrogel will have ‘enormous implications for the development of novel therapeutics for craniofacial bone regeneration’.

Sources

Rice University. "Liquid to gel to bone: Temperature-sensitive gelling scaffolds made to regenerate craniofacial bone." ScienceDaily, 11 Dec. 2013. [Accessed 12 Dec. 2013]

VO, T.N., EKENSEAIR, A.K., KASPER, F.K. and MIKOS, A.G. (2013). Synthesis, Physicochemical Characterization, and Cytocompatibility of Bioresorbable, Dual-Gelling Injectable Hydrogels. Biomacromolecules, 2013; : 131210033924002 DOI: 10.1021/bm401413c