In situ cell manipulation through enzymatic hydrogel photopatterning

The physicochemical properties of hydrogels can be manipulated in both space and time through the controlled application of a light beam. However, methods for hydrogel photopatterning either fail to maintain the bioactivity of fragile proteins and are thus limited to short peptides, or have been used in hydrogels that often do not support three-dimensional (3D) cell growth. Here, we show that the 3D invasion of primary human mesenchymal stem cells can be spatiotemporally controlled by micropatterning the hydrogel with desired extracellular matrix (ECM) proteins and growth factors. A peptide substrate of activated transglutaminase factor XIII (FXIIIa)-a key ECM crosslinking enzyme-is rendered photosensitive by masking its active site with a photolabile cage group. Covalent incorporation of the caged FXIIIa substrate into poly(ethylene glycol) hydrogels and subsequent laser-scanning lithography affords highly localized biomolecule tethering. This approach for the 3D manipulation of cells within gels should open up avenues for the study and manipulation of cell signalling

Injectable Gels for Dental and Craniofacial Applications

The use of injectable scaffolds is considered a promising approach in craniofacial tissue regeneration, as they can be introduced with minimally invasive surgery, thus reducing the risk of surgery complications and improving postoperative recovery. In this chapter, comprehensive descriptions of chemically and physically cross-linked hydrogels that can be used as injectable scaffolds for dental and craniofacial application are presented. Nanocomposite hydrogels, in which nano-sized particles may serve as reinforcing agents and impart functionality to the hydrogels, are also discussed. Special attention is given to peptide amphiphiles which can self-assemble into supramolecular configuration mimicking the extracellular matrix (ECM) structure. Finally, injectable microspheres and different techniques of fabrication are discussed in this chapter