Mineralisation of alginate hydrogels

Due to a highly complex architecture across wide length scales (nm-cm), the hierarchical structure of bone is not easily replicated in the laboratory [1,2]. One strategy to overcome this obstacle when engineering synthetic bone tissue scaffolds is to provide a simpler material which inherent or implanted cells can remodel into natural bone. We envisage formation of constructs which include hydrogel beads, fibres and/or films with different mineral phases, mineral content or mineralising potential. This can done in combination with a possibility to co-culture different cell types resident to bone, such as osteoblasts and osteoclasts, in order to stimulate remodelling and formation of new bone [3]. Controlled mineralisation of hydrogel based materials is however challenging. This is due to non-homogeneous and time dependent driving forces for mineral phase formation, interaction between biopolymer network and the crystal nucleation and growth processes nucleation in dynamic conditions of pH during mineralization. In addition, the calcium phosphate system consists of many crystal phases, which can be stable under different conditions, form at greatly varying rates, as well as transform under actual or simulated physiological conditions [4]. I will present two approaches which allow for better control and description of the mineralisation of an alginate hydrogel. One method is based on controlling nucleation of desired crystal phase using well defined seed crystals. The second approach aims at achieving a better description of various processes during mineralisation by using a variety of physicochemical analysis techniques in situ, therefore allowing for improvement in the design of controlled fabrication processes. [1] Stevens, M. M., & George, J. H. (2005). Exploring and engineering the cell surface interface. Science, 310, 1135–1138. [2] Wegst, U. G. K. et al. (2014). Bioinspired structural materials.Nature Materials,14(1), 23–36. [3] Raggatt et al. (2010). Cellular and molecular mechanisms of bone remodeling. The Journal of Biological Chemistry, 285(33), 25103–8. [4] Boistelle, R., & Lopez-Valero, I. (1990). Growth units and nucleation: The case of calcium phosphates. Journal of Crystal Growth, 102(3), 609–617.