Biomimetic materials presenting extracellular matrix components to study bone morphogenetic protein bioactivity

The extracellular matrix (ECM) is a complex 3D microenvironment around cells composed of structural and adhesion proteins, proteoglycans-carrying glycosaminoglycans (GAGs) that bind and release growth factors to cellular receptors. In particular, bone morphogenetic protein 2 (BMP2) is bound to GAGs on the ECM and cell surface. 3D biomaterials are a good approximation to the real in vivo microenvironment, they allow cells to maintain their original shape, have higher stability and longer lifespan by showing a less altered genotype. On the contrary, 2D culture is not representative of the chemical and physical properties of the ECM. However, precise chemical functionalization of 3D biomaterials is still a challenge, and high-throughput methods for designing and functionalizing 3D biomaterials are rare. In addition, the analysis of cellular responses in 3D is more complex than in 2D.

For these reasons, we propose "2.5D" biomaterials with controlled chemical and mechanical properties that can be functionalized by a liquid handling robot followed by automated cellular readout based on immunofluorescence. Thanks to these 2.5D biomaterials, we have demonstrated the existence of a bidirectional cross-talk between BMP2 and integrin adhesion ligands. We have also shown that the glycosaminoglycan (GAG) heparan sulfate (HS) has a positive role on BMP2-mediated signaling when presented to the cell by a biomaterial, compared to the other GAGs chondroitin sulfate and hyaluronic acid. On the contrary, cell surface CS has a positive effect on BMP2 signaling.

We are developing well-characterized biomimetic materials for high-throughput in vitro cell culture studies. In the future, we expect to use these materials as coatings for 3D scaffolds.