Biomimetic ECM Modification

The extracellular matrix (ECM), surrounding cells in the body and comprised of a natural web of protein and polysaccharides, not only physically supports cells but also plays important functions to regulate cellular activities such as cell survival, migration, proliferation, and differentiation [53, 54]. 

Therefore, as a temporary ECM for regenerative cells, scaffold needs to be developed for in vitro tissue reconstruction as well as for cell-mediated tissue regeneration in vivo. Although die hydrophilicity is improved by introducing polar groups onto the surface of PLA materials and the cell spread on materials. 

The entrapment method, initially invented by Desai and Hubbell, appears promising to modify biomaterial surfaces to improve their hydrophilicity [61,62]. With this method, the biomaterial surface can be non-covalently but stably modified with water-soluble polymers. The sketch map of this method is presented in Fig. 7.6. A PLA sample is immersed in an ECM solution in a solvent mixture (e.g., a good solvent of PLA and a non-solvent of PLA). Then PLA is moved to a non-solvent of the scaffold material. The ECM is successfully immobilized (entrapped) on the surfaces of PLA. The immersion of PLA in the ECM solution in the solvent mixture makes the PLA surfaces swelled to a certain extent, allowing the ECM molecules to at least partially penetrate into the swelled pore surfaces. The immersion in the non-solvent afterwards makes the porous PLA surfaces solidified, resulting in the entrapment of the ECM molecules 

The cell biocompatibility problem of PLA materials can be resolved by Biofunctional modifications. However, such polymers on their own are too weak to be used in load bearing situations and not generally considered osteoinductive. PLA molecules would lower the in situ pH level, which raises difficulties in controlling its degradation rate and may induce an inflammatory reaction. In addition, PLA materials tend to be too flexible and of insufficient strength to meet the mechanical demands as hard tissue replacement. 

Apatite, as an inorganic component of bone, has sufficient biocompatibility, high strength and excellent corrosion resistance [85-87]. Ceramics are very 

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