Tailoring the Interface of Biomaterials to Design Effective Scaffolds

Abstract

Tissue engineering (TE) is a multidisciplinary science, which including principles from material science, biology and medicine aims to develop biological substitutes to restore damaged tissues and organs. A major challenge in TE is the choice of suitable biomaterial to fabricate a scaffold that mimics native extracellular matrix guiding resident stem cells to regenerate the functional tissue. Ideally, the biomaterial should be tailored in order that the final scaffold would be (i) biodegradable to be gradually replaced by regenerating new tissue, (ii) mechanically similar to the tissue to regenerate, (iii) porous to allow cell growth as nutrient, oxygen and waste transport and (iv) bioactive to promote cell adhesion and differentiation. With this perspective, this review discusses the options and challenges facing biomaterial selection when a scaffold has to be designed. We highlight the possibilities in the final mold the materials should assume and the most effective techniques for its fabrication depending on the target tissue, including the alternatives to ameliorate its bioactivity. Furthermore, particular attention has been given to the influence that all these aspects have on resident cells considering the frontiers of materiobiology. In addition, a focus on chitosan as a versatile biomaterial for TE scaffold fabrication has been done, highlighting its latest advances in the literature on bone, skin, cartilage and cornea TE.

Keywords: biomaterials; chitosan; tissue engineering.

Figure 1

Tissue Engineering. (a) In vitro TE. Autologous cells and growth factors are co-seeded on the biomaterial scaffold and maintain in culture until tissue neo-formation. Tissue regeneration occurs ex vivo and once formed, the tissue is grafted; (b) In vivo TE. Biomaterial scaffold is directly implanted in the damaged anatomical site. Tissue regeneration occurs in vivo.

Figure 2

Cell phenotype is shaped by the stiffness of the substrate.

Figure 3

Control of cell adhesion through biomaterial coating with ECM-derived molecules. (a) Scaffold can be directly coated with the ECM-derived molecules; (b) Scaffold surface may be activated in order to expose functionalities able to bind ECM circulating molecules (i.e., fibronectin); (c) Selective binding molecules may be grafted on scaffold surface to retain ECM circulating.

Figure 4

Control of cell fate and function through bioactive molecules immobilization. (a) Bioactive molecules may be physically immobilized on the scaffold, by encapsulation, simply adsorption or through LbL assembly; (b) Scaffold surface may be activated in order to covalently bind bioactive molecules; (c) Scaffold direct coating with ECM molecules may be exploited to bind bioactive molecules by affinity.

Figure 5

Chemical structure of chitin and of chitosan after chitin N-Deacetylation.