Biodegradable Polymer-Based Scaffolds for Bone Tissue Engineering

The aim of tissue engineering is to develop cell, construct, and living system technologies to restore the structures and functions of damaged or degenerated tissues. Surgical strategies that have evolved to deal with tissue loss include organ transplantation from one individual to another, tissue transfer from a healthy site to an affected site in the same individual, and replacement of tissue functions with synthetic material devices. All of these strategies have limitations. Organ transplantation is not always feasible as the number of organ donors is far less than the number of patients waiting for organ transplantation. The complications of immuno-suppressive agents are also trouble for the organ recipients. Tissue engineering (TE) seeks to provide a new solution to tissue loss. Scaffolds with porous microstructures are commonly used in TE. This chapter reviews and reports the TE strategy, requirements of scaffolds in TE, as well as different biomaterials that are often used to fabricate tissue engineering scaffolds.

The development of porous materials for use as scaffolds for the sustained 3D growth of tissue is a fast growing area in TE that has attracted commercial interest to a large extent. To fabricate both polymer scaffold and composite scaffold, many techniques are available. By using proper technique, the porous structure of polymeric and composite scaffolds could be controlled by varying the processing or formulation parameters. It is often necessary to modify the surface properties of biomaterials without changing the bulk attributes as a biomaterial rarely possess good surface characteristics suitable for bone tissue engineering. This chapter reviews the various existing methodologies to fabricate scaffolds and to modify the surface properties of scaffolds. It also discusses the study of interactions between tissues and biomaterials.

This chapter reports the emulsion freezing/freeze-drying technique for the formation of three-dimensional porous scaffolds for bone tissue engineering applications. Poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV), which is a natural, biodegradable polymer, was used as the main polymer for fabricating various tissue engineering scaffolds. Nano-sized hydroxyapatite (HA), a widely used bioceramic, was incorporated in the scaffolds in order to obtain bioactive (i.e., osteoconductive) composite scaffolds. The chapter focused in two areas: (1) investigations into scaffold fabrication using the emulsion freezing/freeze-drying technique and the influence of processing parameters on the formation of PHBV polymer scaffolds, HA/PHBV composite scaffolds and HA-containing PHBV/PLLA blend-based composite scaffolds; (2) evaluation of different scaffolds in terms of their porous structure, porosity, pore size, polymer crystallinity, compressive mechanical properties, in vitro biodegradation behavior and in vitro biological performance.