Abstract
Abstract Globally, bone fractures due to osteoporosis occur every 20 s in people aged over 50 years. The significant healthcare costs required to manage this problem are further exacerbated by the long healing times experienced with current treatment practices. Novel treatment approaches such as tissue engineering, is using biomaterial scaffolds to stimulate and guide the regeneration of damaged tissue that cannot heal spontaneously. Scaffolds provide a three-dimensional network that mimics the extra cellular micro-environment supporting the viability, attachment, growth and migration of cells whilst maintaining the structure of the regenerated tissue in vivo. The osteogenic capability of the scaffold is influenced by the interconnections between the scaffold pores which facilitate cell distribution, integration with the host tissue and capillary ingrowth. Hence, the preparation of bone scaffolds with applicable pore size and interconnectivity is a significant issue in bone tissue engineering. To be effective however in vivo, the scaffold must also cope with the requirements for physiological mechanical loading. This review focuses on the relationship between the porosity and pore size of scaffolds and subsequent osteogenesis, vascularisation and scaffold degradation during bone regeneration.
Highlights
Tissue engineering techniques to produce biocompatible scaffolds populated with autogenous cells has recently been shown to be an ideal alternative method to provide bone substitutes [1]
Natural variation in bone density occurs in the axial direction of long bones, displaying a gradient in porous structure from cortical bone to cancellous bone [36]. This suggests bone implants made of porous gradient biomaterials that can mimic the properties of natural bone with a porosity-graded structure, may perform significantly better in bone regeneration applications
Xu et al reported that the release of Ca, P and Si ionic products from NAGEL, Ca7Si2P2O16 scaffolds accelerated the proliferation of human umbilical vein endothelial cells (HUVECs) in at high concentrations (12.5 mg mlÀ1) of NAGEL extracts by promoting angiogenesis and endothelial cells for bone engineering [47]
Summary
Tissue engineering techniques to produce biocompatible scaffolds populated with autogenous cells has recently been shown to be an ideal alternative method to provide bone substitutes [1]. Proliferation, differentiation and migration abilities of these cells are affected by the size and geometry of the scaffold's pores and the degree of vascularisation [5]. The pore distribution and geometry of scaffold strongly influences cells ability to penetrate, proliferate and differentiate as well as the rate of scaffold degradation. The products of the degradation process should be nontoxic and not stimulate an inflammatory response [9]. As such the appropriate physical and chemical surface properties of the scaffold are an inherent requirement for promoting the attachment, infiltration, growth, proliferation and migration of cells [10]
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