17 - Fabrication of Tissue Engineering Scaffolds

Abstract

Tissue engineering is an interdisciplinary field aimed at the development of biological substitutes that restore, maintain, or improve tissue function [1] . A highly porous biodegradable scaffold is essential to accommodate mammalian cells and guide their growth in three dimensions [2] . In the past, natural and synthetic polymers have routinely been used as substrates to provide this temporary scaffolding for transplanted cells as they excrete their extracellular matrix (ECM) and form new tissues or organs [1] ; [2] ; [3] ; [4] . Although extensive research has been performed with both types of polymers, synthetic polymers offer several advantages over natural polymers such as collagen and fibrin. They can be prepared in a reproducible manner in almost unlimited quantities, and their physical, chemical, and mechanical properties may be easily altered by chemical modifications. In addition, they can be easily processed with conventional polymer processing equipment [5] . Some common synthetic biodegradable polymers currently used as scaffolding materials include polylactide (PLA), polyglycolide (PGA), and their copolymers, and polycaprolactone (PCL) [2] ; [3] ; [4] . Myriads of new materials including tyrosine-derived polycarbonates and trimethylene carbonate-based materials are also being explored as alternative synthetic polymers for tissue engineering scaffolds [5] ; [6] . Many tissue engineering scaffold fabrication processes have been developed in order to meet the demands of tissue engineers. However, the majority of current scaffold fabrication techniques can be described as batch processes and/or use organic solvents, which can be detrimental to cell survival and tissue growth [7] . While these techniques may be adequate and essential for studying the effects of the substrate material, porosity, pore size, interconnectivity of the pores, mechanical and chemical properties, growth factors, and nutrient transport on the effects of tissue regeneration both in vitro and in vivo , they do not address the need for cost-effective manufacturing processes to meet patient needs. The ability to mass produce highly porous, highly interconnected scaffolds with complex geometries is essential to provide off-the-shelf availability [8] . Some of the most important and widely used fabrication methods using synthetic biodegradable polymers are explored here.