Scaffold design and fabrication technologies for engineering tissues--state of the art and future perspectives

Today, tissue engineers are attempting to engineer virtually every human tissue. Potential tissue-engineered products include cartilage, bone, heart valves, nerves, muscle, bladder, liver, etc. Tissue engineering techniques generally require the use of a porous scaffold, which serves as a three-dimensional template for initial cell attachment and subsequent tissue formation both in vitro and in vivo. The scaffold provides the necessary support for cells to attach, proliferate, and maintain their differentiated function. Its architecture defines the ultimate shape of the new grown soft or hard tissue. In the early days of tissue engineering, clinically established materials such as collagen and polyglycolide were primarily considered as the material of choice for scaffolds. The challenge for more advanced scaffold systems is to arrange cells/tissue in an appropriate 3D configuration and present molecular signals in an appropriate spatial and temporal fashion so that the individual cells will grow and form the desired tissue structures--and do so in a way that can be carried out reproducibly, economically, and on a large scale. This paper is not intended to provide a general review of tissue engineering, but specifically concentrate on the design and processing of synthetic polymeric scaffolds. The material properties and design requirements are discussed. An overview of the various fabrication techniques of scaffolds is presented, beginning with the basic and conventional techniques to the more recent, novel methods that combine both scaffold design and fabrication capabilities.