4 - Melt-molding technologies for 3D scaffold engineering

Abstract

The successful regeneration of functional tissue in scaffold-based tissue engineering heavily relies on the scaffold design and fabrication. Generally acknowledged material, chemical, mechanical, and structural requirements of scaffolds have placed strict pre-requisites and challenges on the fabrication technologies. In general, a feasible and practical technology is anticipated to simultaneously form the internal and external architecture of the scaffold in a scalable, reproducible, controllable, and cost-effective manner. During the past two decades, biomedical research has advanced extensively to develop potentially applicable scaffolds. From a manufacturing and ecological point of view, the preparation of porous structures from a thermoplastic polymer melt is a convenient route; it allows feasible, reproducible and rapid production of scaffolds of many shapes and sizes in an economical way without involving any solvents. Melt-based scaffold fabrication technologies are derived from the conventional polymer fabrication methods; however, they are combined with other means to produce porosity in the product. Pore-generating techniques include the use of particulate porogens, gas foaming, and/or phase separation methods. Most melt-based technologies involve, in one way or another, the use of molds to produce complex 3D external shapes. These techniques typically include compression molding, extrusion, and injection molding, in addition to several modifications typically for the generation of porosity. They offer several advantages for clinical applications. For instance, scaffolds of any desired shape can be created by simply changing the mold. Moreover, various solid fillers such as hydroxyapatite fibers, as well as bioactive molecules can be employed as additives. However, drawbacks of these techniques include the possibility of excessively high molding temperatures, which can degrade and inactivate the biodegradable polymer or the bioactive molecules.