Tissue engineering (TE) is an important emerging area in regenerative medicine. In TE, a porous scaffold that accommodates cells, guiding their growth and differentiation in three dimensions is essential. However, existing 3-D scaffolds fabricated using conventional techniques have proven to be less than ideal for actual applications because of deficiencies in mechanical strength, sufficiently sized pore interconnections, and reproducibly controlled variations of porosity and/or morphology within the matrix. To overcome these problems, we have applied an engineering-based scaffold fabrication technique, namely fused deposition modeling (FDM). FDM belongs to the so-called "mold-less" manufacturing operations which are commonly known as solid free-form fabrication (SFF) or rapid prototyping (RP). Ours was the first group which championed the design and fabricated biodegradable scaffolds via FDM. The paper is therefore of great interest and potential benefit to the TE community. It also has considerable significance to the whole field of biomaterials.

The discipline of biomedical engineering translates fundamental knowledge in physics, chemistry, and biology into materials, devices, systems, and strategies to achieve practical benefits. Research on the manufacturing of porous scaffold structures for tissue engineering has been carried out for more then three decades. Conventional techniques include solvent casting, fiber bonding, membrane lamination, etc.

SFF and RP had been applied in the 1990s in order to fabricate complex shaped scaffolds. Unlike conventional machining, which involves constant removal of materials, SFF is able to built scaffolds by selectively adding materials, layer by layer, as specified by a computer program. Each layer represents the shape of the cross-section of the CAD model at a specific level. Today, SFF is viewed as a highly potential fabrication technology for the generation of scaffold technology platforms. In addition, one of the potential benefits offered by SFF technology is the ability to create parts with highly reproducible architecture and compositional variation across the entire matrix due to its computer controlled fabrication. The FDM process offers unique ways to precisely control matrix architecture size, shape, interconnectivity, branching, geometry, and orientation-yielding biomimetic structures of various design and material compositions and also enhances control over the mechanical properties, biologic effects, and degradation kinetics. In addition, computer-aided technologies, medical imaging, and rapid prototyping have created new possibilities in biomedical engineering. FDM is easily automated and integrated with imaging techniques to produce scaffolds which can be customized in overall size and shape allowing tissue-engineered grafts to be tailored to specific applications or even to individual patients.

TE is the application of that knowledge to the building or repairing of tissue and organs. In most cases, tissue engineers use a combination of living cells and a support structure called a scaffold. The process of tissue engineering is that tissues can be isolated from a patient, expanded in tissue culture, and seeded into a scaffold prepared from a biomaterial to form a tissue-engineered construct (TEC). The construct can then be grafted into the same patient to function as a replacement tissue. Blood vessels attach themselves to the new tissue, the scaffold dissolves, and the newly grown tissue eventually blends in with its surroundings. Our group is currently focusing on bone engineering as the need for bone substitutes is of particular importance. Bone substitutes are often required to help repair or replace damaged or diseased tissues, in cases ranging from trauma to congenital and degenerative diseases, to cancer and cosmetic surgeries. There are approximately 3 million surgical procedures performed every year around the world which require bone substitutes. Currently available bone substitutes, including autografts, allografts, and synthetic materials, are the most implanted materials, second only to transfused blood products. We should point out that our FDM scaffold technology platform allows us to create TEC for clinical bone grafting.

  How did you become involved in this research?

Currently, I hold a joint faculty position as a member of both the Bioengineering and Orthopaedic Surgery Departments at the National University of Singapore. Hence, I am interested in translational research with a strong emphasis in moving novel treatment concepts into the clinical environment. Research on the manufacturing of porous scaffold structures for TE has been carried out for more then three decades.

SFF and rapid prototyping RP have been applied in the 1990s to fabricate complex shaped scaffolds. After studying the scaffold literature, we concluded that, unlike conventional machining, which involves constant removal of materials, SFF is able to build scaffolds by selectively adding materials, layer by layer, as specified by a computer program. Each layer represents the shape of the cross-section of the CAD model at a specific level. We concluded that FDM and SFF’s in general have a high potential as fabrication technology for the generation of novel scaffold technology platforms. Based on this background, we did start a major research thrust on the design and fabrication of scaffolds via SFF techniques.