Computer Aided Tissue Engineering Scaffolds

Abstract

A novel CAD system of structures based on convex polyhedral units has been created for use with rapid prototyping (RP) technology in tissue engineering applications. The prototype system is named the Computer Aided System for Tissue Scaffolds or CASTS. CASTS consists of a basic library of units that can assemble uniform matrices of various shapes. Each open-cellular unit is a unique configuration of linked struts. Together with an algorithm which allows the designer to specify the unit cell and the required dimensions, the system is able to automatically generate a structure that is suitable for the intended tissue engineering application. Altering the parameters can easily change the desired shape and spatial arrangement of the structures. The main advantage of CASTS is the elimination of reliance on user skills, much unlike conventional techniques of scaffold fabrication. From a small range of basic units, many different scaffolds of controllable architecture and desirable properties can be designed. The system interface of CASTS in Pro/ENGINEER is user friendly and allows complete transfer of knowledge between users without the need for complex user manuals. A femur implant was successfully fabricated using selective laser sintering (SLS) and a standard commercial material Duraform™ polyamide. However, it was seen that there was some raw powder trapped inside the concept model and further investigations were carried out to minimise the incidence of trapped powder in the scaffolds. A disc shape scaffold was designed for this purpose. In this disc-shaped design, four different strut lengths were used, resulting in four different pore sizes and porosity. Scaffolds of the one-unit layer cells built using Duraform™ polyamide were then examined under a light microscope to check the consistency and reproducibility of the microstructures. Three types of biomaterials were tested on CASTS: PEEK, PEEK-HA biocomposite, and PCL. The scaffolds built showed very good definition of the pre-designed microarchitecture and were readily reproducible. While delamination occurred at larger unit cell sizes, this had no effect on the overall shape or the structural integrity of the scaffolds. The potential of this system lies in its ability to design and fabricate scaffolds with varying properties through the use of different unit cells and biomaterials to suit different tissue engineering applications.