Annemie Houben

Indirect Rapid Prototyping: Opening Up Unprecedented Opportunities in Scaffold Design and Applications

Over the past decades, solid freeform fabrication (SFF) has emerged as the main technology for the production of scaffolds for tissue engineering applications as a result of the architectural versatility. However, certain limitations have also arisen, primarily associated with the available, rather limited range of materials suitable for processing. To overcome these limitations, several research groups have been exploring novel methodologies through which a construct, generated via SFF, is applied as a sacrificial mould for production of the final construct. The technique combines the benefits of SFF techniques in terms of controlled, patient-specific design with a large freedom in material selection associated with conventional scaffold production techniques. Consequently, well-defined 3D scaffolds can be generated in a straightforward manner from previously difficult to print and even “unprintable” materials due to thermomechanical properties that do not match the often strict temperature and pressure requirements for direct rapid prototyping. These include several biomaterials, thermally degradable materials, ceramics and composites. Since it can be combined with conventional pore forming techniques, indirect rapid prototyping (iRP) enables the creation of a hierarchical porosity in the final scaffold with micropores inside the struts. Consequently, scaffolds and implants for applications in both soft and hard tissue regeneration have been reported. In this review, an overview of different iRP strategies and materials are presented from the first reports of the approach at the turn of the century until now.

Synthetic biodegradable medical polyesters: poly-ε-caprolactone

This chapter reports an overview of poly-e-caprolactone (PCL)-based biomaterials for tissue applications. As a first issue we will discuss the different strategies adopted for the synthesis of this polyester. Successively, we discuss two of the most common techniques used for the preparation of PCL materials for tissue repair (ie, electro-spinning and 3D melt-plotting), together with the mechanical properties and degradation behaviour of such materials. The chapter also includes the issues concerning the hydrophobic nature of the polymer as well as the current surface treatments applied to enhance the biomaterials cell-binding ability. The final section describes the commercially available biomaterials based on this polyester, joint with their clinical applications.This chapter reports an overview of poly-e-caprolactone (PCL)-based biomaterials for tissue applications. As a first issue we will discuss the different strategies adopted for the synthesis of this polyester. Successively, we discuss two of the most common techniques used for the preparation of PCL materials for tissue repair (ie, electro-spinning and 3D melt-plotting), together with the mechanical properties and degradation behaviour of such materials. The chapter also includes the issues concerning the hydrophobic nature of the polymer as well as the current surface treatments applied to enhance the biomaterials cell-binding ability. The final section describes the commercially available biomaterials based on this polyester, joint with their clinical applications.

Indirect Solid Freeform Fabrication of an Initiator-Free Photocrosslinkable Hydrogel Precursor for the Creation of Porous Scaffolds

In the present work, a photopolymerized urethane-based poly(ethylene glycol) hydrogel is applied as a porous scaffold material using indirect solid freeform fabrication (SFF). This approach combines the benefits of SFF with a large freedom in material selection and applicable concentration ranges. A sacrificial 3D poly(ε-caprolactone) structure is generated using fused deposition modeling and used as template to produce hydrogel scaffolds. By changing the template plotting parameters, the scaffold channel sizes vary from 280 to 360 μm, and the strut diameters from 340 to 400 μm. This enables the production of scaffolds with tunable mechanical properties, characterized by an average hardness ranging from 9 to 43 N and from 1 to 6 N for dry and hydrated scaffolds, respectively. Experiments using mouse calvaria preosteoblasts indicate that a gelatin methacrylamide coating of the scaffolds results in an increased cell adhesion and proliferation with improved cell morphology.