Papers by Author: Jan Schrooten

Abstract: The degradation rate of custom made calcium phosphate scaffolds, designed for bone tissue engineering applications, influences the healing process of critical size bone defects. An optimal degradation rate exists at which the neo-formed bone replaces the CaP (calcium phosphate) scaffold [1]. Consequently investigating the complex degradation behavior (dissolution, reprecipitation, osteoclast activity) of custom made CaP structures gains interest. In this work different in vitro dissolution experiments were performed to study the degradation behavior of 4 by composition different calcium phosphates. Ideally these experiments should have a predictive power regarding the in vivo degradation behavior. In vitro dissolution tests still lack standardization. Therefore this study focuses on the influence of two dissolution constraints: (i) the material’s macrostructure (porous - dense), (ii) the regenerated fluid flow (bath shaking - perfusion). From 4 different CaP compositions porous structures and as a reference dense disks were produced, using the same starting powder and heat treatment. To compare the different dissolution tests, all data was normalized to the CaP surface area. Results show that besides the structural appearances of the CaP structures, also the design of the dissolution test influences the in vitro dissolution behavior. Moreover there is a need to take the morphology of the dissolved material into account. The CaP perfusion tests show dissolution dynamics that resemble the in vivo reality more closely than the shaking bath experiments.

Abstract: Tissue engineering (TE) aims/seeks to achieve the substitution of organ transplantation by the creation of living, functional tissues. It has been suggested that biocompatible porous materials (scaffolds) and a controllable 3D environment are required to aid in the 3D cell organisation and their development into functional tissue. Our research envisions a TE-approach towards the repair of large, load bearing defects in long bones. In vitro standardised, systematic, quantitative screening of potential bone scaffolds is required to understand how scaffolds can affect cell behaviour. This screening will avoid a trial-and-error approach and thus limit the number of animal experiments. Such a screening should be based on the knowledge of mechanical, physical and (bio)chemical scaffold properties and their interaction with cell behaviour. In addition, the design and production of a clinically relevant scaffold requires control over its mechanical behaviour and a new approach for cell seeding in a 3D scaffold, as well as providing nutrition for the engrafted cells. The objective of this research is to gain substantial knowledge about guided bone regeneration and to develop quantitative methodologies that can lead to consistent and reproducible bone regeneration.

Abstract: There are only limited ways to improve the interface bond strength of SMA wire reinforced composites. In this paper, the effect of the additional reinforcing fibers on the interface debond temperature of a TiNiCu wire reinforced epoxy matrix composite was studied. It was shown that the Kevlar fiber composite had a better interface between the TiNiCu wire and the epoxy matrix than that in the glass fiber composite. The negative thermal expansion coefficient of the Kevlar fibers were thought to be beneficial for relieving the thermal stresses at the SMA/epoxy interface. From this angle of view, the Kevlar fiber composites are better candidates as the matrix of the SMA composites than the glass fiber composites.