Mw Marcel Wijlaars

Deformation-controlled load application in heart valve tissue engineering.

In cardiovascular tissue engineering, mechanical stimulation of tissue-engineered constructs is known to improve tissue properties. During tissue culture, the mechanical properties of the tissue construct change. To impose a predefined deformation protocol and to avoid negative effects of excessive strain, it is desired to monitor and control deformations during load application. In a previous study, load application and resulting deformation of tissue-engineered heart valve leaflets were monitored during culture inside a bioreactor in real time and noninvasively. A combined experimental-numerical approach was applied to assess volumetric and local leaflet deformation of the cultured heart valve in a diastolic configuration. In this study, this approach was further developed and a feedback controller to regulate deformation was incorporated into the bioreactor system. Functionality of this technique was demonstrated in two tissue engineering experiments in which a total of eight heart valves were cultured by application of two different deformation protocols. Results indicated a good correspondence between the measured and the prescribed deformation values in both experiments. In addition, the cultured heart valves showed mechanical properties in the range of previous tissue engineering studies. The bioreactor system including the deformation measurement and control features has promising possibilities of systematically elucidating the effects of loading protocols on tissue properties. In conclusion, it facilitates the development of an optimal conditioning protocol for tissue engineering of aortic heart valves.

Measurements of deformations and electrical potentials in a charged porous medium

When a biological tissue is subjected to a mechanical load, an electrical potential gradient is generated. Such potential gradient is associated with the flow of charged particles through a matrix with fixed charges. A deformation of the matrix causes a fluid flow relatively to the solid matrix. This fluid flow tends to separate the freely moving ions in the fluid from the oppositely charged particles, that are attached to the matrix. In this way, an electrical field is created collinear to the fluid flow. This results in an electrical potential. A similar effect appears when charged particles start moving because of a chemical load.