AVS 46th International Symposium
    Biomaterial Interfaces Group Wednesday Sessions
       Session BI-WeM

Paper BI-WeM10
Mechanical Properties of a Bone Marrow Cell-Knit Composite for Tissue Engineering: Evolution under Mechanical Load

Wednesday, October 27, 1999, 11:20 am, Room 613/614

Session: Cell Solid-Surface Interactions
Presenter: B. Müller, ETH Zürich, Switzerland
Authors: B. Müller, ETH Zürich, Switzerland
G. Ettel, ETH Zürich, Switzerland
D. Siragusano, ETH Zürich, Switzerland
T. Brandsberg, ETH Zürich, Switzerland
F. Brandsberg, ETH Zürich, Switzerland
M. Petitmermet, ETH Zürich, Switzerland
A. Bruinink, ETH Zürich, Switzerland
J. Mayer, ETH Zürich, Switzerland
E. Wintermantel, ETH Zürich, Switzerland
Correspondent: Click to Email
Knitted textiles provide a 3D scaffold for optimal spatial and nutritional conditions in engineering biological tissue in vitro. The vital-avital composite formed by the textile fabric and the ingrown cells can be stimulated by mechanical load. Introduced by cyclic stretching it affects the proliferation and differentiation of bone cells as indicated by specific protein synthesis and cell mass increase. As an additional parameter, the evolution of the mechanical properties of the vital-avital composite is in situ measured by a piezoelectric force sensor. The system for the stimulation of in vitro cell cultures is calibrated by the use of a coil spring minimizing frictional losses. Reference measurements are performed using multifilament PET-knits as untreated ones and others saturated with serum proteins. After autoclaving and under constant load, both types of knits show an exponential run-in behavior with a time constant of about 2h. In the frequency range investigated (0.1 to 3.0Hz) the amplitude raise lies between 10 and 15%. Long-term experiments (5 days) with cyclic mobile and immobile phases of 3 and 6 hours, respectively exhibit a linear decrease of 5% in amplitude for the protein saturated knits, however. Finally, the preliminary experiments using primary adult rat bone marrow cells demonstrate that the stiffness of the vital-avital composite increases by a power law as a result of mechanical stimulation (Stretching is as low as 2%). Therefore, the successive force measurements reflect the physiological mechanical state of the cells and, consequently, enable optimizing the properties of the forming tissue. Determinants are the cell density, the stretching, the frequency of mechanical excitation, and the time span for mobile and immobile phases. A mathematical model developed on the basis of nonlinear mesoscopic elasticity theory describes the experimental observations.