Viscoelastic Testing Methodologies for Tissue Engineered Blood Vessels
Joseph Berglund, Robert Nerem and Athanassios Sambanis
Journal of Biomech Engineering 2005 Vol 27

http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JBENDY000127000007001176000001&idtype=cvips&gifs=yes


Matching the complex mechanical behavior of native blood vessels is one of several obstacles in creating a suitable tissue engineered blood vessel. Many of the TE vessel mechanical testing methodologies have used single-point burst pressures measurements and uniaxial tensile testing as an indication of mechanical suitability. However,since blood flow is a pulsatile behavior, and native blood vessels exhibit a time-varying behavior, other methods are needed to correctly characterize the mechanical properties of TE vessels. In addition to performing uniaxial tensile testing, this paper reports the use of viscoelastic characterization methods to model the time-dependent behavior of TE and native vessels.

TE vessels were made from rat collagen (2 mg/ml) and human dermal fibroblast (1 x 106 cells/ml). TE vessels were made to form a tubular structure with a 3mm inside diameter. Some TE vessels were combined with acellular support sleeves made from untreated and glutaraldehyde crosslinked collagen. Common carotid arteries were taken from 1 to 2 year old pigs.

Uniaxial tensile testing was used to measure overall strength (ultimate tensile strength). Stepwise stress relaxation and creep testing was performed (for more details see paper link). Mathematical modeling, using 3 and 4 parameter constitutive, models was used to characterize stress relaxation and creep data.

This paper also reports geometrical changes for all samples after 8 and 23 days in culture. Interestingly, this study found that the addition of acellular support sleeves had minimal effect on gel compaction. However, a difference in mechanical properties was observed amoung the samples. The Glutaraldehyde treated vessel constructs exhibited the highest burst strength but were still inferior to the native arteries. The untreated vessel constructs seemed to match the overall behavior of the native vessels the best.

I chose this article because it provides a framework for characterizing the mechanical suitability of TE vessels. It also illustrates the use of mathematical models which is something of interest to me.