Cryopreservation is used to preserve cells and tissues at low temperatures for short and long term uses. Some examples of where cryopreservation is used include the storage of organs, blood, embryos, and artificial tissues. A current challenge of cryopreservation is being able to understand and quantify the effects of freezing/thawing on the functional properties of tissues such as mechanical properties. This study investigated the changes in viscoelastic parameters of engineered tissues before and after freezing by performing creep-relaxation tests using a dynamic mechanical analyzer. Three types of engineered tissues were studied with varying cell and collagen concentrations for two different cell types, human dermal fibroblast (BR5) and breast cancer cells (MCF-7). The three types of engineered tissues include 3mg/ml of collagen with 200,000 cells/ml, 3mg/ml of collagen with 400,000 cells/ml, and 6mg/ml of collagen with 200,000 cells/ml. A Kelvin-Voigt model was used to characterize the viscoelastic properties of the engineered tissue. The viscoelastic properties of all engineered tissues were evaluated and compared to characterize the effects of freeze/thaw, cell concentration, collagen concentration and cell types. The results were discussed considering the structural changes of the extracellular matrix due to each parameter.
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