Effects of chemical and physical deimmunogenicity methods on the biological and biomechanical properties of allogeneic tendons.

To compare the differences in biological and biomechanical characteristics of cadaver tendon treated by deep freezing, 95wt.% ethanol, tributyl phosphate (TBP), and sodium dodecyl sulfate (SDS) respectively. A total of 50 fresh tendon specimens were randomly divided into five groups, and four groups were treated with deep freezing (- 80 °C), 95wt.% ethanol, 1% TBP, or 1% SDS, respectively. Hematoxylin-eosin (HE), toluidine blue (TB) and 4',6-diamidino-2-phenylindole (DAPI) staining, and transmission/scanning electron microscope observations were performed. Then, cyclic creep and tensile tests were conducted to investigate the biomechanical properties. The content of residual DNA was tested. The HE, TB and DAPI staining showed a significant decrease in tendon cells following treatments, compared with fresh specimens. SDS, TBP, alcohol can almost completely decellularize the tendon, and deep-frozen group remained a few number of tendon cells. The residual DNA content was significantly lowered, with an average percentage of 50.97%, 79.16%, 88.91% and 72.56%, for groups of deep freezing, alcohol, TBP and SDS, respectively. The arrangement of collagen fibers was significantly disrupted, and the gap between fibers was widened, following treatments by alcohol, TBP and SDS. However, the biomechanical properties were generally similar among the five groups, with significantly lowered cyclic creep for ethanol group and lowered Young's modulus for SDS group exclusively. The four treatments can effectively reduce the number of residual cells and DNA content. Among them, cryogenic treatment has almost no damage to tendon histology and biomechanics, while ethanol, SDS and TBP decellularization methods cause different degrees of damage.