The bovine pericardial xenograft: III. Effect of uniaxial and sequential biaxial stress during fixation on the tensile viscoelastic properties of bovine pericardium

Abstract

Our previous two articles have shown that glutaraldehyde-fixed bovine pericardium is nearly isotropic, whether fixed without constraints, with tethering, or with pressure. In this study, we have used uniaxial stress during fixation to produce bovine pericardial material with marked tensile anisotropy. Rectangular and cruciate pericardial samples have been mechanically examined after one of four treatments: (i) fixation under 88-kPa uniaxial stress, (ii) fixation under 176-kPa uniaxial stress, (iii) 3 h of 176-kPa uniaxial stress in saline followed by 24-h fixation under the same stress, (iv) fixation under 176-kPa uniaxial stress followed by a second fixation under 176-kPa stress in a direction normal to the first. Strips of material were cut at 0 degree, 30 degrees, 60 degrees, and 90 degrees to direction of the initial stress, and tested for response to cyclic loading, stress relaxation, plastic deformation, and fracture properties. Fixation under uniaxial stress produced anistropy similar to that seen in porcine aortic valve leaflets; however, the overall extensibility of the material depended on the applied stress and the aspect ratio of the stressed sample. While loading in saline produced no change, the sequential biaxial stressing produced a reduction in anisotropy, suggesting exposure of additional crosslinking sites. Uniaxial stress during fixation may be a useful method for construction of anisotropic heart valve leaflets.

Effect of cyclic deformation on xenogeneic heart valve biomaterials

“…Previous reports detailing the immediate effects of glutaraldehyde fixation indicate that specifics of the fixative process (e.g., free vs tethered), material orientation (e.g., circumferential vs longitudinal) and pressures (e.g., high vs low) may alter the material’s mechanical properties by cross-linking elastin and collagen fibers [37–39]. Specifically, pressure fixation has been associated with variable degrees of tissue shrinkage and flattening of collagen crimping depending on the stress imposed [37, 40]. Although the fixative process of the material assessed in this manuscript is proprietary, it is known to be fixed under low pressure and as expected pre-cycling histology images demonstrate flattening of the collagen crimps.…”

“…Although the fixative process of the material assessed in this manuscript is proprietary, it is known to be fixed under low pressure and as expected pre-cycling histology images demonstrate flattening of the collagen crimps. The process of fixation, even under low pressure, imposes a pre-stress on the material [37–40]. The observed negative longitudinal cycle dependent strain of glutaraldehyde-fixed bovine pericardium is likely due to release of the pre-stress imposed by the pressure fixation process, allowing the material to contract.…”

Biomechanical Restoration Potential of Pentagalloyl Glucose after Arterial Extracellular Matrix Degeneration

“…Enzymatic damage introduces some degree of changes to the ECM and in many cases, a change in anisotropic behavior was observed in porcine arterial tissues [30]. To measure these changes in the mechanical anisotropy, we calculated the anisotropy index (AI, illustrated in Figure 2B) according to Equation (4) [39,40], Anisotropy Index (AIn) = abs(εa−εb)[εa+εb2]| Rn…”

“…( A ) Schematic for calculation of area under the curve (AUC) and maximum tensile stress (σmax). ( B ) Procedure for calculation of anisotropy index (AI) at each reference stress level, as reported in [39,40]. The reference stresses for each specimen were calculated by estimating 33rd, 66th, and 95th percentiles of σmax in each stress–strain curve.…”

Comparison of Autogenous Cartilage, Acellular Dermis, and Solvent-Dehydrated Pericardium for the Prevention and Correction of Dorsal Nasal Irregularities: An Experimental Study

“…SDP (solvent-preserved, gamma-sterilized bovine pericardium; Tutoplast, Tutogen Medical, West Patterson, NJ, USA) is an allograft used for orbital reconstruction, ophthalmic surgery, tympanoplasty, duraplasty, closure of nasal septal perforations, suspension procedures in facial palsy, filling of parotidectomy defects, hernia repairs, corporoplasty, and Peyronie's disease [23][24][25][26][27][28][29][30][31]. SDP is quite stable, permeable to antibiotics, soft and flexible, easily sutured, and easily integrated into the recipient tissues [28,30,32]. SDP has not been used as an onlay graft for the nasal dorsum but these properties suggest that it may be quite suitable and satisfactory for this region.…”