Age Dependent Differences in Collagen Alignment of Glutaraldehyde Fixed Bovine Pericardium

Abstract

Bovine pericardium is used for heart valve leaflet replacement where the strength and thinness are critical properties. Pericardium from neonatal animals (4–7 days old) is advantageously thinner and is considered as an alternative to that from adult animals. Here, the structures of adult and neonatal bovine pericardium tissues fixed with glutaraldehyde are characterized by synchrotron-based small angle X-ray scattering (SAXS) and compared with the mechanical properties of these materials. Significant differences are observed between adult and neonatal tissue. The glutaraldehyde fixed neonatal tissue has a higher modulus of elasticity (83.7 MPa) than adult pericardium (33.5 MPa) and a higher normalised ultimate tensile strength (32.9 MPa) than adult pericardium (19.1 MPa). Measured edge on to the tissue, the collagen in neonatal pericardium is significantly more aligned (orientation index (OI) 0.78) than that in adult pericardium (OI 0.62). There is no difference in the fibril diameter between neonatal and adult pericardium. It is shown that high alignment in the plane of the tissue provides the mechanism for the increased strength of the neonatal material. The superior strength of neonatal compared with adult tissue supports the use of neonatal bovine pericardium in heterografts.

Poisson's ratio of collagen fibrils measured by small angle X-ray scattering of strained bovine pericardium

“…For collagen in bovine pericardium, at low strain, the Poisson's ratio appears to have a very high value (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27), but for strain above 0.09, the Poisson's ratio is in the range 2.1-2.8. For the total strain (from 0 to 0.25), the change in d-spacing and diameter gives 0 ¼ 2.1 6 0.7 (these values of 0 can be calculated from Fig.…”

“…Bovine pericardium is used as a model material for this work because it is elastic and strong and has application in medical devices. 21 …”

Evaluation of transcatheter heart valve biomaterials: Biomechanical characterization of bovine and porcine pericardium

“…An attractive aspect of using GL-treated PP tissue for TAV leaflet fabrication lies in its lower thickness (~ 0.14–0.2 mm) compared to GL-treated BP (~ 0.32–0.42 mm). Similarly, younger BP has also been shown to be thinner than older BP [5], giving it a potential physical advantage for TAV production. It is important to note that the thickness of pericardium leaflet tissues are not only of crucial importance for TAV delivery, but also for the performance and long-term durability of the valve, where the use of thinner tissues may compromise the structural integrity of the device.…”

“…To the authors’ knowledge, the only published study that has compared the mechanical response of younger, thinner BP with thicker, older BP tissue was performed by Sizeland et al [5] through uniaxial testing. However, uniaxial mechanical testing is non-physiologic for soft tissues, as the coupling between the tissue’s directional responses is ignored.…”

Transcatheter Heart Valve Crimping and Expansion: Commentary

“…Endothelialisation of the flow surfaces and utilization of induced human pluripotent stem cells (iPSCs) necessitate more research while patients deserve immediate treatments [31]. Currently, the durability is mostly attained with preservation of the geometry of the valves with pericardium of young animals [32]. Hemodynamic deficits must be avoided.…”