Neomycin and pentagalloyl glucose enhanced cross-linking for elastin and glycosaminoglycans preservation in bioprosthetic heart valves

Abstract

Glutaraldehyde cross-linked bioprosthetic heart valves fail within 12–15 years of implantation due to limited durability. Glutaraldehyde does not adequately stabilize extracellular matrix components such as glycosaminoglycans and elastin, and loss of these components could be a major cause of degeneration of valve after implantation. We have shown earlier that neomycin-based cross-linking stabilizes glycosaminoglycans in the tissue but fails to stabilize elastin component. Here, we report a new treatment where neomycin and pentagalloyl glucose (PGG) were incorporated into glutaraldehyde cross-linking neomycin-PGG-Glutaraldehyde (NPG) to stabilize both glycosaminoglycans and elastin in porcine aortic valves. In vitro studies demonstrated a marked increase in extracellular matrix stability against enzymatic degradation after cross-linking and 10 month storage in NPG group when compared to glutaraldehyde controls. Tensile properties showed increased lower elastic modulus in both radial and circumferential directions in NPG group as compared to glutaraldehyde, probably due to increased elastin stabilization with no changes in upper elastic modulus and extensibility. The enhanced extracellular matrix stability was further maintained in NPG-treated tissues after rat subdermal implantation for three weeks. NPG group also showed reduced calcification when compared to glutaraldehyde controls. We conclude that NPG cross-linking would be an excellent alternative to glutaraldehyde cross-linking of bioprosthetic heart valves to improve its durability.

Comparison of physical and biological properties of CardioCel® with commonly used bioscaffolds

“…Both PhotoFix and CorMatrix recorded a Td significantly lower than the 3 GA-cross-linked tissues. The mean obtained for CorMatrix (57.88 C) is similar to what has been reported previously for porcine valve leaflets (approximately 56 C) [21], which is presumably lower than normal BP (62.8 C) [22] because of species and/or tissue-specific differences. However, the Td of PhotoFix (53.96 C) was also lower than un-cross-linked BP, and it is possible that an aspect of the processing of PhotoFix may explain these results, as has been suggested in studies of other products [15].…”

A novel crosslinking method for improved tear resistance and biocompatibility of tissue based biomaterials

“…T d has been shown to effectively correlate with tissue collagen stabilization [6]. Both GLUT and TRI treated leaflets showed adequate increase in T d (88 ± 1.2°C or 89 ± 0.9°C, respectively compared to fresh tissue 56± 3.2 °C [6]), suggesting complete collagen stabilization (Figure 1A). …”

“…Fresh leaflets were treated with 0.6% glutaraldehyde in 50 mM 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) buffered saline (pH 7.4) at room temperature with gentle shaking for 24 hours, solution decanted, and replaced with 0.2% glutaraldehyde in 50 mM HEPES buffered saline (pH 7.4) and the crosslinking was continued for at least six days [6]. …”

“…Following 24 hours incubation, leaflets were washed in distilled water 3x for 5 min, frozen, and lyophilized. Total hexosamine content was measured using the hexosamine assay as previously reported [6]. Elson and Morgan’s modified hexosamine assay was used to measure GAG-related hexosamines [18].…”

“…Facing the opposite side towards the ventricle, the ventricularis contains radially aligned elastin along with collagen. Elastic fibers are coupled with collagen bundles and brings the collagen fiber structure back to a resting configuration between loading cycles, thus the ventricularis provides elasticity and recoil to the leaflet [6–9]. Between the fibrosa and ventricularis lies the spongiosa that primarily contains glycosaminoglycans (GAGs).…”