Solvent environment modulates effects of glutaraldehyde crosslinking on tissue-derived biomaterials

Abstract

Bioprosthetic materials utilized in the construction of heart valves and vascular grafts possess limited performance and viability in vivo. This is due (in part) to the failure of these materials to mimic the mechanical properties of the host tissue they replace. If bioprosthetic materials could be engineered to meet the mechanical performance required in vivo, the functional lifetime of implants would be increased. In this study, glutaraldehyde/solvent solutions of decreasing dielectric constant (polarity) were utilized to modify the properties of crosslinked collagen in whole bovine pericardial tissue. Solvents included phosphate buffer, methanol, 95% (w/w) ethanol, n-propanol, and n-butanol. Exogenous crosslinking was verified in collagen by thermal denaturation tests and amino acid analyses. Tensile mechanical behavior of collagenous pericardial samples was found to depend upon the dielectric constant (polarity) of the glutaraldehyde/solvent solutions employed; however, treatment in the solvents alone had little, if any, effect. As the dielectric constant of the solvents decreased, three mechanical properties were systematically altered: plastic strain fell from a mean of 8.9 +/- 1.5% (buffer) to 1.6 +/- 0.4% (n-butanol); strain at fracture increased from 32.2 +/- 2.6% (buffer) to 55.6 +/- 4.6% (n-butanol); and percent stress remaining after 1000-s stress relaxation from an 80-g initial load fell from 86.3 +/- 1.1% (buffer) to 76.9 +/- 1.0% (n-butanol). Crosslinking using a glutaraldehyde/n-butanol solution produced materials with tensile mechanical behavior that was very close to that of fresh tissue; however, the flexural properties of the treated tissue were different from those of fresh tissue. This decoupling of the flexural and tensile mechanical behaviors of crosslinked bioprosthetic materials is unique to this form of treatment. The observed phenomena may be the results of conformational changes in collagen facilitated by polar/nonpolar interactions with the solvent that are "locked in" by the action of glutaraldehyde. This technique may aid in the "customized" design of mechanical properties in tissue-derived biomaterials.

High-concentration glutaraldehyde fixation of bovine pericardium in organic solvent and post-fixation glycine treatment: in vitro material assessment and in vivo anticalcification effect☆

“…_ 6 ) T D $ F I G ] additional fixation using 2% GA in organic solvent (mixture of 65% ethanol and 5% 1-octanol) was performed. Cross-linking of bovine pericardium using GA in pure organic solvent environment produced optimal cross-linking and produced materials with tensile mechanical behavior that was very close to that of fresh pericardium, and this phenomenon was hypothesized to be the result of conformational changes in collagen facilitated by polar/non-polar interactions with the solvent that are locked in by the action of glutaraldehyde [22]. In our study, tensile strengths of differently treated bovine pericardial tissue (groups 1-4) were not significantly different from that of fresh pericardial tissue.…”

Diamine extension of glutaraldehyde crosslinks mitigates bioprosthetic aortic wall calcification in the sheep model

“…The loss of pliability is one of the best-documented mechanisms for bioprosthetic valve failure, 21 and glutaraldehyde is well known for its concentration-dependent effect on tissue stiffness. Although it recently was shown that solvent conditions are capable of modulating tissue stiffness, 22 it remains the most likely limitation to increasing glutaraldehyde concentrations for tissue fixation. Therefore, it seems more appropriate to extrapolate the principle of better crosslinking to modern fixation approaches than to propagate the use of high concentrations of glutaraldehyde itself.…”

Mechanical, thermal and morphological properties of glutaraldehyde crosslinked bovine pericardium followed by glutamic acid treatment

“…To minimize these problems, besides the classical procedure using glutaraldehyde (GA) many alternative processes were introduced for the manufacture bioprosthetic heart valves (BHV) and includes the crosslinking with azide 3 , epoxydes 4 , carbodiimides 5 and diisocyanates 6 , the treatment with GA in non-aqueous solvents 7 , diphosphonates 8 and α-amino oleic acid treatment 9 .…”