ALTERED MECHANICAL-PROPERTIES IN AORTIC ELASTIC TISSUE USING GLUTARALDEHYDE SOLVENT SOLUTIONS OF VARIOUS DIELECTRIC-CONSTANT/

The extent to which elastic tissue can be crosslinked in aldehydes and the mechanism of such action is unresolved in the literature. We have used glutaraldehyde/solvent solutions of decreasing dielectric consta nt (phosphate buffer, methanol, 95% ethanol, n-propanol, n-butanol) to alter the mechanical properties of aortic elastic tissue obtained fro m autoclaved and CNBr-purified bovine aortae. Treated and untreated ho op samples were examined for stress-strain and stress relaxation behav ior and for residual stress using opening angle experiments as per Fun g. The extent of exogenous crosslinking was analyzed through amino aci d analysis. Mechanical properties of autoclaved elastic tissue varied with dielectric constant in glutaraldehyde/solvent treatments; however , solvent treatment alone produced no effect. Extensibility decreased with decreasing dielectric constant while tensile modulus changed over a range from -2.4% (-0.86 kPa) for glutaraldehyde/buffer to +35.3% (14.3 kPa) for glutaraldehyde/n-propanol (untreated-treated). Residual stress experiments similarly showed a systematic decrease in opening a ngle with decreasing dielectric constant. Differences ranged from 10.5 degrees for glutaraldehyde/buffer to 22.2 degrees for glutaraldehyde/ n-butanol. Interestingly, purification of aortae with CNBr reduced the effects of glutaraldehyde/n-butanol treatment. We hypothesize that CN Br differentially degraded the elastin-associated microfibrillar prote ins in aortic elastic tissue, thus producing the observed differences in mechanical behavior. The observed phenomena in this study may be at tributed to the composite structure of elastic tissue: elastin and mic rofibrillar protein. During treatment, conformational changes in elast in facilitated by polar/nonpolar interactions occurred which then were ''locked'' in by glutaraldehyde crosslinking of the microfibrillar pr oteins. By this mechanism the increases in both stiffness and time-dep endent behavior observed after treatment may be explained. (C) 1997 Jo hn Wiley & Sons, Inc.