THERMOMECHANICAL ANALYSIS OF COLLAGEN CROSS-LINKING IN THE DEVELOPINGLAMB PERICARDIUM

In a developing lamb model, we have used hydrothermal isometric tensio n (HIT) techniques to assess collagen crosslink stability and its cont ribution to the mechanical properties of the pericardium. Strip sample s of tissue were either: (i) heated to a 90 degrees C isotherm or (ii) heated in 5 degrees C increments between 60-90 degrees C and then 93 and 97 degrees C isotherms. This half-life of stress relaxation associ ated with peptide bond hydrolysis (t(1/2)) was calculated at each isot herm. The activation energy, E-act, for the hydrolysis-associated rela xation process was also calculated using the data from the stepwise HI T tests-a technical improvement which significantly reduces the experi mental time required to develop statistically valid measurements. Cros slinking in the pericardium increased during development and was demon strated both by thermoelasticity and by resistance to enzymatic solubi lization. We observed greater conversation to thermally stable crossli nks upon maturation, the ratio of the NaBH4-stabilized/unstabilized ha lf-lives peaking at 21 days postnatal. Whereas tissue from lambs (119 day fetal, and 3 day and 21 day postpartum) showed an early maximum an d rapid decay of force, NaBH4 stabilization significantly increased th ermal stability and yielded profiles similar to those in adult tissue. (C) 1998 Elsevier Science Ltd.