title: Collagen and bone viscoelasticity: a dynamic mechanical analysis.
abstract: The purpose of this study was to explore the effects of changes in Type I collagen on the viscoelasticity of bone. Bone coupons were heated at either 100 or 200 degrees C to induce the thermal denaturation of Type I collagen. Half of these specimens were rehydrated after heat treatment; the other half were tested in a dry condition. The degree of denatured collagen (DC%) was analyzed by a selective digestion technique with the use of alpha-chymotrypsin. Isothermal (37 degrees C) and variable temperature tests (scans from 35 to 200 degrees C) were performed with the use of a dynamic mechanical analyzer to evaluate changes in bone viscoelastic properties as a function of collagen damage, specifically, changes in the loss factor (tan delta) and storage modulus (E') were assessed. Significant collagen denaturation occurred only when bone was heated at 200 degrees C irrespective of the hydration condition. Also, DC% did not show a significant effect on tan delta. However, higher values of tan delta were observed in wet samples compared to dry specimens. The temperature-scan tests revealed that the hydration condition, but not DC%, significantly affected the behavior of tan delta. However, E' was not strongly influenced either by DC% or by water content. These results suggest that at a constant frequency the denaturation of collagen triple-helical molecules may have few effects on the viscoelasticity of bone, but moisture may play a prominent role in determining this property.
authors.affiliation: Center for Clinical Bioengineering, The University of Texas Health Science Center, San Antonio, Texas 78284, USA.
authors.forename: Junro
authors.initials: J
authors.lastname: Yamashita
authors.forename: Xiaoe
authors.initials: X
authors.lastname: Li
authors.forename: Benjamin R
authors.initials: BR
authors.lastname: Furman
authors.forename: H Ralph
authors.initials: HR
authors.lastname: Rawls
authors.forename: Xiaodu
authors.initials: X
authors.lastname: Wang
authors.forename: C Mauli
authors.initials: CM
authors.lastname: Agrawal
mesh_terms: D001696:Biomechanical Phenomena; D001834:Body Water; D001842:Bone and Bones / Q000737:chemistry*; D002918:Chymotrypsin / Q000494:pharmacology; D003094:Collagen / Q000737:chemistry* / Q000187:drug effects; D003890:Desiccation; D004548:Elasticity; D006358:Hot Temperature; D006801:Humans; D011489:Protein Denaturation; D013314:Stress, Mechanical; D014783:Viscosity
chemical_list: D003094:Collagen; D002918:Chymotrypsin; C117608:alpha-chymotrypsin