title: Swelling of Collagen-Hyaluronic Acid Co-Gels: An In Vitro Residual Stress Model.
abstract: Tissue-equivalents (TEs), simple model tissues with tunable properties, have been used to explore many features of biological soft tissues. Absent in most formulations however, is the residual stress that arises due to interactions among components with different unloaded levels of stress, which has an important functional role in many biological tissues. To create a pre-stressed model system, co-gels were fabricated from a combination of hyaluronic acid (HA) and reconstituted Type-I collagen (Col). When placed in solutions of varying osmolarity, HA-Col co-gels swell as the HA imbibes water, which in turn stretches (and stresses) the collagen network. In this way, co-gels with residual stress (i.e., collagen fibers in tension and HA in compression) were fabricated. When the three gel types tested here were immersed in hypotonic solutions, pure HA gels swelled the most, followed by HA-Col co-gels; no swelling was observed in pure collagen gels. The greatest swelling rates and swelling ratios occurred in the lowest salt concentration solutions. Tension on the collagen component of HA-Col co-gels was calculated from a stress balance and increased nonlinearly as swelling increased. The swelling experiment results were in good agreement with the stress predicted by a fibril network + non-fibrillar interstitial matrix computational model.
authors.affiliation: Department of Chemical Engineering, University of Minnesota, Duluth, MN, USA.
authors.forename: Victor K
authors.initials: VK
authors.lastname: Lai
authors.affiliation: Department of Biomedical Engineering, University of Minnesota - Twin Cities, 7-105 Nils Hasselmo Hall, 312 Church St. SE, Minneapolis, MN, 55455, USA.
authors.forename: David S
authors.initials: DS
authors.lastname: Nedrelow
authors.affiliation: Department of Mechanical Engineering & Materials Science, Washington University in St. Louis, St. Louis, MO, USA.
authors.forename: Spencer P
authors.initials: SP
authors.lastname: Lake
authors.affiliation: Department of Biomedical Engineering, University of Minnesota - Twin Cities, 7-105 Nils Hasselmo Hall, 312 Church St. SE, Minneapolis, MN, 55455, USA.
authors.forename: Bumjun
authors.initials: B
authors.lastname: Kim
authors.affiliation: Department of Biomedical Engineering, University of Minnesota - Twin Cities, 7-105 Nils Hasselmo Hall, 312 Church St. SE, Minneapolis, MN, 55455, USA.
authors.forename: Emily M
authors.initials: EM
authors.lastname: Weiss
authors.affiliation: Department of Biomedical Engineering, University of Minnesota - Twin Cities, 7-105 Nils Hasselmo Hall, 312 Church St. SE, Minneapolis, MN, 55455, USA.|Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN, USA.
authors.forename: Robert T
authors.initials: RT
authors.lastname: Tranquillo
authors.affiliation: Department of Biomedical Engineering, University of Minnesota - Twin Cities, 7-105 Nils Hasselmo Hall, 312 Church St. SE, Minneapolis, MN, 55455, USA. baroc001@umn.edu.
authors.forename: Victor H
authors.initials: VH
authors.lastname: Barocas
mesh_terms: D024042:Collagen Type I / Q000737:chemistry*; D005782:Gels; D006820:Hyaluronic Acid / Q000737:chemistry*; D008962:Models, Theoretical; D013314:Stress, Mechanical
chemical_list: D024042:Collagen Type I; D005782:Gels; D006820:Hyaluronic Acid
keywords: Biomechanics; Donnan; Fiber; Multiscale; Network; Osmotic; Pre-stress; Tissue