Interaction of Cartilage Biopolymers

Section on Tissue Biophysics and Biomimetics, NICHD, National Institutes of Health, 13 South Drive, Bethesda, MD 20892, USA E-mail: [email protected] Summary: Aggrecan is a charged biopolymer whose complexes with hyaluronic acid provide the compressive resistance of cartilage. In cartilage extracellular matrix aggrecan-hyaluronic acid complexes are enmeshed within a network of collagen fibrils. Osmotic pressure measurements and small angle neutron scattering (SANS) measurements are reported on solutions of aggrecan and aggrecan-hyaluronic acid complexes. These techniques probe the length scales relevant to the biological functions of cartilage. Osmotic pressure measurements indicate that dissolved aggrecan monomers form microgel-like assemblies. The osmotic pressure of aggrecan-hyaluronic acid complexes decreases with decreasing the ratio of aggrecan to hyaluronic acid. SANS reveals that there is no significant interpenetration between the neighboring aggrecan molecules. Both osmotic pressure measure­ ments and SANS indicate weak interactions between the aggrecan bottlebrushes and collagen fibers.