title: Viscosity changes in hyaluronic acid: irradiation and rheological studies.
abstract: Hyaluronic acid (HA) is a significant component of the extracellular matrix (ECM), particular interest being shown herein in synovial fluid. The present study aims to investigate the degrading effects of X-ray radiation on HA at radiotherapy doses. Measurements of viscosity and shear stresses on HA solutions have been made at different shear rates using various types of viscometer for different concentrations in the range 0.01-1% w/v of HA. The HA has been subjected to doses of 6 MV photon radiation ranging from 0 to 20 Gy, the major emphasis being on doses below 5 Gy. It is found that there is a dose-dependent relationship between viscosity and shear rate, viscosity reducing with radiation dose, this being related to polymer scissions via the action of radiation-induced free radicals. The dependency appears to become weaker at higher concentrations, possibly due to the contribution to viscosity from polymer entanglement becoming dominant over that from mean molecular weight. Present results, for HA solutions in the concentration range 0.01% to 1% w/v, show reduced viscosity with dose over the range 0-4 Gy, the latter covering the dose regime of interest in fractionated radiotherapy. The work also shows agreement with previous Raman microspectrometry findings by others, the possible bond alterations being defined by comparison with available published data.
authors.affiliation: Department of Physics, University of Surrey, Guildford, Surrey, UK. e.daar@surrey.ac.uk
authors.forename: Eman
authors.initials: E
authors.lastname: Daar
authors.forename: L
authors.initials: L
authors.lastname: King
authors.forename: A
authors.initials: A
authors.lastname: Nisbet
authors.forename: R B
authors.initials: RB
authors.lastname: Thorpe
authors.forename: D A
authors.initials: DA
authors.lastname: Bradley
mesh_terms: D004307:Dose-Response Relationship, Radiation; D055119:Elastic Modulus / Q000528:radiation effects; D006820:Hyaluronic Acid / Q000737:chemistry* / Q000528:radiation effects*; D008422:Materials Testing; D008970:Molecular Weight; D011829:Radiation Dosage; D033081:Shear Strength / Q000528:radiation effects; D014783:Viscosity / Q000528:radiation effects
chemical_list: D006820:Hyaluronic Acid