title: Substrate concentration influences effective radial diffusion coefficient in canine cortical bone.
abstract: Transport of nutrients and waste across osseous tissue is dependent on the dynamic micro and macrostructure of the tissue; however little quantitative data exists examining how this transport occurs across the entire tissue. Here we investigate in vitro radial diffusion across a section of canine tissue, at dimensions of several hundred microns to millimeters, specifically between several osteons connected through a porous microstructure of Volkmann's canals and canaliculi. The effective diffusion coefficient is measured by a "sample immersion" technique presented here, in which the tissue sample was immersed in solution for 18-30 h, image analysis software was used to quantify the solute concentration profile in the tissue, and the data were fit to a mathematical model of diffusion in the tissue. Measurements of the effective diffusivity of sodium fluorescein using this technique were confirmed using a standard two-chamber diffusion system. As the solute concentration increased, the effective diffusivity decreased, ranging from 1.6 × 10(-7) ± 3.2 × 10(-8) cm(2)/s at 0.3 μM to 1.4 × 10(-8) ± 1.9 × 10(-9) cm(2)/s at 300 μM. The results show that there is no significant difference in mean diffusivity obtained using the two measurement techniques on the same sample, 3.3 × 10(-8) ± 3.3 × 10(-9) cm(2)/s (sample immersion), compared to 4.4 × 10(-8) ± 1.1 × 10(-8) cm(2)/s (diffusion chamber).
authors.affiliation: Department of Chemical and Biomedical Engineering, Cleveland State University, 2121 Euclid Ave, Cleveland, OH, 44141, USA, k.w.farrell@vikes.csuohio.edu.
authors.forename: Kurt
authors.initials: K
authors.lastname: Farrell
authors.forename: Daniel
authors.initials: D
authors.lastname: O'Conor
authors.forename: Mariela
authors.initials: M
authors.lastname: Gonzalez
authors.forename: Caroline
authors.initials: C
authors.lastname: Androjna
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Midura
authors.forename: Surendra N
authors.initials: SN
authors.lastname: Tewari
authors.forename: Joanne
authors.initials: J
authors.lastname: Belovich
mesh_terms: D000818:Animals; D001692:Biological Transport; D004058:Diffusion; D004285:Dogs; D019793:Fluorescein / Q000737:chemistry; D008954:Models, Biological; D010710:Phosphates / Q000737:chemistry; D012965:Sodium Chloride / Q000737:chemistry; D013977:Tibia / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D010710:Phosphates; D012965:Sodium Chloride; D019793:Fluorescein