Hyaluronic acid probe diffusion

S. C. De Smedt, A. Lauwers, J. Demeester, Y. Engelborghs, G. De Mey, and M. Du. Structural information on hyaluronic acid solutions as studied by probe diffusion experiments. Macromolecules 27 141-146 (1993). 

Laurent, et al. examine ten biomacromolecules and colloidal silica in 1.7 MDa hyaluronic acid(5). For all probe particles, s had a stretched-exponential dependence on matrix c, with v = 0.5. 5 was independent of the centrifugal acceleration, i.e., experiments were in a linear domain in which solution viscoelastic properties were not evident. Contrast is to be made with the electrophoretic mobility, as discussed in the next chapter, in which one can enter a nonlinear domain in which particle mobility depends on the applied field E. The constant B was found, to good accuracy, to be linear in the particle radius, except for the very largest spheres. Laurent, et al. also measured the diffusion coefficients D of four smaller probes in the same polymer solutions. Within experimental error, s/D was independent of matrix concentration. 

De Smedt, etal. used FRAP to examine diffusion of fluorescein-labeled dextrans and polystyrene latex spheres through hyaluronic acid solutions(17). Dextrans had molecular weights 71, 148, and 487 kDa. The hyaluronic acid had and of 390 and 680 kDa. The dextran diffusion coefficients depend on matrix polymer c as stretched exponentials in c, as seen in Figure 9.9b. Hyaluronic acid solutions are somewhat more effective at retarding the larger dextran probes. Viscosities for these solutions were reported by De Smedt, et a/. (18). The concentration dependence of rj is stronger than the concentration dependence of Dp of the polystyrene spheres, which is in turn stronger than the concentration dependence of Dp of the dextrans. Spheres and dextrans both diffuse more rapidly than expected from the solution viscosity and the Stokes-Einstein equation. 

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