Streaming Potentials of Hyaluronic Acid Hydrogel Films

The streaming potentials of hyaluronic acid (HA) hydrogel films are measured and theoretically interpreted by systematically varying the HA concentration and the streaming electrolyte pH and ionic strength. While Donnan potentials are expected to vanish with sufficient added salt, apparent zeta-potentials from the Helmholtz-Smoluchowski interpretation remain of the order -20 mV. To theoretically interpret these data, we derived an electrokinetic model (valid in the Debye-Huckel regime) that accounts for ionic and hydrodynamic permeability of the gels. The films could then be ascribed an effective acid dissociation constant pK(a) approximate to 4.2, specific HA charge approximate to-0.1e mmol g(-1), and Brinkman/hydrodynamic permeability l(2) similar to l(0)(2) S-1/3, where l(0) is the Brinkman length for HA solutions in the as-prepared reference state and S is the hydrogel swelling ratio. At an ionic strength of 10 mmol L-1, for example, the HA surface potentials are only psi(D)/2 approximate to -8 mV, where psi(D) is the Donnan potential, considerably lower than zeta-potentials furnished by the Helmholtz-Smoluchowski interpretation. This insight significantly changes how the films are expected to interact with other surfaces and colloids via Derjaguin-Landau-Vervey-Overbeek-type forces. Our analysis furnishes formulas for the swelling ratio S and hydrodynamic permeability l(2), expressed explicitly as simple power-law functions of the asprepared HA concentration c(ha) (wt %), consistent with independent assessments of the HA solution permeability and polyelectrolyte-hydrogel swelling theory. These may prove valuable for extrapolating the results to other combinations of ionic strength, pH, and HA and cross-linking concentrations.

Automated summary

The streaming potentials of hyaluronic acid hydrogel films were measured and interpreted by varying the HA concentration and the streaming electrolyte pH and ionic strength. The study found that the forces affecting the interaction of the films with other surfaces and colloids, as well as the factors influencing the swelling ratio and hydrodynamic permeability of hydrogels.