title: Dynamic interfacial behavior of viscoelastic  aqueous hyaluronic acid: effects of molecular  weight, concentration and interfacial velocity.
abstract: An aqueous hyaluronic acid (HA(aq)) pericellular coat, when mediating the tactile aspect of cellular contact inhibition, has three tasks: interface formation, mechanical signal transmission and interface separation. To quantify the interfacial adhesive behavior of HA(aq), we induce simultaneous interface formation and separation between HA(aq) and a model hydrophobic, hysteretic Si-SAM surface. While surface tension γ remains essentially constant, interface formation and separation depend greatly on concentration (5 ≤ C ≤ 30 mg mL(-1)), molecular weight (6 ≤ MW ≤ 2000 kDa) and interfacial velocity (0 ≤ V ≤ 3 mm s(-1)), each of which affect shear elastic and loss moduli G′ and G′′, respectively. Viscoelasticity dictates the mode of interfacial motion: wetting-dewetting, capillary necking, or rolling. Wetting-dewetting is quantified using advancing and receding contact angles θ(A) and θ(R), and the hysteresis between them, yielding data landscapes for each C above the [MW, V] plane. The landscape sizes, shapes, and curvatures disclose the interplay, between surface tension and viscoelasticity, which governs interfacial dynamics. Gel point coordinates modulus G and angular frequency ω appear to predict wetting-dewetting (G < 75 ω0.2), capillary necking (75 ω0.2 < G < 200 ω0.075) or rolling (G > 200ω0.075). Dominantly dissipative HA(aq) sticks to itself and distorts irreversibly before separating, while dominantly elastic HA(aq) makes contact and separates with only minor, reversible distortion. We propose the dimensionless number (G′V)/(ω(r)γ), varying from 10(-5) to 10(3) in this work, as a tool to predict the mode of interface formation-separation by relating interfacial kinetics with bulk viscoelasticity. Cellular contact inhibition may be thus aided or compromised by physiological or interventional shifts in [C, MW, V], and thus in (G′V)/(ω(r)γ), which affect both mechanotransduction and interfacial dynamics. These observations, understood in terms of physical properties, may be broadened to probe interfacial dynamics of other viscoelastic aqueous biopolymers.
authors.forename: Katherine
authors.initials: K
authors.lastname: Vorvolakos
authors.forename: James C
authors.initials: JC
authors.lastname: Coburn
authors.forename: David M
authors.initials: DM
authors.lastname: Saylor
mesh_terms: D055119:Elastic Modulus; D004548:Elasticity; D006820:Hyaluronic Acid / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D008970:Molecular Weight; D014783:Viscosity; D014867:Water / Q000737:chemistry
chemical_list: D014867:Water; D006820:Hyaluronic Acid