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 ω^0.2), capillary necking (75 ω^0.2 < G < 200 ω^0.075) or rolling (G > 200ω^0.075). 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_rγ), varying from ∼10⁻⁵ to ∼10³ 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_rγ), 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.