Detection of viscoelasticity in aggregating dilute protein solutions through dynamic light scattering-based optical microrheology

Abstract

This study illustrates the applicability of dynamic light scattering (DLS)-based optical microrheology in generating new insights into the rheological response of dilute protein solutions as they start to form insoluble aggregates under the influence of a thermal stress. The technique is also shown to provide a quick method for measuring the viscosity in protein solutions. The optical microrheological technique, which is based on DLS with improved single scattering detection, is shown here to capture the rich dynamics in these systems, where traditional mechanical rheometry cannot be effectively employed due to low torque generation and high sample volume requirements and the more widely known diffusing wave spectroscopy microrheology technique is not desirable due to the required high probe particle concentrations The study illustrates the careful consideration which must be given to the tracer particle surface chemistry, tracer particle concentration and tracer particle size in order to extract out rheological responses that are truly representative of the underlying protein dynamics and microstructure. We outline a procedure for ensuring that the pitfalls inherent to this type of measurement are avoided.

Nanogel Formation from Dilute Solutions of Clickable Elastin-like Recombinamers and its Dependence on Temperature: Two Fractal Gelation Modes

“…Polystyrene particles gave rise to a 30-35% change compared to the previous zeta potential for the click-reactive ELR solution obtained without tracer, whereas only a 5-7% change was found for melamine particles. These findings are in agreement with literature data for similar systems 19,25 . As a result, melamine resin particles were used for the microrheological measurements in this work.…”

“…However, at 37°C the slope decreases as the concentration increases. According to the literature, this corresponds to a subdiffusive behavior 25 . The motion of the tracer particles is hampered by the slight increase in the size of the nanogels at 1 mg/mL and, as a result, the MSD slope decreases, thus reflecting an increase in the magnitude of their complex modulus 30 .…”

“…The particle concentration for the microrheological measurements was selected to ensure that the lightscattering process was dominated by the particles, thus meaning that a single, narrow peak was observed in the lightscattering experiment. For each experiment, 10 µL of tracer was added to 500 µL of sample 25 .…”

A novel combination of DLS-optical microrheology and low frequency Raman spectroscopy to reveal underlying biopolymer self-assembly and gelation mechanisms

“…Tracer particles were chosen according to the optimal surface chemistry and size to minimize aggregation in the agarose solution. 19 The thermally-driven motion of the particles suspended in a complex fluid, such as agarose, is linked to the rheological properties of the surrounding fluid. Due to the inherent microstructural features present in these fluids, most have the ability to partially store and dissipate energy upon shearing, which render them as viscoelastic materials.…”

A Microliter Capillary Rheometer for Characterization of Protein Solutions

“…This happens whenever protein solutions form large aggregates and thus become heterogeneous . Guidelines involving a series of double checks to avoid the pitfalls of this method are elaborated by Amin et al…”