A tracer microrheology for determination of viscoelasticity of dilute ovalbumin colloids

This study seems to be the first effort to determine the viscoelastic properties of dilute ovalbumin colloids using dynamic-light-scattering-based optical microrheology using carboxylated melamine microparticles as the tracer probe. A generalized form of the Stokes-Einstein equation constructed based on Laplace transformation of the mean square displacement, 〈Δr 2(t)〉, was employed to compute the viscoelastic moduli (storage modulus, G′, and loss modulus, G″). 〈Δr 2(t)〉 was determined to increase with time by reaching a maximum plateau at a time between 10-3 and 10-1 s with no further increase, revealing the elastic nature of dilute ovalbumin colloids within the given time. On the other hand, ovalbumin colloids exhibited different viscoelastic properties at two different frequency ranges. The measurements and interpretation of data revealed that the technique used seems to ensure a fast and effective method for measuring the viscoelastic properties of ovalbumin colloids at very low concentration levels.