Transition in the Glassy Dynamics of Melts of Acid-Hydrolyzed Phytoglycogen Nanoparticles

Abstract

The deformability, responsiveness, and tunability of soft nanoparticles (NPs) offer unique opportunities to learn about their complex properties and the interactions between particles. In the present study, we provide new insights into the physical properties of phytoglycogen (PG) NPs, which are soft, compact particles with a dendritic architecture that are produced in the kernels of sweet corn. In particular, we study PG NPs modified using acid hydrolysis, which not only reduces their diameter but also alters their stiffness, internal structure, and the interactions between particles in aqueous dispersions. We used steady shear rheology to determine the dependence of the relative zero-shear viscosity ηr of aqueous dispersions of acid-hydrolyzed PG NPs on the effective volume fraction ϕeff, which indicated a reduction in stiffness of the particles relative to that of native PG NPs. We quantified this difference by analyzing the nature of the colloidal glasses formed at high ϕeff. We measured a smaller value of the fragility index m for acid-hydrolyzed PG NP glasses than that for native PG NP glasses, indicating that acid-hydrolyzed PG NPs form stronger glasses and are therefore softer than native PG NPs. Unlike the native PG NPs, we observed a distinctive change in the character of the glass transition of the acid-hydrolyzed PG NPs as ϕeff was increased above ϕeff∼1: a crossover in the dependence of ηr on ϕeff from Vogel–Fulcher–Tammann behavior to a more gradual, Arrhenius-like behavior. By expressing the steady shear and oscillatory rheology data in terms of generalized Péclet numbers, we obtained collapse of the data onto master curves. We interpret this result in terms of the acid-hydrolyzed PG NPs predominantly interpenetrating neighboring particles at large ϕeff, for which fluctuations of the outer chains enhance the mobility of the particles and make α-relaxation times τα experimentally accessible.

Tuning the Phytoglycogen Size and Aggregate Structure with Solvent Quality: Influence of Water–Ethanol Mixtures Revealed by X-ray and Light Scattering Techniques

“…The value obtained here (R n = 24.2 ± 7.7 nm) is in good agreement with their work. However, they (R H = 37.6 nm), Liu et al ( 2020) 58 (R H = 33−39 nm) and Shamana and Dutcher (2022) 59 (R H ≈ 34 nm), report a somewhat higher intensity-weighted hydrodynamic size for sweet corn PG. Generally, PG can be found in the singlegranule form, termed β-particles, which can form larger aggregates termed α-particles similar to mammalian glycogen.…”

Binding Affinity of Concanavalin A to Native and Acid-Hydrolyzed Phytoglycogen Nanoparticles

“…Acid-hydrolyzed PG was prepared as described in ref . Briefly, native PG was added to Milli-Q water (resistivity of 18.2 MΩ-cm) at room temperature to a concentration C ∼ 2% w/w and mixed overnight using a magnetic stir bar.…”

“…Many of these applications of PG rely on the binding or association of biomolecules with PG. The applications of PG can be further extended by modifying the particles, e.g., through covalent attachment of functional groups, partial digestion of the glycosidic bonds in the particles, , or by subjecting the particles to high shear . In the present study, we consider the effect of acid hydrolysis on the binding properties of PG.…”

“…PG is produced in the kernels of sweet corn as dense, compact nanoparticles consisting of a very large number of glucose units that are bonded in a distinctive dendritic or tree-like architecture. We have studied the structure, morphology, hydration, and mechanical properties of PG nanoparticles using a wide variety of different techniques, − and the picture that has emerged is of soft, porous, hydrated, hairy nanoparticles. These desirable physical properties, together with their nontoxicity, high-safety profile, and digestibility, make PG an attractive choice for applications that involve the human body, such as personal care, nutrition, and biomedicine.…”

“…Recently, we showed that acid hydrolysis results in not only a decrease in the particle radius but also a significant decrease in the mechanical stiffness of the particles. 18 Decreases in the PG particle radius and stiffness not only result in improved optical transparency of personal care formulations due to a reduction in light scattering from the particles but also offer the potential for penetration through pore diameters less than that of the particles in targeted drug delivery applications. To evaluate the binding of small bioactive molecules to PG, we use surface plasmon resonance (SPR).…”