Gelation and yielding behavior of polymer–nanoparticle hydrogels

Abstract

Polymer-nanoparticle hydrogels are a unique class of self-assembled, shearthinning, yield-stress fluids that have demonstrated potential utility in many impactful applications. Here, we present a thorough analysis of the gelation and yielding behavior of these materials with respect to the polymer and nanoparticle component stoichiometry. Through comprehensive rheological and diffusion studies, we reveal insights into the structural dynamics of the polymer nanoparticle network that identify that stoichiometry plays a key role in gelation and yielding, ultimately enabling the development of hydrogel formulations with unique shear-thinning and yield-stress behaviors. Access to these materials opens new doors for interesting applications in a variety of fields including tissue engineering, drug delivery, and controlled solution viscosity.

Subcutaneous delivery of an antibody against SARS-CoV-2 from a supramolecular hydrogel depot

“…Previous findings show that a P:NP stoichiometric ratio between 0.1 and 1 (P:NP = 0.2 for both formulations) promotes bridging between components and thus gelation in this PNP hydrogel system; the 2:10 network likely recovers more quickly compared to the network 1:5 due to higher overall content of polymer and nanoparticles to form bridging interactions. 49…”

“…Previous findings show that a P:NP stoichiometric ratio between 0.1 and 1 (P:NP = 0.2 for both formulations) promotes bridging between components and thus gelation in this PNP hydrogel system; the 2:10 network likely recovers more quickly compared to the network 1:5 due to higher overall content of polymer and nanoparticles to form bridging interactions. 49 Finally, the yield stress of each formulation was determined to assess the ability of the depot to retain its shape under the forces present the site of injection; it has previously been demonstrated that yield stress is an important rheological property for subcutaneous depot formation and retention. 34,50 Yield stresses of 70 and 350 Pa were measured for the 1:5 and 2:10 formulations, respectively (Figure 2e).…”

“…Again, previous work has shown that increasing nanoparticle content results in higher yield stress values. 49 Both of these formulations exhibit sufficiently high yield stress to form a persistent depot in the mouse subcutaneous space upon injection. 50 In addition, the hydrogel is rheologically stable for more than 5 weeks at room temperature (Figure S2).…”

Supramolecular Hydrogels: Design Strategies and Contemporary Biomedical Applications

“…[85,86] PNP hydrogels are highly tunable viscoelastic materials, displaying useful shear-thinning and yield stress responses. [87] This enables facile clinical administration of these materials by spraying or injection directly into the required site, which is followed by the hydrogel regaining robust mechanical properties in the absence of high shear forces. As a result, the hydrogel is able to rapidly form a coating or drug depot after application.…”

Yield-Stress and Creep Control Depot Formation and Persistence of Injectable Hydrogels Following Subcutaneous Administration

“…[40,41,42,43,44] The rheological properties of both calcium-alginate and PNP hydrogels can be easily tuned. For example, either increasing the concentration of alginate at a constant calcium content or increasing the concentration of PEG-PLA NPs at a constant HPMC-C12 concentration [45] yields hydrogels with more solid-like properties, higher yield stresses, higher preshear viscosities, and decreased creep (Figure 2b, e). By thoroughly characterizing the mechanical properties of these materials and monitoring their behavior upon subcutaneous administration in mice, we aim to elucidate relationships between rheological behaviors and the ability to form and maintain depots following injection that can yield generalizable design criteria for injectable hydrogels.…”