Evolution of hierarchical porous structures in supramolecular guest–host hydrogels

Abstract

Macromolecular interactions are used to form supramolecular assemblies, including through the interaction of guest-host chemical pairs. Microstructural heterogeneity has been observed within such physical hydrogels; yet, systematic investigation of the microstructure and its determining inputs are lacking. Herein, we investigated the hierarchical self-assembly of hyaluronic acid (HA) modified by the guest-host pair adamantane (Ad-HA, guest) and β-cyclodextrin (CD-HA, host), as well as with methacrylate groups to both tether fluorescent agents and to covalently stabilize the material structure. We observed microporous materials in the hydrated state, which temporally arose from initially homogenous hydrogels composed of the two polymers. Independent fluorescent labeling of Ad-HA and CD-HA demonstrated spatiotemporal co-localization, indicative of guest-host polymer condensation on the microscale. The hydrogel void fractions and pore diameters were independently tuned through incubation time (0-7 days), polymer concentration (1.25-10 wt%), and polymer modification (25-50% Ad-HA modification). Void fractions as great as 93.3±2.4% were achieved and pore diameters ranged from 2.1±0.5 to 1025.4±209.4 μm. The segregation of discrete solid and solute phases was measured with both atomic force microscopy and diffusive microparticle tracking analysis, where the solute phase contained only dilute polymer. The study represents a systematic investigation of hierarchical self-assembly in binary associating hydrogels, and provides insights on mechanisms that control microstructure within supramolecular hydrogels.

Functional Hydrogels With Tunable Structures and Properties for Tissue Engineering Applications

“…Specifically, guest–host pair, adamantane (guest) and β-cyclodextrin (host), is widely used to synthesize corresponding macromers. The guest-host bonding can translate mixed solution into hydrogels easily (Rodell et al, 2016 ). In another study, acrylate β-cyclodextrin can build guest-host binding with the benzene ring of gelatin to form supramolecular hydrogels.…”

A Biocompatible Therapeutic Catheter‐Deliverable Hydrogel for In Situ Tissue Engineering

“…As a result, self‐assembly via noncovalent cross‐linking mechanisms has emerged as a promising approach to minimally invasive hydrogel delivery. Such systems include Dock‐and‐Lock hydrogels, leucine‐zipper hydrogels, two‐component protein motif recognition hydrogels, and host–guest interaction hydrogels . In each of these platforms, dynamic and reversible crosslinking behavior was observed, allowing for injectability.…”

Jammed Microgel Inks for 3D Printing Applications

“…The printed microgel ink resisted gravitational forces within the hydrogel to maintain the designed structure. With such an approach, inks printed into supports must generally resist internal forces that can result in breaking into droplets or being dragged by the print nozzle, as well as external forces from the support such as dynamic rearrangements during self‐healing that might compress and cause flow of deposited inks.…”