Astral hydrogels mimic tissue mechanics by aster-aster interpenetration

Abstract

Many soft tissues are compression-stiffening and extension-softening in response to axial strains, but common hydrogels are either inert (for ideal chains) or tissue-opposite (for semiflexible polymers). Herein, we report a class of astral hydrogels that are structurally distinct from tissues but mechanically tissue-like. Specifically, hierarchical self-assembly of amphiphilic gemini molecules produces radial asters with a common core and divergently growing, semiflexible ribbons; adjacent asters moderately interpenetrate each other via interlacement of their peripheral ribbons to form a gel network. Resembling tissues, the astral gels stiffen in compression and soften in extension with all the experimental data across different gel compositions collapsing onto a single master curve. We put forward a minimal model to reproduce the master curve quantitatively, underlying the determinant role of aster-aster interpenetration. Compression significantly expands the interpenetration region, during which the number of effective crosslinks is increased and the network strengthened, while extension does the opposite. Looking forward, we expect this unique mechanism of interpenetration to provide a fresh perspective for designing and constructing mechanically tissue-like materials.

Compressional stress stiffening & softening of soft hydrogels – how to avoid artefacts in their rheological characterisation

“…S1 and S2 of ESI. † Notably, our results are in very good agreement with those reported by Xie et al 29 in Fig. 6a of their manuscript for both agarose and polyacrylamide gels and for comparable compressional axial strains (i.e., axial strain r30%).…”

“…The viscoelastic properties of hydrogels designed for mimicking biological specimens [26][27][28][29] are fully described by their frequency-dependent shear complex modulus G*(o) = G 0 (o) + iG 00 (o), which is a complex number whose real (G 0 (o), also known as storage modulus) and imaginary (G 00 (o), also known as loss modulus) parts provide valuable information on the elastic and viscous nature of the sample, respectively. Conventionally, these are determined via oscillatory measurements performed by means of rotational rheometers.…”

Controlling Mechanical Properties of Poly(methacrylic acid) Multilayer Hydrogels via Hydrogel Internal Architecture

“…32 Another study used self-assemblies of synthetic colloids made of amorphous core and radial crystalline ribbons to obtain hydrogels through colloid−colloid interpenetration. 33 Extension-softening and compression-stiffening mechanical responses that mimic biological tissues were observed by controlling the interpenetration of these densely packed colloids. 33 Moreover, hierarchically structured anisotropic hydrogels of poly(vinyl alcohol) (PVA) nanofibrils obtained through freezing and salting out of PVA solution demonstrated a two-to fourfold improvement in strength and toughness, compared to a nonfibril chemically cross-linked PVA hydrogel.…”

“…Zarket and Raghavan demonstrated that a cross-linked alginate gel exhibits different mechanical responses to compression when its onion-like shell comprises layers with different chemical compositions . Another study used self-assemblies of synthetic colloids made of amorphous core and radial crystalline ribbons to obtain hydrogels through colloid–colloid interpenetration . Extension-softening and compression-stiffening mechanical responses that mimic biological tissues were observed by controlling the interpenetration of these densely packed colloids .…”

Recent Advances in Macroporous Hydrogels for Cell Behavior and Tissue Engineering

“…Biomimetic modification of the hydrogel polymeric network can mimic the biochemical and physical properties of the ECM, enabling cell loading and repair of damaged tissue. The selection of precursors with good biocompatibility to prepare hydrogels is a prerequisite for successful applications, such as biological components [ 8 , 9 , 10 , 11 ] or inert polymers [ 12 , 13 ]. Excellent water retention capacity is the most notable feature of hydrogels, which lays the foundation for mimicking the softness and water content of ECM [ 14 , 15 ].…”