Abstract
Cartilage wounds result in chronic pain and degradation of the quality of life for millions of people. A synthetic cellular scaffold able to heal the damage by substituting the natural tissue is of great potential value. Here, it is shown for the first time that the unique interplay between the molecular components of cartilage can be reproduced in composite materials made of a polyelectrolyte hydrogel embedding a collagen scaffold. These composites possess a mechanical response determined by osmotic and electrostatic effects, comparable to articular cartilage in terms of elastic modulus, time-dependent response, and permeability to interstitial fluid flow. Made entirely from biocompatible materials, the cartilage-like composite materials developed permit 3D culture of chondrocyte-like cells through their microporosity. The biomimetic materials presented here constitute an entirely new class of osmotically stiffened composites, which may find use outside of biomedical applications.
Highlights
Cartilage wounds result in chronic pain and degradation of the quality of life the tissue.[1,2] Despite large research efforts for millions of people
Tissue engineering scaffolds must guarantee the viability of patient-specific cells a mechanical response determined by osmotic and electrostatic effects, while the synthetic construct is integrated comparable to articular cartilage in terms of elastic modulus, time-dependent response, and permeability to interstitial fluid flow
Blends of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA) can be cross-linked by repeated freeze-thawing cycles, yielding microporous cryogels where PVA acts as the mechanically stable cross-linked backbone, while PAA possesses negative charges that are active at physiological pH and ionic strength.[11,17]
Summary
The properties of the proteoglycan gel matrix found in cartilage can be reproduced using polyelectrolyte hydrogels These materials present fixed negative charges reminiscent of those found on the GAGs of cartilage, and have recently attracted attention as cellular scaffolds for the repair of this and other electroactive tissues like bone and muscle.[15,16] Blends of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA) can be cross-linked by repeated freeze-thawing cycles, yielding microporous cryogels where PVA acts as the mechanically stable cross-linked backbone, while PAA possesses negative charges that are active at physiological pH and ionic strength.[11,17] An increasing number of freeze-thaw cycles results in a larger amount of both polymers fixed in the cross-linked network, in a larger fixed charge density. The effect of the collagen constraint can be included in this analysis by considering the polyelectrolyte hydrogel contained within each collagen scaffold pore to be constrained in 3D by all other pores surrounding it,[31]
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