Theta-Gel-Reinforced Hydrogel Composites for Potential Tensile Load-Bearing Soft Tissue Repair Applications

Abstract

Engineering synthetic hydrogels for the repair and augmentation of load-bearing soft tissues with simultaneously high-water content and mechanical strength is a long-standing challenge. Prior formulations to enhance the strength have involved using chemical crosslinkers where residues remain a risk for implantation or complex processes such as freeze-casting and self-assembly, requiring specialised equipment and technical expertise to manufacture reliably. In this study, we report for the first time that the tensile strength of high-water content (>60 wt.%), biocompatible polyvinyl alcohol hydrogels can exceed 1.0 MPa through a combination of facile manufacturing strategies via physical crosslinking, mechanical drawing, post-fabrication freeze drying, and deliberate hierarchical design. It is anticipated that the findings in this paper can also be used in conjunction with other strategies to enhance the mechanical properties of hydrogel platforms in the design and construction of synthetic grafts for load-bearing soft tissues.

Keywords: hydrogel; load-bearing; polyvinyl alcohol; soft tissue; theta-gel.

Figure 1

Photograph of the PVA toric theta gels. (a) Undrawn (DR−); (b) Drawn (DR+).

Figure 2

(a,b) Photograph and (c,d) accompanying schematic of the cross-section of the freeze-dried theta-gel-reinforced hydrogels. (a,c) LD-TRH; (b,d) HD-TRH.

Figure 3

Scanning electron micrographs of the PVA theta gels; (a,b) DR−/FD+; (c,d) DR+/FD+. The scale bar represents 20 µm.

Figure 4

Equilibrium water content exhibited by the toric theta gels and theta-gel-reinforced hydrogels. *: p < 0.05 vs. DR−/FD− and DR+/FD−; **: p < 0.05 vs. DR−/FD−, DR+/FD−, DR−/FD+, and DR+/FD+.

Figure 5

(a) Ultimate tensile strength and (b) tensile modulus of the theta gels and theta-reinforced hydrogels. All groups are statistically significantly different from each other (p < 0.05).