Investigation of a 2D WS2 nanosheet-reinforced tough DNA hydrogel as a biomedical scaffold: preparation and in vitro characterization

Abstract

Hydrogels, prepared from natural polymers, are attractive biomaterials for diverse biomedical applications due to their excellent biocompatibility and bioactivity. However, the majority of conventional hydrogels are mechanically weak and unsuitable for use in the repair of load-bearing tissues. Herein, we utilized DNA as a natural biopolymer and two-dimensional nanosheets of tungsten disulfide (WS₂) to engineer mechanically tough nanocomposite hydrogels. Single network hydrogels were formed via covalent crosslinking of DNA chains in the presence of alginate-exfoliated WS₂ nanosheets. A polyethylene glycol-based bi-functional crosslinker with epoxide end groups was used to join the DNA strands via chemical crosslinking. Thereafter, the alginate chains in the hydrogel formulation were ionically crosslinked with Ca²⁺ ions to form double network polymeric hydrogels. Oscillatory shear rheology and uniaxial compression testing elucidated the beneficial effects of nanosheets and the formation of double network on the mechanical and structural properties of resulting hydrogels. Significant enhancement in compressive moduli and yield stress further corroborated the reinforcing effects of WS₂ and secondary network. Improved mechanical properties increase the applicability of these nanocomposites because of their enhanced tissue-mimicking abilities. In vitro cytotoxicity assays with human stem cells confirmed the biocompatibility of formulated nanocomposite hydrogels. To conclude, we envision these tough DNA-based hydrogels can be effectively used in the future as a scaffold for various biomedical applications, including delivery of drugs such as proteins, growth factors, small molecules, among others.