Cytocompatible carbon nanotube reinforced polyethylene glycol composite hydrogels for tissue engineering

Hydrogels are attractive materials for stimulating 3D cell growth and tissue regeneration, and they provide mechanical support and physical cues to guide cell behavior. Herein, we developed a robust methodology to increase the stiffness of polyethylene glycol (PEG) hydrogels by successfully incorporating carbon nanotubes (CNTs) within the polymer matrix. Interestingly, hydrogels containing pristine CNTs showed a higher stiffness (1915 +/- 102 Pa) than both hydrogels without CNTs (1197 +/- 125 Pa) and hydrogels incorporating PEG-grafted CNTs (867 +/- 103 Pa) (p < 0.005). The swelling ratio was lower for hydrogels with pristine CNTs (45.4 +/- 3.5) and hydrogels without CNTs (46.7 +/- 5.1) compared to the hydrogels with PEG-grafted CNTs (62.8 +/- 2.6). To confirm that the CNT-reinforced hydrogels were cytocompatible, the viability, proliferation, and morphology of encapsulated L929 fibroblasts was investigated. All hydrogel formulations supported cell proliferation, and the addition of pristine CNTs increased initial cell viability (83.3 +/- 10.7%) compared to both pure PEG hydrogels (51.9 +/- 8.3%) and hydrogels with PEG-CNTs (63.1 +/- 10.9%) (p < 0.005). Altogether, these results demonstrate that incorporation of CNTs could effectively reinforce PEG hydrogels and that the resulting cytocompatible nanocomposites are promising scaffolds for tissue engineering.