Although tough double network hydrogel (DN gel) has been fabricated for years, the practical applications haven't achieved. One of the reasons is the limited polymer choices. The recent researches indicated that the addition of the Proteoglycans (PG), a heavily glycosylated protein, can make soft DN gel tough. However, the extract of natural PG and synthesize of its substitute are expensive and time consuming. In this work, chondroitin sulfate coated carbon nanotube (CS-T), a nanostructure biomimic PG, was synthesized to make soft hydrogel tough. 295% and 360% enhancements have been found on compressive strength and toughness after adding small amount of CS-T, respectively. As the PG plays a critical role in the cartilage to resist compression and maintain microstructure, this novel nanostructure paves an affordable way to produce substitutes for load-bearing tissue and multi-functional hydrogel. (C) 2015 Elsevier B.V. All rights reserved.