Fig. 1From: A comparative study of chondroitin sulfate and heparan sulfate for directing three-dimensional chondrogenesis of mesenchymal stem cellsYoung’s Modulus of 18 hydrogel groups with varying heparin sulfate (HS) or chondroitin sulfate (CS) concentration (0–10% (w/v)). Hydrogel stiffness was maintained constant to be either soft (~ 7.5 kPa) or stiff (~ 36 kPa) by adding different concentrations of PEG. Control hydrogel is made of PEG onlyBack to article page