Carbon nanotubes as structural nanofibers for hyaluronic acid hydrogel scaffolds. 
We have successfully dispersed functionalized single-walled carbon nanotubes (SWNTs) within hyaluronic acid-water solutions.  Hybrid hyaluronic acid (HA) hydrogels with SWNTs were then formed by cross-linking with divinyl sulfone.  We have found a considerable change in the morphology of the lyophilized hybrid hydrogels compared to HA hydrogels.  The high water uptake capacity, an important property of HA hydrogels, remained almost unchanged after 2 wt % SWNT (vs HA) incorporation, despite a dramatic enhancement in the dynamic mechanical properties of the hybrid hydrogels compared to native ones.  We have found a 300% enhancement in the storage modulus of hybrid hydrogel with only 2 wt % of SWNTs vs HA (0.06 wt % vs total weight including water content).  This apparent contradiction can be explained by a networking effect between SWNTs, mediated by HA chains.  As in biological tissue, HA plays a dual role of matrix and linker for the rigid reinforcing nanofibers.