Development of halloysite nanotube/carboxylated-cellulose nanocrystal-reinforced and ionically-crosslinked polysaccharide hydrogels.

We report the development of halloysite nanotubes (HNTs)/carboxylated-cellulose nanocrystals (cCNCs) - reinforced and ionically-crosslinked k-carrageenan (k-CG)/xanthan gum (XG) hydrogels. In this study, cCNCs were extracted from microcrystalline cellulose using ammonium persulfate and exhibit 'spindle-like' nanocrystals with approximate diameter of 15-30 nm and length of 30-120 nm. The freeze-dried hydrogels showed highly porous microstructure with good pore-interconnectivity. Further, tunable swelling ratio and in vitro degradation rate of hydrogels under physiological condition (pH 7.4 PBS, 37 °C) were observed. In wet or dry states, the dynamic mechanical analysis of kCXGHN20cCN20 hydrogel showed significantly improved compressive strengths (at 50% strain: 8.1 ± 1.35 kPa or 81.33 ± 1.66 kPa, whereas at 70% strain: 11.84 ± 0.61 kPa or 120.7 ± 1.16 kPa) when reinforced with HNTs (20 wt%)/cCNCs (20 wt%), respectively. The stiffness values are reported at different compressive strains. All hydrogels showed excellent attachment and proliferation of human skin fibroblasts (CCD-986Sk) cells on hydrogels for 7 and 14 days of culture periods. The results showed that these hydrogels may have potential application in soft tissue engineering.