Designing hydrogel nanocomposites using TiO2 as clickable cross-linkers
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Titanium dioxide (TiO2) nanoparticles with clickable functional groups were prepared to allow for the Diels–Alder “click” reaction with a furan-modified pigskin gelatin. Bifunctional dopamine-maleimide linker was employed for TiO2 functionalization with maleimide group. The obtained nanoparticles were characterized using TEM, Zeta potential and FTIR spectroscopy. Functional nanoparticles were subsequently used, together with chondroitin sulphate, as cross-linkers for gelatin hydrogels. Hydrogel controls with bare TiO2 and without nanoparticles were prepared for comparison. The swelling and rheological properties of the nanocomposite hydrogels confirmed the formation of the covalently linked heterogeneous networks. An increase in the storage moduli values was recorded when using maleimide-coated nanoparticles. At the same time, the swelling of the network was significantly reduced indicating the formation of more cross-linked networks. The participation of the surface attached maleimide functional groups through the Diels–Alder cycloaddition was thus confirmed. In addition, hydrogels responded to electrostatic forces as observed by electrostatic force microscopy.
KeywordsStorage Modulus Chondroitin Sulphate Maleimide Simulated Intestinal Fluid Hydrogel Sample
Financial support from the Basque Country Government in the frame of Grupos Consolidados (IT-776-13) is gratefully acknowledged. C. García-Astrain wishes to acknowledge the Universidad del País Vasco/Euskal Herriko Unibertsitatea (Ayudas para la Formación de Personal Investigador) for PhD grant PIFUPV10/034. M. M. acknowledges financial support of DAAD. Moreover, technical and human support provided by SGIker (UPV/EHU, MINECO, GV/EJ, ERDF and ESF) is also gratefully acknowledged.