Chitosan Nanocrystals Synthesis via Aging and Application Towards Alginate Hydrogels for Sustainable Drug Release

Marine biomass waste is a remarkable source of functional molecules and materials. Yet material extraction, conversion and processing are often chemically intensive, preventing the widespread and clean use of these abundant resources for high-end applications. Moreover, current challenges in biomedicine call for the design of novel materials with better functional and mechanical properties. Herein, we present a novel chemical process to afford chitosan nanocrystals (ChsNCs), which uniquely combine a high degree of deacetylation, rod shape and high crystallinity for mechanical robustness. This method is a simple solid-state aging process starting from chitin nanocrystals (ChNCs) and requiring limited chemical and energetic input, which we have quantified using process mass intensity as the sustainability metric. This method, as well as a previously reported solution-based method, afforded a family of novel nanomaterials, which we used to form alginate hydrogels. The resulting materials are the first examples of ChsNC-based hydrogels and featured superior performances in terms of both rheological properties, as well as sustained drug release, as compared to previously reported chitosan/alginate systems. This work opens an avenue for functional soft materials using a green resource via a clean process.