Anions reversibly responsive luminescent nanocellulose hydrogels for cancer spheroids culture and release

Artificial stimuli-responsive hydrogels that can mimic natural extracellular matrix for growth and release of cancer spheroids (CSs) have attracted much attention. However, such hydrogels still face a challenge in regulating CSs growth and controlled release as well as keeping CSs integrity. Herein, a new class of ClO^-/SCN^- reversibly responsive nanocellulose hydrogel with fluorescence on-off reporter is developed. Upon addition of ClO^-, the gel network of nanocellulose hydrogel was destructed, accompanying by the fluorescent quenching. Notably, when introducing of SCN^-, a red fluorescence filamentous hydrogel was recovered by coordination cross-linking. The hydrogel reforms in a completely reversible process through the regulation of ClO^-/SCN^-. Benefit from the above response features of the hydrogel, the growth of cancer spheroids (CSs) in the hydrogel and on demand release of CSs from the hydrogel could be easily achieved through ClO^-/SCN^- regulation. Importantly, the growth and release of CSs can be monitored in real time by fluorescence imaging. Overall, such design strategy based on ClO^-/SCN^--responsive fluorescent hydrogels provided a new type of multi-responsive hydrogels as main scaffolds for cancer research and cancer drug screening.