Oxidation triggered formation of polydopamine-modified carboxymethyl cellulose hydrogel for anti-recurrence of tumor

• A biodegradable dopamine-modified sodium carboxymethyl cellulose hydrogel. • Sodium periodate was used to oxidize the CMC-DA for the hydrogel formation. • The formed NaI enables the CT imaging to monitor the degradation. • Ce6 was loaded by the hydrogel via soaking the hydrogel in the Ce6 solution. • Ce6 produced ROS and PDA produced heat for the combined tumor therapy. In this research, a hydrogel that combined the tumor photodynamic therapy (PDT) and photothermal therapy (PTT) ability was designed, using dopamine-modified sodium carboxymethyl cellulose (CMC-DA) as the matrix and Chlorin e6 (Ce6) as the photosensitizer. The gel formation was initiated by adding the oxidizing agent sodium periodate (NaIO 4 ) to the CMC-DA solution, during which the dopamine was simultaneously oxidized to polydopamine (PDA) and NaIO 4 was reduced to sodium iodide (NaI). The formed NaI was encapsulated in the hydrogel and endowed the hydrogel with computerized tomography (CT) imaging ability to monitor the hydrogel degradation and the tumor therapy process. Moreover, the photosensitizer Ce6 can be loaded by the gel system via directly soaking the hydrogel in the Ce6 solution. Under the near-infrared light irradiation, Ce6 can produce cytotoxic reactive oxygen species and the PDA can produce heat to trigger the tumor PDT and PTT respectively to eradicate the tumor recurrence. In general, the designed hydrogel is biocompatible and biodegradable, has a good photothermal conversion, drug loading and CT imaging ability, which laid the foundation for the rational design of biodegradable hydrogels for multifunctional applications.