pH-Sensitive Carbon Dots for Enhancing Photomediated Antitumor Immunity

Recent cancer immunotherapy has attracted much attention due to high specificity and recurrence prevention of tumor. Nevertheless, its therapeutic effects are still challenging in solid cancer. To establish superior antitumor immunity, chlorin e6 (Ce6)-loaded pH sensitive carbon dots were investigated (Ce6@IDCDs). At tumoral pH 6.5, Ce6 was released four times compared with the release at physiological pH 7.4 due to an imbalance between hydrophilic and hydrophobic forces via protonation of imidazole groups in Ce6@IDCDs. This result led to the superior singlet oxygen generating activity of Ce6@IDCDs without Ce6 quenching. The maturation effects of dendritic cells after co-incubation with supernatant media obtained from Ce6@IDCDs with laser-treated cells at pH 6.5 were much higher than at physiological pH. Furthermore, Ce6@IDCDs following a laser at pH 6.5 significantly promoted calreticulin exposure and high-mobility group box 1 release, as major immunogenic cell death markers. In bilateral CT-26-bearing mice model, the Ce6@IDCDs elicited significant antitumoral effects at laser treated-primary tumor regions via therapeutic reactive oxygen species. Furthermore, Ce6@IDCDs upon laser irradiation induced a large amount of activated CD8⁺ T cells, natural killer cells, and mature dendritic cells recruitment into tumoral tissue and hampered tumor growth even at untreated sites approximately four-fold compared with those of others. Overall, this pH-sensitive immunoinducer can accomplish primary and distant tumor ablation via photomediated cancer immunotherapy.