Fig. 3: ROS-responsive delivery of doxorubicin in cancer cells.

a ROS-activated tetrazine ligation enabled delivery of Dox from TCO-Dox 8 via a click-to-release two-step process is shown on the left, and direct activation of ROS-sensitive B-Dox is shown on the right. Dox, doxorubicin; TCO-Dox, trans-cyclooctene modified doxorubicin; B-Dox, boronate-caged doxorubicin (Created in BioRender. lab, L. (2026) https://BioRender.com/bm3fqz5). b The reaction was carried out by incubating 1 (5 µM) and TCO-Dox 8 (1.5 µM) with 100 µM of H₂O₂ in PBS solution (containing 1% DMSO) at 37 °C. Samples were taken from the reaction mixtures at different time points and examined by HPLC. (absorbance monitored at 254 nm). c IC₅₀ curves of MC38 cells treated with BTz 1 (3.3 eq) + TCO-Dox 8 (1 eq) + H₂O₂ (100 µM), BTz 1 (3.3 eq) + TCO-Dox 8 (1 eq), TCO-Dox 8 + H₂O₂ (100 µM), Dox + H₂O₂ (100 µM) or Dox at 37 °C for 18 h. Data were presented as mean ± SEM (n = 3 biologically independent samples). d Cell viability of MC38 cells after treatments with BTz 1 (13.2 µM), TCO-Dox 8 (4 µM), Dox (4 µM), or B-Dox 9 (4 µM) with or without H₂O₂ (100 µM), followed by incubation at 37 °C for 18 h. Data were presented as mean ± standard error of the mean (SEM), open circles indicate independent experiments (n =  3 biologically independent samples). Statistically significant differences in cell viability between no treatment and other treatments were indicated using an independent t-test (two-tailed): ^****P < 0.0001, ^**P < 0.01, ^*P < 0.05. Source data are provided as a Source Data file.