a TEM image of 3s-TiO2–HoMS. The scale bar is 500 nm. b STEM image of MIT-3s-TiO2–HoMS. The scale bar is 200 nm. c TEM-EDX mapping images of MIT-3s-TiO2–HoMS. The scale bar is 200 nm. d TEM-EDX spectra of 3s-TiO2–HoMS (top) and MIT-3s-TiO2–HoMS (bottom). e FTIR spectra of MIT, 3s-TiO2–HoMS and MIT-3s-TiO2–HoMS with different drug-loading period. f Enlarged FTIR spectra in the selected region. Source data are provided as a Source Data file.