Fig. 5. (a) Schematic illustration of the sensing and drug release mechanism of THPDINs. The THPDINs are self-assembled with pH-sensitive HPDI (green), an anticancer drug of DOX (blue), and a pH-inert IR825 (gold). (b) UV-vis absorption spectra of THPDINs. (c) In vivo PA imaging of tumor pH. Representative PA images of a subcutaneous U87MG tumor in a nude mouse after intravenous administration of the THPDINs at post-injection times of 0, 4, 24, and 48 h. (d) Representative photographs of tumor-bearing mice with resected U87MG tumors in different treatment groups on day 18. Adapted from ref. 81. Copyright© Ivyspring International Publisher.