(a) Chemical structure of Gd-IR780 and proposed macrocyclization
followed by in situ self-assembly into Gd-IR780-NPs in response to caspase-3 and GSH and schematic illustration of the
mechanism of Gd-IR780 for bimodal imaging of tumor apoptosis
in mice via PAI and MRI. (b) PA images (overlaid with ultrasound images)
and PA intensity enhancement (ΔPA) of saline-treated or DOX-treated
U87MG tumors in living mice before (Pre) and at 2, 6, 10, and 24 h
after iv injection of Gd-IR780 (0.1 mmol kg–1). PA images were acquired at 855 nm. Values are mean ± SD,
***P < 0.001. Red dashed circles indicate the
tumors (top row). Representative T1-weighted
MR images and (g) quantification of % SE in tumors before (Pre) and
at 2, 6, 10, and 24 h after iv injection of Gd-IR780 (0.1
mmol kg–1). Values are mean ± SD (n = 3), ***P < 0.001. Tumors are marked with red
arrows. White arrows indicate the Dotarem solution (1 mM) as the internal
standard. Reproduced with permission from ref (99). Copyright 2022 Elsevier
Ltd.