Figure 1.

Characterization of ICG-p28. a, NIR fluorescence from ICG-p28 or ICG in a 5% intralipid emulsion was recorded with the PDE unit at 3 mW/cm² excitation intensity (N = 3). The intralipid solution alone showed no fluorescence and thus served as a control. The fluorescence quantum yield (ΦF) of ICG-p28 was similar to that of ICG at picomolar to micromolar concentrations. b, The signal-to-noise ratio (signal at 800 nm: tumour, noise: surrounding normal tissue, thigh muscles) in MDA-MB-231 tumour-bearing mice was recorded with the PDE unit and quantitatively analysed in a dose-dependent manner. The prescans were performed before injection of the NIR agent. ***: P < 0.001, *: P < 0.05 (ANOVA), n.s.: not significant mpk: mg/kg. c, The specific NIR signals (800 nm) of tumour-simulating inclusions of different sizes (1–3 and 5 mm) containing 200 nM ICG-p28 were measured. d, The specific NIR signals (800 nm) of tumour-simulating inclusions containing 200 nM ICG-p28 inserted into phantoms at depths of 0–2 cm were measured. d(i), Side view of the phantom. d(ii), Top view of the phantom. Red arrows: locations of the tumour-simulating inclusions. The distance between the PDE camera (which captured images at 3 mW/cm² excitation intensity) and the phantom was fixed at 200 mm. The results are presented as the mean+SD. e, NIR fluorescence (800 nm) from various numbers of MDA-MB-231 cells (N = 3 in each cell number) exposed to ICG-p28 at 0.5 mg/kg for 2 h were recorded with the PDE unit.