Figure 5.

After topical application, AKRO-QC-ICG probe penetrates tissue to the depth of a few cancer cells. (A)—H/E histology of the PDX cancer xenograft with surrounding normal tissue (abdominal wall muscles). Vertical dotted lines indicate tumor borders. (B)—Fluorescent scan of consecutive tissue slide represents AKRO-QC-ICG-induced fluorescence (false green color), indicating that the probe was activated only at the area of the fresh cut surface of the tumor without a tendency to spread to surrounding tissues. Dotted line—contour of the sample. (C)—Fluorescent microscopy consecutive tissue sections of different thickness indicate that AKRO-QC-ICG penetrates from the surface (where it was applied) to a depth of up to 120 μm in 10 min. Thicker tissue sections were required to visualize probe fluorescence in tissue, avoiding the need for inking fluorescence prior to tissue preparation. For these studies, mice were treated with AKRO-QC-ICG imaging gel#30 and imaged as in Figure 3. Next, tissue was snap frozen and consecutive slides were sliced for routine histology, fluorescent scan (Odyssey CLx, resolution = 24 μm, 800 nm filter set, Li-Cor) in (B) and microscopy (Leica, NIR filter set) in (C). Vertical red arrows indicate the surface of application and direction of future penetration of the probe in (A).