Enhanced intratumoral delivery of molecular probes (ICG) using renal clearable nanocarriers. From tumor fluorescence imaging with 24 h post-intravenous treatment of ICG4-GS-Au25, ICG (green) was efficiently taken up by tumor cells and located in endosome-like membrane-bound compartments (lower left, enlarged view), indicating the renal clearable nanocarriers, AuNCs, effectively deliver these molecular probes into tumor sites, ref. [174]. BF, bright field, FL, fluorescence; Scale bars, 6 μm for the enlarged view lower left and 20 μm for the rest. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)