Fig. 2. (a) Chemical structures of 800CW-PEGn; n represents the number of repeat ethylene oxide units. (b) Renal clearance efficiencies (RCE) of 800CW-PEGn at 2 h post-intravenous injection (p.i.) as functions of molecular weight and the number of repeat ethylene oxide units. (c) Representative NIRF images of mice before and after intravenous injection of 800CW and 800CW-PEG45. NIRF images acquired at 790 nm following excitation at 720 nm. (d) The dynamic NIRF intensities of kidneys and skin as a function of time post-injection of 800CW and 800CW-PEG45. (e) The kidney contrast index (KCI) at 5 min post-injection of 800CW and 800CW-PEG45. **p < 0.005. (f) Representative NIRF images of the ventral side of mice and ex vivo images of excised kidneys (kid), liver, spleen (spl), heart, and muscle at 30 min post-injection of 800CW-PEG45. (g) Representative haematoxylin and eosin (H&E) staining and fluorescence images of glomerulus and tubules from kidney slices at 5 min post-injection of 800CWPEG45. Glomerulus (G); proximal tubule (PT). Scale bar: 20 μm. Reproduced with permission from ref. 63. Copyright 2019 American Chemical Society.