Figure 3: Ex vivo analyses of targeting of the SWNT probe.

Mice were euthanized at t=24 h post injection (p.i.) after the imaging sequence was completed. (a,b) Representative muscle tissue, denoting the right flank (R, site of infection) and the left flank (L, PBS control). (a) Mouse 1 received the targeted anti-S. aureus-M13-SWNT probe, while (b) Mouse 4 was injected non-targeted M13-SWNT probe. (c) Excised organs; Sp: Spleen, St: Stomach, Li: Liver, Ki: Kidneys, Bl: Bladder, It: Intestine, Ht: Heart, Lu: Lungs. (d) NAWI plot showing relative distribution of the probe, as mean ±s.e.m. for N=5 observations. See Methods for definition of NAWI. Inset is magnified for the thigh muscle tissues, showing a ~6.9 × increase in the probe accumulation at the site of infection. (e–j) Microscopy analysis of excised muscle tissue. (e–g) Bright-field images, with Gram staining. (h–j) Fluorescence images, using a green dye labelled on the M13. (e,h) The left muscle (control PBS injection) shows no evidence of Gram-positive S. aureus bacteria and negligible green fluorescence. (f,i) The right muscle (site of infection) shows the presence of clumps of violet-stained cocci of S. aureus. There is marked enhancement in the fluorescence intensity in the regions of large bacterial infection. Insets to parts of f and i, indicated by the red boxes, are shown in g and j respectively, at × 100 magnification. In g, individual cocci, ~0.5–0.8 μm in diameter are resolved. In j, the more heavily infected area shows brighter fluorescence compared with the less infected region. See Supplementary Fig. 7 and Supplementary Note 7 of Supplementary Information for additional analysis. Scale bar, 67.5 μm (e,f,h,i) and 13.7 μm (g,j).