Figure 4. NIRF imaging of whole-organ NP uptake.

a, 12 mice were used to confirm in vivo MRI patterns of IOSPM NP biodistribution with ex vivo organ fluorescence intensity measurement. Consecutive panels show blood (200 μl) and whole organs (brain, bone, muscle, heart, lung, liver, kidney, and spleen) from mice sacrificed at 1 h, 2 h, and 3.5 h. Organs at each experimental timepoint were imaged alongside organs from separate non-injected control mice. Images display highest IOSPM-Cy5.5 NP uptake in the liver, with visible fluorescence change in the blood, bone, lung, kidney, and spleen. b, Fluorescence intensity in all organs was calculated, and is displayed graphically for each time point. Error bars represent ± standard deviation of the mean from the three independent measurements. c, A direct comparison between MR and fluorescence results suggests a linear relationship between the two measurement techniques. Such linearity is demonstrated both for examples using QT2 imaging (displayed for the kidney and liver), and with T2*-W imaging (shown in the marrow and brain). R² values ranging from 0.93 to 0.96 are shown, adjacent to the respective linear fits.