Fig. 4.

Particle biodistribution with fluorescence measurement of homogenized organs. a) Measurements of fluorescence emission linearity within the Alexa-647-labeled PSPs dilution range of the biodistribution experiment (R² = 0.94). The x-axis shows the particle volume dispersed in 100 μL of PBS, from a solution containing 320 million PSPs/mL. b) Measurements of linearity of tissue attenuation by addition of Alexa-647-labeled PSPs to homogenized tissue (R² = 0.99 for liver, lungs, spleen, kidneys, R² = 0.93 or blood). c) Measurements of the tissue attenuation coefficient calculated as the average of the ratios between fluorescence of PSPs in phosphate buffered saline (PBS) (true fluorescence, I) divided by the fluorescence of the same amount of PSPs dispersed in organ homogenate (attenuated fluorescence I₀). d) Serial dilutions images of homogenized organs used for plate reader measurements. Intensities are measured for all dilutions with a plate reader (ex = 640 nm, em = 678 nm, slit aperture 20/20). e) %ID/g calculated from fluorescence emission from the tissue well with the use of the correction factor. f) Visual comparison of results from IVIS and fluorescence from homogenized organs. g) Visual comparison of results from confocal imaging and fluorescence from homogenized organs.