Macro to Micro Detection from Whole Animal to Cellular Level

Biodistribution studies are critical in the investigation of novel pharmacological agents, yielding vital information about tissue distribution of drug formulations as well as to characterize non-pharmaceutical agents, particularly in an in vivo model. Fluorescent markers, either in the form of genetic reporters like green fluorescent protein (GFP), NIR dyes, organic/inorganic dyes or nanoparticles, can be attached to the molecule of interest. UVP's iBox® Explorer™² Imaging Microscope is a versatile instrument capable of monitoring the distribution of fluorescent materials throughout organs and tissues of small animals in vivo. The iBox Explorer² is well suited for imaging the distribution of dye in a whole animal and allows:

• Macro to micro detection from the whole animal to the cellular level
• Non-invasive monitoring of fluorescence in vivo

Qualitative data analysis revealed NIR dye conjugated to anti-CEA monoclonal antibody (MAb) is seen concentrating in the mouse liver (Figure 1 in the Application Note) over 4 hours. No NIR signal detected at 0 time. At 10 minutes post-injection, dye rapidly accumulated in liver and vasculature running along the vertebral column. Post-experiment surgical exposure (Figure 2 in the Application Note) revealed presence of dye in the liver, bladder and region of inflammation in subcutaneous tissue. Ex vivo analysis of vital organs confirmed that much of the dye had been sequestered by the liver.

Rapid dye accumulation in the liver and lymph node shows a linear increase in intensity over time, suggesting sequestration of dye in this organ in order to clear the conjugate from the systemic circulation. Accumulation of the dye is possibly a result of its unique chemical structure. Presence of dye in the neck lymph nodes suggests expression of surface antigen CEA or non-specific binding of this antibody to the reticular cells. These data show possible mechanisms for uptake of dye in the nude mouse model and can form the foundation for future biodistribution studies.

iBox Explorer² is an ideal system for imaging distribution of fluorescent markers within small animals for pre-clinical research. Imaging of whole animal is possible and can accommodate up to two mice. The cooled, scientific-grade CCD camera rapidly captures publication quality images. A bright xenon arc lamp provides excitation light from the visible to NIR range, accommodating a host of in vivo studies and fluorescent markers. Application-specific filter sets can be tailored for imaging in pre-clinical fluorescence studies.