In Vivo Fluorescence Imaging to Localize Antibodies in a Mouse Tumor Xenograft Model

Begin with a syringe containing folate receptor alpha-1 expressing mammalian tumor cells in a basement membrane matrix medium.

Pull the mouse's skin and inject the tumor cell suspension into the subcutaneous layer.

During incubation, the basement membrane forms a semi-solid, gel-like matrix, entrapping the tumor cells and facilitating their attachment at the injection site.

Over time, attached mammalian tumor cells proliferate and become vascularized, forming a solid tumor xenograft.

Inject the folate receptor targeting fluorescent antibodies into the tail vein of the anesthetized tumor-bearing mouse.

Post-injection, the labeled antibodies reach the tumor site.

The antibodies bind to the folate receptors on the tumor cells, leading to their specific localization on the tumor xenograft.

Transfer the mouse to the imaging chamber and measure the fluorescence signal at regular intervals.

The enhanced fluorescence signal within the tumor xenograft confirms the selective localization of antibodies.

To develop mouse xenografts, gently lift the skin of the animal and separate it from the underlying muscle layer. Slowly inject 100 microliters of cell suspension under the skin with a 26-gauge needle. Wait for a few seconds before taking the needle out so that basement matrix medium can form the semi-solid gel-like structure along with cells under the skin, which will prevent the mixture from coming out of the injection site.

To perform in vivo imaging, inject the dye-labeled antibody via the tail vein. After anesthetizing the mouse, check for the lack of response to fetal reflexes, and dilate the vein by applying warm water.

Use a 1-cc insulin syringe with a 26-gauge needle to inject 25 micrograms of the labeled antibody in a volume of 100 microliters. As a negative control, label and inject the nonspecific IgG isotype antibody, which does not target cancer cells.

Perform in vivo imaging 8, 24, and 48 hours after antibody injections. In the imaging software, click Initialize and confirm that the stage temperature is 37 degrees Celsius. In the control panel, set up fluorescence imaging through the imaging wizard and set the excitation to 773 nanometers and emission to 792 nanometers.

Transfer the anesthetized mouse into the imaging chamber and position it on the imaging field using the nose cone. When ready, click Acquire on the control panel for the image acquisition and click Auto Expose. The generated image is the overlay of the fluorescence on the photographic image with optical fluorescence intensity displayed in units of counts or photons.