Begin the surgical procedure on the properly anesthetized mouse by injecting buprenorphine hydrochloride subcutaneously to reduce the pain. Apply ophthalmic ointment to the eyes to prevent dryness. Place the mouse in a dorsal posture and secure the limbs in a stretching position with tapes.
Disinfect the back skin using alternating swabs of iodine and alcohol, at least three times each. Next, using surgical scissors, cut a 0.5-to-one-centimeter incision on the left back side of the animal. Carefully use forceps to separate the muscle and fat tissues until the chest wall and lung motion are visible.
Using a pipette, transfer one selected multicellular steroid, or MCS, from a microplate into a glass Petri dish containing ice-cold PBS. Attach a 20-gauge needle to a 100-microliter glass syringe and pre-cool them on ice. Then draw 20 microliters of a pre-cooled mixture of PBS and Matrigel.
Use the syringe to quickly aspirate one MCS from the Petri dish in a minimum volume of PBS-Matrigel mixture, keeping the spheroid in the metal part of the needle. Gently insert the needle vertically between two rib bones to a depth of approximately three millimeters and slowly inject all 20 microliters of the mixture containing the aspirated MCS. Then carefully remove the needle.
Apply triple antibiotic ointment to the wound. Seal the incision with surgical clips to be removed after two weeks. Place the animal on an infrared heat pad and cover it with laboratory wipes to maintain the body temperature.
Monitor the animal for at least 30 to 60 minutes until it wakes up and moves properly. Using a small animal imaging system at a 700-nanometer channel, measure the IRFP fluorescent signal from the tumor xenograft of the anesthetized mouse every three to four days. Measure the fluorescence in four postures, left, right, dorsal and ventral.
The net fluorescence intensity from both the left and ventral sides showed a similar trend of tumor progression, with fluorescence from the ventral side growing slightly slower than the fluorescence from the left side.
