Gelfoam size 4

500,000 cells (T-HEp3 CDK2 sensor and H2B-RFP) were resuspended in 100μl of 1X sterile DPBS and injected in the interscapular region of the neck of nude mice. 5 mice were used per group. Tumor sizes were monitored every 4 days for 19 days. At day 19 after tumor cell injections, tumors were removed following the surgery procedure described in the previous section. One group of mice received a dental sponge rehydrated in DPBS and the other group received a dental sponge rehydrated in DPBS and incubated with type III collagen 1mg/ml polymerized for 4hrs at 37°C. Dental sponge reference Gelfoam® size 4 was purchased from Pfizer. They were cut in three pieces, each animal received one piece of sponge. The wound was closed using 9mm AutoClips® (reference 205016) from Braintree Scientific. Clips were removed 10 days after surgery. Local tumor relapse was monitored up to 40 days (20 days after surgery). Mice were sacrificed with CO2 when tumors reached 1cm in diameter. At day 40, all remaining mice with no local relapses were sacrificed. For each animal, the area of resection was reopened to image residual cancer cells where the sponge was places by using a multiphoton microscope.