Figure 3. Drug accumulation in 9L tumor spheroids imaged by dual-photon excitation confocal microscopy.

Confocal laser scanning microscopy with multi-photon excitation was used to image cell-associated gefitinib, irradiating with a 700 nm laser line (350 nm excitation) and an emission band of 390–465 nm. (A) MCF7 human breast cancer cells incubated in monolayer culture for 18 h with 2 µM free gefitinib. (B) Spheroids of rat 9L brain tumor cells grown in a serum-free Neural Stem Cell medium supplemented with EGF and other components ²² and incubated for 18 h with 10 µM free gefitinib, which approximates its IC₅₀. The images are false-colored to represent gefitinib as green. Bar: 20 micrometers.