To determine the presence of the drug localized in tumor tissues, doxorubicin autofluorescence was detected using a Zeiss Axiovert 200 M inverted microscope with a 100 W HBO mercury light source equipped with a 546/12 nm excitation and a 590 nm emission filter set. Tissue sections were imaged with a FLUAR 106/0.50 NA lens and captured with a Roper Scientific CoolSnap HQ CCD camera. All images were captured in 8-bit signal depth and subsequently pseudo-colored.