PCL(4k)-PEG(5k)-FITC is a diblock amphiphilic copolymer with tethered fluorescein dye. The FITC can be used for staining cells, tissues, biomarkers or nanoparticles. FITC has peak absorption or excitation at 494 nm and maximum emission at 521 nm and can be easily traced by fluorescence microscopy. The polymer self-assembles in aqueous media with polycaprolactone (PCL) at the core and PEG facing the water. The core regions can be used to encapsulate hydrophobic drugs. Reagent grade, for research purpose.