Folic acid-functionalized polythiophene for targeted cellular imaging

Polythiophene containing pendant N-hydroxysuccinimide (NHS) ester groups was reacted with poly(ethylene glycol) (PEG) and oleylamine, which was subsequently modified with folic acid to prepare a targeting fluorescent cellular imaging probe. The amphiphilic character of the folic acidfunctionalized polythiophene induced the formation of nanoparticles with an average diameter of 95.3 nm in water. This polymer shows good photostability and low toxicity toward KB cells at a high concentration (100 μg/mL), which meets the crucial requirement for cellular imaging and other biological applications. The folic acid-functionalized polythiophene could be internalized efficiently into KB cells and accumulated in the cytoplasm to yield bright fluorescence, indicating that it is a good candidate material for the fluorescence imaging of living cells.