Enhanced two-photon excitation fluorescence by fluorescence resonance energy transfer using conjugated polymers

Abstract

The use of conjugated polymers in enhanced two-photon excitation fluorescence by fluorescence resonance energy transfer is discussed. The conjugated polymers can function as light harvesting materials and exhibit enhanced quenching efficiency by electron transfer or optical amplification via Förster resonance energy transfer (FRET). Two photon excitation phototherapy and imaging methods have advantage over one-photon by offering the ability of working with a smaller, more confined treatment area and treatment deeper into diseased tissues. Applications of two-photon excitation fluorescence microscopy and two-photon photodynamic therapy usually make use of a Ti:sapphire oscillator, the most readily available femto-second excitation source, which has a central wavelength of around 800 nm. However, two-photon induced emission of DNA intercalators can be significantly enhanced by using cationic conjugated polymers.