A series of polymer dots (Pdots) doped with near infrared fluorescent organic dyes has been synthesized using poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(1,4-benzo-2,1’,3-thiadiazole)] (PFBT). This polymer forms stable nanometer size particles in aqueous suspension. Here we characterize the fluorescence properties of Pdots that have been doped with a series of hydroporphyrin and phthalocynine dyes with different fluorescence wavelengths to form resonance energy transfer pairs with the polymer. The polymer absorbs light at 440nm and transfers the energy to the organic dyes. The fluorescence emission spectrum of the dye-doped Pdot is therefore determined by the doped organic dyes acting as the energy transfer acceptors. Using home-built single-molecule fluorescence microscope, we found that the dye-doped Pdots exhibit several characteristics suitable for super resolution fluorescence microscopy. The Pdots showed bright fluorescence emission, requiring 2 orders of magnitude lower excitation laser power than typical single organic dye molecules for comparable emission photon rates due to their large absorption cross sections. In addition, the Pdots showed distinctive emission peaks. With single excitation laser at 440nm, the different dye-doped Pdots showed different emission spectra ranging from 600nm to 900nm, determined by the organic dyes. Importantly, single dots showed photo-blinking similar to photo-switching single molecules, even though multiple molecules were embedded in a single Pdot. Together, these Pdots can be used for tagging biological molecules to support multiplexed super resolution fluorescence imaging using similar approaches as single molecule localization-based super resolution microscopy.

Fluorescence microscopy characterization of near infrared dye-doped polymer dots for super resolution imaging

ACS Spring Meeting 2021

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