Scheme 1.

Schematic showing the preparation of polymer nanoparticle using nanoprecipitation and subsequent bioconjugation. Briefly, a THF solution of PFBT, the amphiphilic polymer PS-PEG-COOH and matrix polymer P70 is quickly injected into water under high sonication power to precipitate nanoparticles. The hydrophobic fluorescent PFBT is trapped within the core of the nanoparticle. The THF is removed by heating and bubbling the solution with nitrogen. The nanoparticles are then bioconjugated to streptavidin and PEG. Although P70 and PS-PEG-COOH are both amphiphilic polymers and should fulfill the same role within the nanoparticles, it was found empirically that adding both polymers resulted in the smallest nanoparticles with the greatest sensitivity to excitation polarization and the most polarized emission.