Optimization of the molecular orbital energies of conjugated polymers for optical amplification of fluorescent sensors

J Am Chem Soc. 2006 Feb 1;128(4):1188-96. doi: 10.1021/ja055382t.

Abstract

Cationic water-soluble poly(fluorene-co-phenylene)s with electron withdrawing or donating substituents on the conjugated backbone were designed and synthesized. Fluorescence resonance energy transfer (FRET) experiments between these conjugated polymers and dye-labeled single-stranded DNA (ssDNA-C*) reveal the importance of matching donor and acceptor orbital energy levels to improve the sensitization of C* emission. Quenching of polymer fluorescence with ssDNA-C* and differences in C* emission suggest involvement of photoinduced charge transfer (PCT) as an energy wasting mechanism. The HOMO and LUMO energy levels of the conjugated polymers and C serve as a preliminary basis to understand the competition between FRET and PCT. Dilution of C in polymer/ssDNA-C complexes by addition of ssDNA yields insight into C*...C self-quenching. Under optimized conditions, where there is no probe self-quenching and minimum PCT, efficient signal amplification is demonstrated despite poor spectral overlap between polymer and C.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Biosensing Techniques / methods
  • DNA, Single-Stranded / chemistry*
  • Fluorenes / chemistry
  • Fluorescein / chemistry
  • Fluorescence Resonance Energy Transfer / methods
  • Fluorescent Dyes / chemistry*
  • Luminescent Measurements / methods
  • Polymers / chemistry*
  • Thermodynamics
  • Xanthenes / chemistry

Substances

  • DNA, Single-Stranded
  • Fluorenes
  • Fluorescent Dyes
  • Polymers
  • Xanthenes
  • Texas red
  • Fluorescein