title: Optimization of the molecular orbital energies of conjugated polymers for optical amplification of fluorescent sensors.
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.
authors.affiliation: Department of Materials and Chemistry and Biochemistry, Institute for Polymers and Organic Solids, University of California at Santa Barbara, 93106, USA.
authors.forename: Bin
authors.initials: B
authors.lastname: Liu
authors.forename: Guillermo C
authors.initials: GC
authors.lastname: Bazan
mesh_terms: D015374:Biosensing Techniques / Q000379:methods; D004277:DNA, Single-Stranded / Q000737:chemistry*; D005449:Fluorenes / Q000737:chemistry; D019793:Fluorescein / Q000737:chemistry; D031541:Fluorescence Resonance Energy Transfer / Q000379:methods; D005456:Fluorescent Dyes / Q000737:chemistry*; D008163:Luminescent Measurements / Q000379:methods; D011108:Polymers / Q000737:chemistry*; D013816:Thermodynamics; D014966:Xanthenes / Q000737:chemistry
chemical_list: D004277:DNA, Single-Stranded; D005449:Fluorenes; D005456:Fluorescent Dyes; D011108:Polymers; D014966:Xanthenes; C034657:Texas red; D019793:Fluorescein