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

POLY 26

Bin Liu, cheliub@nus.edu.sg, Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore, 117576, Singapore and Guillermo C. Bazan, bazan@chem.ucsb.edu, Department of Chemistry and Materials, Institute for Polymers and Organic Solids, University of California, Santa Barbara, Santa Barbara, CA 93106.
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 sensitization of C* emission. Quenching of polymer fluorescence with ssDNA-C* and differences in C* emission suggest involvement of photo induced 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 the polymer and C*.
 

Polymers in Biosensors and Biochips
8:30 AM-12:10 PM, Sunday, 10 September 2006 San Francisco Marriott -- Salon 12/13, Oral

Division of Polymer Chemistry

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006