Solvent-assisted optical modulation of FRET-induced fluorescence for efficient conjugated polymer-based DNA detection.
The solvent effects were studied in fluorescence resonance energy transfer (FRET) from a cationic polyfluorene copolymer (FHQ, FPQ) to a fluorescein (Fl)-labelled oligonucleotide (ssDNA-Fl). Upon addition of dimethyl sulfoxide (DMSO), the optical properties of polymers and the probe dye were substantially modified and the FRET-induced PL signal was enhanced 3.8-37 times, relative to that in phosphate buffer solution (PBS). The hydrophobic interaction between polymers and ssDNA-Fl is expected to decrease in the presence of DMSO, which induces the weaker polymer/ssDNA-Fl complexation with longer intermolecular donor-acceptor separation and perturbs the competition between the FRET and PL quenching processes such as photo-induced charge transfer. The gradual decrease in Fl PL quenching with increasing the DMSO content was investigated by measuring the Stern-Volmer quenching constants (3.3-4.2 × 10(6) M(-1) in PBS, 0.56-1.1 × 10(6) M(-1) in 80 vol% DMSO) and PL lifetime of the excited Fl* in polymer/ssDNA-Fl (600 ps in PBS and 2120 ps in 80 vol% DMSO for FHQ/ssDNA-Fl) in PBS/DMSO mixtures. The substantially reduced PL quenching would amplify the resulting FRET Fl signal. The signal amplification in real DNA detection was also demonstrated with fluorescein-labelled PNA (probe PNA) in the presence of a complementary target DNA and noncomplementary DNA in aqueous DMSO solutions. This approach suggests a simple way of modifying the fine-structure of polymer/ssDNA-Fl and improving the detection sensitivity in conjugated polymer-based FRET bioassays.
Department of Nanofusion Technology, Pusan National University, Miryang 627-706, Republic of Korea.
Mijeong
M
Kang
Okhil Kumar
OK
Nag
Sungu
S
Hwang
Inhong
I
Kim
Haesik
H
Yang
Kwangseuk
K
Kyhm
Han Young
HY
Woo
D004277:DNA, Single-Stranded / Q000737:chemistry*; D004121:Dimethyl Sulfoxide / Q000737:chemistry; D005449:Fluorenes / Q000737:chemistry; D019793:Fluorescein / Q000737:chemistry; D031541:Fluorescence Resonance Energy Transfer / Q000379:methods*; D020135:Peptide Nucleic Acids / Q000737:chemistry; D011108:Polymers / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry*
D004277:DNA, Single-Stranded; D005449:Fluorenes; D020135:Peptide Nucleic Acids; D011108:Polymers; D012997:Solvents; C041509:fluorene; D019793:Fluorescein; D004121:Dimethyl Sulfoxide