Shape-Adaptable Water-Soluble Conjugated Polymers

Liu, Bin; Wang, Shu; Bazan, Guillermo C.; Mikhailovsky, Alexander

doi:10.1021/ja0365072

Cited by 191 publications

(180 citation statements)

References 14 publications

(23 reference statements)

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“…Only with the all-meta polymer do we observe a big shift in the emission maximum. This particular observation is quite similar to that reported for water-soluble copolymers containing meta-links, 38 and indicates that Fö rster energy transfer occurs from shorter conjugation length regions of the chain to more conjugated regions with lower energy. No long-wavelength emission (>500 nm) is observed in the photoluminescence spectra which is in accordance with the polymer chains being well separated in solution, minimizing the formation of excimers.…”

Section: Absorption and Emission Spectra In Solutionsupporting

confidence: 87%

Effect of meta-linkages on the photoluminescence and electroluminescence properties of light-emitting polyfluorene alternating copolymers

et al. 2006

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Alternating copolymers poly [9,9-dihexylfluorene-alt-(1,3-phenylene) x (1,4-phenylene) 12x ] (x = 0, 0.05, 0.1, 0.25, 0.5, 0.75, 1.0) were prepared, and the absorption spectra showed the expected hypsochromic shift with increasing meta linkages. In the solution photoluminescence (PL) emission spectra, all but the all-meta polymer (x = 1) showed a spectrum similar to the all-para polymer, indicating rapid intrachain energy transfer to para-linked segments. Similar spectra were observed from thin films in which inter-chain energy transfer is also available. Annealing of the thin films in air above the T g of the polymer for several hours led to an increase in long wavelength emission, but the increase was smaller for the polymers containing more meta linkages. IR experiments confirmed the formation of fluorenone defects during the annealing process. For those polymers with high meta-linkage incorporation (i.e. 75% and 100% meta) the long wavelength emission is suppressed. This suggests that when the conjugation length of the polymer is reduced then energy transfer to fluorenone defects is less likely, due to lower exciton delocalisation and mobility. The long wavelength emission was more prominent in the electroluminescence (EL) spectra of devices prepared from the polymer, and, while initially less intense in the high meta linkages polymers, became dominant even for the all-meta linked polymer after a few minutes of operation. In summary, the meta linkages had a beneficial effect in suppressing the undesirable long wavelength emission in both the PL and EL output.

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Section: Absorption and Emission Spectra In Solutionsupporting

confidence: 87%

Effect of meta-linkages on the photoluminescence and electroluminescence properties of light-emitting polyfluorene alternating copolymers

et al. 2006

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“…conjugated polymers ͉ DNA sensors ͉ time-resolved anisotropy ͉ ultrafast spectroscopy C ationic conjugated polymers (CCPs) have been demonstrated to have utility in DNA sequence detection (1)(2)(3). In the approach initially proposed by Gaylord et al (1), the luminescent conjugated polymer serves as the light-harvesting entity with subsequent energy transfer to a fluorescein (FL) molecule attached to a peptide nucleic acid (PNA) oligomer comprised of a specific sequence of bases that defines the target.…”

mentioning

confidence: 99%

The fluorescence resonance energy transfer (FRET) gate: A time-resolved study

Wang²,

Korystov³

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

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106

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The two-step energy-transfer process in a self-assembled complex comprising a cationic conjugated polymer (CCP) and a dsDNA is investigated by using pump-dump-emission spectroscopy and time-correlated single-photon counting; energy is transferred from the CCP to an ethidium bromide (EB) molecule intercalated into the dsDNA through a fluorescein molecule linked to one terminus of the DNA. Time-dependent anisotropy measurements indicate that the inefficient direct energy transfer from the CCP to the intercalated EB results from the near orthogonality of their transition moments. These measurements also show that the transition moment of the fluorescein spans a range of angular distributions and lies between that of the CCP and EB. Consequently, the fluorescein acts as a fluorescence resonance energy-transfer gate to relay the excitation energy from the CCP to the EB. conjugated polymers ͉ DNA sensors ͉ time-resolved anisotropy ͉ ultrafast spectroscopy C ationic conjugated polymers (CCPs) have been demonstrated to have utility in DNA sequence detection (1-3). In the approach initially proposed by Gaylord et al. (1), the luminescent conjugated polymer serves as the light-harvesting entity with subsequent energy transfer to a fluorescein (FL) molecule attached to a peptide nucleic acid (PNA) oligomer comprised of a specific sequence of bases that defines the target. Fluorescence resonance energy transfer (FRET) from the CCP to the PNA-FL occurs by self-assembly of the CCP and the PNA in a double helix with a complementary single-stranded DNA target. In this approach, the electrostatic interaction between the CCP and the negatively charged PNA-FL͞DNA duplex brings the donor (CCP) and the acceptor (FL) in sufficiently close proximity to enable efficient FRET. When the base sequence on the DNA is not complementary to the base sequence on the FL-labeled PNA, the PNA-FL remains as a charge-neutral single-strand oligomer. At the dilute concentrations used, the typical distance between a neutral PNA-FL and a CCP is too large for efficient FRET. By using this FRET-based biosensor, specific targeted sequences of DNA were detected at concentrations as low as 10 pM (1).Wang et al. (2) reported an alternative DNA sequencedetection scheme (Scheme 1) based on intercalation of ethidium bromide (EB) within a dsDNA. Considering that the synthesis and purification of labeled DNA is more straightforward and that both single-stranded DNA and dsDNA have good solubility in buffered water (whereas with PNA, hydrophobic interactions are important), the EB intercalation approach is attractive. However, direct FRET from the CCP to EB was found to be inefficient despite the excellent spectral overlap between the donor emission and acceptor absorption. The absence of efficient FRET was attributed to the orthogonality of the transition dipoles of the CCP and EB in the self-assembled structure (see Scheme 1). When a FL molecule is linked to one terminus of the dsDNA as shown in Scheme 1B, the EB emission is significantly enhanced after excitation...

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“…Because the energy transfer process shows strong distance dependence, it is important to consider the relative length scales of the target DNA and cationic CP. Based on the molecular weight of the polymer (M w Ϸ 13,000 g͞mole, Ϸ13 Å per repeat unit), it is evident that the CP is longer than the oligonucleotide (15-28 base) target sequences tested previously (27)(28)(29)(30)(31)44).…”

Section: Resultsmentioning

confidence: 98%

“…This collective behavior gives rise to optical enhancement or amplification if the lowenergy site comprises a reporter fluorophore. The water solubility of these macromolecules is achieved by attaching ionic side chains pendent to the otherwise hydrophobic main chain, whereas the spectral properties are tuned by altering the actual conjugated backbone structure (26)(27)(28)(29)(30)(31).…”

mentioning

confidence: 99%

SNP detection using peptide nucleic acid probes and conjugated polymers: Applications in neurodegenerative disease identification

Gaylord

Massie

Feinstein

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

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165

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A strategy employing a combination of peptide nucleic acid (PNA) probes, an optically amplifying conjugated polymer (CP), and S1 nuclease enzyme is capable of detecting SNPs in a simple, rapid, and sensitive manner. The recognition is accomplished by sequence-specific hybridization between the uncharged, fluorescein-labeled PNA probe and the DNA sequence of interest. After subsequent treatment with S1 nuclease, the cationic water soluble CP electrostatically associates with the remaining anionic PNA͞ DNA complex, leading to sensitized emission of the labeled PNA probe via FRET from the CP. The generation of fluorescent signal is controlled by strand-specific electrostatic interactions and is governed by the complementarity of the probe͞target pair. To assess the method, we compared the ability of the sensor system to detect normal, wild-type human DNA sequences, and those sequences containing a single base mutation. Specifically, we examined a PNA probe complementary to a region of the gene encoding the microtubule associated protein tau. The probe sequence covers a known point mutation implicated in a dominant neurodegenerative dementia known as frontotemporal dementia with parkinsonism linked to chromosome 17 (FTDP-17), which has clinical and molecular similarities to Alzheimer's disease. By using an appropriate PNA probe, the conjugated polymer poly[(9,9-bis(6 -N,N,Ntrimethylammoniumhexylbromide)fluorene)-co-phenylene] and S1 nuclease, unambiguous FRET signaling is achieved for the wildtype DNA and not the mutant sequence harboring the SNP. Distance relationships in the CP͞PNA assay are also discussed to highlight constraints and demonstrate improvements within the system. biosensor ͉ energy transfer ͉ hybridization probes ͉ polyelectrolyte ͉ fluorescence

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Shape-Adaptable Water-Soluble Conjugated Polymers

Cited by 191 publications

References 14 publications

Effect of meta-linkages on the photoluminescence and electroluminescence properties of light-emitting polyfluorene alternating copolymers

Effect of meta-linkages on the photoluminescence and electroluminescence properties of light-emitting polyfluorene alternating copolymers

The fluorescence resonance energy transfer (FRET) gate: A time-resolved study

SNP detection using peptide nucleic acid probes and conjugated polymers: Applications in neurodegenerative disease identification

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