Cationic Polythiophene Derivative Research Articles

Colorimetric detection of copper ions based on a supramolecular complex of water-soluble polythiophene and ATP

A colorimetric probe for the detection of copper(II) ions in aqueous media by the naked eye has been developed based on a supramolecular complex comprised of a cationic polythiophene derivative and ATP with a detection limit as low as 0.05 mM.

New Conjugated Polymers for Photoinduced Unwinding of DNA Supercoiling and Gene Regulation

Three cationic polythiophene derivatives (P1, P2, P3) were synthesized and characterized. Under white light irradiation (400-800 nm), they sensitize oxygen molecule in the surrounding to generate reactive oxygen species (ROS) that can efficiently unwind the supercoiled DNA in vitro. Further study shows that this relaxation of the DNA supercoiling results in the decrease of gene (pCX-EGFP plasmid) expression level. The ability of these conjugated polymers for regulating gene expression will add a new dimension to the function of conjugated polymers.

Synthesis of a New Cationic Polythiophene Derivative and Its Application for Colorimetric and Fluorometric Detection of Iodide Ion and Anionic Surfactants in Water

AbstractA new cationic polythiophene derivative poly[3‐(1,1′‐dimethyl‐4‐piperidinemethylene)thiophene‐2,5‐diyl chloride] (PDPMT‐Cl) is synthesized and applied as a colorimetric and fluorometric probe for the detection of iodide ion and anionic surfactants with high selectivity and sensitivity. Upon adding iodide ion or anionic surfactant into the aqueous solution of PDPMT‐Cl, the maximum absorption of the polymer is blue‐shifted with a naked‐eye color change from red‐violet to yellow, signifying that iodide ion or anionic surfactants can cause the dissociation of PDPMT‐Cl aggregates. More sensitive results are obtained in the fluorometric detection to iodide ion or anionic surfactant, thereinto, the detection limit to surfactants can be extended to the order of 10−9 M.

Work Function Control of Interfacial Buffer Layers for Efficient and Air‐Stable Inverted Low‐Bandgap Organic Photovoltaics

AbstractA water‐soluble cationic polythiophene derivative, poly[3‐(6‐{4‐tert‐butylpyridiniumyl}‐hexyl)thiophene‐2,5‐diyl] [P3(TBP)HT], is combined with anionic poly(3,4‐ethylenedioxythiophene):poly(p‐styrenesulfonate) (PEDOT:PSS) on indium tin oxide (ITO) substrates via electrostatic layer‐by‐layer (eLbL) assembly. By varying the number of eLbL layers, the electrode's work function is precisely controlled from 4.6 to 3.8 eV. These polymeric coatings are used as cathodic interfacial modifiers for inverted‐mode organic photovoltaics that incorporate a photoactive layer composed of either poly[(3‐hexylthiophene)‐2,5‐diyl] (P3HT) and the fullerene acceptor [6,6‐phenyl‐C61‐butyric acid methyl ester (PC61BM) or the low bandgap polymer [poly({4,8‐di(2‐ethylhexyloxyl)benzo[1,2‐b:4,5‐b′]dithiophene}‐2,6‐diyl)‐alt‐({5‐octylthieno[3,4‐c]pyrrole‐4,6‐dione}‐1,3‐diyl) (PBDTTPD)] and the electron acceptor [6,6‐phenyl‐C71‐butyric acid methyl ester (PC71BM)]. The power conversion efficiency (PCE) of the resulting photovoltaic device is dependent on the composition of the eLbL‐assembled interface and permits the fabrication of devices with efficiencies of 3.8% and 5.6% for P3HT and PBDTTPD donor polymers, respectively. Notably, these devices demonstrate significant stability with a P3HT:PC61BM system maintaining 83% of its original PCE after 1 year of storage and a PBDTTPD:PC71BM system maintaining 97% of its original PCE after over 1000 h of storage in air, according to the ISOS‐D‐1 shelf protocol.

A novel polythiophene derivative as a sensitive colorimetric and fluorescent sensor for anionic surfactants in water

A novel cationic polythiophene derivative, poly[N,N,N-trimethyl-4-(thiophen-3-ylmethylene)cyclohexanaminium chloride] (PTCA-Cl), has been prepared successfully and applied as a colorimetric and fluorometric probe for the detection of anionic surfactants. In particular, a new method for the polymerization of cationic polythiophene derivatives is found, which has not been reported previously. The colorimetric and fluorescent response of PTCA-Cl to anionic surfactants have been investigated by absorption and emission spectroscopy. The sensing interaction can be apparently observed by the naked eye, which presents a great advantage for its practical applications. Moreover, the sensor (PTCA-Cl) shows high selectivity towards anionic surfactants in the presence of other negatively charged analytes, as well as high sensitivity with a detection limit at 10−9 M by using fluorimetry, which is the lowest ever achieved among all synthetic anionic surfactants sensors available. Therefore, the water soluble polythiophene derivative can be applied as a colorimetric and fluorescent probe for the detection of anionic surfactants with high selectivity and sensitivity.

Colorimetric and fluorescent dual probe based on a polythiophene derivative for the detection of cysteine and homocysteine

Colorimetric and fluorescent dual detection of cysteine (Cys) and homocysteine (Hcy) has been realized based on the ionic self-assembly of a cationic polythiophene derivative with aromatic derivatives of Cys and Hcy formed in situ.

DNA biosensors based on water-soluble conjugated polymers

Conjugated polymers (CPs) with large, delocalised molecular structures exhibit unique optical and electrochemical characteristics that can be used as excellent sensing elements. Recently, research on chemical and biological sensors that use water-soluble CPs as transducers has generated intense interest. Two main sensing mechanisms are used for the detection of DNA-related events, such as hybridisation, mismatch, single nucleotide polymorphism (SNP), SNP genotyping, conformational changes, and cleavage of the nucleic acids. One mechanism takes advantage of the fluorescence resonance energy transfer (FRET) between CPs and a chromophore label on the nucleic acid probes in which a series of cationic polyfluorene, polythiophene and polyarylene derivatives are frequently used. The other mechanism relies on the conformational effects of CPs, which is induced by combination of the specific targets in which cationic polythiophene derivatives are often used. The electron transfer property of CPs are always used to design high sensitive electrochemical DNA biosensors. Here we review recent progress in the development of optical and electrochemical DNA biosensors based on water-soluble CPs.

2008 Macromolecular Science and Engineering Division Award Lecture — Conjugated polymers: From micro-electronics to genomics

Conjugated polymers have received a lot of attention, since they combine the best features of metals or semiconductors with those of synthetic polymers. For instance, solar cells based on poly(2,7-carbazole) derivatives have revealed power-conversion efficiencies up to 6%. This class of materials could lead to printable and flexible photovoltaic devices. Moreover, water-soluble luminescent polythiophenes have allowed the specific, rapid, and ultra-sensitive detection of unlabelled DNA, RNA, or proteins. This new optical detection mechanism is based on electrostatic interactions between a cationic polythiophene derivative and negatively charged oligonucleotides. This method makes now possible the rapid assessment of the identity of single nucleotide polymorphisms (SNPs), genes, and pathogens without the need for nucleic acid amplification.

Colorimetric detection of microRNA and RNase H activity in homogeneous solution with cationic polythiophene derivative

A colorimetric assay for convenient detection of miRNA and RNase H activity was established in a homogeneous and label-free manner based on conformational and colorimetric changes of a polythiophene derivative (PMNT) in the duplex of DNA/PMNT and triplex of DNA/miRNA/PMNT.

Optical Detection of DNA and Proteins with Cationic Polythiophenes

In recent years, intense research has been carried out worldwide with the goal of developing simple, sensitive, and specific detection tools for biomedical applications. Along these lines, we reported in 2002 on cationic polythiophene derivatives able to provide ultrasensitive detection levels and the capability to distinguish perfect matches from oligonucleotides having as little as a single base mismatch. It was shown that the intrinsic fluorescence of the random-coil polymers quenches as a result of the planar, highly conjugated conformation adopted by the polymers when complexed with a single-strand DNA (ssDNA) capture probe but increases again after hybridization with the perfectly matched complementary strand. This change in fluorescence intensity is mainly due to a modification in the delocalization of pi electrons along the carbon chain backbone that occurs when switching between the two conformations. Thus, by monitoring, via the change in fluorescence intensity, the hybridization of the complementary ssDNA target with the "duplex", one could detect as little as 220 complementary target molecules in a 150 microL sample volume (0.36 zmol) in less than 1 hour. Building on this initial concept, we then reported that tagging the DNA probe with a suitable fluorophore dramatically increases the detection sensitivity. This novel molecular system involves the self-assembly of aggregates of duplexes in solution, prior to the introduction of the target, which allows a highly efficient resonance energy transfer (RET) between a "donor" (being the complex formed of the DNA double helix and the polymer chain wrapped around it) and a large number of neighboring "acceptors" (the fluorophores attached to the DNA probes). The massive intrinsic signal amplification (fluorescence chain reaction or FCR) provided by this novel integrated molecular system allows the specific detection of as little as five dsDNA copies in a 3 mL sample volume in only 5 minutes, without the need for prior amplification of the target. Clearly, direct and reliable detection of DNA hybridization without prior PCR amplification or chemical tagging of the genetic target is now possible with this methodology. We have also shown that proteins can be detected following a similar strategy. Impressive results have also been reported by direct and specific staining of targeted proteins. All these features have recently allowed the development of responsive polymeric supports for the detection of DNA and proteins. All these assays that do not require any chemical manipulation of the biological targets or sophisticated experimental procedures should soon lead to major advances in genomics and proteomics.

Analyte‐Induced Aggregation of a Water‐Soluble Conjugated Polymer for Fluorescent Assay of Oxalic Acid

AbstractAn assay method has been developed to detect oxalic acid from other structurally similar dicarboxylic acids using a cationic polythiophene derivative (PFT). Upon adding oxalic acid, the PFT can be cross‐linked through the bifunctional diacids of oxalic acid to form tense interpolymer π‐stacking aggregation, which results in the fluorescence self‐quenching of the PFT. Upon adding other dicarboxylic acids with a longer tether, loose interpolymer π‐stacking aggregation forms and the PFT fluorescence is less quenched. The fluorescence analysis was carried out in solution for the aggregates prior to precipitation. As a result of the short tether of oxalic acid, the unique fluorescent response from the PFT/oxalic acid assembly can be used to detect oxalic acid.magnified image

Direct Visualization of Enzymatic Cleavage and Oxidative Damage by Hydroxyl Radicals of Single-Stranded DNA with a Cationic Polythiophene Derivative

A new method has been developed for the label-free, convenient, and real-time monitoring of the cleavage of single-stranded DNA by single-strand-specific S1 nuclease and hydroxyl radical based on cationic water-soluble poly[3-(3'-N,N,N-triethylamino-1'-propyloxy)-4-methyl-2,5-thiophene hydrochloride](PMNT). The PMNT can form an interpolyelectrolyte complex with ssDNA (duplex) through electrostatic interactions, in which PMNT takes a highly conjugated and planar conformation, and thus PMNT exhibits a relatively red-shifted absorption wavelength. When ssDNA is hydrolyzed by S1 nuclease or hydroxyl radical into small fragments, the PMNT/ssDNA duplex cannot form. In this case, the PMNT remains in random-coil conformation and exhibits a relatively short absorption wavelength. The nuclease digestion or oxidative damage by hydroxyl radical of DNA can be monitored by absorption spectra or just visualized by the "naked-eye" in view of the observed PMNT color changes in aqueous solutions. This assay is simple and rapid, and there is no need to label DNA substrates. The most important characteristic of the assay is direct visualization of the DNA cleavage by the "naked-eye", which makes it more convenient than other methods that rely on instrumentation. The assay also provides a promising application in drug screening based on the inhibition of oxidative damage of DNA.

Protein Detecting Arrays Based on Cationic Polythiophene–DNA‐Aptamer Complexes

Novel biosensors are always needed for improving modern biomedical research as well as for environmental and forensic sciences. Among the proposed techniques, the (micro) fabrication of addressable 2D arrays (biochips) has become a powerful tool. However, in most cases this method relies on fluorescent tagging of the analytes for detection. In addition to implying the use of careful synthetic procedures, it is worth noting that labeling may even alter the binding properties of the analytes. Assays that do not require any chemical manipulation of the biological targets or sophisticated experimental techniques (mass spectrometry, surface plasmon resonance, etc.) would be greatly advantageous. These limitations could be solved by a new generation of responsive supports with optical or electrical properties modified upon specific and efficient binding of a specific label-free target. In parallel, because of their central importance in many biological processes and as biomarkers related to human diseases, there is a high demand for convenient methodologies for detecting specific proteins. Along these lines, RNA and DNA aptamers have recently received considerable attention as new protein recognition elements. Aptamers are usually isolated from combinatorial libraries of synthetic nucleic acids by an iterative process of adsorption, recovery, and amplification. Therefore, by combining smart polymeric transducers and aptamer ligands, we report new responsive supports for the reagentless, sensitive, and specific optical detection of proteins. For instance, these simple integrated biochips allow the direct and specific detection of human thrombin in the attomole range in less than one hour at room temperature. The development of these novel responsive biochips is based on the utilization of a chromic, cationic, water-soluble polythiophene derivative (Scheme 1). This polymer exhibits different conformational structures and optical properties when it is in the presence of free single-stranded (ss) nucleic acids or bound nucleic acids. More precisely, stoichiometric complexes between this polythiophene derivative and ssDNA form neutral rigid-rod moieties that self-assemble into nanoaggregates and result in significant quenching of the fluorescence of the conjugated polymer. In solution, it has been shown that the polythiophene becomes fluorescent again through specific hybridization or DNA-aptamer– protein interactions. For instance, the negatively charged DNA aptamer bound to a specific protein undergoes a conformational transition from an unfolded to a folded (G-quadruplex) structure that can be detected by the cationic polythiophene derivative. Moreover, it has been recently reported that a significant fluorescence signal amplification (fluorescence chain reaction (FCR)) takes place within micelle-like structures formed from labeled ssDNA–polythiophene complexes in solution. This new detection method is based on the efficient and fast energy transfer (Forster resonance energy transfer (FRET)) between one resulting fluorescent polythiophene chain and many fluorophores attached to neighboring ssDNA probes. Stoichiometric complexes (duplexes) were therefore prepared by mixing the polythiophene optical transducer with a Cy3-3′-labeled ssDNA aptamer. This chromophore was chosen because its absorption spectrum overlaps well with the emission spectrum of the polythiophene, a necessary condition for efficient FRET. However, to allow the covalent binding of these aggregated duplexes onto surface-treated glass slides, an amine group was also inserted at the 5′-end of the ssDNA capture probes. Upon spotting, these aggregates made of hybrid polythiophene–ssDNA complexes were therefore bound onto glass slides (Scheme 1). Then, for the specific detection of human thrombin, the following strategy was designed: First, P1 (5′-NH2-C6-GGT TGG TGT GGT TGG-Cy3-3′), P2 (5′-NH2-C6-GGT TGG TGT GGT TGG3′), or P3 (5′-NH2-C6-GGT GGT GGT TGT GGT-Cy3-3′) were combined with cationic polythiophene in order to form stoichiometric duplexes. P1 and P2 are both sequences specific to thrombin; however, P1 is labeled with Cy3 fluorophore whereas P2 is not. P3 is a labeled sequence that does not bind to thrombin. The diameter of the spots is about 1.5–1.7 mm (see Fig. 1), each including about 1 × 10 probes. C O M M U N IC A IO N S

Optical Sensors Based on Hybrid DNA/Conjugated Polymer Complexes

Single-stranded DNA (ss-DNA) can specifically bind to various targets, including a complementary ss-DNA, ions, proteins, drugs, and so forth. When binding takes place, the oligonucleotide probe often undergoes a conformational transition. This conformational change of the negatively charged ss-DNA can be detected by using a water-soluble, cationic polythiophene derivative, which transduces the complex formation into an optical (colorimetric or fluorometric) signal without any labeling of the probe or the target. This simple and rapid methodology has enabled the specific and sensitive detection of nucleic acids and human thrombin. This new biophotonic tool can easily be applied to the detection of various other biomolecules and is also useful in the high-throughput screening of new drugs.

Optical sensors based on hybrid aptamer/conjugated polymer complexes.

Single-stranded DNA (aptamer) can specifically bind potassium ions or human alpha-thrombin. When binding takes place, the aptamer undergoes a conformational transition from an unfolded to a folded structure. This conformational change of the negatively charged oligonucleotide can be detected by adding a water-soluble, cationic polythiophene derivative, which transduces the new complex formation into an optical (colorimetric or fluorometric) signal without any labeling of the probe or of the target. This simple and rapid methodology has enabled the detection of human thrombin in the femtomole range. This new biophotonic tool can easily be applied to the detection of various other proteins as well as being useful in the high-throughput screening of new drugs.

New colorimetric and fluorometric chemosensor based on a cationic polythiophene derivative for iodide-specific detection.

Electrostatic interactions between anions and a new water-soluble, cationic, affinitychromic poly(3-alkoxy-4-methylthiophene) derivative provide a new tool for a selective optical detection method (colorimetric or fluorometric) for iodide ions.

Colorimetric and Fluorometric Detection of Nucleic Acids Using Cationic Polythiophene Derivatives

Unterschiede in den elektrostatischen Wechselwirkungen und Konformationen zwischen einzel- oder doppelsträngigen negativ geladenen oberflächengebundenen Nucleinsäuremolekülen und wasserlöslichen kationischen Poly(3-alkoxy-4-methylthiophen)-Derivaten (siehe Bild) bilden die Grundlage einer neuen empfindlichen optischen Detektionsmethode (kolorimetrisch oder fluorimetrisch) für die Oligonucleotidhybridisierung. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2001/2002/z18191_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Colorimetric and Fluorometric Detection of Nucleic Acids Using Cationic Polythiophene Derivatives

Simple and reliable sequence-specific methods are needed for the rapid detection of oligonucleotides, to diagnose infections and various genetic diseases. In this regard, interesting optical and electrochemical DNA-hybridization sensors have been proposed.[1±5] The recognition capabilities of DNA are well established but, to transduce the recognition event into a physically measurable value, a fluorescent or electroactive tag is often bound to the analyte. Electrochemical and optical sensors based on conjugated polymers have also been reported[6±9] and some oligonucleotide-functionalized conjugated polymers can also transduce hybridization events into an electrical signal without labeling of the oligonucleotide target.[10±12] The detection relies on a modTo our knowledge this is the first report on the use of singlemolecule atomic-force spectroscopy to study the reduction pathway of multiple disulfide bonds in proteins and to evaluate the distributions of intermediates obtained under different reducing conditions without separating them and without any blocking and fractionation steps. The characterization of these intermediates has so far been accomplished by first blocking them with reagents such as alkylalkanethiosulfonates and then by fractionation by ion-exchange chromatography, 2D or capillary gel electrophoresis, or gel filtration.[11] The determination of thiol groups and disulfide bonds in a polythiol systems has always been a very challenging problem.[12] The single-molecule force-spectroscopy data presented here show: 1) how a redox environment can modulate the mechanical properties of angiostatin; 2) how this modulation relies, at the single-molecule level, on the extent of reduction of the disulfide bonds; and 3) how, at the level of a large sample of molecules, the distribution of the different thiol/ disulfide intermediates after reduction can be estimated by statistical analysis of the force curves.