Water-soluble Conjugated Polymers Research Articles

CO2-Responsive Water-Soluble Conjugated Polymers as a Multifunctional Fluorescent Probe for Bioimaging Applications.

We describe important progress in the synthesis and development of gas-responsive water-soluble conjugated polymers (WSCPs) with potential as multifunctional fluorescent materials for biomedical imaging and probes. A water-soluble WSCP (I-PT) composed of a hydrophobic fluorescent polythiophene backbone and a hydrophilic imidazole side chain was successfully prepared through a facile and efficient two-step synthetic route. Owing to the repulsive force between the hydrophilic and hydrophobic segments and the highly sensitive carbon dioxide (CO2)- and nitrogen (N2)-responsive imidazole groups in its structure, I-PT can spontaneously self-assemble into spherical-like nanoparticles in an aqueous environment, and thus exhibits unique light absorption and fluorescence properties as well as rapid responsiveness to CO2 and N2. In addition, its structure, optical absorption/fluorescence behavior, and surface potential can be quickly turned on and off through alternating cycles of CO2 and N2 bubbling and exhibit controllable cyclic switching stability, thereby allowing effective manipulation of its hierarchical structure and chemical-physical characteristics. More importantly, a series of in vitro cell experiments confirmed that, compared to the significant cytotoxicity of pristine and N2-treated I-PT nanoparticles, CO2-treated I-PT nanoparticles exhibit extremely low cytotoxicity in normal and cancer cells and undergo greatly accelerated cellular uptake, resulting in a significant increase in the intensity and stability of their fluorescence signal in the intracellular environment. Overall, this newly discovered CO2/N2-responsive system provides new insights to effectively enhance the biocompatibility, cellular internalization, and intracellular fluorescence characteristics of WSCPs and holds great potential for biomedical imaging/sensing applications.

Water-soluble conjugated polymers for bioelectronic systems.

Bioelectronics is an interdisciplinary field of research that aims to establish a synergy between electronics and biology. Contributing to a deeper understanding of bioelectronic processes and the built bioelectronic systems, a variety of new phenomena, mechanisms and concepts have been derived in the field of biology, medicine, energy, artificial intelligence science, etc. Organic semiconductors can promote the applications of bioelectronics in improving original performance and creating new features for organisms due to their excellent photoelectric and electrical properties. Recently, water-soluble conjugated polymers (WSCPs) have been employed as a class of ideal interface materials to regulate bioelectronic processes between biological systems and electronic systems, relying on their satisfying ionic conductivity, water-solubility, good biocompatibility and the additional mechanical and electrical properties. In this review, we summarize the prominent contributions of WSCPs in the aspect of the regulation of bioelectronic processes and highlight the latest advances in WSCPs for bioelectronic applications, involving biosynthetic systems, photosynthetic systems, biophotovoltaic systems, and bioelectronic devices. The challenges and outlooks of WSCPs in designing high-performance bioelectronic systems are also discussed.

Unexpected Photocatalytic Degeneration of NAD + for Inducing Apoptosis of Hypoxia Cancer Cells

Unexpected Photocatalytic Degeneration of NAD ⁺ for Inducing Apoptosis of Hypoxia Cancer Cells

Functionalization of Water-Soluble Conjugated Polymers for Bioapplications.

Water-soluble conjugated polymers (WS-CPs) have found widespread use in bioapplications ranging from in vitro optical sensing to in vivo phototherapy. Modification of WS-CPs with specific molecular functional units is necessary to enable them to interact with biological targets. These targets include proteins, nucleic acids, antibodies, cells, and intracellular components. WS-CPs have been modified with covalently linked sugars, peptides, nucleic acids, biotin, proteins, and other biorecognition elements. The objective of this article is to comprehensively review the various synthetic chemistries that have been used to covalently link biofunctional groups onto WS-CP platforms. These chemistries include amidation, nucleophilic substitution, Click reactions, and conjugate addition. Different types of WS-CP backbones have been used as platforms including poly(fluorene), poly(phenylene ethynylene), polythiophene, poly(phenylenevinylene), and others. Example applications of biofunctionalized WS-CPs are also reviewed. These include examples of protein sensing, flow cytometry labeling, and cancer therapy. The major challenges and future development of functionalized conjugated polymers are also discussed.

Visible-Light-Driven Asymmetric TiO2-Based Photocatalytic Micromotor Hybridized with a Conjugated Polyelectrolyte and Glucose Oxidase.

We fabricated a TiO2-based micromotor that was asymmetrically decorated with a water-soluble conjugated polymer (WSP) on one hemisphere and glucose oxidase (GOx) on the opposite hemisphere. The WSP, which had photocatalytic activity for H2O2 decomposition, enabled motion of the micromotor under visible light. The GOx on the other hemisphere of the micromotor decomposed glucose to produce H2O2 and enabled motion of the micromotor without light irradiation. In addition, WSP and GOx were attached to TiO2 by chemical bonds, providing stability during use. As a result, the micromotor could move by self-generating H2O2 for its own fuel by consuming glucose even without photoirradiation. The micromotor could move faster than without visible light irradiation through the synergistic decomposition of glucose and H2O2 under visible light by the diffusiophoretic mechanism with a speed of 7.49 μm/s.

CO2-Responsive Water-Soluble Conjugated Polymers for In Vitro and In Vivo Biological Imaging.

Water-soluble conjugated polymers (WCPs) composed of a hydrophobic polythiophene main chain with hydrophilic tertiary amine side-chains can directly self-assemble into sphere-like nano-objects in an aqueous solution due to phase separation between the hydrophilic and hydrophobic segments of the polymeric structure. Due to the presence of gas-responsive tertiary amine moieties in the spherical structure, the resulting polymers rapidly and reversibly tune their structural features, surface charge, and fluorescence performance in response to alternating carbon dioxide (CO2) and nitrogen (N2) bubbling, which leads to significantly enhanced fluorescence and surface charge switching properties and a stable cycle of on and off switching response. In vitro studies confirmed that the CO2-treated polymers exhibited extremely low cytotoxicity and enhanced cellular uptake ability in normal and tumor cells, and thus possess significantly improved fluorescence stability, distribution, and endocytic uptake efficiency within cellular organisms compared to the pristine polymer. More importantly, in vivo assays demonstrated that the CO2-treated polymers displayed excellent biocompatibility and high fluorescence enhancement in living zebrafish, whereas the fluorescence intensity and stability of zebrafish incubated with the pristine polymer decreased linearly over time. Thus, these CO2 and N2-responsive WCPs could potentially be applied as multifunctional fluorescent probes for in vivo biological imaging.

Synthesis of Structurally Defined Cationic Polythiophenes for DNA Binding and Gene Delivery.

Water-soluble conjugated polymers (WCPs) have prospective applications in the field of bioimaging, disease diagnosis, and therapy. However, the use of WCPs with controllability and regioregularity for bioapplications have scarcely been reported. In this work, we synthesized polythiophenes containing ester side chains (P3ET) via Kumada catalyst-transfer polycondensation (KCTP) and confirmed a quasi-"living" chain-growth mechanism. In addition, we obtained cationic regioregular polythiophenes (cPTs) by aminolysis of P3ET with varied chain lengths, and studied DNA binding capability and gene delivery performance. Benefiting from photocontrolled generation of intracellular reactive oxygen species (ROS), the cationic polythiophenes successfully delivered DNA into tumor cells without additional polymer species.

Hybridizing Carbon Nitride Colloids with a Shell of Water-Soluble Conjugated Polymers for Tunable Full-Color Emission and Synergistic Cell Imaging.

We present the preparation of a new multicolor emission system constructed from two complementary conjugated materials that are highly photoluminescent, that is, phenyl-modified carbon nitride (PhCN) colloids as the core and water-soluble conjugated polymers (WSCPs) adsorbed as the shell. The fluorescence bands of the PhCN and WSCPs effectively complement each other and the overall emission can be simply adjusted to fully cover the visible light spectrum with white light emission also accessible. Photophysical insights imply that the interactions between PhCN and WSCPs preserve the binary system from emission distortion and degradation, which is essential to delicately tune the overall fluorescence bands. Notably, the continuously tunable emission color is achieved under single-wavelength excitation (365 nm). This hybrid shows a synergistic permeation performance in cell imaging, that is, PhCN nanoparticles help the WSCP to enter the cells and therefore multicolor cellular imaging achieved.

Multiresponsive Behavior of Functional Poly(p-phenylene vinylene)s in Water.

The multiresponsive behavior of functionalized water-soluble conjugated polymers (CPs) is presented with potential applications for sensors. In this study, we investigated the aqueous solubility behavior of water-soluble CPs with high photoluminescence and with a particular focus on their pH and temperature responsiveness. For this purpose, two poly(phenylene vinylene)s (PPVs)—namely 2,5-substituted PPVs bearing both carboxylic acid and methoxyoligoethylene glycol units—were investigated, with different amount of carboxylic acid units. Changes in the pH and temperature of polymer solutions led to a response in the fluorescence intensity in a pH range from 3 to 10 and for temperatures ranging from 10 to 85 °C. Additionally, it is demonstrated that the polymer with the largest number of carboxylic acid groups displays upper critical solution temperature (UCST)-like thermoresponsive behavior in the presence of a divalent ion like Ca2+. The sensing capability of these water-soluble PPVs could be utilized to design smart materials with multiresponsive behavior in biomedicine and soft materials.

Increasing the efficiency of a multilayer bulk heterojunction solar cell using water-soluble conjugated polymer as an electron injection layer

A bulk heterojunction solar cell (BHJ-SC) was fabricated from the conventional active polymer blend P3HT:PCBM by constructing a polymer multilayer structure with novel electron-transporting water-soluble conjugated polymers (WSCPs), poly[9,9′-bis[2-(2-(2-(6′′-(N,N,N-trimethylammonium) ethoxy) ethoxy) ethoxy) ethyl]fluorine, and its copolymer with a phenyl on top of the polymer active layer. In the multilayer structure BHJ-SC, each WSCP coordinated by Na+ ions to the oxygen site on the side chain of the polymer acts as a good electron injection layer for the higher electron collection at the cathode metal. This causes up to 85% increase in the BHJ-SC's power conversion efficiency (PCE) compared to that of the BHJ-SC without WSCPs. This report will discuss the effect of the electron injection layer in the BHJ-SC in terms of the current/voltage characteristics, PCE, electron affinity, and charge mobility of water-soluble polymers.

A water-soluble conjugated polymer with azobenzol side chains based on “turn-on” effect for hypoxic cell imaging

A water-soluble conjugated polymer (WSCP) with enzymatic cleavable linkage (azobenzene) side chains for hypoxia imaging.

A Water‐soluble Conjugated Polymer for Thiol Detection Based on "Turn‐off" Effect

AbstractWe investigated a novel water‐soluble conjugated polymer (WSCP) for thiol detection based on "turn‐off" effect. This WSCP was modified with poly(ethylene glycol) (PEG) by disulfide linkages to achieve good solubility in aqueous solution (34 mg/mL) and high quantum yield (0.47). The separation of water‐soluble PEG chains from the conjugated backbone induced by the cleavage of the disulfide linkages would lead to a significant decrease of the water solubility and a dramatical fluorescence quenching of the probe. The combined intuitive images and fluorescence spectrophotometer further confirmed that decreased solubility produced an aggregation of the hydrophobic conjugated backbone. The fluorescence intensity of the probe showed a good linear relationship with glutathione (GSH) (1–200 nmol·L−1), and the detection limit was 16 nmol·L−1. This WSCP probe was confirmed to be a good sensing material with high selectivity to thiols by testing various biological molecules. And this WSCP probe exhibited good detection effect to intracellular thiols by testing Hela cells. Considering the good sensitivity and selectivity, the probe could be further used in vivo. In conclusion, this conjugated polymer probe made up for the drawbacks of the micromolecue probes and contributed to the development of new probes based on conjugated polymers.

A Water-Soluble Conjugated Polymer with Pendant Disulfide Linkages to PEG Chains: A Highly Efficient Ratiometric Probe with Solubility-Induced Fluorescence Conversion for Thiol Detection

We investigated a water-soluble conjugated polymer (WSCP) with pendant disulfide linkages to poly(ethylene glycol) (PEG) chains, which is a highly efficient ratiometric probe with solubility-induced fluorescence conversion for thiol detection. This WSCP was doped with a low-bandgap fluorophore, 1,4-dithienyl benzothiadiazole (DBT), and was modified with PEGs by disulfide linkages to increase its water solubility. The free probe exhibited good solubility in aqueous solution (28 mg/mL) and showed purple fluorescence because of the low doping ratio of DBT. The separation of water-soluble PEG chains from the conjugated backbone induced by the cleavage of the disulfide linkages would lead to a significant decrease of the water solubility of the probe. The combined utilization of scanning electron microscopy, dynamic light scattering, and fluorescence spectrophotometer further confirmed that decreased solubility produced an aggregation of the hydrophobic conjugated backbone and subsequently increased fluorescen...

Streptavidin sensor and its sensing mechanism based on water-soluble fluorescence conjugated polymer

Fluorescence quenching effect of water-soluble anionic conjugated polymer (CP) (poly[5-methoxy-2-(3-sulfopoxy)-1,4-phenylenevinylene] (MPS-PPV)) by [Re(N-N)(CO)3(py-CH2-NH-biotin)](PF6) [N-N=2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline; py-CH2-NH-biotin=N-[(4-pyridyl) methyl] biotinamide] (Re-Biotin) and fluorescence recovery in the presence of streptavidin (or avidin) were investigated using Re-Biotin as quencher tether ligand (QTL) probe. Meanwhile, the mechanisms of fluorescence quenching and recovery were discussed to provide new thoughts to design biosensor based on water-soluble CPs. The results indicate that the sensing mechanisms of streptavidin sensor or avidin sensor, using Re-Biotin as QTL probe, are the same and stable, whether in non-buffer system (aqueous solution) or different buffer systems [0.01mol·L−1 phosphate buffered solution (pH=7.4), 0.1mol·L−1 ammonium carbonate buffered solution (pH=8.9)]. There exists specific interactions between streptavidin (or avidin) and biotin of Re-Biotin. Fluorescence quenching and recovery processes of MPS-PPV are reversible. Mechanisms of Re-Biotin quenching MPS-PPV fluorescence can be interpreted as strong electrostatic interactions and charge transferences between Re-Biotin and MPS-PPV. Fluorescence recovery mechanisms of Re-Biotin—MPS-PPV system can be interpreted as specific interactions between streptavidin (or avidin) and biotin of Re-Biotin making Re-Biotin far away from MPS-PPV. Avidin or strptavidin as re-Biotin probe can not only be quantitatively determinated, but also be identified.

Coordinatable and High Charge‐Carrier‐Mobility Water‐Soluble Conjugated Copolymers for Effective Aqueous‐Processed Polymer–Nanocrystal Hybrid Solar Cells and OFET Applications

AbstractA water‐soluble conjugated polymer (WCP) poly[(3,4‐dibromo‐2,5‐thienylene vinylene)‐co‐(p‐phenylene‐vinylene)] (PBTPV), containing thiophene rings with high charge‐carrier mobility and benzene rings with excellent solubility is designed and prepared through Wessling polymerization. The PBTPV precursor can be easily processed by employing water or alcohols as the solvents, which are clean, environmentally friendly, and non‐toxic compared with the highly toxic organic solvents such as chloroform and chlorobenzene. As a novel photoelectric material, PBTPV presents excellent hole‐transport properties with a carrier mobility of 5 × 10−4 cm2 V−1 s−1 measured in an organic field‐effect transistor device. By integrating PBTPV with aqueous CdTe nanocrystals (NCs) to produce the active layer of water‐processed hybrid solar cells, the devices exhibit effective power conversion efficiency up to 3.3%. Moreover, the PBTPV can form strong coordination interactions with the CdTe NCs through the S atoms on the thiophene rings, and effective coordination with other nanoparticles can be reasonably expected.

Enhanced Performance in Polymer Light-Emitting Diodes (PLEDs) by Using Water Soluble Conjugation Polymer

Organic and polymeric materials have generated interest in recent year for their potential applications in flat panel displays, such as TVs, monitors, and mobile displays, due to their wide viewing angle, fast response time, and low operating voltage with high external quantum efficiency. A well-balanced charge injection leads to an increase in the external quantum efficiency in polymer-based light-emitting diodes (PLEDs). This can be achieved by forming a multilayer structure in device fabrication and considering the charge mobility, the ionization potentials and the electron affinities of the organic materials, and the work functions of the metal electrodes. When taking the hole favor property in most conjugated polymers into consideration, it is important to introduce electron injection and transport layers for more balanced charge injection into the emission zone. The electron injection can be enhanced by using a metal cathode with a low work function, such as Ca or ionic compounds like LiF or CsF. However, active metals like Ca are known to diffuse into the organic layer due to the strong electric field inside the device, which forms quenching sites in the emission layer near the cathode. Brown et al. announced that ionic compounds could also be partially ionized and migrate into the emission layer. In fact, the multilayer structure with selected electron injection and transport layers can enhance the device performance by not only reducing the electron injection barrier and controlling the electron mobility but also preventing the migration of metals or ionic compounds into the emission layer. In general, most conjugated polymers are soluble incommon organic solvents, which cause difficulty for fabrication of multilayer polymer films. During the last decade, considerable research efforts have been carried out on multilayer PLEDs to enhance the device performance to make them suitable for practical use. Lee et al. introduced an ionomer layer next to the emitting polymer for electron injection and a hole blocking layer, which lowered the operating voltage by up to 60%. Niu et al. reported that the use of neutral surfactants blended with poly(ethylene glycol) as an electron injection layer with an Al cathode could improve the current efficiency to almost twice that of Ca/Al cathode. Recently, Tseng et al. showed a general method to solution-process multilayer PLEDs by using an intermediate liquid buffer between polymer layers. Several papers have also reported the enhancement of electron injection by using ion-conducting polymer, cross-linkable inter-layers, and water/ methanolsoluble copolymers. In spite of those improvements in multilayer PLEDs fabrication, however, it is true that we still need more materials for effective hole blocking and electron injection with an easy process. In this study, we synthesized new types of water soluble conjugated polymer and showed enhanced performance on the multi-layered polymer light-emitting diodes (PLEDs) by introducing the water soluble conjugated polymer FPQ as an electron transport layer between the emitting polymer and the cathode metal. The device performances with and without water soluble polymer layer will be compared in terms of the current-voltage characteristics, the luminance, and the external quantum efficiencies.

Room‐Temperature Phosphorescence From Films of Isolated Water‐Soluble Conjugated Polymers in Hydrogen‐Bonded Matrices

AbstractIt is well known that luminescent conjugated polymers suffer serious loss of photoluminescence quantum yield (PLQY) in the solid state compared to dilute solution. This is due to efficient exciton migration in the solid, which enables the excitons to readily find low energy quenching sites. Here a new method to fabricate solid films with densely packed non‐interacting luminescent polymer chains, which yield very high PLQY and more astonishingly room temperature phosphorescence, is reported. Using water‐soluble conjugated polymers (WSCP) and polymeric surfactants such as poly(vinyl alcohol) (PVA) and poly(vinyl‐pyrrolidone) (PVP), films at 1:1 wt% or higher WSCP are produced and show room temperature phosphorescence; such behavior has never been observed before and clearly shows the very high degree of chain isolation that can be achieved in these hosts. The PVA or PVP not only breaks up WSCP aggregates in solution as an effective surfactant, PVA‐PVA or PVP‐PVP hydrogen bond formation upon drying locks in the isolation of the WSCP, avoiding segregation and yielding long time stability to these polymer/polymer nanomixtures. The method is found to work with a wide variety of WSCPs.

水溶性共轭聚合物研究与应用进展

In the past dacades, water-soluble conjugated polymers (CPs) have gained increasing attention, which is not only due to their good optical properties, but also their amazing solubility in polar solvents, especially in aqueous solution. For these two factors, water-soluble CPs have been widely used as advanced functional materials for sensitive biosensors, polymer light-emitting diodes (PLEDs), polymer solar cells (PSCs), as well as organic field effect transistors (OFETs). In this review, we summarize the recent advances in the synthesis of CPs and their applications in organic optoelectronics and point out the prospects for the future development of water-soluble CPs.

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.

Solvent Polarity Effect on Chain Conformation, Film Morphology, and Optical Properties of a Water-Soluble Conjugated Polymer

The solvent polarity effect on chain conformation, film morphology, and photophysical properties of a nonionic water-soluble conjugated polymer (WSCP), poly[2,5-bis(diethylaminetetraethylene glycol)phenylene vinylene] (DEATG-PPV) is investigated in detail. The combination of stationary absorption and photoluminescence (PL) spectroscopy, time-resolved PL spectroscopy, and fluorescence correlation spectroscopy methods enables us to probe the chain conformation of DEATG-PPV, down to the level of a single chain when working with extremely diluted solutions. The use of correlated atomic force microscopy and confocal fluorescence lifetime imaging microscopy measurements of drop-casted DEATG-PPV films reveals the intrinsic relationship between chain conformation, film morphology, and optical properties. Depending on solvent polarity, DEATG-PPV presents extended, coiled, and collapsed chain conformations in solutions, which lead to distinct morphology and optical properties in solid films. Our work presents a pathway to control and characterize the film morphologies of WSCPs toward the optimal performance of various optoelectronic devices.