Fluorescence Ratiometric Assay Strategy for Chemical Transmitter of Living Cells Using H2O2-Sensitive Conjugated Polymers

Recent theranostic applications of hydrogen peroxide-responsive nanomaterials for multiple diseases

It is well established that hydrogen peroxide (H2O2) is associated with the initiation and progression of many diseases. With the rapid development of nanotechnology, the diagnosis and treatment of those diseases could be realized through a variety of H2O2-responsive nanomaterials. In order to broaden the application prospects of H2O2-responsive nanomaterials and promote their development, understanding and summarizing the design and application fields of such materials has attracted much attention. This review provides a comprehensive summary of the types of H2O2-responsive nanomaterials including organic, inorganic and organic-inorganic hybrids in recent years, and focused on their specific design and applications. Based on the type of disease, such as tumors, bacteria, dental diseases, inflammation, cardiovascular diseases, bone injury and so on, key examples for above disease imaging diagnosis and therapy strategies are introduced. In addition, current challenges and the outlook of H2O2-responsive nanomaterials are also discussed. This review aims to stimulate the potential of H2O2-responsive nanomaterials and provide new application ideas for various functional nanomaterials related to H2O2.

A short review article on conjugated polymers

This article provides a brief review of conjugated polymers and the various typical polymerization reactions exploited by the community to synthesise different conjugated polyelectrolytes with varied conjugated backbone systems. We further discuss with detailed emphasises the mechanism involved such as photo-induced electron transfer, resonance energy transfer, and intra-molecular charge transfer in the detection or sensing of various analytes. Owing to their excellent photo-physical properties, facile synthesis, ease of functionalization, good biocompatibility, optical stability, high quantum yield, and strong fluorescence emission. Conjugated polymers have been explored for wide applications such as chemical and biological sensors, drug delivery and drug screening, cancer therapeutics and imaging. As such we believe it will be a timely review article for the community.

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.

Conjugated Polymers-based Luminescent Probes for Ratiometric Detection of Biomolecules

Accurate monitoring of the biomolecular changes in biological and physiological environments is of great significance for pathogenesis, development, diagnosis and treatment of diseases. Compared with traditional luminescent probes on the...

Biofunctionalization of Water-Soluble poly(Phenylene Ethynylene)s

We report the use of amide coupling chemistry to covalently link five different biofunctional groups onto an anionic water-soluble poly(phenylene ethynylene) (PPE) polymer. Two of the biofunctionalized PPEs are used in prototype applications, including pH sensing and flow cytometry labeling. The PPE is functionalized with carboxylate (R-CO2-) and sulfonate (R-SO3-) ionic groups. By using an activated ester, the amine-functionalized groups are covalently linked to the PPE polymer via amide linkages. The reaction chemistry is optimized using biotin-ethylene diamine, making it possible to control the loading of the biotin functionality on the PPE chains. Using the optimized approach, a family of five PPEs were prepared that contain biotin, rhodamine, cholesterol, mannose, or folic acid moieties appended to the polymer backbones. The rhodamine- and biotin-modified PPEs were further applied for pH response and flow cytometry applications. The reported approach can be utilized for other classes of water-soluble conjugated polymers, allowing facile development of a variety of new functionalized water-soluble conjugated polymers for a range of applications including sensing, bioimaging, and flow cytometry analysis.

Bactericidal activity-tunable conjugated polymers as a human-friendly bactericide for the treatment of wound infections

Photodynamic therapy (PDT) has been reported to be an effective alternative to combat bacterial infections even those triggered by drug-resistant strains as there is little chance to develop resistance to this therapy. Therefore, it is imperative to design and synthesize a superior photo-active bactericide for the treatment of bacterial infections. Herein, we synthesized three bactericidal activity-tunable conjugated polymers (P1-P3) with various photoactive capabilities and employed them for the treatment of wound infections with little damage to cells; by altering the construction unit of π-conjugated backbone structures with electron-rich and electron-deficient aromatic heterocycles, the optical properties and ability of reactive oxygen species (ROS) generation could be regulated; this resulted in a tunable killing ability. The cationic quaternary ammonium (QA) groups on the side chains endowed the CPs with not only good dispersibility but also a better interaction with the negatively charged membrane of bacteria. The antibacterial experiments towards ampicillin-resistant Escherichia coli TOP10 (E. coli) and the treatment of wound infections in mice indicate that the P1-P3 have varied bactericidal activities; moreover, P3 has been demonstrated to be a human-friendly bactericide with excellent antibacterial capability. It not only acts as a potential bactericide for the practical treatment of infectious wounds, but also offers guidance for the design and structure control of photo-active bactericides.

Quantum Dots for Monitoring Choline Consumption Process of Living Cells via an Electrostatic Force-Mediated Energy Transfer

In this work, a ratiometric nanoprobe CdS/ZnS-FB was designed for H₂O₂ detection based on FRET assay. Furthermore, CdS/ZnS-FB could work for detecting choline (Ch) and acetylcholine (ACh) since H₂O₂ is the enzyme cascade reaction product. Significantly, the Jurkat T's choline consumption could also be quantitatively measured by monitoring FRET ratio (I₅₂₂/I₄₂₆). Thus, the biosensor could be applied as a universal tool for the detection of choline consumption of living cells, which provides a good potential for the applications in detecting chemical transmitter and cancer diagnosis.

A modular theranostic platform for tumor therapy and its metabolic studies

Theranostic systems are able to detect and treat diseases with only one procedure, thus greatly lessening the pain of patients. Since each patient's disease can be considered as a new clinical subtype, it is essential to develop theranostic nanomaterials with changeable functions for personal treatment. In this work, a novel modular theranostic platform was designed to control the stimuli-responsive drug release. As a patch board, mesoporous silica nanoparticles (MSNs) were functionalized with a linear pH-responsive benzimidazole (Bz)-polyethylene glycol (PEG) chain containing a redox-responsive ferrocene (Fc) oxide stopper at the end. As the plug, the β-CD ring was initially located at the Bz position. In an acidic tumor microenvironment, the pH sensitive Bz was protonated and the complex formation constant between Bz and β-CD decreased. At the same time, the complex formation constant between Fc and β-CD increased remarkably. As a result, the β-CD ring would depart from the nanoparticle surface to the Fc position at pH 6.2 & 10 mM GSH, physically causing an "And" logic gate type drug release. Herein, a "plug and play" method was used to achieve changeable functions with only one platform. By plugging modified β-CD into the patch board, theranostic systems with changeable functions can be achieved easily.

Facile core–shell nanoparticles with controllable antibacterial activity assembled by chemical and biological molecules

A newly switchable antibacterial self-assembly was developed by conjugated polymer nanoparticles, DNA, Hoechst 33258 and deoxyribonuclease I.

Detection of Hydrogen Peroxide with Fluorescent Dyes

SIGNIFICANCE

Hydrogen peroxide (H₂O₂) is a powerful effector of redox signaling. It is able to oxidize cysteine residues, metal ion centers, and lipids. Understanding H₂O₂-mediated signaling requires, to some extent, measurement of H₂O₂ level. Recent Advances: Chemically and genetically encoded fluorescent probes for the detection of H₂O₂ are currently the most sensitive and popular. Novel probes are constantly being developed, with the latest progress particular with boronates and genetically encoded probes.

CRITICAL ISSUES

All currently available probes display limitations in terms of sensitivity, local and temporal resolution, and specificity in the detection of low H₂O₂ concentrations. In this review, we discuss the power of fluorescent probes and the systems in which they have been successfully employed. Moreover, we recommend approaches for overcoming probe limitations and for the avoidance of artifacts.

FUTURE DIRECTIONS

Constant improvements will lead to the generation of probes that are not only more sensitive but also specifically tailored to individual cellular compartments. Antioxid. Redox Signal. 29, 585-602.

Solvent Additive-Assisted Anisotropic Assembly and Enhanced Charge Transport of π-Conjugated Polymer Thin Films

Charge transport in π-conjugated polymer films involves π-π interactions within or between polymer chains. Here, we demonstrate a facile solution processing strategy that provides enhanced intra- and interchain π-π interactions of the resultant polymer films using a good solvent additive with low volatility. These increased interactions result in enhanced charge transport properties. The effect of the good solvent additive on the intra- and intermolecular interactions, morphologies, and charge transport properties of poly(3-hexylthiophene) (P3HT) films is systematically investigated. We found that the good solvent additive facilitates the self-assembly of P3HT chains into crystalline fibrillar nanostructures by extending the solvent drying time during thin-film formation. As compared to the prior approach using a nonsolvent additive with low volatility, the solvent blend system containing a good solvent additive results in enhanced charge transport in P3HT organic field-effect transistor (OFET) devices [from ca. 1.7 × 10^-2 to ca. 8.2 × 10^-2 cm² V^-1 s^-1 for dichlorobenzene (DCB) versus 4.4 × 10^-2 cm² V^-1 s^-1 for acetonitrile]. The mobility appears to be maximized over a broad spectrum of additive concentrations (1-7 vol %), indicative of a wide processing window. Detailed analysis results regarding the charge injection and transport characteristics of the OFET devices reveal that a high-boiling-point solvent additive decreases both the contact resistance ( R_c) and channel resistance ( R_ch), contributing to the mobility enhancement of the devices. Finally, the platform presented here is proven to be applicable to alternative good solvent additives with low volatility, such as chlorobenzene (CB) and trichlorobenzene (TCB). Specifically, the mobility enhancement of the resultant P3HT films increases in the order CB (bp 131 °C) < DCB (bp 180 °C) < TCB (bp 214 °C), suggesting that solvent additives with higher boiling points provide resultant films with preferable molecular ordering and morphologies for efficient charge transport.

Versatile Routes to Functional RAFT Chain Transfer Agents through the Passerini Multicomponent Reaction

The widespread adoption of RAFT polymerization stems partly from the ease and utility of installing a functional chain transfer agent onto the ends of the generated polymer chains. In parallel, the Passerini multicomponent reaction offers great versatility in converting a wide range of easily accessible building blocks to functional materials. In this work, we have combined the two approaches such that a single, commonly available, RAFT agent is used in Passerini reactions to generate a variety of multifunctional RAFT chain transfer agents containing ester linkages. Reactions to generate the multifunctional RAFT agents took place under mild conditions and in good yields. The resulting Passerini-RAFT agents were able to exert control over radical polymerization to generate materials of well-defined molecular weights and dispersity. Furthermore, the presence in these polymer cores of ester and amide functionality through the Passerini chemistries, provided regions in the materials which are inherently biodegradable, facilitating any subsequent biomedical applications. The work overall thus demonstrates a versatile and facile synthetic route to multi functional RAFT chain transfer agents and biodegradable polymers.

H2O2-Depleting and O2-Generating Selenium Nanoparticles for Fluorescence Imaging and Photodynamic Treatment of Proinflammatory-Activated Macrophages

Macrophages have a pivotal role in chronic inflammatory diseases (CIDs), so imaging and controlling activated macrophage is critical for detecting and reducing chronic inflammation. In this study, photodynamic selenium nanoparticles (SeNPs) with photosensitive and macrophage-targeting bilayers were developed. The first layer of the photosensitive macromolecule was composed of a conjugate of a photosensitizer (rose bengal, RB) and a thiolated chitosan (chitosan-glutathione), resulting in a plasmonic coupling-induced red shift and broadening of RB absorption bands with increased absorption intensity. Electron paramagnetic resonance (EPR) and diphenylanthracene (DPA) quenching studies revealed that the SeNPs that were coated with the photosensitive layer were more effective than RB alone in producing singlet oxygen (¹O₂) under photoirradiation. The second layer of the activated macrophage-targetable macromolecule was synthesized by conjugation of hyaluronic acid with folic acid using an ethylenediamine linker. Proinflammatory-activated macrophages rapidly internalized the SeNPs that were covered with the targeting ligand, exhibiting a much stronger fluorescence signal of the SeNPs than did the nonactivated macrophages. Since proinflammatory-activated macrophage was known to generate a substantial amount of H₂O₂ while the inflamed site generally caused inflammation-associated tissue hypoxia, the SeNPs were further modified with O₂ self-sufficient function for photodynamic therapy. Catalase was immobilized on the SeNPs by the formation of disulfide bonds. Intracellular reduction of disulfide bonds induced the subsequent release of catalase, which catalyzed the decomposition of H₂O₂. The H₂O₂-depleting and O₂-generating photodynamic SeNPs efficiently killed activated macrophages and quenched the intracellular H₂O₂ and NO that are associated with inflammation. The SeNPs may have potential as a theranostic nanomaterial to image and control the activation of macrophages.

Lanthanoid-Doped Phosphate/Vanadate Mixed Hollow Particles as Ratiometric Luminescent Sensors

Rare earth (RE) phosphates and vanadates are structurally similar compositions that display distinct but complementary luminescent properties. The properties of these phosphors can be combined in REPO₄-REVO₄ heterostructures during the development of new sensing technologies for biological applications. This work presents the synthesis of hollow RE phosphate/vanadate colloidal particles and evaluates their applicability as luminescent markers. Hydrothermal treatments of RE hydroxycarbonate particles in the presence of the PO₄^3- and VO₄^3- precursors afforded the final REPO₄-REVO₄ solids in a two-step template synthesis. We converted precursor hydroxycarbonate particles into the final heterostructures and characterized their structure and morphology. According to our detailed study into the spectroscopic properties of Eu³⁺-doped particles and their luminescence response to several species, the presence of the phosphate and vanadate phases in a single particle provided different chemical environments and enabled the design of a ratiometric approach to detect H₂O₂. These results open new perspectives for the development of new intracellular luminescent markers.

Aggregation-Induced Energy Transfer of Conjugated Polymer Materials for ATP Sensing

Water-soluble conjugated polymers are attractive fluorescent materials for applications in chemical and biological sensing. The molecular wire effect of such polymers amplifies changes in the fluorescence signal, which can be used for detecting various analytes with high sensitivity. In this work, we report an efficient ratiometric fluorescent probe based on a water-soluble conjugated polymer that showed high sensitivity and selectivity toward adenosine 5'-triphosphate (ATP). The macromolecular probe consisted of a polyfluorene backbone doped with 5 mol % 1,4-dithienylbenzothiadiazole (DBT) modified by bis-imidazolium and oligo(ethylene glycol) moieties. Solutions of the polymer emitted purple fluorescence, which changed to red upon addition of ATP molecules. The addition of ATP caused the polymer to aggregate, which enhanced fluorescence resonance energy transfer efficiency from the fluorene segments to DBT units, leading to an increase in red emission. The ratio of the fluorescence at these different wavelengths (I₆₅₅/I₄₂₃) showed a strong dependence on the ATP concentration. PF-DBT-BIMEG also exhibited high selectivity for ATP sensing over other representative anions and discriminated it from adenosine 5'-diphosphate (ADP) and adenosine 5'-monophosphate (AMP). This can be explained by the much stronger electrostatic interactions between the polymer and ATP than the interactions between the polymer and ADP or AMP, as confirmed through molecular dynamics simulations.

FRET-assisted selective detection of flavins via cationic conjugated polyelectrolyte under physiological conditions

Cationic conjugated polyelectrolyte PMI performs ppb level detection and discrimination of flavins (RF, FMN and FAD) in aqueous media as well as in biological medium like serum.