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Temozolomide (TMZ) is a prodrug of 5-(3-methyltriazene-1-yl)imidazole-4-carboxamide (MTIC, short-lived) and used as a first-line therapy drug for glioblastoma multiforme (GBM). However, little progress has been made in regulating the kinetics of TMZ to MTIC degradation to improve the therapeutic effect, particularly in the case of TMZ-resistant GBM. In this work, we introduced a strategy to cage MTIC by N-acylation of the triazene moiety to boost the MTIC stability, designed a diblock copolymer-based MTIC prodrug installed with a disulfide linkage, and achieved self-assembled polymer micelles without the concern of MTIC leakage under physiological conditions. Polymer micelles could be induced to disassemble by stimuli factors such as glutathione (GSH) and visible light irradiation through thiol/sulfide exchange and homolytic sulfide scission mechanisms, which contributed to MTIC release in GSH-dependent and GSH-independent pathways. The in vitro results demonstrated that microenvironment-responsive polymeric micelles benefited the suppression of both TMZ-sensitive and TMZ-resistant GBM cells. The chemistry of polymer-MTIC prodrug provided a new option for TMZ-based glioma treatment.

Photoactivated trimerization of 2,3,3-trimethyl-3 H -indole derivatives created near infrared fluorophore Cy5. The synthetic method is air-tolerant, photosensitizer free, metal free, and condensation agent free. Living cells make Cy5 on a time scale of minutes under white light irradiation at a low power intensity, with the monomer as the only exogenous agent. The new method is promising to find applications in cell studies for in situ spatiotemporally controlled fluorescence imaging in living cells with low background signal.

We designed a conjugated compound by coupling temozolomide (TMZ) with doxorubicin (DOX) via an acylhydrazone linkage as a potential prodrug used for glioblastoma multiforme (GBM) treatment. Viscosity and spectroscopic studies revealed that the drug conjugate could act as a nonclassical double intercalating agent. Although free TMZ is an inefficient DNA binder in comparison to DOX, the TMZ moiety interacted with DNA as an induced intercalator, arising from the synergistic effect of DOX moiety that mediated conformational changes of the DNA helix. Two binding modes were proposed to interpret the double intercalating effect of the drug conjugate on intra- and inter-DNA interactions that could cause DNA cross-linking and fibril aggregates. We also developed a delivery nanoplatform with a loading efficiency of 83% using copper-bound apoferritin as a nanocarrier. In sharp contrast to the short half-life of free TMZ, the nanocomposite was stable under physiological conditions without detectable drug decomposition after a 2 week storage, and drug release was activatable in the presence of glutathione at millimolar levels. The antitumor effect of the drug conjugate and nanocomposite against GBM cells was reported to demonstrate the potential therapeutic applications of double intercalating materials.

Currently, photosensitizers (PSs) that are microenvironment responsive and hypoxia active are scarcely available and urgently desired for antitumor photodynamic therapy (PDT). Presented herein is the design of a redox stimuli activatable metal-free photosensitizer (aPS), also functioning as a pre-photosensitizer as it is converted to a PS by the mutual presence of glutathione (GSH) and hydrogen peroxide (H2 O2 ) with high specificity on a basis of domino reactions on the benzothiadiazole ring. Superior to traditional PSs, the activated aPS contributed to efficient generation of reactive oxygen species including singlet oxygen and superoxide ion through both type 1 and type 2 pathways, alleviating the aerobic requirement for PDT. Equipped with a triphenylphosphine ligand for mitochondria targeting, mito aPS showed excellent phototoxicity to tumor cells with low light fluence under both normoxic and hypoxic conditions, after activation by intracellular GSH and H2 O2 . The mito aPS was also compatible to near infrared PDT with two photon excitation (800 nm) for extensive bioapplications.

The surface engineering of the apoferritin shell by means of traditional chemical modifications usually suffers from site inaccuracy and insufficient conjugation. This report describes a non-covalent method for precise modulation of the apoferritin surface without alteration of amino acid residues. A bifunctional macromolecule, structured as azide-poly(ethylene glycol)-porphyrin (termed TPA), was synthesized. TPA was observed to be able to recognize and bind apoferritin in a 12 : 1 stoichiometry with a higher binding affinity than arachidonate, thanks to the specific host-guest interaction between the pocket of each two-fold channel and the porphyrin moiety. This method allows for site-specific engineering of the apoferritin surface with on demand functionalities and optimization of drug encapsulation.

To imitate the protein microenvironment surrounding the Fe2S2 active site, we established a convenient method to prepare self-assembled ovalbumin (OVA) nanogels that noncovalently incorporated hydr...

The antialcoholic drug disulfiram (DSF) has attractive biomedical interests for its anticancer effects, particularly in combination use with copper. CuET, the complex of copper and diethyldithiocarbamate (DTC) that is derived from disulfiram, exhibits high redox stability against glutathione, cysteine, and hydrogen peroxide, but appears reactive to ascorbic acid and superoxide ions. By virtue of the copper binding property, apoferritin is developed as a carrier of CuET to alleviate concerns of poor water solubility and nonspecific toxicity and shows superior stability and protection over human serum albumin in nanocomposite manipulation. CuET and doxorubicin are codelivered by apoferritin with excellent efficiency (97%). The glutathione-responsive system demonstrates enhanced antitumor effect and potentials for combination tumor therapy.

The short half-life of temozolomide (TMZ) limits its therapeutic effect on highly aggressive glioblastoma (GBM). Few approaches attempting to intervene the metabolic kinetics of TMZ are successful. Herein, we designed anionic copolymers via radical polymerization to prepare polymer-coated small copper nanoclusters, taking advantage of the role of pendent thymine groups as a template. The active and key intermediate of TMZ, typically called 3-methyl-(triazen-1-yl)imidazole-4-carboxamide (MTIC), was stabilized by copper under physiological (slightly alkaline) conditions, alleviating concerns associated with spontaneous drug degradation and nonspecific drug activation. Importantly, the complexes formed by MTIC and copper nanoclusters could catalyze the Fenton reaction to generate hydroxyl radicals and also respond to pH and glutathione to release therapeutic MTIC, which allows combined chemotherapy and chemodynamic therapy against GBM cells and paves a way for circumventing the complication of TMZ resistance.

Radiation-induced lung injury (RILI) is one of the most common and fatal complications of thoracic radiotherapy, whereas no effective interventions are available. Andrographolide, an active component extracted from Andrographis paniculate, is prescribed as a treatment for upper respiratory tract infection. Here we report the potential radioprotective effect and mechanism of Andrographolide on RILI. C57BL/6 mice were exposed to 18 Gy of whole thorax irradiation, followed by intraperitoneal injection of Andrographolide every other day for 4 weeks. Andrographolide significantly ameliorated radiation-induced lung tissue damage, inflammatory cell infiltration, and pro-inflammatory cytokine release in the early phase and progressive fibrosis in the late phase. Moreover, Andrographolide markedly hampered radiation-induced activation of the AIM2 inflammasome and pyroptosis in vivo. Furthermore, bone marrow-derived macrophages (BMDMs) were exposed to 8 Gy of X-ray radiation in vitro and Andrographolide significantly inhibited AIM2 inflammasome mediated-pyroptosis in BMDMs. Mechanistically, Andrographolide effectively prevented AIM2 from translocating into the nucleus to sense DNA damage induced by radiation or chemotherapeutic agents in BMDMs. Taken together, Andrographolide ameliorates RILI by suppressing AIM2 inflammasome mediated-pyroptosis in macrophage, identifying Andrographolide as a novel potential protective agent for RILI.

Studies of methylene blue-backboned polymers (MBPs) are hindered by the limited availability of polymerization methods. Herein, we developed an oxidative polymerization method to produce MBPs. The polymerization is performed in aqueous medium, and is organic solvent-free, heavy metal-free, time-efficient (on a timescale of minutes), and does not need pre-formed methylene blue chromophores. The effects of the alkyl chains of the MBPs on the photophysical properties and self-assembly behavior (e.g., vesicles and nanorings) are significant, which highlights the possibility of controlling the MBP properties via rationally tailoring the functionality of the MBP monomers prior to polymerization. Importantly, the self-assembly structures can be predicted using the dissipative particle dynamics (DPD) simulation method.

Inspired by the bioinorganic structure of natural [FeFe]-hydrogenase ([FeFe]-H2ase) that possesses iron sulfur clusters to catalyze proton reduction to hydrogen (H2), we design a supramolecular photosystem by sequentially integrating hydrophobic ruthenium complex (as a photosensitizer) and diiron dithiolate complex (as a photocatalyst) into the inner surface or cavity of apoferritin via noncovalent interactions. This platform allows photosensitizer and catalyst to localize in a close proximity and short-distance electron transfer process to occur within a confined space. The resulted uniform core-shell nanocomposites were stable and well dispersed in water, and showed enhanced H2 generation activity in acidic solution as compared to the homogenous system without apoferritin participation.

Reactive signaling molecules participate in varieties of biochemical reactions, and methods to detect their mutual existence and crosstalk are in urgent demand. A benzothiadiazole-based handle was designed to fluorescently respond to the co-existence of H2 S and H2 O2 under pseudo-physiological conditions on a basis of a thiyl-radical-mediated mechanism that accounts for the rapid and efficient domino-like reaction processes. Then the handle motif was attached to a rhodamine moiety by means of an ethynylene linkage, and achieved a significant H2 S-H2 O2 mutual response in the mitochondria of living cells. Theoretical calculations supported that a through bond energy transfer mechanism contributes to the drastic fluorescence response.

A gene delivery system using spiropyran as a photoswitchable photosensitizer for the controlled photochemical internalization effect was developed by engineering the outer coating of a polyethylenimine/DNA complex with a small amount of spiropyran-containing cationic copolymers. The successful binding of cationic polymers by the polyethylenimine coating was detected by the distance-sensitive fluorescence resonance energy-transfer technique that evidenced the occurrence of energy transfer between fluorescein-labeled cationic copolymers and polyethylenimine-condensed rhodamine-labeled DNA. The ternary polyplexes feature reversible controllability of singlet oxygen generation based on the dual effect of spiropyrans in photochromism and aggregation-induced enhanced photosensitization, allowing significant light-induced amplification of bPEI-mediated in vitro transgene efficiency (from original 15% to final 91%) at a low DNA dose, with the integrity of supercoiled DNA structure unaffected. The use of spiropyran without the need of other photosensitizers circumvents the issue of uncontrolled long-lasting photocytotoxicity in gene delivery.

We took advantage of the iron binding affinity of apoferritin to immobilize iron–sulfur clusters into apoferritin up to 312 moieties per protein, with a loading rate as high as 25 wt%. The photocatalytic hydrogen generation activity in acidic aqueous solutions was achieved with TONs up to 31 (based on a single catalyst moiety) or 8.3 × 103 (based on a single protein) upon 3 h of visible light irradiation. The present study provides a versatile strategy to construct uniform protein/photocatalyst supramolecular systems with FeFe-H2ase activity.

The two-photon absorption properties of anionic poly(phenylene ethynylene)-type conjugated oligo- and polyelectrolytes are studied in molecularly dissolved and aggregated forms in aqueous solution. Several different polyvalent cations are used to induce aggregation. It is found that both materials in the aggregated form exhibit enhanced two-photon excited fluorescence (2PEF) and two-photon cross section (σ2) compared with the molecularly dissolved structures. The 2PEF and σ2 are unaffected by the nature of the polyvalent cation that is used to induce aggregation. The two-photon absorption cross section enhancement arises because of the increase in the difference dipole moment (Δμ) in the aggregates of the conjugated materials, an effect that is attributed to the introduction of charge transfer character into the aggregate excited state.

Functionalization of π-conjugated polymers is dispensable for solubilization of the rigid and hydrophobic backbones in water. However, polymer aggregation is always present and leads to issues with complication and reproducibility in spectral properties. Herein, we reported a simple and robust method to make a series of conjugated polymer nanostructures by a crosslinking strategy. In favor of multivalency effect, polythionenes with various chain lengths were functionalized with branched polyethylenimine (PEI) via ester aminolysis reaction under mild conditions. Photophysical studies revealed the conjugated backbones could be well stabilized and dispersed in water. By taking advantage of intermolecular recognition interaction between copper ions and cationic PEI, we applied crosslinked polythiophenes as a nano probe at very low concentration (0.01 mg/mL) to fluorescently detect copper ions with high sensitivity up to 10 nM and selectivity over other metal ions in aqueous solutions, without occurrence of detectable aggregates. The overall performance of our nano probes outperforms reported water-soluble polymers-based probes, particularly in probe availability and manipulation as well as selective copper detection capability.

We reported a near-infrared biosensor that features a dihydromethylene blue and an S-alkyl thiocarbamate linker to detect hypochlorous acid in a drastic fluorescence turn-on response. We achieved high sensitivity at the nanomolar level and high selectivity that resolves the interference issue with mercury ions and other transition metal ions. We demonstrated the response mechanism by analysing the released segments, and investigated the imaging capability to detect both exogenous and endogenous hypochlorous acid in living cells.

Reversibly controlled generation of singlet oxygen from photosensitizing nanosystems has the benefits of selective cell killing and controllable effect time, but is a challenging option for photodynamic therapies. We report a strategy for integrating photochromic spiropyrans into biocompatible cationic polymers, which involved assembling nucleic acids into functional nanoparticles without introducing additional photosensitizers and imaging agents. We found that spiropyran-containing nanoparticles have photoswitching properties for both fluorescence (with a quantum yield of up to 0.27) and singlet oxygen generation (with a quantum yield of up to 0.22) in aqueous solutions and cells, and demonstrated that spiropyrans in nanoassemblies featuring aggregation-induced enhanced photosensitization and emission could be potentially applied in photodynamic therapy studies on tumor cells.

We took advantage of gasotransmitter H2S as a chemical reaction-based trigger for controlled release of doxorubicin which is precoordinated by copper ions and enclosed in horse spleen apoferritin. The nanocomposite is stable at physiological pH and temperature before H2S activation. The drug release process avoids disassembly of protein shells and is controllable by the strong affinity of sulfide with copper ions. The in vitro cytotoxicity assay indicates the antitumor effect of doxorubicin toward tumor cells could be achievable by H2S activation.

A photoactive NO releasing system was constructed by incorporation of NO-bound Fe-S clusters into horse spleen apoferritin cavities with high loading efficacy. The composites retained intact core-shell structure and indicated advantages such as enhanced stability, reduced cytotoxicity, efficient cellular uptake, and photocontrolled NO releasing property.

Current treatment of recurrent glioblastoma multiforme (GBM) demands dose-intense temozolomide (TMZ), a prodrug of 5-(3-methyltriazen-1-yl) imidazole-4-carboxamide (MTIC), based on the spontaneous hydrolysis of TMZ at basic pH. However, how to control the activity of MTIC remains unknown, which poses a particular challenge to search a reliable MTIC receptor. We reported that copper, for the first time, is found to recognize and bind MTIC in the process of TMZ degradation, which means copper can play an important role in enhancing the bioavailability of MTIC derived from TMZ. Using apoferritin as a model copper-bound protein, we studied the copper-TMZ interaction in protein and observed efficient MTIC immobilization with high binding efficiency (up to 92.9% based on original TMZ) and capacity (up to 185 MTIC moieties per protein). The system was stable against both alkaline and acidic pH and could be activated by glutathione to liberate MTIC, which paves a way to deliver a DNA-alkylating agent for both TMZ-sensitive and TMZ-resistant GBM chemotherapy. Our study provides a new insight for understanding the potential relationship between the special GBM microenvironment (specific copper accumulation) and the therapeutic effect of TMZ.

In this report, noncovalent encapsulation of hydrophobic ruthenium(II) polyridyl complexes, Ru(bpy)2dppz(2+) and Ru(phen)2dppz(2+), into apoferritin cavity was achieved with high loading contents by effective prevention of Ru complex-induced protein aggregation, without disruption of protein native architecture. The Ru-loaded luminescent nanocomposites have demonstrated improved water solubility, easy manipulation, reduced cytotoxicity, and enhanced cellular uptake as compared to the nontreated Ru complexes.

We designed a water soluble benzotriazole-cored donor-acceptor-donor molecule bearing four triphenylphosphonium moieties for mitochondria targeting. The organic molecule showed strong singlet oxygen sensitizing capability (ΦΔ 0.64), minimal dark cytotoxicity and high photocytotoxicity. The molecule is efficient in photodynamic killing of tumour cells under normal and hypoxia conditions using a very low light flux, and has potential in near-infrared two-photon imaging and photodynamic therapy.

Cationic side chains on conjugated polyelectrolytes play crucial roles in the state of polymer chains in water as well as the interactions with live cells. However, it is difficult to compare the effect of different cationic side chains due to the structural defect and severe aggregation issue. We synthesized structurally defined cationic polythiophenes with pendent phosphonium-, quaternary ammonium- and imidazolium-substituted side chains, and confirmed molecularly dispersed state of them in aqueous solutions by spectroscopic characterizations. We also investigated the cytotoxicity as well as cell binding and intracellular trafficking by imaging live cells in the absence and presence of hyaluronic acid.

Conjugated polymers can serve as good photosensitizers in biomedical applications. However, it remains unknown whether they are phototoxic to the supercoiled structure of DNA in improving gene delivery by the photochemical internalization (PCI) strategy, which complicates the application of conjugated polymers in gene delivery. In this work, we introduced a trace amount of cationic poly(phenylene ethynylene)s (cPPEs) into the polymeric shell of branched polyethylenimine (BPEI)/DNA complexes, studied the photosensitization of singlet oxygen by cPPEs, and confirmed that the supercoiled DNA is undamaged by the singlet oxygen generated by the photoexcitation of cPPEs. By taking advantage of the cPPE-mediated PCI effect, we report that the addition of the trace amount of cPPEs to the outer shell of the BPEI/DNA polyplexes could greatly amplify the transfection of gene green fluorescent protein on tumor cells with the efficiency from 14 to 86% without decreasing the cell viabilities, well solving the problem with a poor transfection capability of BPEI under low DNA-loading conditions. Our strategy to employ conjugated polymers as photosensitizing agents in gene delivery systems is simple, safe, efficient, and promising for broad applications in gene delivery areas.

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.

In this report, two biodegradable star-shaped polyasparamide derivatives and four analogues modified with either mannose or folic acid moiety for preferential targeting of a difficult-to-transfect immune cell type, i.e., macrophage, have been synthesized. Each of the prepared star polymers complexes with plasmid DNA to form nanosized particles featuring a core-shell-like morphology. Mannose or folate functionalized star polymers can greatly improve the transfection performance on a macrophage cell line RAW 264.7. As a result, a combination of targeting ligand modification and topological structures of gene carriers is a promising strategy for immune cells-based gene therapy.

There is urgent demand of easily available and highly effective method to improve transgene performance of polymeric gene carriers at low consumption of delivery materials. We developed biocompatible multicomponent nanocomposites in which small quantities of cationic polythiophenes were engineered into the outer shell of polypeptide/DNA polyplexes without covalent linkages. We revealed the introduction of polythiophenes in small quantities led to multiple outcomes including modulation of polyplex size and zeta potential, increase in polyplex stability, promotion of endolysosome membrane disruption, light-induced generation of reactive oxygen species (ROS), and significant enhancement of gene delivery to tumor cells. The factors such as structural architectures, molecular weights, photosensitizing capability, and percentage composition of polythiophenes were investigated.

A new class of nonaggregating conjugated polyelectrolytes exhibits efficient fluorescence in aqueous solution. Analysis by optical spectroscopy and transmission electron microscopy reveals a unique structure-property correlation between oxygen substitution and aggregation.

An efficient P(V)-N activation strategy for the preparation of high-quality 5-hydroxymethyl-, 5-formyl-, and 5-carboxyl-2′-deoxycytidine triphosphates has been developed. The method was also optimized for gram-scale synthesis of the corresponding parent nucleosides from 2′-deoxythymidine.

Advancement of RNAi therapies is mainly hindered by the development of efficient delivery vehicles. The ability to create small size (

Fluorescence correlation spectroscopy (FCS) is applied to investigate aggregation behavior of an anionic conjugated polyelectrolyte (CPE) featuring branched carboxylate groups (PPE-(d)CO2) upon the addition of different metal ions. FCS results reveal that monovalent metal ions (Na(+), K(+)) bind to the CPE chain but do not induce aggregation, and divalent metal ions (Ca(2+), Cu(2+)) bind and induce the formation of small aggregates. Iron cations (Fe(2+) and Fe(3+)) bind strongly and induce the formation of large CPE aggregates. This is believed to be because of the propensity of these metals to bind to six ligands and thus bridge two of the triacid units on adjacent PPE-(d)CO2 chains. A comparison between the Stern-Volmer (SV) fluorescence quenching and the relative diffusion time change from FCS demonstrates that the most efficient SV quenching is observed for the ions that give rise to large increases in FCS diffusion time, underscoring the importance of ion-induced aggregation in the amplified quenching effect.

We report the photophysics and fluorescence quenching of a series of monodisperse, anionic π-conjugated oligomers that are molecularly dissolved in aqueous solution. These structurally well-defined oligomers feature oligo(phenylene ethynylene) backbones with two -CH2COO(-) units on each repeat unit, with overall lengths of 5, 7, and 9 repeats. The ionic oligomers display a structured fluorescence band with high quantum efficiency in water, in contrast to the low fluorescence quantum efficiency and pronounced aggregation displayed by structurally similar oligomeric and polymeric (phenylene ethynylene) conjugated polyelectrolytes studied previously. Stern-Volmer (SV) fluorescence quenching studies using cationic charge- and energy-transfer quenchers reveal that all of the oligomers give rise to SV quenching constants (KSV) in excess of 10(6) M(-1), with values increasing with oligomer length, consistent with the amplified quenching effect. The amplified quenching effect is proposed to occur due to the formation of comparatively small oligomer aggregates.

Conjugated polyelectrolyte dendrimers (CPDs) are monodisperse macromolecules that feature a fully π-conjugated dendrimer core surrounded on the periphery by ionic solubilizing groups. CPDs are soluble in water and polar organic solvents, and they exhibit photophysics characteristic of the π-conjugated chromophores comprising the dendrimer core. Here we describe the synthesis and photophysical characterization of series of three generations of CPDs based on a phenylene ethynylene repeat unit structure that is surrounded by an array of anionic sodium carboxylate groups. Molecular dynamics simulations indicate that the first-generation CPD is flat while the second- and third-generation CPDs adopt oblate structures. Photophysical studies, including absorption, fluorescence spectroscopy, and lifetimes, show that the ester protected precursor dendrimers exhibit highly efficient blue fluorescence in THF solution emanating from the phenylene ethynylene chromophore that is in the dendrimer core. By contrast, the water-soluble CPDs have much lower fluorescence quantum yields and the absorption and fluorescence spectra exhibit features of strong chromophore-chromophore interactions. The results are interpreted as suggesting that the CPDs exist as dimer or multimer aggregates, even in very dilute solution. Fluorescence quenching of the anionic CPDs with the dication electron acceptor N,N'-dimethylviologen (MV(2+)) is very efficient, with Stern-Volmer quenching constants (K(SV)) increasing with generation number. The third-generation CPD exhibits highly efficient amplified quenching, with K(SV) ∼ 5 × 10(6) M(-1).

We report the "light switch" effect of [Ru(bpy)2(dppz)](2+) (where bpy = 2,2'-bipyridine and dppz = dipyrido[3,2-a:2',3'-c] phenazine, Ru-dppz) in the presence of anionic conjugated polyelectrolyte dendrimers (CPDs). The metal-to-ligand charge-transfer luminescence from Ru-dppz is efficient in the presence of CPD because the complex is shielded from water by binding to the hydrophobic dendrimer core.

We report on the comparison of the electronic and photophysical properties of a series of related donor-acceptor-donor oligomers incorporating the previously known 2H-benzo[d][1,2,3]triazole (BTz) moiety as the acceptor and the recently reported BTzTD acceptor, a hybrid of BTz and 2,1,3-benzothiadiazole (BTD). Although often implied in the polymer literature that BTz has good acceptor character, we show that this moiety is best described as a weak acceptor. We present electrochemical, computational, and photophysical evidence supporting our assertion that BTzTD is a strong electron acceptor while maintaining the alkylation ability of the BTz moiety. Our results show that the identity of the central atom (N or S) in the benzo-fused heterocyclic ring plays an important role in both the electron-accepting and the electron-donating ability of acceptor moieties with sulfur imparting a greater electron-accepting ability and nitrogen affording greater electron-donating character. We report on the X-ray crystal structure of a BTzTD trimer, which exhibits greater local aromatic character in the region of the triazole ring and contains an electron-deficient sulfur that imparts strong electron-accepting ability. Additionally, we examine the transient absorption spectra of BTzTD and BTz oligomers and report that the BTz core promotes efficient intersystem crossing to the triplet state, while the presence of the thiadiazole moiety in BTzTD leads to a negligible triplet yield. Additionally, while BTz does not function as a good acceptor, oligomers containing this moiety do function as excellent sensitizers for the generation of singlet oxygen.

This protocol describes a homogeneous, convenient and sensitive DNA methylation detection method, using an optically amplifying cationic conjugated polymer (CCP, poly((1,4-phenylene)-2,7-[9,9-bis(6'-N,N,N-trimethyl ammonium)-hexyl fluorene] dibromide)). Genomic DNA from cancer cells is pretreated with a methylation-sensitive restriction endonuclease, followed by PCR amplification in the presence of fluorescein-labeled dNTP and Taq polymerase. The PCR only occurs for methylated DNA. DNA methylation of the gene sequence of interest is detected as a result of the fluorescence resonance energy transfer (FRET) between CCP and fluorescein that is incorporated into DNA. The methylated statuses of the p16, HPP1 and GALR2 promoters of five cancer cell lines (HT29, HepG2, A498, HL60 and M17) were assayed to provide an association study between the cancers and susceptibility genes, which shows great potential for early cancer diagnosis. This protocol simplifies previously available procedures by avoiding the need for primer labeling, isolation or purification steps, and sophisticated instruments. The assay takes about 20 h to obtain the methylated statuses of cancer cells.

Nuclear magnetic resonance imaging (MRI) has become a powerful technique in clinical diagnostics. In this work, a new MRI contrast agent by covalently linking Gd(III) chelates to the side chain of conjugated polymer (PF–Gd) is synthesized by Suzuki cross-coupling reaction. The PF–Gd exhibits a higher relaxivity and a pronounced enhancement in contrast than that of (NMG) 2 –Gd–DTPA widely used for clinical diagnosis. This work should be feasible to potentially lead to a new class of imaging contrast agents.

A simple, rapid, continuous and homogeneous fluorescent assay for β-galactosidase was developed, combining an enzyme-coupled reaction and signal amplification property of conjugated polyelectrolytes (CPs). The procedure is based on a sequence of two coupled biocatalytic steps in which the β-galactosidase hydrolyzes its substrate to a phenol derivative followed by conversion to quinone (secondary product) with fluorescence quenching ability by the tyrosinase. The fluorescence of PFP-SO 3 - is efficiently quenched by the quinone via an electron transfer process. The limit of detection (LOD) of this assay is less than 0.0005 U mL -1 , which is better than that of electrochemical method and is comparable to that of most sensitive chemiluminescent techniques. In principle, this sensor mechanism will extend the application window of CPs for wide-spectrum enzyme detections. This "mix-and-detect" approach could be expanded to a high-throughput manner.

An energy-transfer cascade is generated from a cationic conjugated polymer (PFP) and negatively charged, Y-shaped DNA labeled with three dyes at its termini (fluorescein (Fl), Tex Red, and Cy5). Multistep fluorescence resonance energy transfer regulates the fluorescence intensities of PFP and the dyes. Different types of logic gates can be operated by observing the emission wavelengths of different dyes with multiplex nucleases as inputs.

A new platform has been developed for DNA lesion detection using a cationic conjugated polymer (CCP). DNA that contains two adjacent thymine bases is irradiated with ultraviolet light to allow for the formation of cyclobutane pyrimidine dimers and pyrimidine-pyrimidone dimers. The DNA lesions block the primer extension, and the base labeled with fluorescein cannot be incorporated into the DNA strand. Addition of the CCP leads to inefficient fluorescence resonance energy transfer (FRET) from CCP to fluorescein. For the case without DNA lesions, successful primer extension allows for efficient FRET between them. In view of the FRET signal changes, the DNA lesions can be detected. This new protocol offers a convenient detection for DNA lesions in aqueous solution without any isolation and washing steps.

A new water-soluble oligo(phenylenevinylene) containing a tyrosine unit (OPV-Tyr) was synthesized as a fluorescent probe to optically detect tyrosinase activity. Upon the addition of tyrosinase, the tyrosine moiety was oxidized to quinone, which quenched the fluorescence of OPV-Tyr via intramolecular electron transfer from the phenylenevinylene unit to the quinone site. OPV-Tyr was elaborated to detect tyrosinase activity both in aqueous buffer solution and in agarose gel.

A new fluorescence method has been developed for DNA detection at room temperature in a sensitive, selective, economical, and real-time manner that interfaces the superiority of a molecular beacon in mismatch discrimination with the light-harvesting property of water-soluble conjugated polyelectrolytes. The probe solution contains a cationic conjugated polyelectrolyte (PFP-NMe3+), a molecular beacon with a five base pairs double-stranded stem labeled at the 5'-terminus with fluorescein (DNA P-Fl), and ethidium bromide (EB, a specific intercalator of dsDNA). The electrostatic interactions between DNA P-Fl and PFP-NMe3+ keep them in close proximity, facilitating the fluorescence resonance energy transfer (FRET) from PFP-NMe3+ to fluorescein. Upon adding a complementary strand to the probe solution, the conformation of DNA P-Fl transits into dsDNA followed by the intercalation of EB into the grooves. Two-step FRET, from PFP-NMe3+ to DNA P-Fl (FRET-1), followed by FRET from DNA P-Fl to EB (FRET-2) takes place. In view of the observed fluorescein or EB emission changes, DNA can be detected in aqueous solution. Because the base mismatch in target DNA inhibits the transition of DNA P-Fl from the stem-loop to duplex structure, single nucleotide mismatch can be clearly detected.

Water-soluble conjugated polymers have attracted much attention in the biosensor community because of recent exciting experimental results. The transfer of excitation energy along the whole backbone of the conjugated polymer to the reporter results in an amplified fluorescence signal, which makes them useful as optical platforms in highly sensitive chemical and biological sensors. In this Research News Article, we provide a brief review of recent developments in this field, focusing especially on the application of water-soluble optical conjugated polymers in biomacromolecule (DNA and protein) detection.