Superoxide-responsive fluorogenic molecular probes for optical bioimaging of neurodegenerative events in Alzheimer's disease.

Since oxidative stress has been recognized as a major factor contributing to the progression of several neurodegenerative disorders, reactive oxygen species (ROS) including superoxide have received great attention as a representative molecular marker for the diagnosis of Alzheimer's disease (AD). Here, superoxide-sensitive fluorogenic molecular probes, benzenesulfonylated resorufin derivatives (BSRs), were newly devised for optical bioimaging of oxidative events in neurodegenerative processes. BSRs, fluorescence-quenched benzenesulfonylated derivatives of resorufin, were designed to recover their fluorescence upon exposure to superoxide through a selective nucleophilic uncaging reaction of the benzenesulfonyl cage. Among BSRs, BSR6 presented the best sensitivity and selectivity to superoxide likely due to the optimal reactivity matching between the nucleophilicity of superoxide and its electrophilicity ascribed to the highly electron-withdrawing pentafluoro-substitution on the benzenesulfonyl cage. Fluorescence imaging of inflammatory cells and animal models presented the potential of BSR6 for optical sensing of superoxide in vitro and in vivo. Furthermore, microglial cell (Bv2) imaging with BSR6 enabled the optical monitoring of intracellular oxidative events upon treatment with an oxidative stimulus (amyloid beta, Aß) or the byproduct of oxidative stress (4-hydroxynonenal, HNE).

Doubly resonant sum frequency spectroscopy of mixed photochromic isomers on surfaces reveals conformation-specific vibronic effects.

Doubly resonant infrared-visible sum-frequency generation (DR-IVSFG) spectroscopy, encompassing coupled vibrational and electronic transitions, provides a powerful method to gain a deep understanding of nuclear motion in photoresponsive surface adsorbates and interfaces. Here, we use DR-IVSFG to elucidate the role of vibronic coupling in a surface-confined donor-acceptor substituted azobenzene. Our study reveals some unique features of DR-IVSFG that have not been previously reported. In particular, vibronic coupling resulted in prominent SFG signal enhancement of selective stretching modes that reveal electronic properties of coexisting photochromic isomers. Our analysis explores two concepts: (1) In partially isomerized azobenzene at the surface, coupling of the fundamental vibrations to the S0 → S1 transition is more prominent for the cis isomer due to symmetry breaking, whereas coupling to the S0 → S2 transition was dominant in the trans isomer. (2) A strong coupling between the fundamental vibrations and the valence π-electron density, promoted by the initial absorption of an infrared photon, may result in suppression of the intensity of the hot band vibronic transition. This may translate into a suppressed sum-frequency generation signal at sum frequency wavelengths resonant with the S0 → S2 transition of the trans isomer. The weaker coupling of the fundamental vibrations to the non-bonding electron density localized on the azo group can therefore produce detectable sum-frequency generation at the resonance wavelength of the weaker S0 → S1 transition in the cis form. These results are explained in the framework of a linear coupling model, involving both Franck-Condon and Herzberg-Teller coupling terms. Our theoretical analysis reveals the important role played by molecular conformation, orientation, and vibronic interference in DR-SFG spectroscopy.

Fluorescent Molecular Rotors for Viscosity Sensors.

Fluorescent molecular rotors (FMRs) can act as viscosity sensors in various media including subcellular organelles and microfluidic channels. In FMRs, the rotation of rotators connected to a fluorescent π-conjugated bridge is suppressed by increasing environmental viscosity, resulting in increasing fluorescence (FL) intensity. In this minireview, we describe recently developed FMRs including push-pull type π-conjugated chromophores, meso-phenyl (borondipyrromethene) (BODIPY) derivatives, dioxaborine derivatives, cyanine derivatives, and porphyrin derivatives whose FL mechanism is viscosity-responsive. In addition, FMR design strategies for addressing various issues (e.g., obtaining high FL contrast, internal FL references, and FL intensity-contrast trade-off) and their biological and microfluidic applications are also discussed.

Molecular Viscosity Sensors with Two Rotators for Optimizing the Fluorescence Intensity-Contrast Trade-Off.

A series of fluorescent molecular rotors obtained by introducing two rotational groups ("rotators"), which exhibit different rotational and electron-donating abilities, are discussed. Whereas the control molecular rotor, PH, includes a single rotator (the widely used phenyl group), the PO molecular rotors consist of two rotators (a phenyl group and an alkoxy group), which exhibit simultaneous strongly electron-donating and easy rotational abilities. Compared with the control rotor PH, PO molecular rotors exhibited one order of magnitude higher quantum yield (fluorescence intensity) and simultaneously exhibited significantly higher fluorescence contrast. These properties are directly related to the strong electron-donating ability and low energy barrier of rotation of the alkoxy group, as confirmed by dynamic fluorescence experiments and quantum chemical calculations. The PO molecular rotors exhibited two fluorescence relaxation pathways, whereas the PH molecular rotor exhibited a single fluorescence relaxation pathway. Cellular fluorescence imaging with PO molecular rotors for mapping cellular viscosity was successfully demonstrated.

Polymorphic Self-Assembly with Procedural Flexibility for Monodisperse Quaternary Protein Structures of DegQ Enzymes.

As large molecular tertiary structures, some proteins can act as small robots that find, bind, and chaperone target protein clients, showing the potential to serve as smart building blocks in self-assembly fields. Instead of using such intrinsic functions, most self-assembly methodologies for proteins aim for de novo-designed structures with accurate geometric assemblies, which can limit procedural flexibility. Here, a strategy enabling polymorphic clustering of quaternary proteins, exhibiting simplicity and flexibility of self-assembling paths for proteins in forming monodisperse quaternary cage particles is presented. It is proposed that the enzyme protomer DegQ, previously solved at low resolution, may potentially be usable as a threefold symmetric building block, which can form polyhedral cages incorporated by the chaperone action of DegQ in the presence of protein clients. To obtain highly monodisperse cage particles, soft, and hence, less resistive client proteins, which can program the inherent chaperone activity of DegQ to efficient formations of polymorphic cages, depending on the size of clients are utilized. By reconstructing the atomic resolution cryogenic electron microscopy DegQ structures using obtained 12- and 24-meric clusters, the polymorphic clustering of DegQ enzymes is validated in terms of soft and rigid domains, which will provide effective routes for protein self-assemblies with procedural flexibility.

Photonic control of ligand nanospacing in self-assembly regulates stem cell fate.

Extracellular matrix (ECM) undergoes dynamic inflation that dynamically changes ligand nanospacing but has not been explored. Here we utilize ECM-mimicking photocontrolled supramolecular ligand-tunable Azo+ self-assembly composed of azobenzene derivatives (Azo+) stacked via cation-π interactions and stabilized with RGD ligand-bearing poly(acrylic acid). Near-infrared-upconverted-ultraviolet light induces cis-Azo+-mediated inflation that suppresses cation-π interactions, thereby inflating liganded self-assembly. This inflation increases nanospacing of "closely nanospaced" ligands from 1.8 nm to 2.6 nm and the surface area of liganded self-assembly that facilitate stem cell adhesion, mechanosensing, and differentiation both in vitro and in vivo, including the release of loaded molecules by destabilizing water bridges and hydrogen bonds between the Azo+ molecules and loaded molecules. Conversely, visible light induces trans-Azo+ formation that facilitates cation-π interactions, thereby deflating self-assembly with "closely nanospaced" ligands that inhibits stem cell adhesion, mechanosensing, and differentiation. In stark contrast, when ligand nanospacing increases from 8.7 nm to 12.2 nm via the inflation of self-assembly, the surface area of "distantly nanospaced" ligands increases, thereby suppressing stem cell adhesion, mechanosensing, and differentiation. Long-term in vivo stability of self-assembly via real-time tracking and upconversion are verified. This tuning of ligand nanospacing can unravel dynamic ligand-cell interactions for stem cell-regulated tissue regeneration.

Glutathione displacement assay based on a fluorescent Au(I) complex.

Glutathione (GSH) is an essential molecule that plays a pivotal role in maintaining intracellular redox homeostasis, as well as other physiological processes. However, the chemical mechanisms underlying the GSH-induced processes remain insufficiently understood due to the lack of appropriate detection tools. Fluorescence GSH imaging can serve as a useful principle for the rapid, convenient, and non-destructive detection of GSH in living organisms. In this study, we developed a fluorescent GSH probe based on a linear, homoleptic Au(I) complex with two 1,3-diphenylbenzimidazolium carbene ligands. The Au(I) complex produced a fluorescence turn-on response to GSH. Fluorescence GSH signaling was characterized with a short response time of a few seconds. The rapid response was attributed to the displacement of the carbene ligand with GSH, which involved a labile inner-sphere coordination interaction. Finally, we demonstrated the biological utility of our GSH probe by unambiguously discriminating between different GSH levels in normal and senescent preadipocytes.

Self-deprotonation and colorization of 1,3-bis(dicyanomethylidene)indan in polar media: a facile route to a minimal polymethine dye for NIR fluorescence imaging.

Colorless 1,3-bis(dicyanomethylidene)indan is an organic acid (pK(a) ≈3.0) that turns blue in polar media owing to self-deprotonation. Moreover, its colored conjugate base shows potential as a minimal anionic polymethine dye for probing biomolecules in cells and in vivo through noncovalent complexation and near-infrared fluorescence signaling.

Solid-state phosphorescence-to-fluorescence switching in a cyclometalated Ir(III) complex containing an acid-labile chromophoric ancillary ligand: implication for multimodal security printing.

In this study, we have demonstrated the reconstruction of encrypted information by employing photoluminescence spectra and lifetimes of a phosphorescent Ir(III) complex (IrHBT). IrHBT was constructed on the basis of a heteroleptic structure comprising a fluorescent N^O ancillary ligand. From the viewpoint of information security, the transformation of the Ir(III) complex between phosphorescent and fluorescent states can be encoded with chemical/photoirradiation methods. Thin polymer films (poly(methylmethacrylate), PMMA) doped with IrHBT display long-lived emission typical of phosphorescence (λ(max) = 586 nm, τ(obs) = 2.90 µs). Meanwhile, exposure to HCl vapor switches the emission to fluorescence (λ(max) = 514 nm, τ(obs) = 1.53 ns) with drastic changes in both the photoluminescence color and lifetime. Security printing on paper impregnated with IrHBT or on a PMMA film containing IrHBT and photoacid generator (triphenylsulfonium triflate) enables the bimodal readout of photoluminescence color and lifetime.

Photoswitchable Microgels for Dynamic Macrophage Modulation.

Dynamic manipulation of supramolecular self-assembled structures is achieved irreversibly or under non-physiological conditions, thereby limiting their biomedical, environmental, and catalysis applicability. In this study, microgels composed of azobenzene derivatives stacked via π-cation and π-π interactions are developed that are electrostatically stabilized with Arg-Gly-Asp (RGD)-bearing anionic polymers. Lateral swelling of RGD-bearing microgels occurs via cis-azobenzene formation mediated by near-infrared-light-upconverted ultraviolet light, which disrupts intermolecular interactions on the visible-light-absorbing upconversion-nanoparticle-coated materials. Real-time imaging and molecular dynamics simulations demonstrate the deswelling of RGD-bearing microgels via visible-light-mediated trans-azobenzene formation. Near-infrared light can induce in situ swelling of RGD-bearing microgels to increase RGD availability and trigger release of loaded interleukin-4, which facilitates the adhesion structure assembly linked with pro-regenerative polarization of host macrophages. In contrast, visible light can induce deswelling of RGD-bearing microgels to decrease RGD availability that suppresses macrophage adhesion that yields pro-inflammatory polarization. These microgels exhibit high stability and non-toxicity. Versatile use of ligands and protein delivery can offer cytocompatible and photoswitchable manipulability of diverse host cells.

Hybrid Curdlan Poly(γ -Glutamic Acid) Nanoassembly for Immune Modulation in Macrophage.

A nanoformulation composed of curdlan, a linear polysaccharide of 1,3-ß-linked d-glucose units, hydrogen bonded to poly(γ -glutamic acid) (PGA), was developed to stimulate macrophage. Curdlan/PGA nanoparticles (C-NP) are formulated by physically blending curdlan (0.2 mg mL-1 in 0.4 m NaOH) with PGA (0.8 mg mL-1 ). Forster resonance energy transfer (FRET) analysis demonstrates a heterospecies interpolymer complex formed between curdlan and PGA. The 1 H-NMR spectra display significant peak broadening as well as downfield chemical shifts of the hydroxyl proton resonances of curdlan, indicating potential intermolecular hydrogen bonding interactions. In addition, the cross peaks in 1 H-1 H 2D-NOESY suggest intermolecular associations between the OH-2/OH-4 hydroxyl groups of curdlan and the carboxylic-/amide-groups of PGA via hydrogen bonding. Intracellular uptake of C-NP occurs over time in human monocyte-derived macrophage (MDM). Furthermore, C-NP nanoparticles dose-dependently increase gene expression for TNF-α, IL-6, and IL-8 at 24 h in MDM. C-NP nanoparticles also stimulate the release of IL-lß, MCP-1, TNF-α, IL-8, IL-12p70, IL-17, IL-18, and IL-23 from MDM. Overall, this is the first demonstration of a simplistic nanoformulation formed by hydrogen bonding between curdlan and PGA that modulates cytokine gene expression and release of cytokines from MDM.

A fluorogenic molecular nanoprobe with an engineered internal environment for sensitive and selective detection of biological hydrogen sulfide.

A nanoreactor approach based on the amphiphilic assembly of various molecules offers a chance to finely engineer the internal reaction medium to enable highly selective and sensitive detection of H2S in biological media, being useful for microscopic imaging of cellular processes and in vitro diagnostics with blood samples.

Rational design for enhancing inflammation-responsive in vivo chemiluminescence via nanophotonic energy relay to near-infrared AIE-active conjugated polymer.

H2O2-specific peroxalate chemiluminescence is recognized as a potential signal for sensitive in vivo imaging of inflammation but the effect of underlying peroxalate-emitter energetics on its efficiency has rarely been understood. Here we report a simple nanophotonic way of boosting near-infrared chemiluminescence with no need of complicated structural design and synthesis of an energetically favored emitter. The signal enhancement was attained from the construction of a nanoparticle imaging probe (∼26 nm in size) by dense nanointegration of multiple molecules possessing unique photonic features, i.e., i) a peroxalate as a chemical fuel generating electronic excitation energy in response to inflammatory H2O2, ii) a low-bandgap conjugated polymer as a bright near-infrared emitter showing aggregation-induced emission (AIE), and iii) an energy gap-bridging photonic molecule that relays the chemically generated excitation energy to the emitter for its efficient excitation. From static and kinetic spectroscopic studies, a green-emissive BODIPY dye has proven to be an efficient relay molecule to bridge the energy gap between the AIE polymer and the chemically generated excited intermediate of H2O2-reacted peroxalates. The energy-relayed nanointegration of AIE polymer and peroxalate in water showed a 50-times boosted sensing signal compared to their dissolved mixture in THF. Besides the high H2O2 detectability down to 10(-9) M, the boosted chemiluminescence presented a fairly high tissue penetration depth (>12 mm) in an ex vivo condition, which enabled deep imaging of inflammatory H2O2 in a hair-covered mouse model of peritonitis.

Resonance Raman Probes for Organelle-Specific Labeling in Live Cells.

Raman microspectroscopy provides for high-resolution non-invasive molecular analysis of biological samples and has a breakthrough potential for dissection of cellular molecular composition at a single organelle level. However, the potential of Raman microspectroscopy can be fully realized only when novel types of molecular probes distinguishable in the Raman spectroscopy modality are developed for labeling of specific cellular domains to guide spectrochemical spatial imaging. Here we report on the design of a next generation Raman probe, based on BlackBerry Quencher 650 compound, which provides unprecedentedly high signal intensity through the Resonance Raman (RR) enhancement mechanism. Remarkably, RR enhancement occurs with low-toxic red light, which is close to maximum transparency in the biological optical window. The utility of proposed RR probes was validated for targeting lysosomes in live cultured cells, which enabled identification and subsequent monitoring of dynamic changes in this organelle by Raman imaging.

Pyrrolic molecular rotors acting as viscosity sensors with high fluorescence contrast.

New pyrrolic viscosity sensors exhibit one order of magnitude higher fluorescence contrast compared to that of the conventional phenolic analogues due to the viscosity-sensitive rotation of the asymmetric pyrrole group and successfully demonstrate mapping of intracellular viscosity by fluorescence lifetime imaging microscopy.

Fluorogenic nanoreactor assembly with boosted sensing kinetics for timely imaging of cellular hydrogen peroxide.

The precise detection of endogenous H2O2 has been considered to be a useful tool for understanding cell physiology. Here, we have developed a nanoreactor co-incorporated with a H2O2-responsive fluorogenic molecule and a catalytic additive. The fast sensing kinetics allows us to visualize a subcellular response in real-time.

Organelle specific imaging in live cells and immuno-labeling using resonance Raman probe.

Raman microspectroscopy is one of the most powerful tools in molecular sensing, offering a non-invasive and comprehensive characterization of the intracellular environment. To analyze and monitor molecular content in specific cellular compartments, different parts of cellular architecture must be unambiguously identified to guide Raman image/spectra acquisition. In this regards, the development of Raman molecular probes, producing spectrally distinct and intense signal is of outmost practical importance. Here we report on a new generation of Raman molecular probes, designed for application in live cells and immuno-labeling, capable of providing unprecedentedly high detection sensitivity through Resonance Raman (RR) enhancement. In contrast to existing Raman markers, the proposed RR reporter is designed to produce RR enhancement under excitation in the visible spectral range, far away from absorption of cellular biomolecules. We show that this concept allows for facile identification of labeled cellular domains, simultaneously with mapping of the macromolecules using spontaneous Raman technique. We demonstrate the breakthrough potential of these RR probes for selective labeling and rapid Raman imaging of membranes as well as mitochondria in live cells. We also show that these resonant Raman probes open the way for Raman-based intracellular immuno-labeling.

Factors associated with breast and cervical cancer screening in Korea: data from a national community health survey.

This study investigated factors associated with breast and cervical cancer screening using data from a nationwide community survey. A nationwide cross-sectional study was performed in all 253 administrative districts of Korea. The breast and cervical cancer screening rate was negatively associated with the obesity (ß = -2.91, 95% confidence interval [CI] = -4.73 to -1.03; ß = -1.93, 95% CI = -3.43 to -0.43), positively associated with the European Quality of Life-5 Dimensions scale (ß =2.53, 95% CI = 0.24 to 4.81; ß = 2.51, 95% CI = 0.68 to 4.34). Moreover, higher alcohol consumption rate was negatively related to screening rates for breast cancer, while areas with higher proportion of diabetes were found to have higher screening rates. Area with higher rate of osteoarthritis had a lower screening rate for cervical cancer. This study showed breast and cervical cancer screening was associated with particular area characteristics. This ecological approach is thought to be a major complement to measures of health attributes.

Gadolinium-coordinated elastic nanogels for in vivo tumor targeting and imaging.

Coordination polymer gels have been recognized as promising hybrid nanoplatforms for imaging and therapeutic applications. Here we report functional metal-organic coordinated nanogels (GdNGs) for in vivo tumor imaging, whose non-crystalline and elastic nature allows for long blood circulation, as opposed to the rapid systemic clearance of common nanohybrids with rigid/crystalline frameworks. The deformable structure of GdNGs was constructed by random crosslinking of highly flexible polyethyleneimines (PEI) with gadolinium (Gd(3+)) coordination. The in vitro characterization revealed that GdNGs have elasticity with an apparent Young's modulus of 3.0 MPa as well as minimal cytotoxicity owing to the tight chelation of Gd(3+) ions. In contrast to common T1-enhancing gadolinium complexes, GdNGs showed the capability of enhancing negative T2 contrast (r2 = 82.6 mm(-1)s(-1)) due to the Gd(3+)-concentrated nanostructure. Systemic administration of fluorescently labeled GdNGs with core and overall hydrodynamic sizes of ~65 and ~160 nm manifested efficient targeting and dual-modality (magnetic resonance/fluorescence) imaging of tumor in a mouse model. The minimal filtration by the reticuloendothelial system (RES) suggests that the structural deformability helps the large colloids circulate in the blood stream for tumor accumulation. The unusual performance of a large Gd(3+)-complexed colloid (minimal RES sequestration and high T2 contrast enhancement) represents the versatile nature of nanoscopic organic-inorganic hybridization for biomedical applications.

Nanophotosensitizers toward advanced photodynamic therapy of Cancer.

UNLABELLED: Photodynamic therapy (PDT) is a non-invasive treatment modality for selective destruction of cancer and other diseases and involves the colocalization of light, oxygen, and a photosensitizer (PS) to achieve photocytotoxicity. Although this therapeutic method has considerably improved the quality of life and life expectancy of cancer patients, further advances in selectivity and therapeutic efficacy are required to overcome numerous side effects related to classical PDT. The application of nanoscale photosensitizers (NPSs) comprising molecular PSs and nanocarriers with or without other biological/photophysical functions is a promising approach for improving PDT. In this review, we focus on four nanomedical approaches for advanced PDT: (1) nanocarriers for targeted delivery of PS, (2) introduction of active targeting moieties for disease-specific PDT, (3) stimulus-responsive NPSs for selective PDT, and (4) photophysical improvements in NPS for enhanced PDT efficacy. HIGHLIGHTS: ► Conservation of normal tissues demands non-invasive therapeutic methods. ► PDT is a light-activated, non-invasive modality for selective destruction of cancers.► Success of PDT requires further advances to overcome the limitations of classical PDT. ►Nanophotosensitizers help improve target selectivity and therapeutic efficacy of PDT.