Ionic Hydrogels Based Wearable Sensors to Monitor the Solar Radiation Dose for Vitamin D Production and Sunburn Prevention.

Wearable solar radiation sensors based on ionic hydrogels are facilely prepared to simultaneously monitor the radiation dose for the production of vitamin D and the prevention of sunburn. Tetramethylethylenediamine (TEMED) is neutralized with acrylic acid (AA) to obtain tetramethylethylenediamine acrylate (TEMEDA), which is further polymerized with acrylamide by a free radical reaction. By simply adding MB or NR during the polymerization, the final obtained ionic hydrogels can indicate solar radiation. Due to the extent of discoloration, the discoloration speed of MB and NR is correlated to the radiation dose. This wearable sensor can indicate the solar radiation dose required by the human body to synthesize vitamin D through the discoloration of the ionized hydrogel of MB, whereas those with NR are able to illustrate the threshold of radiation dose that causes potential skin hurt. Therefore, the benefit and drawback of solar radiation can be well balanced by optimizing the exposure time to solar irradiation. In addition, polyurethane cross-linked with a thermoresponsive coating is used as band for this wearable sensor. Due to the hydrophilicity below its transition temperature, the cross-linked band possesses the easy cleaning capability of stains after the daily wear. Such type of wearable sensor can be broadly used for monitoring the solar radiation, especially in outdoor activities.

Survey of X-ray induced Cherenkov excited fluorophores with potential for human use.

X-ray induced molecular luminescence (XML) is a phenomenon that can be utilized for clinical, deep-tissue functional imaging of tailored molecular probes. In this study, a survey of common or clinically approved fluorophores was carried out for their megavoltage X-ray induced excitation and emission characteristics. We find that direct scintillation effects and Cherenkov generation are two possible ways to cause these molecules' excitation. To distinguish the contributions of each excitation mechanism, we exploited the dependency of Cherenkov radiation yield on X-ray energy. The probes were irradiated by constant dose of 6 MV and 18 MV X-ray radiation, and their relative emission intensities and spectra were quantified for each X-ray energy pair. From the ratios of XML, yield for 6 MV and 18 MV irradiation we found that the Cherenkov radiation dominated as an excitation mechanism, except for aluminum phthalocyanine, which exhibited substantial scintillation. The highest emission yields were detected from fluorescein, proflavin and aluminum phthalocyanine, in that order. XML yield was found to be affected by the emission quantum yield, overlap of the fluorescence excitation and Cherenkov emission spectra, scintillation yield. Considering all these factors and XML emission spectrum respective to tissue optical window, aluminum phthalocyanine offers the best XML yield for deep tissue use, while fluorescein and proflavine are most useful for subcutaneous or superficial use.

Shuttle-Shape Carrier-Free Platinum-Coordinated Nanoreactors with O2 Self-Supply and ROS Augment for Enhanced Phototherapy of Hypoxic Tumor.

The synergistic nanotheranostics of reactive oxygen species (ROS) augment or phototherapy has been a promising method within synergistic oncotherapy. However, it is still hindered by sophisticated design and fabrication, lack of a multimodal synergistic effect, and hypoxia-associated poor photodynamic therapy (PDT) efficacy. Herein, a kind of porous shuttle-shape platinum (IV) methylene blue (Mb) coordination polymer nanotheranostics-loaded 10-hydroxycamptothecin (CPT) is fabricated to address the abovementioned limitations. Our nanoreactors possess spatiotemporally controlled O2 self-supply, self-sufficient singlet oxygen (1O2), and outstanding photothermal effect. Once they are taken up by tumor cells, nanoreactors as a cascade catalyst can efficiently catalyze degradation of the endogenous hydrogen peroxide (H2O2) into O2 to alleviate tumor hypoxia. The production of O2 can ensure enhanced PDT. Subsequently, under both stimuli of external red light irradiation and internal lysosomal acidity, nanoreactors can achieve the on-demand release of CPT to augment in situ mitochondrial ROS and highly efficient tumor ablation via phototherapy. Moreover, under the guidance of near-infrared (NIR) fluorescent imaging, our nanoreactors exhibit strongly synergistic potency for treatment of hypoxic tumors while reducing damages against normal tissues and organs. Collectively, shuttle-shape platinum-coordinated nanoreactors with augmented ROS capacity and enhanced phototherapy efficiency can be regarded as a novel tumor theranostic agent and further promote the research of synergistic oncotherapy.

Synthesis, photocatalytic and antidiabetic properties of ZnO/PVA nanoparticles.

A series of ZnO and ZnO/poly(vinyl alcohol) (PVA) catalysts were prepared using sol-gel method. An X-ray diffraction analysis confirmed the existence of the wurtzite ZnO phase, and scanning electron microscopy (SEM) observation revealed the formation of spherical ZnO and ZnO/PVA nanoparticles. The decomposition of methylene blue (MB) and methyl orange (MO) induced by the synthesized pure ZnO and ZnO/PVA nanoparticles was studied under ultraviolet-visible irradiation. Among the catalysts evaluated, ZnO/5PVA was the most active in the decomposition of MB, whereas ZnO/7PVA was the most active catalyst in the decomposition of MO. Moreover, an investigation of the biological activity of pure ZnO and ZnO/PVA indicated that ZnO/5PVA exhibited the best performance in lowering the glucose level in diabetic rats.

Selective Imaging of HClO in the Liver Tissue In Vivo Using a Near-infrared Hepatocyte-specific Fluorescent Probe.

Liver injury is typified by an inflammatory response. Hypochlorous acid (HClO), an important endogenous reactive oxygen species, is regarded as a biomarker associated with liver injury. Near-infrared (NIR) fluorescent probes with the advantage of deep tissue penetrating and low auto-fluorescence interference are more suitable for bioimaging in vivo. Thus, in this work, we designed and synthesized a novel NIR hepatocyte-specific fluorescent probe named NHF. The probe NHF showed fast response (<3 s), large spectral variation, and good selectivity to trace HClO in buffer solution. By employing N-acetylgalactosamine (GalNAc) as the targeting ligand, probe NHF can be actively delivered to the liver tissue of zebrafish and mice. It is important that probe NHF is the first NIR hepatocyte-specific fluorescent probe, which successfully visualized the up-regulation of endogenous HClO in the oxygen-glucose deprivation/reperfusion (OGD/R) model HepG2 cells and dynamically monitored APAP-induced endogenous HClO in the liver tissue of zebrafish and mice.

Facile production of three-dimensional chitosan fiber embedded with zinc oxide as recoverable photocatalyst for organic dye degradation.

Herein we report on a facile and green strategy for continuous production of chitosan-zinc oxide fibers and then compare their photodegradation performance against three organic dyes (i.e., methylene blue (MB), methyl orange (MO) and Rhodamine B, respectively) under different lights. Chitosan-zinc hydrogel fibers (CS/Zn) with different zinc loadings are obtained by direct mixing of chitosan and zinc acetate solutions using a double-syringe injection device. The as-prepared CS/Zn fibers are then immersed into glutaraldehyde (GA) and sodium hydroxide solutions, respectively, and dried at T = 50 °C. The resultant CS/ZnO/GA fibers of ca. 617 µm in diameter are characterized using X-ray diffraction (XRD), thermogravimetric analysis and field emission scanning electron microscope (FE-SEM). XRD and FE-SEM data confirm that the CS/ZnO/GA fibers consist of a large amount of hexagonal wurtzite ZnO nanorods up to 550 nm in length, and exhibit three-dimensional interconnected macroporous architecture. Photodegradation results clearly show that the CS/ZnO/GA fibers are effective for the removal of organic dyes upon UV irradiation and can be easily recovered and reused for at least 6 consecutive cycles. Unlike most reported CS/ZnO nanocomposites, the current CS/ZnO/GA fiber shows a higher adsorption of cationic MB rather than anionic MO, the mechanism of which is proposed.

Liposome encapsulated electron donor strategy for signal-on CYFRA 21-1 photoelectrochemical analysis.

A novel electron donor controlled-release system is proposed based on liposome encapsulated L-cysteine for the sensitive determination of cytokeratin 19 fragment 21-1 (CYFRA 21-1). On the one hand, a defective TiO2 modified with methylene blue was employed as a photoactive platform which exhibited a high photoelectrochemical (PEC) response owing to the introduction of oxygen vacancies and the high  photosensitivity of the dye. On the other hand, L-cysteine as the sacrificial electron donor was encapsulated in the vesicles of liposomes, and this composite was used as the signal amplification factor, which is labeled on the secondary antibody of CYFRA 21-1 to further improve the photocurrent sensitivity. The excellent electron transfer path in photoactive materials coupled with the skilful electron donor controlled-release system, contributed to the sensitive  PEC analysis of CYFRA 21-1 underoptimum conditions. The PEC immunoassay showed a linear current response in the range 0.0001-100 ng/mL with a detection limitof 37 fg/mL. Enhanced stability and satisfactory reproducibility were also achieved. The proposed concept  provides a novel signal-on strategy for the sensitive detection of other cancer markers in the electrochemical sensing field.

Optimization and utilization of single chain metallocatanionic vesicles for antibacterial photodynamic therapy (aPDT) against E. coli.

Currently, bacterial infection due to multi-drug-resistant bacteria is one of the foremost problems in public health. Photodynamic therapy plays a significant role against bacterial infection, without causing any side effects. But the photosensitizers are associated with many drawbacks, which lessen their photodynamic efficiency. In this context, the current study describes the synthesis of new metallocatanionic vesicles and employs them in photodynamic therapy. These vesicles were synthesized by using a single-chain cationic metallosurfactant (CuCPC I) and sodium oleate (NaOl) as an anionic component. These vesicles were characterized from conductivity, dynamic light scattering, zeta potential, field emission scanning electron microscopy, and confocal microscopy measurements. Methylene blue (MB) was used as a photosensitizer and its singlet oxygen quantum yield in the presence of these vesicles was determined by irradiating with 650 nm wavelength laser light. These vesicles play a dual-functional role, one helping in delivering the photosensitizer and the second doubling their singlet oxygen production capability due to the presence of metal ions. Antibacterial photodynamic therapy (aPDT) was studied against E. coli bacteria (Gram-negative bacteria). These vesicles also inherit their antibacterial activity and MB-encapsulated metallocatanionic vesicles on irradiation have shown 100% killing efficiency. In summary, we offer metallocatanionic vesicles prepared via a facile approach, which encapsulate a photosensitizer and can be used to combat E. coli infection through photodynamic therapy. We envisage that these synthesized metallocatanionic vesicles will provide a new modification to the catanionic mixture family and could be used for various applications in the future.

Photocatalytic degradation of methylene blue dye by fluorite type Fe2Zr2-xWxO7 system under visible light irradiation.

Nano-sized Fe2Zr2-xWxO7 system was prepared using the Pacini method where x = 0, 0.05, 0.1 and 0.15. All the samples were characterized using chemical analysis, X-ray diffraction (XRD), Fourier-transform infrared (FT-IR), transmission electron microscopy (TEM), UV-vis diffuse reflectance measurements (DRS) and surface area measurements. The undoped Fe2Zr2O7 was crystallised in the cubic fluorite phase as a major phase in addition to rhombohedral phase of Fe2O3 and monoclinic phase of ZrO2 as the minor phases. Meanwhile, single cubic fluorite phase was defined for Fe2Zr0.85W0.15O7 sample. The last has the lowest band gap (1.69 eV) and the highest surface area (106 m2/g). From TEM, the average particle size of the prepared samples was in the range of (3-7 nm). The photocatalytic efficiency of the prepared Fe2Zr2-xWxO7 system was manifested by the degradation of methylene blue and real textile wastewater of blue colour. Ascending degradation efficiency was exhibited with increasing tungsten concentration which is in accordance with their band gap as well as their surface area values. The degradation rate using Fe2Zr0.85W0.15O7 sample obeys the pseudo-first order kinetic at the optimum degradation conditions (1.5 g/L catalyst and pH11). Fe2Zr0.85W0.15O7 showed promising photocatalytic activity for real textile wastewater where the 69% COD removal was obtained under the same conditions used for methylene blue degradation.

Eco-benign approach to synthesize spherical iron oxide nanoparticles: A new insight in photocatalytic and biomedical applications.

Iron oxide nanoparticles (Fe2O3NPs) are an interested and attractive area of research as they have numerous effective environmental and biomedical applications. Herein we have reported a simple and eco-benign synthesis Fe2O3NPs using Tamarix aphylla extract. The extract of the Tamarix aphylla acts both as a reducing and capping agent which leads to the fast and successful eco-benign synthesis of Fe2O3NPs.UV/Vis spectroscopy, XRD, EDX, SEM and TEM techniques were used to characterize and explore different features of Fe2O3NPs. UV/Vis studies showed asharppeak at 390 nm due to surface plasmon resonance absorption of Fe2O3NPs. XRD studies indicated that Fe2O3NPs were crystalline in nature. Structural features, elemental composition and geometry of Fe2O3NPswere confirmed by SEM, EDX and TEM. The as synthesized Fe2O3NPs showed efficient efficacy to degrade 100% of Methylene blue (MB) dye by 4 mg/25 ml MB and revealed 90% scavenging of the more stable DPPH free radical(1 mg/ml). Furthermore, Fe2O3NPs showed excellent antimicrobial activity against pathogenic multidrug resistant bacterial strains. The results of the present study explored the potential reducing, capping property of Tamarix aphylla extract, photocatalytic and biomedical applications of eco-benignly synthesized Fe2O3NPs which could be an alternative material for effective remediation of lethal organic pollutants and microbes.

The Contribution of Photodynamic Inactivation vs. Corsodyl Mouthwash to the Control of Streptococcus mutans Biofilms.

This work compared the inhibition effect of the commercially available mouthwash Corsodyl, containing 0.1% chlorhexidine digluconate, and photodynamic inactivation (PDI) employing methylene blue (MB) with irradiation from a red laser on 24-h biofilms formed by Streptococcus mutans strains on hydroxyapatite surfaces. The cytotoxicity of Corsodyl and MB was evaluated by Galleria mellonella surviving assay. The viability of biofilm cells after exposure to mouthwash and PDI was determined by counting colony-forming units. The inhibitory effect of antimicrobial agents was confirmed by confocal scanning laser microscopy. MB did not exhibit a cytotoxic effect on larval survival. Non-diluted Corsodyl slightly decreased the survival of larvae. Using our PDI parameters achieved better inhibition than with non-PDI, proving a significant effect on the eradication of S. mutans biofilms and therefore could be an appropriate supplement for the eradication of dental caries.

An effective strategy for boosting photoinduced charge separation of Ag3PO4 by BiVO4 with enhanced visible light photodegradation efficiency for levofloxacin and methylene blue.

In this paper, a Z-scheme Ag3PO4/BiVO4 photocatalyst was successfully prepared by precipitation-deposition method. The Ag3PO4/BiVO4 composite exhibited enhanced photocatalytic activity and recyclability for levofloxacin and methylene blue degradation under visible light irradiation. In the Ag3PO4/BiVO4-0.4 system, up to 92.44% of the levofloxacin molecules can be decomposed within 180 min and the photocatalytic degradation efficiency can maintain at 92.02% for methylene blue after recycled for 5 times. The enhanced photocatalytic activity of Ag3PO4/BiVO4 heterojunctions could be mainly attributed to the fabrication of hetero-structure between BiVO4 and Ag3PO4. The photogenerated electron-hole pair separation was effectively enhanced based on the photocurrent, electro-chemical impedance spectra and photoluminescence data. Furthermore, the electrons transfer from photoinduced BiVO4 to Ag3PO4 and the visible light harvesting efficiencies were significantly increased due to the BiVO4 hybridization. The ·OH was the main oxidative species in the Ag3PO4/BiVO4 system for the methylene blue decomposition. Finally, a purposed photocatalytic mechanism for methylene blue degradation was discussed in detail on the basis of experimental results.

Synthesis and application of V2O5-CeO2 nanocomposite catalyst for enhanced degradation of methylene blue under visible light illumination.

Methylene blue dye is among the toxic, mutagenic, and carcinogenic pollutants. Hence, its treatment via photocatalytic degradation is an important remediation method for the sake of a healthy environment. Herein, the V2O5-CeO2 nanocomposite catalysts were synthesized via a simple precipitation-thermal decomposition approach and used for the photodegradation of methylene blue in the presence of H2O2 as an effective electron scavenger under visible light illumination. The nanocomposite catalysts were systematically characterized to investigate the effects of V2O5 with the aids of X-ray, morphology, light absorption, catalytic activity, and charge transfer properties of the nanocomposite catalysts. The VC-2 nanocomposite prepared with NH4VO3:CeO2 molar ratios at 0.15:1 was found to be the best efficient catalyst where ≥98% of methylene blue was degraded within 25 min irradiation time. From the kinetics analysis, its rate constant was found to be higher than those of the pure V2O5 and CeO2 catalysts by a factor of 12.0 and 13.5, respectively. The plausibly mechanistic elucidation of charge transfer and utilization of reactive species are conspicuous allegations of the combined effects of the nanocomposite catalyst, H2O2 sacrificial agent, and visible light for the photodegradation of the dye.

A label-free photoelectrochemical aptasensor for facile and ultrasensitive mercury ion assay based on a solution-phase photoactive probe and exonuclease III-assisted amplification.

In typical photoelectrochemical (PEC) biosensing assays, electrodes are generally modified with photoactive probes and/or target recognition probes, which makes the processes complicated, time-consuming, and difficult to achieve excellent reproducibility. Hence, to overcome such shortcomings, we propose here an immobilization-free and label-free PEC aptasensor using solution-phase methylene blue (MB) as the PEC signal probe. Based on the unique T-Hg2+-T base pairs, and the diffusivity difference between free MB molecules and the MB/G-quadruplex composite towards the ITO electrode surface with negative charge, the "signal-off" approach for Hg2+ detection is developed. In the presence of target Hg2+, via the T-Hg2+-T bond formation, the two sticky ends of the hairpin DNA probe form a rigid duplex stem, which triggers the exonuclease III-facilitated target cycling amplification, and the formation of multiple G-quadruplexes. Upon the intercalation of MB in G-quadruplexes, significantly decreased photocurrent is obtained owing to the increased electrostatic repulsion between the MB/G-quadruplex composite and the ITO electrode. Therefore, highly sensitive and ultrasensitive Hg2+ determination is achieved, with a low detection limit of 1.2 pM, well below the maximum allowable Hg2+ level in drinking water defined by the WHO, China's Ministry of Health, and the US EPA. Due to the avoidance of sophisticated electrode modification and recognition probe immobilization processes, as well as an expensive labeling procedure, the PEC aptasensor proposed here demonstrates the advantages of simplicity, good reproducibility, rapidness and low cost.

In-situ mineralized robust polysiloxane-Ag@ZnO on cotton for enhanced photocatalytic and antibacterial activities.

A bifunctional interfacial layer was introduced onto the surface of cotton fabric which not only enhanced the interfacial bonding between Ag@ZnO and organic substrates but also improved the photocatalytic performance simultaneously. In detail, a modified cotton fabric (denoted as Cot-g-Si/Ag@ZnO) was fabricated through radiation-induced graft polymerization of γ-methacryloxypropyl trimethoxysilane and followed the in-situ formation of ZnO and loading of Ag nanoparticles simultaneously. Owing to ZnOSi between the graft chains and Ag@ZnO photocatalyst, the charge carrier concentration increased and Ag was prevented from oxidizing through the partial separation from ZnO, leading to enhanced near-field amplitudes of the localized surface plasmon resonance. Cot-g-Si/Ag@ZnO also exhibited excellent photocorrosion resistance, photostability and laundering durability. Its photocatalytic activity was fully maintained after several photodegradation cycles; moreover, after laundering durability test, the photocatalytic activity was improved compared with the newly prepared one. Credible mechanism for the photocatalytic activity of Cot-g-Si/Ag@ZnO under sunlight irradiation is proposed.

Photosensitizer-Conjugated Bi2Te3 Nanosheets as Theranostic Agent for Synergistic Photothermal and Photodynamic Therapy.

Phototherapy, including photothermal therapy (PTT)/photodynamic therapy (PDT), is usually considered as a promising strategy for cancer treatment due to its noninvasive and selective therapeutic effect by laser irradiation. A light-activatable nanoplatform based on bovine serum albumin (BSA)-coated Bi2Te3 nanosheets conjugated with methylene blue (MB) was successfully designed and constructed for bimodal PTT/PDT combination therapy. The resultant nanoconstruct (BSA-Bi2Te3/MB) exhibited high stability in various physiological solutions and excellent biocompatibility. Especially, the nanoconstruct not only possessed strong near-infrared absorption and high photothermal conversion as a photothermal agent for efficient tumor ablation but also could successfully load photosensitizer for PDT of tumor. When exposed to laser irradiation, tumors in mice with BSA-Bi2Te3/MB injection were completely eliminated without recurrence within 15 d, demonstrating the potential of the nanoconstruct as a bimodal PTT/PDT therapeutic platform for cancer treatment.

Dual application of Shewanella oneidensis MR-1 in green biosynthesis of Pd nanoparticles supported on TiO2 nanotubes and assisted photocatalytic degradation of methylene blue.

Biosynthesised nanocomposites have attracted growing interests attributed to their 'green' synthesis nature in recent years. Shewanella oneidensis MR-1, a dissimilatory metal-reducing bacterium, was used to reduce palladium (II) nitrate to palladium (0) nanoparticles (Pd NPs) under anaerobic conditions, resulting in the in situ formation of Pd NPs immobilised on TiO2 nanotubes (TNTs) (Pd/TNTs nanocomposites). The Pd/TNTs nanocomposites were characterised by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, energy dispersive X-ray, and electron spin resonance, respectively. The results indicated that Pd NPs are successfully grown on the TNTs without aggregation. Photocatalytic degradation of methylene blue (MB) by Pd/TNTs nanocomposites under simulated sunlight was also investigated. Pd/TNTs nanocomposites had photocatalytic efficiency superior to that of single TiO2 nanomaterials. The photocatalytic activity of Pd/TNTs nanocomposites can be enhanced by S. oneidensis MR-1. The results showed that after only 10 min, the degradation ratio of MB reached 98.7% by Pd/TNTs nanocomposites when simultaneously assisted with S. oneidensis MR-1.

The photocatalytic degradation of methylene blue by green semiconductor films that is induced by irradiation by a light-emitting diode and visible light.

This study develops a low-energy rotating photocatalytic contactor (LE-RPC) that has Cu-doped TiO2 films coated on stainless-steel rotating disks, to experimentally evaluate the efficiency of the degradation and decolorization of methylene blue (MB) under irradiation from different light sources (visible 430 nm, light-emitting diode [LED] 460 nm, and LED 525 nm). The production of hydroxyl radicals is also examined. The experimental results show that the photocatalytic activity of TiO2 that is doped with Cu2+ is induced by illumination with visible light and an LED. More than 90% of methylene blue at a 10 mg/L concentration is degraded after illumination by visible light (430 nm) for 4 hr at 20 rpm. This study also demonstrates that the quantity of hydroxyl radicals produced is directly proportional to the light energy intensity. The greater the light energy intensity, the greater is the number of hydroxyl radicals produced. IMPLICATIONS: The CuO-doped anatase TiO2 powder was successfully synthesized in this study by a sol-gel method. The catalytic abilities of the stainless-steel film were enhanced in the visible light regions. This study has successfully modified the nano-photocatalytic materials to drop band gap and has also successfully fixed the nano-photocatalytic materials on a substratum to effectively treat dye wastewater in the range of visible light. The results can be useful to the development of a low-energy rotating photocatalytic contactor for decontamination purposes.

Methylene Blue Location in (Hydroperoxized) Cardiolipin Monolayer: Implication in Membrane Photodegradation.

We present molecular dynamics simulations of cardiolipin (CL) and CL monohydroperoxized derivative (CLOOH) monolayers to investigate the initial steps of phospholipid oxidation induced by methylene blue (MB) photoexcitation under continuous illumination. We considered different MB atomic charge distributions to simulate the MB electronic distribution in the singlet ground and triplet excited states. Simulation results allied to experimental data revealed that initial CL photooxidation probably occurs via a type II mechanism, to produce lipid hydroperoxide by singlet oxygen attack to the alkyl chain unsaturations. The resulting hydroperoxide group prefers to reside near the aqueous interface, to increase the membrane surface area and to decrease lipid packing. Interestingly, MB orientation changes from nearly parallel to the water-monolayer interface in the ground state to normal to the interface in its triplet excited state. The latter orientation favors oxidative chain reaction continuity via a type I mechanism, during which the hydrogen atom must be transferred from the hydroperoxide group to triplet MB. Taken together, the present results can be extrapolated to improve our understanding of how oxidation progresses in lipidic biomembrane, which will lead to the formation of oxidized species with shortened chains and will cause severe photodamage to self-organized systems.

Shedding Light on Alzheimer's ß-Amyloidosis: Photosensitized Methylene Blue Inhibits Self-Assembly of ß-Amyloid Peptides and Disintegrates Their Aggregates.

Abnormal aggregation of ß-amyloid (Aß) peptides is a major hallmark of Alzheimer's disease (AD). In spite of numerous attempts to prevent the ß-amyloidosis, no effective drugs for treating AD have been developed to date. Among many candidate chemicals, methylene blue (MB) has proved its therapeutic potential for AD in a number of in vitro and in vivo studies; but the result of recent clinical trials performed with MB and its derivative was negative. Here, with the aid of multiple photochemical analyses, we first report that photoexcited MB molecules can block Aß42 aggregation in vitro. Furthermore, our in vivo study using Drosophila AD model demonstrates that photoexcited MB is highly effective in suppressing synaptic toxicity, resulting in a reduced damage to the neuromuscular junction (NMJ), an enhanced locomotion, and decreased vacuole in the brain. The hindrance effect is attributed to Aß42 oxidation by singlet oxygen (1O2) generated from photoexcited MB. Finally, we show that photoexcited MB possess a capability to disaggregate the pre-existing Aß42 aggregates and reduce Aß-induced cytotoxicity. Our work suggests that light illumination can provide an opportunity to boost the efficacies of MB toward photodynamic therapy of AD in future.