Low-energy Light Irradiation Research Articles

Two-photon absorption of oxindole-based push–pull molecular motors

Future applications of light-driven molecular motors in bio-based systems and soft materials require their operation with benign, low-energy light irradiation. Here we report four rotary molecular motors based on oxindole units which can be driven by near-infrared light. By installing an electron-withdrawing CN group on the oxindole lower half, in direct conjugation through the alkene axle to the electron-donating OMe substituent on the upper half, our design establishes a rigid push–pull system which red-shifts the absorption maximum further into the visible region. We also show that the induced nonlinearity to the system increases their two-photon absorption cross section, and the operation of oxindole based molecular motors with 800 nm light for the very first time. The motors prepared in this work show improved performance compared to previous oxindole based motors, e.g. visible light addressability up to 530 nm and 1.5-fold increase in quantum yields in both directions, whilst retaining their desirable qualities of easy synthesis and fast rotation speed.

From Visible to Near-Infrared Light-Triggered Photochromism: Negative Photochromism.

Photochromic compounds, whose key molecular properties can be effectively modulated by light irradiation, have attracted significant attention for their potential applications in various research fields. The restriction of photoisomerization coloration induced by ultraviolet light limits their applications in the biomedical field and some other fields. Negative photochromism, wherein a relatively stable colored isomer transforms to a colorless metastable isomer under low-energy light irradiation, offers advantages in applications within materials science and life science. This review provides a summary of negatively photochromic compounds based on different molecular skeletons. Their corresponding design strategies and photochromic properties are presented to provide practical guidelines for future investigations. Negatively photochromic compounds can effectively expand the range of photochromic switches for future applications, offering unique properties such as responsiveness to visible to near-infrared light.

Considerations for the Use of Photobiomodulation in the Treatment of Retinal Diseases.

Photobiomodulation (PBM) refers to the beneficial effect produced from low-energy light irradiation on target cells or tissues. Increasing evidence in the literature suggests that PBM plays a positive role in the treatment of retinal diseases. However, there is great variation in the light sources and illumination parameters used in different studies, resulting in significantly different conclusions regarding PBM's therapeutic effects. In addition, the mechanism by which PBM improves retinal function has not been fully elucidated. In this study, we conducted a narrative review of the published literature on PBM for treating retinal diseases and summarized the key illumination parameters used in PBM. Furthermore, we explored the potential molecular mechanisms of PBM at the retinal cellular level with the goal of providing evidence for the improved utilization of PBM in the treatment of retinal diseases.

Additive-free photo-assisted selective partial oxidation at ambient conditions of 5-hydroxymethylfurfural by manganese (IV) oxide nanorods

The valorization of natural and renewable resources, like lignocellulosic biomass, towards value-added chemicals by low energy and economically viable processes still remains a global research and technological challenge. 5-hydroxymethylfurfural (HMF) is an important platform chemical that can be easily derived from biomass, and it can be further used as a feedstock for the production of building blocks for polymers or fuels. In this context, the partial oxidation of the hydroxyl group on the HMF molecule leads to the formation of the corresponding aldehyde, 2,5-diformylfuran (DFF), which may find multiple applications in bio-chemical industries. Herein, we present the synthesis and characterization of novel manganese (IV) oxide nanorods as catalyst for the HMF to DFF partial oxidation at ambient conditions. This 1D nanocatalyst operates at low energy light irradiation and without the addition of chemicals (bases or oxidants) as a highly selective photo-assisted catalyst. Under optimized experimental conditions, the HMF conversion was found to be above 99%, while the DFF selectivity was almost 100%. The presence of molecular O2 played a key role in triggering the selective oxidation, while the use of an aprotic and less polar organic solvent, such as acetonitrile, compared to water, further enhanced the reactivity of the catalyst.

Mitochondria-targeted theranostic nanoparticles for optical sensing of oxygen, photodynamic cancer therapy, and assessment of therapeutic efficacy

We report on a novel kind of mitochondria-targeted theranostic nanoparticles (NPs). The NPs are doped with the oxygen-sensitive probe Pt(II)-porphyrins (PtTFPP) which exerts a dual role in acting as a diagnostic tool that can sense oxygen via quenching of luminescence, but also acts as an agent in photodynamic therapy (PDT) of cancer. In addition, it allows therapeutic efficacy to be assessed in-situ. Upon appropriate high-energy photoirradiation, the NPs generate singlet oxygen by energy transfer from triplet PtTFPP to ground state oxygen, and cell death is induced via PDT. Under low-energy light irradiation, in contrast, the NPs can be utilized to detect oxygen consumption rate via time-resolved luminescence measurements in order to study the efficacy of PDT. This is the first report where a single nanoagent is used to stimulate PDT and also to assess the efficacy of PDT. In our perception, the method provides a promising platform for testing anti-cancer drugs.

Photocatalytic degradation of concentrated solutions of 2,4-dichlorophenol using low energy light: Identification of intermediates

This study reports on Fenton and photo-assisted Fenton induced oxidation of 2,4-dichlorophenol (from here on 2,4-DCP). The pre-treatment of concentrated aqueous solutions of 2,4-DCP (453mgl−1) up to bio-compatibility is shown to be possible using low energy 36W black fluorescent mercury light. The degradation process of 2,4-DCP was observed to occur within minutes. Catalytic amounts of Fe3+-ion (10mg) were only necessary to obtain acceptable degradation kinetics. Degradation of the 2,4-DCP was not observed in the dark. The total organic carbon (TOC), the adsorbable organic halogen compounds (AOX) and the amount of free chloride (Cl−) were followed in time during 2,4-DCP oxidation under light irradiation. The rate of disappearance of 2,4-DCP and that of Cl−-ion formation were not similar. This was ascribed to the formation of aliphatic and aromatic chlorinated long-lived intermediates. The latter intermediates were identified by liquid–liquid extraction, solid–liquid extraction and coupled GC/MS analysis. Based on the experimental results obtained, a mechanism for the radical intervention is suggested for the abatement of 2,4-DCP. A relatively short pre-treatment time (54min) was necessary to reduce by 97% the toxicity (ecotoxicity) of a concentrated solution of 2,4-DCP under low energy light irradiation in the photo-reactor.

Photoinhibition of smooth muscle cell migration: potential therapy for restenosis.

Evidence from animal, autopsy, and atherectomy studies demonstrates that migration and proliferation of smooth muscle cells of medial origin result in neointima formation and decreased luminal cross-sectional area. The purpose of this study was to evaluate whether low energy light irradiation can inhibit smooth muscle cell migration and therefore potentially reduce the degree of neointima formation and the incidence of restenosis. The migration kinetics of bovine aortic smooth muscle cell monolayers were examined using a fence assay. The effect on smooth muscle cell migration of irradiation with monochromatic light at wave-lengths ranging from 400 to 700 nm was compared to the migration of cells irradiated with broadband white light or maintained in the dark. Wavelength specific photoinhibition of smooth muscle cell migration was observed; 594-600 nm light reproducibly inhibited migration by 12-29% (P < 0.05). Migration rate was significantly reduced following daily radiant exposures of 1.0 J/cm2 as well as following a single radiant exposure of 0.09 or 0.9 J/cm2. The decrease in migration was not associated with any change in cell proliferation or [3H] thymidine incorporation. We conclude that 594-600 nm light inhibits smooth muscle cell migration in vitro and may potentially be used in vivo to decrease fibrointimal thickening following arterial injury. This application of photoinhibition may be useful in retarding restenosis following angioplasty.

低エネルギー光照射のキノコ菌糸成長への効果の実験的検討

We studied experimentally the effect of low-energy light irradiation, especially the effect of linearly polarized light, on hyphal growth of shiitake-mushroom. In the case of low-power Ar-laser light irradiation, an increase of growth rate was observed compared to that of non-irradiated samples. Irradiating linearly polarized light from a conventional fluorescent lamp, it was observed clearly that the hyphal growth in the direction parallel to the polarization of light is greater than that in the vertical direction. It was also found experimentally that the difference of growth rate between parallel and vertical polarizations of light is remarkable at the illuminance of 50 lx and slightly appreciable at 100 lx, although almost no difference was observed at 1000 lx.

創傷治癒促進仁対する光の偏光特性による照射効果(第2報)

We estimated the low-energy light irradiation effect on wound healing by tensile strength of guinea pig back skin with four straight wounds. In order to examine the dependence of the wound healing effect on polarization properties of light, we employed four kinds of polarized lights, namely linear, left-hand circular, right-hand circular, and non-polarized ones. On 8 and 15 days after making wounds on guinea pig back skin, the tensile strength was measured quantitatively.The main results are the following, (1) different polarized lights were found to give rise to different effects about wound healing acceleration.(2) the tensile strength of linear polarized light irradiation group is larger than that of the control group on both 8 and 15 days after making wounds.(3) the tensile strength of left-hand circular polarized light irradiation group is smaller than that of the control group on both 8 and 15 days after making wounds.