Red light-induced localized release of carbon monoxide for alleviating postoperative cognitive dysfunction.

Inflammation within the central nervous system (CNS), which may be triggered by surgical trauma, has been implicated as a significant factor contributing to postoperative cognitive dysfunction (POCD). The relationship between mitigating inflammation at peripheral surgical sites and its potential to attenuate the CNS inflammatory response, thereby easing POCD symptoms, remains uncertain. Notably, carbon monoxide (CO), a gasotransmitter, exhibits pronounced anti-inflammatory effects. Herein, we have developed carbon monoxide-releasing micelles (CORMs), a nanoparticle that safely and locally liberates CO upon exposure to 650 nm light irradiation. In a POCD mouse model, treatment with CORMs activated by light (CORMs + hv) markedly reduced the concentrations of interleukin (IL)-6, IL-1ß, and tumor necrosis factor-alpha (TNF-α) in both the peripheral blood and the hippocampus, alongside a decrease in ionized calcium-binding adapter molecule 1 in the hippocampal CA1 region. Furthermore, CORMs + hv treatment diminished Evans blue extravasation, augmented the expression of tight junction proteins zonula occludens-1 and occludin, enhanced neurocognitive functions, and fostered fracture healing. Bioinformatics analysis and experimental validation has identified Htr1b and Trhr as potential key regulators in the neuroactive ligand-receptor interaction signaling pathway implicated in POCD. This work offers new perspectives on the mechanisms driving POCD and avenues for therapeutic intervention.

Exploring the effects of red light night break on the defence mechanisms of tomato against fungal pathogen Botrytis cinerea.

Plant infections caused by fungi lead to significant crop losses worldwide every year. This study aims to better understand the plant defence mechanisms regulated by red light, in particular, the effects of red light at night when most phytopathogens are highly infectious. Our results showed that superoxide production significantly increased immediately after red light exposure and, together with hydrogen peroxide levels, was highest at dawn after 30 min of nocturnal red-light treatment. In parallel, red-light-induced expression and increased the activities of several antioxidant enzymes. The nocturnal red light did not affect salicylic acid but increased jasmonic acid levels immediately after illumination, whereas abscisic acid levels increased 3 h after nocturnal red-light exposure at dawn. Based on the RNAseq data, red light immediately increased the transcription of several chloroplastic chlorophyll a-b binding protein and circadian rhythm-related genes, such as Constans 1, CONSTANS interacting protein 1 and zinc finger protein CONSTANS-LIKE 10. In addition, the levels of several transcription factors were also increased after red light exposure, such as the DOF zinc finger protein and a MYB transcription factor involved in the regulation of circadian rhythms and defence responses in tomato. In addition to identifying these key transcription factors in tomato, the application of red light at night for one week not only reactivated key antioxidant enzymes at the gene and enzyme activity level at dawn but also contributed to a more efficient and successful defence against Botrytis cinerea infection.

The efficacy and safety of combination therapy of repeated low-level red light and defocus-incorporated multiple segments spectacle lenses for myopia control in children: the study protocol for a 12-month, randomized, parallel-controlled, and single-center clinical trial.

BACKGROUND: Myopia is increasing in prevalence worldwide. Combination therapy showed a better effect on myopia control than monotherapy. Repeated low-level red light therapy (RLRL) therapy and defocus-incorporated multiple segment (DIMS) spectacle lenses have been reported to retard myopia progression significantly. However, whether these two therapies are better than one is still unknown. The present study aims to report the study protocol of a trial designed to evaluate the efficacy and safety of combination therapy of RLRL and DIMS versus DIMS alone for reducing the progression of myopia among Chinese school-aged children. METHODS: This study is a 12-month, randomized, parallel-controlled, single-center clinical trial. We will recruit children aged 8-12 years with spherical equivalence (SE) between - 0.50 D and - 6.00 D under cycloplegia in both eyes. We will recruit 66 participants with an allocation ratio of 1:1 from our hospital. Participants in the intervention group will be treated with an RLRL therapy device twice a day from Monday to Friday at home, 3 min per session, with a minimum interval of 4 h, under the supervision of their parents/guardians. They will wear DIMS spectacles for myopia correction during the day. Participants in the control group will not receive the RLRL therapy and will only wear DIMS spectacles to correct myopia. Participants from both groups will attend the hospital every 6 months. The primary outcome is the change in axial length at 12 months. Secondary outcomes include changes in refraction under cycloplegia, optical coherence tomography (OCT), multifocal electroretinogram (mfERG), color vision, and participants' self-reporting of adverse events at 12 months. DISCUSSION: This study will report the efficacy and safety outcome of the combination therapy of RLRL and DIMS versus DIMS for school-aged children with myopia in detail. TRIAL REGISTRATION: ChiCTR2300075398. Registered 4 September 2023. https://www.chictr.org.cn/bin/project/edit?pid=200751 .

CircRNAs involved in the red light of effect on follicle selection in pigeons.

Red light (RL) can enhance egg production in poultry. CircRNAs play a crucial role by serving as transcriptional regulators. However, their role in influencing follicle development in White King pigeons remains unexplored. In this study, 54 paired White King pigeons were chosen and divided into RL and white light (WL) groups, each with 3 subgroups. The egg production of paired pigeons in each replicate was recorded for 45 d, and the characteristics of follicle development were monitored during the laying interval (LI). The granulosa cell layer from follicles of the second-largest follicle (F2) was collected, and high-throughput sequencing was performed to elucidate the molecular mechanism of follicle development in pigeons. The study confirmed that RL enhances egg production in pigeons. Additionally, under RL, the F2 follicle was selected, while under WL, small follicles were kept on the third day (LI3). A total of 5,510 circRNAs were identified across all samples, revealing differentially expressed circRNAs (DECs) in various comparisons: 627 in RF1 vs. WF1, 900 in RF2 vs. WF2, 606 in RF1 vs. RF2, and 937 in WF1 vs. WF2. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated that host genes of DECs were enriched in pathways like steroid hormone biosynthesis, oocyte meiosis, GnRH signaling pathway, and apoptosis pathway. Moreover, circRNA_5497, circRNA_2016, and circRNA_3328 were common DECs across 4 groups, sharing miRNA binding sites with follicle selection-associated genes. In conclusion, our findings suggest that RL promotes egg production by stimulating follicle selection during LI, offering insights into the regulatory mechanisms of circRNAs in follicle selection under RL. This knowledge can help enhance the reproductive performance of pigeons.

Comparison of Changes in Retinal Vascular Density and Thickness After Using Low-Level Red Light and 0.01% Atropine in Premyopic Children.

Purpose: To compare changes in superficial retinal vascular density (SRVD), deep retinal vascular density (DRVD), and retinal thickness (RT) of the macular zone after repeated low-level red light (RLRL) and 0.01% atropine exposure in premyopic schoolchildren. Methods: Prospective randomized trial. Sixty-nine schoolchildren with cycloplegic refraction >-0.75 D and ≤0.50 D were randomly assigned to RLRL and 0.01% atropine groups. SRVD, DRVD, and RT were measured using swept-source optical coherence tomography at baseline and six months. The macular zone was divided into three concentric rings (fovea, parafovea, and perifovea) using the Early Treatment Diabetic Retinopathy Study. Results: After six months, the whole, parafoveal, and perifoveal SRVD significantly increased in the two groups (all P < 0.05). Multivariate regression analyses showed that none of these changes varied significantly between the two groups (all P > 0.05), whereas foveal SRVD remained stable in both groups (all P > 0.05). In the RLRL group, the whole and perifoveal DRVD increased significantly (all P < 0.05), whereas no statistical difference was observed in the foveal and parafoveal DRVD. DRVD remained stable in the 0.01% atropine group (all P > 0.05). No significant differences were observed in RT changes between the two groups (all P > 0.05). In comparison, there were no significant changes in SRVD, DRVD, or RT after six months in the placebo group in our previous study. Conclusions: SRVD increased similarly in the RLRL and 0.01% atropine groups, whereas DRVD increased only in the former group. There were no significant RT changes in either group after six months of treatment in premyopic schoolchildren. Translational Relevance: This research observed the effects of low-level red light and 0.01% atropine on retinal vasculature, offering valuable insights into myopia progression prevention.

Single-Photon Deep-Red Light-Triggered Direct Release of an Anticancer Drug: An Investigative Tumor Regression Study on a Breast Cancer Spheroidal Tumor Model.

Breast adenocarcinoma ranks high among the foremost lethal cancers affecting women globally, with its triple-negative subtype posing the greatest challenge due to its aggressiveness and resistance to treatment. To enhance survivorship and patients' quality of life, exploring advanced therapeutic approaches beyond conventional chemotherapies is imperative. To address this, innovative nanoscale drug delivery systems have been developed, offering precise, localized, and stimuli-triggered release of anticancer agents. Here, we present perylenemonoimide nanoparticle-based vehicles engineered for deep-red light activation, enabling direct chlorambucil release. Synthesized via the reprecipitation technique, these nanoparticles were thoroughly characterized. Light-induced drug release was monitored via spectroscopic and reverse-phase HPLC. The efficacy of the said drug delivery system was evaluated in both two-dimensional and three-dimensional spheroidal cancer models, demonstrating significant tumor regression attributed to apoptotic cell death induced by efficient drug release within cells and spheroids. This approach holds promise for advancing targeted breast cancer therapy, enhancing treatment efficacy and minimizing adverse effects.

Catalytic and Selective Red Light-Triggered Photodegradation of a G-Quadruplex DNA by a Zinc (II) Phthalocyanine.

Water-soluble phthalocyanine (Pc) derivatives have been regarded as potential G-quadruplex (G4) nucleic acid-targeting ligands for anticancer therapy and have been extensively studied as effective photosensitizers for photodynamic therapy (PDT). Understanding how photosensitizers interact with nucleic acids and the subsequent photolytic reactions is essential for deciphering the initial steps of PDT, thereby aiding in the development of new photosensitizing agents. In this study, we found that red-light irradiation of a mixture of a Zn(II) Pc derivative and an all-parallel G4 DNA leads to catalytic and selective photodegradation of the DNA by reactive oxygen species (ROS) generated from the Zn(II) Pc derivative bound to DNA through a reaction mechanism similar to that of an enzyme reaction. This finding provides a novel insight into the molecular design of a photosensitizer to enhance its PDT efficacy.

Green/red light-sensing mechanism in the chromatic acclimation photosensor.

Certain cyanobacteria alter their photosynthetic light absorption between green and red, a phenomenon called complementary chromatic acclimation. The acclimation is regulated by a cyanobacteriochrome-class photosensor that reversibly photoconverts between green-absorbing (Pg) and red-absorbing (Pr) states. Here, we elucidated the structural basis of the green/red photocycle. In the Pg state, the bilin chromophore adopted the extended C15-Z,anti structure within a hydrophobic pocket. Upon photoconversion to the Pr state, the bilin is isomerized to the cyclic C15-E,syn structure, forming a water channel in the pocket. The solvation/desolvation of the bilin causes changes in the protonation state and the stability of π-conjugation at the B ring, leading to a large absorption shift. These results advance our understanding of the enormous spectral diversity of the phytochrome superfamily.

Non-transcriptional regulatory activity of SMAX1 and SMXL2 mediates karrikin-regulated seedling response to red light in Arabidopsis.

Karrikins and strigolactones govern plant development and environmental responses through closely related signaling pathways. The transcriptional repressor proteins SUPPRESSOR OF MAX2 1 (SMAX1), SMAX1-like2 (SMXL2), and D53-like SMXLs mediate karrikin and strigolactone signaling by directly binding downstream genes or by inhibiting the activities of transcription factors. In this study, we characterized the non-transcriptional regulatory activities of SMXL proteins in Arabidopsis. We discovered that SMAX1 and SMXL2 with mutations in their ethylene-response factor-associated amphiphilic repression (EAR) motif had undetectable or weak transcriptional repression activities but still partially rescued the hypocotyl elongation defects and fully reversed the cotyledon epinasty defects of the smax1 smxl2 mutant. SMAX1 and SMXL2 directly interact with PHYTOCHROME INTERACTION FACTOR 4 (PIF4) and PIF5 to enhance their protein stability by interacting with phytochrome B (phyB) and suppressing the association of phyB with PIF4 and PIF5. The karrikin-responsive genes were then identified by treatment with GR24ent-5DS, a GR24 analog showing karrikin activity. Interestingly, INDOLE-3-ACETIC ACID INDUCIBLE 29 (IAA29) expression was repressed by GR24ent-5DS treatment in a PIF4- and PIF5-dependent and EAR-independent manner, whereas KARRIKIN UPREGULATED F-BOX 1 (KUF1) expression was induced in a PIF4- and PIF5-independent and EAR-dependent manner. Furthermore, the non-transcriptional regulatory activity of SMAX1, which is independent of the EAR motif, had a global effect on gene expression. Taken together, these results indicate that non-transcriptional regulatory activities of SMAX1 and SMXL2 mediate karrikin-regulated seedling response to red light.

Deep Red Light Driven Hydrogen Evolution by Heterojunction Polymer Dots for Diabetic Wound Healing.

We describe small heterojunction polymer dots (Pdots) with deep-red light catalyzed H2 generation for diabetic skin wound healing. The Pdots with donor/acceptor heterojunctions showed remarkably enhanced photocatalytic activity as compared to the donor or acceptor nanoparticles alone. We encapsulate the Pdots and ascorbic acid into liposomes to form Lipo-Pdots nanoreactors, which selectively scavenge ⋅OH radicals in live cells and tissues under 650 nm light illumination. The antioxidant capacity of the heterojunction Pdots is ~10 times higher than that of the single-component Pdots described previously. Under a total light dose of 360 J/cm2, the Lipo-Pdots nanoreactors effectively scavenged ⋅OH radicals and suppressed the expression of pro-inflammatory cytokines in skin tissues, thereby accelerating the healing of skin wounds in diabetic mice. This study provides a feasible solution for safe and effective treatment of diabetic foot ulcers.

Red light mitigates Cd toxicity in Egeria densa by restricting Cd accumulation and modulating antioxidant defense system.

Controlling light qualities have been acknowledged as an effective method to enhance the efficiency of phytoremediation, as light has a significant impact on plant growth. This study examined the effects of light qualities on cadmium (Cd) tolerance in aquatic plant Egeria densa using a combination of biochemical and transcriptomic approaches. The study revealed that E. densa exhibits higher resistance to Cd toxicity under red light (R) compared to blue light (B), as evidenced by a significant decrease in photosynthetic inhibition and damage to organelle ultrastructure. After Cd exposure, there was a significantly reduced Cd accumulation and enhanced levels of both glutathione reductase (GR) activity and glutathione (GSH), along with an increase in jasmonic acid (JA) in R-grown E. densa compared to B. Transcriptional analysis revealed that R caused an up-regulation of Cd transporter genes such as ABCG (G-type ATP-binding cassette transporter), ABCC (C-type ATP-binding cassette transporter), and CAX2 (Cation/H+ exchanger 2), while down-regulated the expression of HIPP26 (Heavy metal-associated isoprenylated plant protein 26), resulting in reduced Cd uptake and enhanced Cd exportation and sequestration into vacuoles. Moreover, the expression of genes involved in phytochromes and JA synthesis was up-regulated in Cd treated E. densa under R. In summary, the results suggest that R could limit Cd accumulation and improve antioxidant defense to mitigate Cd toxicity in E. densa, which might be attributed to the enhanced JA and phytochromes. This study provides a foundation for using light control methods with aquatic macrophytes to remediate heavy metal contamination in aquatic systems.

Integrating Physiological Features and Proteomic Analyses Provides New Insights in Blue/Red Light-Treated Moso Bamboo (Phyllostachys edulis).

Bamboo is one of the most important nontimber forestry products in the world. Light is not only the most critical source of energy for plant photosynthesis but also involved in regulating the biological processes of plants. However, there are few reports on how blue/red light affects Moso bamboo. This study investigated the growth status and physiological responses of Moso bamboo (Phyllostachys edulis) to blue/red light treatments. The growth status of the bamboo plants was evaluated, revealing that both blue- and red-light treatments promoted plant height and overall growth. Gas exchange parameters, chlorophyll fluorescence, and enzyme activity were measured to assess the photosystem response of Moso bamboo to light treatments. Additionally, the blue light treatment led to a higher chlorophyll content and enzyme activities compared to the red light treatment. A tandem mass tag quantitative proteomics approach identified significant changes in protein abundance under different light conditions with specific response proteins associated with distinct pathways, such as photosynthesis and starch metabolism. Overall, this study provides valuable insights into the physiological and proteomic responses of Moso bamboo to blue/red light treatments, highlighting their potential impact on growth and development.

Red and far-red light improve the antagonistic ability of Trichoderma guizhouense against phytopathogenic fungi by promoting phytochrome-dependent aerial hyphal growth.

Light as a source of information regulates morphological and physiological processes of fungi, including development, primary and secondary metabolism, or the circadian rhythm. Light signaling in fungi depends on photoreceptors and downstream components that amplify the signal to govern the expression of an array of genes. Here, we investigated the effects of red and far-red light in the mycoparasite Trichoderma guizhouense on its mycoparasitic potential. We show that the invasion strategy of T. guizhouense depends on the attacked species and that red and far-red light increased aerial hyphal growth and led to faster overgrowth or invasion of the colonies. Molecular experiments and transcriptome analyses revealed that red and far-red light are sensed by phytochrome FPH1 and further transmitted by the downstream MAPK HOG pathway and the bZIP transcription factor ATF1. Overexpression of the red- and far-red light-induced fluffy gene fluG in the dark resulted in abundant aerial hyphae formation and thereby improvement of its antagonistic ability against phytopathogenic fungi. Hence, light-induced fluG expression is important for the mycoparasitic interaction. The increased aggressiveness of fluG-overexpressing strains was phenocopied by four random mutants obtained after UV mutagenesis. Therefore, aerial hyphae formation appears to be a trait for the antagonistic potential of T. guizhouense.

Visible and Red Light-Triggered Anticancer Profile of a Ferrocene-Re(I)-Tricarbonyl Conjugate: Experimental and Theoretical Studies.

We have red-shifted the light absorbance property of a Re(I)-tricarbonyl complex via distant conjugation of a ferrocene moiety and developed a novel complex ReFctp, [Re(Fctp)(CO)3Cl], where Fctp = 4'-ferrocenyl-2,2':6',2″-terpyridine. ReFctp showed green to red light absorption ability and blue emission, indicating its potential for photodynamic therapy (PDT) application. The conjugation of ferrocene introduced ferrocene-based transitions, which lie at a higher wavelength within the PDT therapeutic window. The time-dependent density functional theory and excited state calculations revealed an efficient intersystem crossing for ReFctp, which is helpful for PDT. ReFctp elicited both PDT type I and type II pathways for reactive oxygen species (ROS) generation and facilitated NADH (1,4-dihydro-nicotinamide adenine dinucleotide) oxidation upon exposure to visible light. Importantly, ReFctp showed effective penetration through the layers of clinically relevant 3D multicellular tumor spheroids and localized primarily in mitochondria (Pearson's correlation coefficient, PCC = 0.65) of A549 cancer cells. ReFctp produced more than 20 times higher phototoxicity (IC50 ∼1.5 µM) by inducing ROS generation and altering mitochondrial membrane potential in A549 cancer cells than the nonferrocene analogue Retp, [Re(CO)3(tp)Cl], where tp = 2,2':6',2″-terpyridine. ReFctp induced apoptotic mode of cell death with a notable photocytotoxicity index (PI, PI = IC50dark/IC50light) and selectivity index (SI, SI = normal cell's IC50dark/cancer cell's IC50light) in the range of 25-33.

Far-red light enrichment affects gene expression and architecture as well as growth and photosynthesis in rice.

Plants use light as a resource and signal. Photons within the 400-700 nm waveband are considered photosynthetically active. Far-red photons (FR, 700-800 nm) are used by plants to detect nearby vegetation and elicit the shade avoidance syndrome. In addition, FR photons have also been shown to contribute to photosynthesis, but knowledge about these dual effects remains scarce. Here, we study shoot-architectural and photosynthetic responses to supplemental FR light during the photoperiod in several rice varieties. We observed that FR enrichment only mildly affected the rice transcriptome and shoot architecture as compared to established model species, whereas leaf formation, tillering and biomass accumulation were clearly promoted. Consistent with this growth promotion, we found that CO2-fixation in supplemental FR was strongly enhanced, especially in plants acclimated to FR-enriched conditions as compared to control conditions. This growth promotion dominates the effects of FR photons on shoot development and architecture. When substituting FR enrichment with an end-of-day FR pulse, this prevented photosynthesis-promoting effects and elicited shade avoidance responses. We conclude that FR photons can have a dual role, where effects depend on the environmental context: in addition to being an environmental signal, they are also a potent source of harvestable energy.

Daily Low-Level Red Light for Spherical Equivalent Error and Axial Length in Children With Myopia: A Randomized Clinical Trial.

Importance: Treatments are needed to slow progression of or reduce incidence of myopia. Objective: To evaluate the efficacy and safety of daily 650-nm low-level red light (LLRL) for myopia treatment. Design, Setting, and Participants: Single-masked, randomized clinical trial at 1 site in China. Baseline measurements were completed from August to September 2021. Participants were children aged 6 to 12 years with spherical equivalent error (SER) of -6 diopters (D) to 3 D. Data were analyzed from March to July 2023. Interventions: Irradiation daily with 650-nm LLRL for 3 minutes twice daily 4 or more hours apart or no intervention. Main Outcomes and Measures: Primary outcomes were changes in cycloplegia SER and axial length (AL) at 6- and 12-month follow-up visits. Safety was assessed on masked fundus photograph evaluations. Results: A total of 336 children were randomly allocated into the LLRL group or control group in a 1:1 ratio. The control group contained 86 female patients (51.2%), and the treatment group contained 90 female patients (53.6%). The mean (SD) age, SER, and AL were 9.0 (1.9) years, -1.3 (1.5) D, and 23.8 (1.0) mm for all patients. A total of 161 (95.8%) in the LLRL group and 159 (94.6%) in the control group returned for the 6-month follow-up. A total of 157 (93.5%) in the LLRL group and 152 (90.5%) in the control group returned for the 12-month follow-up. Mean (SD) changes in SER were 0.15 (0.16) D and -0.26 (0.21) D for the LLRL group and the control group, respectively (difference, -0.41 D; 95% CI, -0.48 to -0.34 D; P < .001), at 6 months and 0.24 (0.27) D and -0.65 (0.33) D for the LLRL group and the control group, respectively (difference, -0.89 D; 95% CI, -0.95 to -0.83 D; P < .001), at 12 months. Mean (SD) changes in AL were -0.06 (0.08) mm and 0.13 (0.12) mm for the LLRL group and control group, respectively (difference, 0.19 mm; 95% CI, 0.16 to 0.22 mm; P < .001), at 6 months and -0.11 (0.10) mm and 0.26 (0.16) mm for the LLRL group and control group, respectively (difference, 0.37 mm; 95% CI, 0.34 to 0.40 mm; P < .001). Masked fundus photograph review did not identify retinal changes in either group. Conclusions and relevance: These findings suggest daily use of 650-nm LLRL for 1 year can slow progression of SER and AL without safety concerns identified. Confirmation of these findings at independent sites seems warranted, as well as determining whether these effects can be sustained with or without continued treatment and whether LLRL has any effect on pathological myopia. Trial Registration: ChiCTR2200058963.

Effect of Far-Red Light on Biomass Accumulation, Plant Morphology, and Phytonutrient Composition of Ruby Streaks Mustard at Microgreen, Baby Leaf, and Flowering Stages.

Far-red (FR) light influences plant development significantly through shade avoidance response and photosynthetic modulation, but there is limited knowledge on how FR treatments influence the growth and nutrition of vegetables at different maturity stages in controlled environment agriculture (CEA). Here, we comprehensively investigated the impacts of FR on the yield, morphology, and phytonutrients of ruby streaks mustard (RS) at microgreen, baby leaf, and flowering stages. Treatments including white control, white with supplementary FR, white followed by singularly applied FR, and enhanced white (WE) matching the extended daily light integral (eDLI) of FR were designed for separating the effects of light intensity and quality. Results showed that singular and supplemental FR affected plant development and nutrition similarly throughout the growth cycle, with light intensity and quality playing varying roles at different stages. Specifically, FR did not affect the fresh and dry weight of microgreens but increased those values for baby leaves, although not as effectively as WE. Meanwhile, FR caused significant morphological change and accelerated the development of leaves, flowers, and seedpods more dramatically than WE. With regard to phytonutrients, light treatments affected the metabolomic profiles for baby leaves more dramatically than microgreens and flowers. FR decreased the glucosinolate and anthocyanin contents in microgreens and baby leaves, while WE increased the contents of those compounds in baby leaves. This study illustrates the complex impacts of FR on RS and provides valuable information for selecting optimal lighting conditions in CEA.

Making a living off the rainbow's edge: How phycobilisomes adapt structurally to absorb far-red light.

Cyanobacteria harvest light by using architecturally complex, soluble, light-harvesting complexes known as phycobilisomes (PBSs). PBS diversity includes specialized subunit paralogs that are tuned to specific regions of the light spectrum; some cyanobacterial lineages can even absorb far-red light. In a recent issue of the Journal of Biological Chemistry, Gisriel et al. reported the cryo-electron microscopic structure of a far-red PBS core, showing how bilin binding in the α-subunits of allophycocyanin paralogs can modify the bilin-binding site to red shift the absorbance spectrum. This work helps explain how cyanobacteria can grow in environments where most of the visible light has been filtered out.

Far-red light-triggered cargo release from liposomes b ound to a photosensitizer-cellulose nanofiber hydrogel.

In our research we used the anionic nanofibrillar cellulose (ANFC) as a platform for far-red light-induced release of cargo from liposomes. In contrast to previous works, where photosensitizers are usually in the liposomal bilayers, we used a cellulose-binding dye. Our phthalocyanine derivative has been shown to bind very strongly to cellulose and cellulose nanofiber hydrogels, allowing us to place it outside of the liposomes. Both the sensitizer and cationic liposomes bind strongly to the ANFC after mixing, making the system easy to fabricate. Upon light activation, the photosensitizer generates reactive oxygen species (ROS) within the ANFC hydrogel, where the reactive oxygen species oxidize unsaturated lipids in the liposomal membrane, which makes the liposomes more permeable, resulting in on-demand cargo release. We were able to achieve ca. 70 % release of model hydrophilic cargo molecule calcein from the hydrogels with a relatively low dose of light (262 J/cm2) while employing the straightforward fabrication techniques. Our system was remarkably responsive to the far-red light (730 nm), enabling deep tissue penetration. Therefore, this very promising novel cellulose-immobilized photosensitizer liposomal platform could be used as a controlled drug delivery system, which can have applications in externally activated coatings or implants.