Photoreduction Research Articles

Performance analysis of functional properties of silk fabric enhanced via in situ grafting modification

AbstractSilk, a natural polymer protein fiber, possesses exceptional properties such as smoothness, softness, breathability, and drapability. However, silk is susceptible to photochemical reactions in light, leading to yellowing, brittleness, and deterioration on the fabric's surface, which significantly affects its service life and performance. In this experiment, we utilized ascorbic acid and hydrogen peroxide as the initiation system, along with glycidyl methacrylate (GMA) as a graft monomer, to conduct graft copolymerization modification on silk fabrics. To enhance the light resistance of silk fabrics in the textile industry, the grafting parameters were optimized and the rate adjusted to impart the anti‐UV and anti‐aging properties. Moreover, the whiteness value drastically increased from 26.71% to 88.23%, the breaking strength surged from 174.6 to 211.5 N, and the contact angle surpassed 90° at an 8.8% grafting rate, resulting in heightened hydrophobicity. Finally, the modified silk fabrics exhibited remarkable light resistance, rendering them better suited for advanced textile applications. This research work provided a window of opportunity to prevent yellowing and improve resistance to light, making modified silk fabrics more suitable for various textile applications in the future.Highlights Grafted silk fabric's whiteness increased from 26.71% to 88.23%. Silk had a contact angle over 90° and increased hydrophobicity at 8.8% grafting. Modification improves silk's optical and mechanical properties. Aging reduces silk's thermal properties and fiber strength.

H2O2 Mediated Photoreduction of Nitrates to Ammonia by Iron Filings under Ambient Conditions.

Herein, a simple ambient conditioned sunlight promoted photochemical reduction reaction is demonstrated for the of nitrate (NO3-) conversion to ammonia (NH3) with the maximum conversion yield of ∼16 mM using iron filings (f-Fe) in the presence of H2O2. Based on a radical scavenging study of reactive species and the characterization of catalyst f-Fe before and after the reaction, a plausible mechanism has been proposed for the ambient conditioned synthesis of NH3. The results associated with the NH3 synthesis have been verified using the 15N isotopic labeled nitrate (15NO3-), which supports the simpler viability of the reported procedure.

Characterization of the oxygen-tolerant formate dehydrogenase from Clostridium carboxidivorans

Fixation of CO2 into the organic compound formate by formate dehydrogenases (FDHs) is regarded as the oldest autotrophic process on Earth. It has been proposed that an FDH-dependent CO2 fixation module could support CO2 assimilation even in photoautotrophic organisms. In the present study, we characterized FDH from Clostridium carboxidivorans (ccFDH) due to its ability to reduce CO2 under aerobic conditions. During the production of recombinant ccFDH, in which the selenocysteine codon was replaced by Cys, we were able to replace the W with Mo as the transition metal in the ccFDH metal cofactor, resulting in a two-fold increase of 6 μmol formate min−1 in enzyme activity. Then, we generated ccFDH variants in which the strict NADH preference of the enzyme was changed to NADPH, as this reducing agent is produced in high amounts during the photosynthetic light process. Finally, we showed that the native ccFDH can also directly use ferredoxin as a reducing agent, which is produced by the photosynthetic light reactions at photosystem I. These data collectively suggest that ccFDH and, particularly, its optimized variants can be regarded as suitable enzymes to couple formate production to photosynthesis in photoautotroph organisms, which could potentially support CO2 assimilation via the Calvin–Benson–Bassham (CBB) cycle and minimize CO2 losses due to photorespiration.

The Trx-Prx redox pathway and PGR5/PGRL1-dependent cyclic electron transfer play key regulatory roles in poplar drought stress.

Understanding drought resistance mechanisms is crucial for breeding poplar species suited to arid and semi-arid regions. This study explored the drought responses of three newly developed 'Zhongxiong' series poplars using integrated transcriptomic and physiological analyses. Under drought stress, poplar leaves showed significant changes in differentially expressed genes (DEGs) linked to photosynthesis-related pathways, including photosynthesis-antenna proteins and carbon fixation, indicating impaired photosynthetic function and carbon assimilation. Additionally, drought stress triggered oxidative damage through increased ROS production, leading to malondialdehyde (MDA) accumulation. Weighted gene co-expression network analysis (WGCNA) revealed that DEGs closely associated with physiological responses were enriched in cell redox homeostasis pathways, specifically the thioredoxin-peroxiredoxin (Trx-Prx) pathway. Key genes in this pathway and in cyclic electron flow (CEF), such as PGR5-L1A, were downregulated, suggesting compromised ROS scavenging and photoprotection under drought stress. Notably, ZX4 poplar exhibited higher drought tolerance, maintaining stronger activity in CEF and the Trx-Prx pathway compared to ZX3 and ZX5. Genes like PGR5-L1A, 2-Cys Prx BAS1, PrxQ, and TPX are promising candidates for enhancing drought resistance in poplars through genetic improvement, with potential applications for developing resilient forestry varieties.

Tracking the Geometric and Positional Isomerization of Lipid C═C Bonds in the Bacterial Stress Responses by Mass Spectrometry.

The position and configuration of the C═C bond have a significant impact on the spatial conformation of unsaturated lipids, which subsequently affects their biological functions. Double bond isomerization of lipids is an important mechanism of bacterial stress response, but its in-depth mechanistic study still lacks effective analytical tools. Here, we developed a visible-light-activated dual-pathway reaction system that enables simultaneous [2 + 2] cycloaddition and catalytic cis-trans isomerization of the C═C bond of unsaturated lipids via directly excited anthraquinone radicals. Density functional theory calculations revealed the oxygen radical addition transition state and the addition-elimination isomerization mechanism of the reaction. A full-dimensional resolution method for C═C bond position and configuration was developed based on the bifunctional reaction and liquid chromatography-mass spectrometry. This method was then applied to the study of bacterial environmental stress response mechanisms. The C═C bond cis-trans and positional isomerization patterns of Pseudomonas membrane lipids under temperature stress were discovered, and the effect of temperature stress on fatty acid biosynthesis was also revealed. This study not only provides an effective tool and key information for the study of bacterial stress response mechanisms, but also enriches the toolbox of visible light chemical reactions.

Chloroplast Vesiculation and Induced Chloroplast Vesiculation and Senescence-Associated Gene 12 Expression During Tomato Flower Pedicel Abscission.

Abscission is a tightly regulated process in which plants shed unnecessary, infected, damaged, or aging organs, as well as ripe fruits, through predetermined abscission zones in response to developmental, hormonal, and environmental signals. Despite its importance, the underlying mechanisms remain incompletely understood. This study highlights the deleterious effects of abscission on chloroplast ultrastructure in the cells of the tomato flower pedicel abscission zone, revealing spatiotemporal differential gene expression and key transcriptional networks involved in chloroplast vesiculation during abscission. Significant changes in chloroplast structure and vesicle formation were observed 8 and 14 h after abscission induction, coinciding with the differential expression of vesiculation-related genes, particularly with upregulation of Senescence-Associated Gene 12 (SAG12) and Chloroplast Vesiculation (CV). This suggests a possible vesicle transport of chloroplast degrading material for recycling by autophagy-independent senescence-associated vacuoles (SAVs) and CV-containing vesicles (CCVs). Ethylene signaling appears to be involved in the regulation of these processes, as treatment with a competitive inhibitor of ethylene action, 1-methylcyclopropene, delayed vesiculation, reduced the expression of SAG12, and increased expression of Curvature Thylakoid 1A (CURT1A). In addition, chloroplast vesiculation during abscission was associated with differential expression of photosynthesis-related genes, particularly those involved in light reactions, underscoring the possible functional impact of the observed structural changes. This work provides new insights into the molecular and ultrastructural mechanisms underlying abscission and offers potential new targets for agricultural or biotechnological applications.

The electrochemical ion membrane system (EIMs) enhanced light reactions of photosynthesis with intermittent electrical stimulation.

Despite the widespread application of electrochemical systems in bioproduction, their detailed effects on photosynthetic organisms remain to be explored. In this study, a three-chamber electrochemical ion membrane system (EIMs) was optimized for minimizing carbon resource interference in the cathode chamber, thereby elucidating the role of EIMs in the light reactions of photosynthesis. By applying intermittent electrical stimulation, the photosynthetic activity of microalgae was enhanced, manifesting as the promoted accumulation of intracellular ATP and NADPH, while allowing the collection of hydrogen and oxygen as by-products. These findings suggest that EIMs not only facilitate photosynthesis by enhancing both light and dark reactions but also provide new avenues for improving the efficiency of photosynthetic production and advancing sustainable biotechnological processes.

Applications of Selectfluor in Organic Synthesis-A Quadrennial Update

Selectfluor, bis(tetrafluoroborate)[1-chloromethyl-4-fluoro-1,4-diazoniabicyclo-[2.2.2] octane] is an extraordinarily stable solid with exceptional properties, such as strong solubility and stability in polar solvents, minimal toxicity, excellent thermal stability, and utility as an oxidant. One of the electrophilic fluorinating compounds that is most frequently employed in fluorination reactions is Selectfluor. In this mini-review, we have briefly updated the various applications of Selectfluor in organic synthesis, particularly in C-C, Cheteroatom and heteroatom-heteroatom bond formation reactions from mid-2020 to date. In addition to these, Selectfluor found useful in heterocyclic ring formations, demethylation, deoxygenation and other miscellaneous reactions. The results that have been published thus far show how extraordinarily promising Selectfluormediated organic molecule skeleton assembly events can be. Visible light, electrochemical, and nano-based reactions still have a lot of room for growth and application, despite the noteworthy advances in these domains. The compilation is subdivided based on the type of reaction/function of Selectfluor organic transformation.

Enhancing crop yields to ensure food security by optimizing photosynthesis.

The crop yields achieved through traditional plant breeding techniques appear to be nearing a plateau. Therefore, it is essential to accelerate advancements in photosynthesis, the fundamental process by which plants convert light energy into chemical energy, to further enhance crop yields. Research focused on improving photosynthesis holds significant promise for increasing sustainable agricultural productivity and addressing challenges related to global food security. This review examines the latest advancements and strategies aimed at boosting crop yields by enhancing photosynthetic efficiency. There has been a linear increase in yield over the years in historically released germplasm selected through traditional breeding methods, and this increase is accompanied by improved photosynthesis. We explore various aspects of the light reactions designed to enhance crop yield, including light harvest efficiency through smart canopy systems, expanding the absorbed light spectrum to include far-red light, optimizing non-photochemical quenching, and accelerating electron transport flux. At the same time, we investigate carbon reactions that can enhance crop yield, such as manipulating Rubisco activity, improving the Calvin-Benson-Bassham (CBB) cycle, introducing CO2 concentrating mechanisms (CCMs) in C3 plants, and optimizing carbon allocation. These strategies could significantly impact crop yield enhancement and help bridge the yield gap.

Decoding the physicochemical basis of resurrection: the journey of lichen Flavoparmelia caperata through prolonged water scarcity to full rehydration

Desiccation tolerance is a complex phenomenon observed in the lichen Flavoparmelia ceparata. To understand the reactivation process of desiccated thalli, completely dried samples were rehydrated. The rehydration process of this lichen occurs in two phases. The first phase, characterized by rapid rehydration, involves the conversion of non-functional reaction centers (RCs) into functional PSII RCs, and the accumulation of ROS along with the increment in SOD antioxidant enzyme. These coordinated mechanisms initiate the light reaction of photosynthesis by forming active light-harvesting complexes (LHCs). This adaptation ensures efficient recovery, as evidenced by specific energy fluxes (ABS/RC, TR/RC, ET/RC, and DI/RC), phenomenological fluxes (ABS/CS, TR/CS, ET/CS, and DI/CS), quantum efficiencies (ФP0, ФE0, and ФD0), primary and secondary photochemistry, photochemical and non-photochemical quenching, and performance index, highlighting the essential role of rapid water uptake in restoring turgor pressure for cell structure and function maintenance. The interconnected network of antioxidant defenses, including catalase (CAT) and peroxidase (POD), underscores the plant's ability to cope with oxidative stress during resilience. The acid phosphomonoesterase (PME) enzymatic activity corresponds to its role in releasing phosphate for essential cellular functions and post-rehydration thallus growth. The activity of CAT, GPOD, and PME signifies the gradual reactivation of lichen F. caperata. Moreover, the investigation into chlorophyll a fluorescence emphasizes the efficient reactivation of the photosynthetic process in F. caperata. In conclusion, lichen F. caperata demonstrates significant potential for desiccation tolerance through the rapid transformation of chloroplasts, chlorophylls, and PSII RCs from their inactive to active states upon rehydration. This research not only enhances our understanding of desiccation tolerance in resurrection plants but also highlights the importance of lichens, particularly F. caperata, as valuable models for studying plant resilience in challenging environments.

The Thermal-Stable LH1-RC Complex of a Hot Spring Purple Bacterium Powers Photosynthesis with Extremely Low-Energy Near-Infrared Light.

Blastochloris (Blc.) tepida is a hot spring purple nonsulfur phototrophic bacterium that contains bacteriochlorophyll (BChl) b. Here, we present a 2.21 Å cryo-EM structure of the thermostable light-harvesting 1-reaction center (LH1-RC) complex from Blc. tepida. The LH1 ring comprises 16 circularly arranged αβγ-subunits plus one αβ-subunit that surround the RC complex composed of C-, H-, L-, and M-subunits. In a comparative study, the Blc. tepida LH1-RC showed numerous electrostatic and hydrophobic interactions both within the LH1 complex itself and between the LH1 and the RC complexes that are absent from the LH1-RC complex of its mesophilic counterpart, Blc. viridis. These additional interactions result in a tightly packed LH1-RC architecture with a reduced accessible surface area per volume that enhances the thermal stability of the Blc. tepida complex and allows the light reactions of photosynthesis to proceed at hot spring temperatures. Moreover, based on high-resolution structural information combined with spectroscopic evidence, the unique photosynthetic property of the Blc. tepida LH1-RC─absorption of energy-poor near-infrared light beyond 1000 nm─can be attributed to strong hydrogen-bonding interactions between the C3-acetyl C═O of the LH1 BChl b and two LH1 α-Trp residues, structural rigidity of the LH1, and the enhanced exciton coupling of the LH1 BChls of this thermophile.

Field integration of shoot gas-exchange and leaf chlorophyll fluorescence measurements to study the long-term regulation of photosynthesis in situ.

Understanding the diurnal and seasonal regulation of photosynthesis is an essential step to quantify and model the impact of the environment on plant function. Although the dynamics of photosynthesis have been widely investigated in terms of CO2 exchange measurements, a more comprehensive view can be obtained when combining gas-exchange and chlorophyll fluorescence (ChlF). Until now, integrated measurements of gas-exchange and ChlF have been restricted to short-term analysis using portable IRGA systems that include a fluorometer module. In this communication we provide a first-time demonstration of long-term, in situ, and combined measurements of photosynthetic gas-exchange and ChlF. We do so by integrating a new miniature PAM-fluorometer into an existing system of automated chambers to track photosynthetic gas-exchange of leaves and shoots in situ. The setup is used to track the dynamics of the light and carbon reactions of photosynthesis at a 20-minute resolution in leaves of silver birch (Betula pendula Roth) during summertime. The potential of the method is illustrated using the ratio between electron transport and net assimilation (ETR/ANET), which reflects the internal electron use efficiency of photosynthesis. The setup successfully captured the diurnal patterns in the ETR/ANET during summertime, including a large increase in noon ETR/ANET in response to a period of high temperatures and relatively low soil moisture, pointing to a drastic decrease in electron use efficiency. The observations emphasize the value of combined and long-term in situ measurements of ChlF and gas-exchange, opening new opportunities to investigate, model and quantify the regulation of photosynthesis in situ and the connection between ChlF and photosynthetic gas-exchange. The next steps, potential and limitations of the approach are discussed.

Analyzing sorbitol biosynthesis using a metabolic network flux model of a lichenized strain of the green microalga Diplosphaera chodatii.

Diplosphaera chodatii, a unicellular terrestrial microalga found either free-living or in association with lichenized fungi, protects itself from desiccation by synthesizing and accumulating low-molecular-weight carbohydrates such as sorbitol. The metabolism of this algal species and the interplay of sorbitol biosynthesis with its growth, light absorption, and carbon dioxide fixation are poorly understood. Here, we used a recently available genome assembly for D. chodatii to develop a metabolic flux model and analyze the alga's metabolic capabilities, particularly, for sorbitol biosynthesis. The model contains 151 genes, 155 metabolites, and 194 unique metabolic reactions participating in 12 core metabolic pathways and five compartments. Both photoautotrophic and mixotrophic growths of D. chodatii were supported by the metabolic model. In the presence of glucose, mixotrophy led to higher biomass and sorbitol yields. Additionally, the model predicted increased starch biosynthesis at high light intensities during photoautotrophic growth, an indication that the "overflow hypothesis-stress-driven metabolic flux redistribution" could be applied to D. chodatii. Furthermore, the newly developed metabolic model of D. chodatii, iDco_core, captures both linear and cyclic electron flow schemes characterized in photosynthetic microorganisms and suggests a possible adaptation to fluctuating water availability during periods of desiccation. This work provides important new insights into the predicted metabolic capabilities of D. chodatii, including a potential biotechnological opportunity for industrial sorbitol biosynthesis.IMPORTANCELichenized green microalgae are vital components for the survival and growth of lichens in extreme environmental conditions. However, little is known about the metabolism and growth characteristics of these algae as individual microbes. This study aims to provide insights into some of the metabolic capabilities of Diplosphaera chodatii, a lichenized green microalgae, using a recently assembled and annotated genome of the alga. For that, a metabolic flux model was developed simulating the metabolism of this algal species and allowing for studying the algal growth, light absorption, and carbon dioxide fixation during both photoautotrophic and mixotrophic growth, in silico. An important capability of the new metabolic model of D. chodatii is capturing both linear and cyclic electron flow mechanisms characterized in several other microalgae. Moreover, the model predicts limits of the metabolic interplay between sorbitol biosynthesis and algal growth, which has potential applications in assisting the design of bio-based sorbitol production processes.

Revisiting gauge invariance and Reggeization of pion exchange

The Reggeized pion is expected to provide the main contribution to the forward cross section in light meson photoproduction reactions with charge exchange at high energies. We discuss the Reggeization of pion exchange in charged pion photoproduction with an emphasis on consistency with current conservation. We show that the gauge-invariant amplitude for the exchange of a particle with a generic even spin J≥2 in the t channel is analytic at J=0 and that it can be interpreted in terms of the nucleon electric current. This enables us to reconcile the dynamics in the s and u channel, which involves also nucleon exchanges, with the amplitude expressed in terms of t-channel partial waves, as required by Regge theory. Published by the American Physical Society 2024

An effector protein of Fusarium graminearum targets chloroplasts and suppresses cyclic photosynthetic electron flow.

Chloroplasts are important photosynthetic organelles that regulate plant immunity, growth, and development. However, the role of fungal secretory proteins in linking the photosystem to the plant immune system remains largely unknown. Our systematic characterization of 17 chloroplast-targeting secreted proteins of Fusarium graminearum indicated that Fg03600 is an important virulence factor. Fg03600 translocation into plant cells and accumulation in chloroplasts depended on its chloroplast transit peptide. Fg03600 interacted with the wheat (Triticum aestivum L.) proton gradient regulation 5-like protein 1 (TaPGRL1), a part of the cyclic photosynthetic electron transport chain, and promoted TaPGRL1 homo-dimerization. Interestingly, TaPGRL1 also interacted with ferredoxin (TaFd), a chloroplast ferredoxin protein that transfers cyclic electrons to TaPGRL1. TaFd competed with Fg03600 for binding to the same region of TaPGRL1. Fg03600 expression in plants decreased cyclic electron flow (CEF) but increased the production of chloroplast-derived reactive oxygen species (ROS). Stably silenced TaPGRL1 impaired resistance to Fusarium head blight (FHB) and disrupted CEF. Overall, Fg03600 acts as a chloroplast-targeting effector to suppress plant CEF and increase photosynthesis-derived ROS for FHB development at the necrotrophic stage by promoting homo-dimeric TaPGRL1 or competing with TaFd for TaPGRL1 binding.

Synergistic role of Rubisco inhibitor release and degradation inphotosynthesis.

Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) exhibits catalytic promiscuity, resulting in error-prone reactions and the formation of inhibitory sugar phosphates. Specifically, Xylulose-1,5-bisphosphate (XuBP) acts as an inhibitor by binding to the active site of Rubisco, thereby impairing its catalytic function. Thermolabile Rubisco activase (Rca) facilitates the release of such inhibitors, including XuBP, by remodelling Rubisco. In Arabidopsis thaliana, the phosphatase pair CbbYA and CbbYB subsequently hydrolyses XuBP to prevent its rebinding to Rubisco. To explore the functional interplay between these components in maintaining photosynthesis, cbbya, cbbyb and cbbyab mutants were crossed with RCA knockdown (rca-2) lines. Additionally, both RCA and CBBYA were overexpressed in wild-type (WT) Arabidopsis thaliana. Phenotypic analyses revealed an exacerbation in decreased growth and photosynthetic efficiency in the cbbyab rca-2 double mutants compared with the control mutants (cbbyab and rca-2), indicating a negative genetic interaction. Furthermore, the co-overexpression of RCA and CBBYA did not improve photosynthesis under short-term heat stress, and light reactions were adversely affected relative to the WT. These findings illustrate the synergistic roles of Rca, CbbYA and CbbYB in maintaining carbon fixation and promoting plant growth in Arabidopsis thaliana. Thus, the coordinated regulation of Rca and CbbY enzymes is crucial for optimizing photosynthetic efficiency.

Study on the Mechanism of Chemical Mechanical Polishing for 4H-SiC Based on Photoelectro-Fenton Reaction

Abstract In order to meet the requirements of atomic-level smoothness and non-damaging wafer surface with a high material removal rate (MRR) of silicon carbide (SiC), a new method assisted by photoelectron-Fenton reaction was studied to assist in chemical mechanical polishing. The coupling effects of ultraviolet light, electric field, and Fenton reaction in improving the slurry oxidation performance and the oxidation ability on the 4H-SiC wafer surface has been verified by measuring the oxidation-reduction potential, using probe detection methods, and conducting electrochemical experiments. Through immersion oxidation experiments, the oxidation mechanisms of SiC wafers were analyzed in depth using scanning electron microscope, energy-dispersive spectrometry, and X-ray photoelectron spectroscopy tests. The results showed that the photoelectro-Fenton reaction greatly enhanced the oxidation ability of the slurry, which improved the efficiency of oxide layer generation on the wafer surface. The high MRR of 102.4 nm/h and the low surface roughness (Ra) of 0.57 nm can be obtained after polishing under the condition of pH = 3, and the polishing and synergistic mechanism of 4H-SiC in the photoelectron-Fenton reaction solution was proposed.

Clinical characterization of mycosis fungoides with abnormal light reactions induced by narrow-band UVB therapy: A review of a single-center experience.

Narrow-band UVB (NB-UVB) therapy at a wavelength of 311 nm is often used to treat mycosis fungoides (MF). However, we occasionally encounter cases of erythema induced by low doses of NB-UVB, known as an abnormal light reaction (ALR). We investigated the incidence of ALR in patients with MF and the association between ALR and clinical and laboratory findings. Forty patients (30 men and 10 women) with MF (excluding patients treated with bexarotene or etretinate) who received NB-UVB therapy at the Department of Dermatology, University of Toyama, from January to December 2022 were analyzed. ALR was defined as erythema caused by NB-UVB irradiation of the nonlesional skin at a dose of ≤0.5 J/cm2. ALR occurred in six of 40 patients (15%). The main symptoms of ALR are erythema, irritation, and itching. ALR was observed in patients with Fitzpatrick skin types II and III, and was more common in patients with T2 and T4 disease than in others. The mechanism underlying its occurrence is unknown; however, it has been suggested that ALR is more likely to occur in patients with extensive skin lesions. In addition, treatment can be continued by reducing the dose of NB-UVB or switching to a 308-nm excimer laser, even when ALR occurs. Accumulation of additional cases is required because there were only six patients with ALR in this study.

Redox-active molecules in bacterial cultivation media produce photocurrent.

Renewable energy concepts such as microbial fuel cells (MFCs) present a promising, yet intrinsically complex electrochemical approach for utilizing bacteria as an electron source. In this work, we show that just the cultivation media for bacterial growth, which is based on yeast extract, is sufficient for generating electrical current in a bio-electrochemical cell (BEC). We apply cyclic voltammetry and 2-dimensional fluorescence spectroscopy to identify redox active molecules such as NADH, NAD+, and flavines that may play key roles in electron donation. Finally, we show that upon illumination, current production is enhanced 2-fold. This photocurrent is generated by a variety of metabolites capable of photochemical reduction, enabling them to donate electrons at the anode of the BEC.

Investigating ocular biomarkers and differential diagnosis of Alzheimer's disease and vascular cognitive impairment based on multimodal imaging.

The eye can be used as a potential monitoring window for screening, diagnosis, and monitoring of neurological diseases. Alzheimer's disease (AD) and vascular cognitive impairment (VCI) are common causes of cognitive impairment and may share many similarities in ocular signs. Multimodal ophthalmic imaging is a technology to quantify pupillary light reaction, retinal reflectance spectrum, and hemodynamics. This provides multidimensional ocular metrics from a non-invasive approach to ocular biomarkers and differential diagnosis of AD and VCI. We aim to investigate the changing pattern of ocular metrics in patients with AD and VCI using multimodal ophthalmic imaging. Patients with subjective cognitive complaints in the memory clinic were subdivided into AD, VCI, and cognitively healthy individuals using neuropsychological and neuroimaging examinations, including positron emission tomography. All subjects underwent a medical history review, blood pressure measurement, medical optometry, intraocular pressure measurement, and custom-built multimodal ophthalmic imaging. Multidimensional parameters were analyzed by one-way analysis of variance and post hoc comparisons. This study included 19 patients with AD, 24 patients with VCI, and 37 cognitively healthy age- and sex-matched subjects. Both AD and VCI patients showed abnormal pupillary light reactions, including decreased resting pupil diameter, pupil constriction amplitude, and maximum constriction velocity. Compared with the control group, the AD group presented increased retinal reflectance at 548nm, whereas the VCI group presented an increased resistivity index and decreased blowout score in retinal hemodynamics. We demonstrate that pupillary light reaction-related neurodegeneration is the common pathological change in both AD and VCI. In addition, AD is characterized by alterations in retinal spectral signatures, whereas VCI is characterized by alterations in retinal hemodynamics. These findings suggest that multimodal ophthalmic imaging may have the potential to be used as a screening tool for detecting AD and VCI.