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Photo-Induced Depletion of Binding Sites in DNA-PAINT Microscopy
摘要： The limited photon budget of fluorescent dyes is the main limitation for localization precision in localization-based super-resolution microscopy. Points accumulation for imaging in nanoscale topography (PAINT)-based techniques use the reversible binding of fluorophores and can sample a single binding site multiple times, thus elegantly circumventing the photon budget limitation. With DNA-based PAINT (DNA-PAINT), resolutions down to a few nanometers have been reached on DNA-origami nanostructures. However, for long acquisition times, we find a photo-induced depletion of binding sites in DNA-PAINT microscopy that ultimately limits the quality of the rendered images. Here we systematically investigate the loss of binding sites in DNA-PAINT imaging and support the observations with measurements of DNA hybridization kinetics via surface-integrated fluorescence correlation spectroscopy (SI-FCS). We do not only show that the depletion of binding sites is clearly photo-induced, but also provide evidence that it is mainly caused by dye-induced generation of reactive oxygen species (ROS). We evaluate two possible strategies to reduce the depletion of binding sites: By addition of oxygen scavenging reagents, and by the positioning of the fluorescent dye at a larger distance from the binding site.
关键词： photo-induced DNA damage,surface-integrated fluorescence correlation spectroscopy (SI-FCS),reactive oxygen species,super-resolution microscopy,DNA-PAINT
更新于2025-09-09 09:28:46
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New Sensitizers Developed on a Methylpheophorbide a Platform for Photodynamic Therapy: Synthesis, Singlet Oxygen Generation and Modeling of Passive Membrane Transport
摘要： This study focuses on the behavior of new potential sensitizers for photodynamic therapy of cancer developed on a chlorophyll a platform. Pheophorbide a 17-(3) methylester and its two glycol derivatives have been synthesized from chlorophyll and identified via visible, UV-, NMR- and MS-spectra. The behavior of photosensitizers in solutions has been studied with various experimental techniques. They are found to generate singlet oxygen with a sufficient quantum yield and reveal a tendency to effectively penetrate into cell membranes due to high lipophilicity. Thermodynamic analysis indicates that the sensitizer transfer from a water-like to a lipid-like medium is controlled by a large and negative enthalpic term excepting the case of the most polar solute, where for phosphate saline buffer the favorable entropic term dominates. Our study highlights the important feature dealing with the temperature dependence of partition coefficients between saline buffer and 1-octanol which is found to be surprisingly strong for hydrophobic solutes and temperature independent for the species containing both H-donor and H-acceptor groups.
关键词： Hydrophobicity,Photosensitizers,Photodynamic therapy,Thermodynamics of solvation,Partition coefficients,Reactive oxygen species
更新于2025-09-09 09:28:46
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Charge separation and ROS generation on tubular sodium titanates exposed to simulated solar light
摘要： The research focuses on a few key points concerning the light-driven processes taking place on TiO2 anatase and sodium titanates with tubular morphology, such as the relationship between the morphology and activity for H2 and CO2 production, density of surface hydroxyl groups, ROS (?OH and ?O2-) production and photocatalytic activity, and charge separation at the interface of semiconducting domains and enhancement of activity. One key point discussed is whether the materials with peculiar morphologies (i.e. tubular) are superior to the conventional ones. The experimental evidences show that the main advantage of the tubular morphology of sodium titanate is given by its significantly higher surface area compared to parental anatase. FTIR and XPS progressive analyses evidence that the density of surface hydroxyl groups decreases with the development of the tubular morphology. The radical trapping experiments show that the variation of surface hydroxyl density is, generally, followed by activities for ?OH and ?O2- generation, as well as by the photocatalytic production of H2 and CO2 from water/methanol mixture. Consequently, the ROS, formed by action of photogenerated electrons and holes on adsorbed O2 and hydroxyl groups, respectively, play an important role in determining the photocatalytic activity of titania-based materials. The other major aspect revealed by this research is that the charge separation at the interfaces formed between anatase and sodium titanate crystalline phases has remarkable effect on the activity formation rates of H2 and CO2.
关键词： titanate nanotubes,reactive oxygen species,charge separation,simulated solar light,photocatalysis
更新于2025-09-09 09:28:46
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Effects of TONS504?photodynamic therapy on mouse mammary tumor cells
摘要： In the present study, TONS504 (C51H58N8O5I2; molecular weight, 1,116.9), a novel cationic hydrophilic photosensitizer, was synthesized from protoporphyrin IX dimethyl ester through a five-step process according to a patented method for use in photodynamic therapy (PDT). The subcellular localization of TONS504 and the cytotoxic effects of TONS504-mediated PDT in the mouse mammary tumor EMT6 cell line were investigated. TONS504 was localized primarily in the lysosomes and partially in the mitochondria. The cytotoxic effects of TONS504-mediated PDT in the mouse mammary tumor EMT6 cell line were investigated using a WST8 assay and an Oxidative Stress kit. The cell viability values following treatment with 10 μg/ml TONS504 at light energies of 0, 1, 5 and 10 J/cm2 were 92.5, 101.8, 27.7 and 1.8%, respectively. The percentages of reactive oxygen species (ROS)(+) cells following the same treatment were 8.6, 8.5, 29.2 and 70.1%, respectively, whereas the percentages of apoptotic cells were 7.1, 5.6, 24.8 and 48.7%, respectively. The percentages of ROS(+) and apoptotic cells in the group subjected to TONS504-mediated PDT increased in a manner dependent on the TONS504 concentration and light energy. Further studies are required to evaluate the in vivo pharmacokinetics, tissue distribution and photodynamic effects of TONS504.
关键词： photodynamic therapy,apoptosis,mammary tumor,reactive oxygen species,TONS504
更新于2025-09-09 09:28:46
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Degradation of Bromate by Fe(II)-Ti(IV) Layered Double Hydroxides Nanoparticles under Ultraviolet Light
摘要： The photocatalytic decomposition of bromate (BrO3-), a possible human carcinogen, has attracted much attention because of its high efficiency and easier combination with ultraviolet (UV) disinfection in water treatment plants. In this study, the Fe(II)-Ti(IV) layered double hydroxides (LDHs) have been made through a facile hydrothermal method and used as an alternative photocatalyst for reduction of BrO3-. LDHs prepared at a Fe/Ti molar ratio of ~0.5 and pH 7.0, denoted as Fe-Ti-0.5 (pH 7.0), exhibited the highest BrO3- removal efficiency (removal rate constant = 0.067 ± 0.002 min-1) compared to commercial TiO2 and the LDHs prepared at different pHs or different Fe/Ti ratios. The presence of alcohols in water enhanced the photocatalytic reduction of BrO3- due to the greater abundance of electrons caused by alcohols effectively reacting with holes. The neutral pH also favors the degradation of BrO3-. However, the presence of nitrate and nitrite can inhibit the degradation process, due to their reactions with hydrated electrons (eaq-) and hydrogen atom radicals (H·). Cyclic degradation runs and magnetic separation techniques demonstrated the superior reusability of the Fe-Ti-0.5 (pH 7.0) LDH for BrO3- removal. The removal rate of BrO3- under UV was higher than that without UV, indicating that the decomposition proceeded primarily via a photo-reductive mechanism induced by eaq- and H· and thus degradation pathways are proposed. Moreover, when tested in tap water, greater than 90% of BrO3- was removed after 60 min reaction in UV/Fe-Ti-0.5 (pH 7.0) LDH systems in the presence of 5‰ (v/v) methanol. This demonstrates the high potential for such systems for removing BrO3- from disinfected drinking water. This work may shed lights on the design of effective photocatalysts for the enhanced degradation of BrO3- in water plants and the influence of constituents in raw water on the treatment.
关键词： Bromate removal,UV/layered double hydroxides system,Alcohols addition,Reductive species,Tap water
更新于2025-09-09 09:28:46
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Accurate Identification of the Sex and Species of Silkworm Pupae Using Near Infrared Spectroscopy
摘要： The present study proposes a novel method to discriminate the sex and species of silkworm pupae using NIR spectroscopy (800–2778 nm). The spectra from 840 silkworm pupae were collected then divided into a calibration set (700) and a test set (140) using the Kennard–Stone (KS) algorithm. The recognition models were built using the radial basis function and neural network (RBF–NN) and support vector machine (SVM) approaches. The species and sex identi?cation results using the RBF–NN and SVM models based on full spectral data achieved a low accuracy of 5% and 33.57%, respectively. To improve the accuracy and decrease the processing time, both principal component analysis (PCA) and linear discriminant analysis (LDA) were used to reduce the data dimensions. The performance of the optimized SVM model (92.14%) was much better than the RBF–NN model (19.29%) based on PCA. Overall, the best discrimination results were obtained using the RBF–NN and SVM models based on LDA, providing an accuracy of 100%. These promising results have shown that the LDA–SVM and LDA–RBF–NN models can accurately recognize the sex and species of silkworm pupae using NIR spectroscopy.
关键词： silkworm pupa,species,NIR spectroscopy,sex
更新于2025-09-09 09:28:46
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A Review on BiOX (X= Cl, Br and I) Nano-/Microstructures for Their Photocatalytic Applications
摘要： In the recent past, bismuth oxyhalides (BiOX) have been widely used for the photocatalytic degradation of the organic pollutants and other environmental remediation because of their higher stability, economic viability, nontoxicity and effective charge separation. We begin with the review of the different approaches adopted so far for BiOX (X = Cl, Br, and I) synthesis and a study of their photocatalytic performances under UV and visible light towards the various organic as well as inorganic pollutants. Later on, a study on further enhancement of the ef?ciency of BiOX under UV and visible light irradiation using recent advancements would be presented. The new approaches involve controlled morphology by forming composite and hybrid materials with other semiconductors and also doping with other metals and nonmetals that would undoubtedly be bene?cial in the interfacial charge transfer and ef?cient inhibition of the photo-generated species. Herein, we would also exploit the recent developments in the research strategies for enhancing photocatalytic activity of BiOX.
关键词： Pollutants,Photocatalysts,Functionalization,Stability,Bismuth Oxyhalides,Heterostructures,Photogenerated Species,Environmental Remediation,Composites,Photodegradation,Visible Light
更新于2025-09-09 09:28:46
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Photochemical and Pharmacokinetic Characterization of Orally Administered Chemicals to Evaluate Phototoxic Risk
摘要： This study aimed to verify the applicability of a proposed photosafety screening system based on a reactive oxygen species (ROS) assay and a cassette-dosing pharmacokinetic (PK) study to chemicals with wide structural diversity. The orally taken chemicals, erythromycin, gati?oxacin, 8-methoxypsoralen (MOP), pirfenidone (PFD), tri?uoperazine (TFP), and voriconazole (VRZ), were selected as test compounds. The ROS assay was conducted to evaluate their photoreactivity, and all test compounds excluding erythromycin generated signi?cant ROS under simulated sunlight exposure. According to the ROS data, TFP had potent photoreactivity, and the photoreactivity of 4 other compounds was judged to be moderate. Regarding the oral cassette-dosing PK test in rats, the skin deposition of MOP, PFD, and VRZ was relatively high, and gati?oxacin and TFP exhibited moderate skin deposition properties. Based on the ROS and PK data of test compounds, PFD and TFP were judged to be potent phototoxic compounds, and MOP and VRZ were deduced to have phototoxic risk. The predicted phototoxic risk of test compounds by proposed screening was mostly in agreement with observed in vivo phototoxicity in the rat skin. The proposed screening system could provide reliable photosafety information on orally administered compounds with wide structural diversity.
关键词： cassette-dosing pharmacokinetic study,phototoxicity,structural diversity,reactive oxygen species,photosafety assessment
更新于2025-09-09 09:28:46
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Tuning Photoinduced Electron Transfer Efficiency of Fluorogenic BODIPY- <i>α</i> -Tocopherol Analogues
摘要： Fluorogenic analogues of α-tocopherol developed by our group have been instrumental in monitoring reactive oxygen species (ROS) within lipid membranes. Prepared as two-segment trap-reporter (chromanol-BODIPY) probes, photoinduced electron transfer (PeT) was utilized to provide these probes with an off/on switch mechanism warranting the necessary sensitivity. Herein we rationalize within the context of Marcus theory of electron transfer how substituents on the BODIPY core and linker length joining the trap and reporter segments, tune PeT efficiency. DFT and electrochemical studies were used to estimate the thermodynamic driving force of PeT in our constructs. By tuning the redox potential over a 400 mV range, we observed over an order of magnitude increase in PeT efficiency. Increasing the linker length between the chromanol and BODIPY by 2.8 angstroms in turn decreased PeT efficiency 2.7-fold. Our results illustrate how substituent and linker choice enable “darkening” the off state of fluorogenic probes based on BODIPY fluorophores, by favoring PeT over radiative emission from the singlet excited state manifold. Ultimately, our work brings light to the sensitivity ceiling one may achieve in developing fluorogenic antioxidants analogues of α-tocopherol. The work provides general guidelines applicable to those developing fluorogenic probes based on PeT.
关键词： electrochemical studies,α-tocopherol,lipid membranes,reactive oxygen species,redox potential,photoinduced electron transfer,Marcus theory,DFT,Fluorogenic analogues,BODIPY
更新于2025-09-09 09:28:46
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A Highly Efficient Au-MoS2 Nanocatalyst for Tunable Piezocatalytic and Photocatalytic Water Disinfection
摘要： Clean water is essential in our daily life. However, nearly one billion people are forced to drink water contaminated with bacteria, leading to diarrhea, dehydration, and even death. Previously, various photocatalysts have been applied to replace high-cost and highly toxic methods for sewage treatment. Nevertheless, the requirement of external light sources limits their application. Herein, we develop a new type of nanocatalyst based on single- and few-layered molybdenum disulfide (MoS2) nanosheets (NSs) that can catalyze the generation of reactive oxygen species (ROS) to inactivate bacteria either through a piezoelectric effect (mechanical vibration) or photocatalytic effect (light irradiation). After 60 minutes of mechanical vibration or visible-light irradiation, the MoS2 NSs can reduce Escherichia coli (E. Coli) by 99.999%. In addition, the ROS generation efficiency and bacterial disinfection performance of the catalyst can be enhanced by depositing Au nanoparticles (NPs) on MoS2 NSs. The period of mechanical vibration or visible-light irradiation that achieves the same 99.999% reduction in E. coli is shortened to 45 minutes. Moreover, a hybridization of the piezoelectric and photocatalytic effects results in a performance superior to that obtained with the individual effects. A 99.999% reduction in E. coli is also accomplished within 15 minutes through a combination of mechanical vibration and near-infrared (NIR)-light irradiation. This MoS2 nanocatalyst is a promising candidate for nextgeneration water purification systems because of its ability to be triggered by diverse environmental stimuli.
关键词： photocatalytic effect,nanosheets,Molybdenum disulfide,piezocatalytic effect,reactive oxygen species,bacterial disinfection
更新于2025-09-09 09:28:46