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Biocompatible photoluminescent silk fibers with stability and durability
摘要： Exploring photoluminescent silk fibers, possessing biocompatibility as well as stable and durable fluorescent properties, is a requirement for the development of novel photoluminescent biomaterials. Herein, we fabricate photoluminescent silk fibers, TPCA@SF, via modifying an organic fluorescent molecule (5-oxo-3,5-dihydro-2H-thiazolo [3,2-a] pyridine-7-carboxylic acid, TPCA) onto silk fibers, along with using quaternary ammonium salt didodecyldimethylammonium bromide (DDAB) as color fixing agent. The hydrogen bonds and electrostatic association among silk fibers, TPCA and DDAB ensure the stable modification. The facile and green fabrication process is achieved in water under mild conditions without using any toxic substances. The TPCA@SF manifests the combining features of high quantum yield, fluorescence water-fastness, anti-photobleaching, good mechanical property and biocompatibility. The strategy holds great potential for exploring various biocompatible photoluminescent substances with stability and durability.
关键词： wash-durability,biocompatibility,photoluminescence,silk fibers,anti-photobleaching
更新于2025-11-21 11:24:58
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Reversible/Irreversible Photobleaching of Fluorescent Surface Defects of SiC Quantum Dots: Mechanism and Sensing of Solar UV Irradiation
摘要： Knowledge about photobleaching properties of the fluorescent surface defects of the semiconductor quantum dots (QDs) is crucial for their applications. Here, the photobleaching properties of the fluorescent surface defects of the colloidal 3C-SiC QDs are reported. The combined experimental and theoretical study reveals that the observed violet fluorescence at around 392 nm stems from the carboxylic acid group-related surface defects. When the SiC QDs are exposed to the UV irradiation, the 392 nm fluorescent surface defects show both reversible and irreversible photobleaching, whereas the 438 nm fluorescent surface defects show only irreversible photobleaching. The photochemical mechanisms dominating these phenomena are explored. The photobleaching property of the SiC QDs is utilized to detect the solar UV irradiation with high accuracy. The photobleaching of the SiC QDs is highly sensitive to the hydrogen or metal ion concentration in the colloid solution. These findings deepen the understanding of the properties of the fluorescent surface defects of the SiC QDs and pave the way for their applications in sensing.
关键词： photobleaching,silicon carbide quantum dots,surface defects,fluorescence mechanism
更新于2025-11-19 16:46:39
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The Impact of Photobleaching on Microarray Analysis
摘要： DNA-Microarrays have become a potent technology for high-throughput analysis of genetic regulation. However, the wide dynamic range of signal intensities of fluorophore-based microarrays exceeds the dynamic range of a single array scan by far, thus limiting the key benefit of microarray technology: parallelization. The implementation of multi-scan techniques represents a promising approach to overcome these limitations. These techniques are, in turn, limited by the fluorophores’ susceptibility to photobleaching when exposed to the scanner’s laser light. In this paper the photobleaching characteristics of cyanine-3 and cyanine-5 as part of solid state DNA microarrays are studied. The effects of initial fluorophore intensity as well as laser scanner dependent variables such as the photomultiplier tube’s voltage on bleaching and imaging are investigated. The resulting data is used to develop a model capable of simulating the expected degree of signal intensity reduction caused by photobleaching for each fluorophore individually, allowing for the removal of photobleaching-induced, systematic bias in multi-scan procedures. Single-scan applications also benefit as they rely on pre-scans to determine the optimal scanner settings. These findings constitute a step towards standardization of microarray experiments and analysis and may help to increase the lab-to-lab comparability of microarray experiment results.
关键词： photobleaching,microarray,cyanine dye,bioanalytics,fluorophore,bioinformatics,DNA
更新于2025-09-23 15:22:29
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Regression Analysis of Protoporphyrin IX Measurements Obtained During Dermatological Photodynamic Therapy
摘要： Photodynamic therapy (PDT) is a light activated drug therapy that can be used to treat a number of dermatological cancers and precancers. Improvement of efficacy is required to widen its application. Clinical protoporphyrin IX (PpIX) fluorescence data were obtained using a pre-validated, non-invasive imaging system during routine methyl aminolevulinate (MAL)-PDT treatment of 172 patients with licensed dermatological indications (37.2% actinic keratosis, 27.3% superficial basal cell carcinoma and 35.5% Bowen’s disease). Linear and logistic regressions were employed to model any relationships between variables that may have affected PpIX accumulation and/or PpIX photobleaching during irradiation and thus clinical outcome at three months. Patient age was found to be associated with lower PpIX accumulation/photobleaching, however only a reduction in PpIX photobleaching appeared to consistently adversely affect treatment efficacy. Clinical clearance was reduced in lesions located on the limbs, hands and feet with lower PpIX accumulation and subsequent photobleaching adversely affecting the outcome achieved. If air cooling pain relief was employed during light irradiation, PpIX photobleaching was lower and this resulted in an approximate three-fold reduction in the likelihood of achieving clinical clearance. PpIX photobleaching during the first treatment was concluded to be an excellent predictor of clinical outcome across all lesion types.
关键词： photobleaching,aminolevulinic acid (ALA; Ameluz),dermatology,protoporphyrin IX (PpIX),imaging,methyl aminolevulinate (MAL; Metvix),photodynamic therapy (PDT),fluorescence,non-melanoma skin cancer (NMSC)
更新于2025-09-23 15:22:29
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Riboflavin-induced Type 1 photo-oxidation of tryptophan using a high intensity 365 nm light emitting diode
摘要： The mechanism of photo-oxidation of tryptophan (Trp) sensitized by riboflavin (RF) was examined employing high concentrations of Trp and RF, with a high intensity 365 nm light emitting diode (LED) source under N2, 20% and 100% O2 atmospheres. Dimerization of Trp was a major pathway under the N2 atmosphere, though this occurred with a low yield (DφTrp = 5.9 x 10-3), probably as a result of extensive back electron transfer reactions between RF●- and Trp(H)●+. The presence of O2 decreased the extent of this back electron transfer reaction, and the extent of Trp dimerization. This difference is attributed to the formation of O2●- (generated via electron transfer from RF●- to O2) which reacts rapidly with Trp● leading to extensive consumption of the parent amino acid and formation of peroxides and multiple other oxygenated products (N-formylkynurenine, alcohols, diols) of Trp, as detected by LC-MS. Thus, it appears that the first step of the Type 1 mechanism of Trp photo-oxidation, induced by this high intensity 365 nm light source, is an electron transfer reaction between the amino acid and 3RF, with the presence of O2 modulating the subsequent reactions and the products formed, as a result of O2●- formation. These data have potential biological significance as LED systems and RF-based treatments have been proposed for the treatment of pathological myopia and keratitis.
关键词： type 1/type 2 mechanisms,dimers,LED,N-formylkynurenine,trimers,riboflavin,photo-oxidation,electron transfer,photobleaching,tryptophan,triplet excited state
更新于2025-09-23 15:21:21
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Pulsed interleaved excitation-based line-scanning spatial correlation spectroscopy (PIE-lsSCS)
摘要： We report pulsed interleaved excitation (PIE) based line-scanning spatial correlation spectroscopy (PIE-lsSCS), a quantitative fluorescence microscopy method for the study of dynamics in free-standing lipid bilayer membranes. Using a confocal microscope, we scan multiple lines perpendicularly through the membrane, each one laterally displaced from the previous one by several ten nanometers. Scanning through the membrane enables us to eliminate intensity fluctuations due to membrane displacements with respect to the observation volume. The diffusion of fluorescent molecules within the membrane is quantified by spatial correlation analysis, based on the fixed lag times between successive line scans. PIE affords dual-color excitation within a single line scan and avoids channel crosstalk. PIE-lsSCS data are acquired from a larger membrane region so that sampling is more efficient. Moreover, the local photon flux is reduced compared with single-point experiments, resulting in a smaller fraction of photobleached molecules for identical exposure times. This is helpful for precise measurements on live cells and tissues. We have evaluated the method with experiments on fluorescently labeled giant unilamellar vesicles (GUVs) and membrane-stained live cells.
关键词： lipid bilayer membranes,dual-color excitation,live cells,line-scanning spatial correlation spectroscopy,fluorescence microscopy,tissues,GUVs,confocal microscope,photobleaching,Pulsed interleaved excitation
更新于2025-09-23 15:21:01
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Photobleaching Enables Super-resolution Imaging of the FtsZ Ring in the Cyanobacterium <em>Prochlorococcus</em>
摘要： Super-resolution microscopy has been widely used to study protein interactions and subcellular structures in many organisms. In photosynthetic organisms, however, the lateral resolution of super-resolution imaging is only ~100 nm. The low resolution is mainly due to the high autofluorescence background of photosynthetic cells caused by high-intensity lasers that are required for super-resolution imaging, such as stochastic optical reconstruction microscopy (STORM). Here, we describe a photobleaching-assisted STORM method which was developed recently for imaging the marine picocyanobacterium Prochlorococcus. After photobleaching, the autofluorescence of Prochlorococcus is effectively reduced so that STORM can be performed with a lateral resolution of ~10 nm. Using this method, we acquire the in vivo three-dimensional (3-D) organization of the FtsZ protein and characterize four different FtsZ ring morphologies during the cell cycle of Prochlorococcus. The method we describe here might be adopted for the super-resolution imaging of other photosynthetic organisms.
关键词： Prochlorococcus,photobleaching,FtsZ ring,Immunology and Infection,STORM,cell division,cyanobacterium,super-resolution imaging,three-dimensional,Issue 141
更新于2025-09-23 15:21:01
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Early-stage identification of encapsulants photobleaching and discoloration in crystalline silicon photovoltaic module laminates
摘要： Commercially different variants of ethylene-vinyl acetate (EVA) encapsulants are available in the photovoltaic (PV) market. Photobleaching and discoloration are the two most commonly observed phenomena, and their initiation may be different for different encapsulants. To investigate the EVA encapsulant photobleaching and discoloration, solar cell laminates having different EVA films (UV-transparent [T], UV-cut [C], and combination of the two [TC]) were tested in Xenon test chamber. High temperatures are created in the laminates during the aging tests by using a thick insulation layer behind the backsheet. The UV fluorescence images and grayscale profile show clear signs of photobleaching and discoloration. It is found that the oxygen diffusion coefficient of the T sample is four and nine times slower than the TC and C samples, respectively, in the photobleached region. Fluorescence imaging and spectra and Raman spectra were taken before and after the accelerated test and indicate that discoloration causing fluorophores generation is higher after the photobleached region for transparent and combined EVAs, whereas higher at the center for UV-cut EVA laminates. A colorimeter was used to measure the Yellowness Index of the samples before and after the accelerated aging test. This work will help in the early detection of photobleaching and discoloration of any encapsulant used in the PV modules. This method will also help to study the behavior of encapsulants in different climatic conditions like hot, cold, dry, humid, and their combinations by simulating the same in an accelerated weathering chamber by using the different insulation thickness.
关键词： fluorophores,discoloration,photovoltaic module,photobleaching,ethylene-vinyl-acetate encapsulant
更新于2025-09-23 15:19:57
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Biodegradable and Photostable Nb2C MXene Quantum Dots as Promising Nanofluorophores for Metal Ions Sensing and Fluorescence Imaging
摘要： Conventional fluorescent probes are either easily photobleached or non-biodegradable, which often leads to the unstable fluorescence signal output and long-term biological toxicity. Therefore, the development of novel fluorescent materials with both excellent photostability and biodegradability is of great significance for further broadening their application in numerous research fields. In this work, Nb2C quantum dots (Nb2C QDs) with pristine crystallographic structures of Nb2C MXene phases and surface oxygen-containing species are synthesized by an ultrasound assisted physicochemical exfoliation in tetrapropylammonium hydroxide. Detailed analyses indicate that the Nb2C QDs not only possess excellent chemical- and photo-stable fluorescence emission but also achieve successful application in fluorescence sensing of heavy metal ions and fluorescence imaging. More importantly, it is confirmed that the Nb2C QDs present high biocompatibility and unique biodegradation property responsive to human myeloperoxidase, implying the application safety of Nb2C QDs in vivo. Under the background of ever-growing and stringent requirements for biosafety and technical stability, the biocompatibility, biodegradability, and most importantly the promising fluorescence sensing/imaging characteristic of the obtained Nb2C QDs may argue well for their future applications in environmental monitoring, biomedical diagnosis, visual display, and anti-counterfeiting.
关键词： MXene quantum dots,biodegradation,fluorescent probes,fluorescence imaging,photobleaching resistance
更新于2025-09-16 10:30:52
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Photobleaching of Submicron DAST Crystals in a PMMA Film by Direct Laser Writing
摘要： Selective photobleaching of DAST (trans-4'-(dimethylamino)-Nmethyl-4-stilbazolium tosylate) non-linear crystals in a 2-μ m-thick polymethacrylate film using direct laser writing at a wavelength of 532 nm at a power of 1–10 mW and a recording speed of 5–35 μ m/s is studied. The laser pattern is established as a function of recording parameters. The destruction of crystals and their transition into the amorphous state enabled one to record a structure that is well resolved in the optical microscope and in the luminescence signal. No layer surface violation at the crystal damage sites is detected. The method ensures the formation of a grating with a periodic modulation of the nonlinearly optical coefficient, which is essential in the quasi-phasematching generation.
关键词： nonlinear optics,DAST,2D grating,photobleaching
更新于2025-09-12 10:27:22