Fluorescence Peak Research Articles

EXTH-39. A BENCH-TOP MODEL FOR THE OPTIMIZATION OF ULTRASOUND PARAMETERS FOR SONODYNAMIC THERAPY OF GLIOBLASTOMA

Abstract BACKGROUND In-vitro studies have demonstrated that low frequency sound waves can interact with hemo-porphyrin molecule to induce the production of reactive oxygen species. This biophysical phenomenon can induce tumour cell death in glioblastoma cells in-vitro. The purpose of this study was to evaluate the production of reactive oxygen species and expression of apoptotic markers in glioblastoma cells in response to varying total treatment time and ultrasound power using a bench-top focused ultrasound (FUS) device. METHODS U251 cells were exposed to 5-Aminolevulenic Acid (5-ALA) at varying concentrations for up to 24 hours. The time point with peak proto-porphyrin IX (PPIX) fluorescence was established using fluorescence activated cell sorting (FACS). A transducer utilized at 0.91MHz was placed on an inverted stage with the focus targeted to the bottom of a standard 96-well cell culture plate. Pressure wave delivery was confirmed using a hydrophone. GBM cells were treated with 5-ALA alone, FUS alone, or 5-ALA + FUS and the cells were incubated for 24 hours prior to measuring ROS induction and cell death. ROS was measured using FACS with the CellROX Green Kit for Oxidative Stress Detection and Annexin-V was measured using the Dead Cell Stain Kit. RESULTS Peak fluorescence intensity for PPIX in the U251 cell line was found to be induced through incubation with 5-ALA for 24 hours with a concentration 200mg/mL. The fluorescence intensity of PPIX was found to be 313% greater in the treated group compared to the control group. Peak ROS was observed using a 0.91MHz transducer frequency for a total time of 120s with 6W average power. ROS was 61% and 66% greater in the SDT group compared to the FUS and 5-ALA group respectively. CONCLUSION Using this bench-top set up we successfully induced ROS and apoptosis in U251 cells. Establishing a reliable in-vitro model will allow us to further investigate the effects of other sonication parameters such as burst length.

On-Off Switching of Singlet Self-Trapped Exciton Emission Endows Antimony-Doped Indium Halides with Excitation-Wavelength-Dependent Luminescence.

Excitation-wavelength-dependent (Ex-De) emitters are a fascinating category of luminescent materials whose emission properties vary with the wavelength of the light used for excitation. Antimony (Sb3+)-doped indium (In)-based metal halides are efficient light emitters; however, the peak fluorescence emission of most Sb3+-activated In-halide remains independent of the excitation wavelength. Here, the study introduces a new Sb3+-doped In-halide cluster, (BDPA)2InCl5:Sb (BDPA+ = C15H18N+, benzyldimethylphenylammonium), which demonstrates efficient Ex-De emission originating from the on-off switchable fluorescence behavior of singlet self-trapped exciton (STE) in 5-coordinate Sb3+ dopant. Interestingly, when excited within the range of 240-370nm, photoluminescence (PL) spectra of (BDPA)2InCl5:Sb show both singlet and triplet STE emission. However, under excitation wavelengths of 370 to 420nm, the singlet STE emission is absent, resulting in a noticeable correlated color temperature change from 1700 to 3800 K. The study provides a new approach to designing color-tunable Sb3+-based luminophores, and also presents a novel application scenario for the widely recognized Sb3+ doping strategy.

Light on abnormal red blood cell subpopulations: Label-free optics-based approach for studying in vitro rigidified blood cells

RBC deformability plays a crucial role in maintaining proper blood flow and oxygen delivery throughout the body. Conventional ektacytometry fails to differentiate between variations in RBC subpopulation deformability as the averaging measurement process obscures these differences. In this study, we introduced an approach that integrates label-free optics-based techniques (flow cytometry, phase-contrast, and two-photon excitation fluorescent microscopy) with ektacytometry to evaluate subpopulations that exhibit decreased RBC deformability upon an in vitro oxidation using 0.5 mM TBHP, as a low-level oxidative agent.We found that flow cytometry can easily detect rigidified and oxidized subpopulations based on FSC/SSC light distribution, as well as RBC fluorescence intensity and peak area likely originating from hemoglobin photo and/or degradation products. Two-photon excitation fluorescence microscopy proved altered morphology and spatial location of fluorescence intensity signal near the membrane of oxidized RBCs, when compared to control RBC, indicating a link with the reduced deformability. The proposed label-free optics-based methodology, which combines established techniques with more sophisticated microscopy, emerges as a promising tool for detecting mechano-biological changes in different RBC subpopulations induced by oxidative stress. The findings suggest potential applications in clinical practice for monitoring pathological conditions influenced by physical or environmental stress and as a quality control measure for stored RBCs.

Mitigating Membrane Fouling in Abattoir Wastewater Treatment: Integration of Pretreatment Step with Zwitterion Modified Graphene Oxide–Polyethersulfone Composite Membranes

Composite polyethersulfone (PES) membranes containing N-aminoethyl piperazine propane sulfonate (AEPPS)-modified graphene oxide (GO) were integrated with either of the two pretreatment processes (activated carbon (AC) adsorption or polyelectrolyte coagulation) to assess their effectiveness in mitigating membrane fouling during the treatment of abattoir wastewater. The AEPPS@GO-modified membranes, as compared to the pristine PES membranes, showed improved hydrophilicity, with water uptake increasing from 72 to 118%, surface porosity increasing from 2.34 to 27%, and pure water flux (PWF) increasing from 235 to 673 L.m−2h−1. The modified membranes presented improved antifouling properties, with the flux recovery ratio (FRR) increasing from 59.5 to 93.3%. This study compared the effectiveness of the two pretreatment processes, AC, coagulation, and the integrated system (coagulation/AC-UF membrane), in the removal of natural organic matter (NOM) and improvement of abattoir wastewater’s pH, electrical conductivity, TDS, and turbidity. The integrated systems produced improved water quality in terms of pH, EC, TDS, turbidity, and organic content. The fluorescence excitation–emission matrix (FEEM) analysis exhibited almost no fluorescence peak post-treatment following organic loading removal. The quality of the water met the South African non-potable water reuse standards. The sole membrane treatment systems exhibited good fouling resistance without the pretreatment systems; however, integrating these systems can offer extended longer filtration periods, thereby assisting in cost aspects of the abattoir wastewater treatment system.

Aqueous photochemical aging of water-soluble smoke particles from crop straws burning

Most aqueous oxidation studies focus on single model precursors, while the photochemical aging of actual water soluble organic matter (WSOM) in particles emitted from biomass burning remains poorly understood. In this study, gas chromatography-mass spectrometry (GC/MS) was first used to analyze the WSOM in smoke particles emitted from three crop straws burning. The results show that the dominant WSOM in three crop straws (CS) smoke are phenolic substances with small differences. Aqueous photochemical aging of WSOM in CS smoke was investigated under simulated sunlight exposure. High-resolution aerosol mass spectrometry (HR-AMS) analyzed aqueous secondary organic aerosol (aqSOA) and it was found that the oxidation degree of aqSOA increased with prolonged aging. No obvious increase in the abundance of N-containing organic ions was observed over the course of aqueous aging. As aqueous aging progresses, the pH of the solution gradually decreases, accompanied by the continuous generation of organic acids. Studies on dithiothreitol (DTT) activity indicate that the impact of aqueous photochemical aging on health is not significant.The solution after photoaging shows relatively lower light absorption ability than the initial solution. The aqueous photochemical aging also led to a gradual reduction of fluorescence at excitation/emission = 250–260 nm/350 nm (protein-like substances) for CS smoke WSOM, suggesting the significant degradation of chromophores. However, three-dimensional excitation-emission matrix (EEM) fluorescence combined with parallel factor analysis (PARAFAC) revealed that aqueous aged CS smoke WSOM contains compounds with high humification index, confirming that the fluorophore composition is altered by aqueous aging. The humic-like substance (HULIS) concentration increased for the first 3 h and then decreased, closely matching the pattern of a new fluorescence peak. Finally, GC/MS analysis of the products indicated that there was obvious decline in proportion of methoxyphenol. The results of this study are important for understanding the aqueous-phase oxidation reactions of CS smoke WSOM in the atmosphere and their light-absorption characteristics and health impacts.

Multi‐Channel Optical Encryption Film With Strong Circularly Polarized Luminescence and High Quantum Yield

AbstractDeveloping a sustainable security module with multiple optical states is important to deter counterfeits, but is challenging. This work designs a kind of chiral luminescent film through the co‐assembly of the CNCs and d‐glucose, simultaneously doped with the lanthanide complex and organic dye. Superior mechanical performance makes it undertake various deformations, including twist, and tension without breaking. Meanwhile, this film has unique optical characteristics. On the one hand, the chiroptical signals can be manipulated through the matching of the photonic bandgap and fluorescence peak. On the other hand, due to the co‐assembly with two luminophores, the film displays the excitation wavelength (Ex)‐dependent circularly polarized luminescence properties. Under the Ex of 275 nm, the film simultaneously integrates a large dissymmetry factor of −0.3898, a high quantum yield of 69.19%, and a considerable lifetime of 1381 µs, which has exceeded most reported chiral luminescent assemblies. These multimodal and convertible optics endow the film with practical applications in the anti‐counterfeit. It can be designed as a security label or used as a written paper to encrypt the information. Even in humid surroundings, this security effect is still ensured.

Single-Extracellular-Vesicle Detection with a Plasmonic Chip and Enhanced Fluorescence Microscopy.

Endocytosis-derived extracellular vesicles (EVs), which can be as small as 100 nm, are useful for disease prediction. However, very small EVs are below the optical diffraction limit and are difficult to visualize with conventional fluorescence microscopy. In this study, single EVs captured on a plasmonic chip, where fluorescently labeled antibodies were bound over the EV surface, were detected as bright spots using plasmon-field enhanced fluorescence without any pretreatment of isolating labeled EVs, followed by analyzing the full width at half-maximum and the fluorescence peak value for each enhanced fluorescence bright spot. Bright spots smaller than the threshold determined by the observation of the fluorescent nanospheres were attributed to single EVs. The number of single EVs was quantitatively evaluated against the concentration of EV solution injected in the 1.4 pM-95 fM range. Furthermore, single EVs were detected by labeling two different membrane proteins. A molecularly imprinted polymer was applied to a capture interface on a plasmonic chip, and it is found that nonspecific adsorption of aggregates was suppressed. To accurately distinguish single EVs from aggregates of labeled antibodies, the fluorescence microscopy with transmitted light was superior to the epifluorescence method. Finally, single EVs were successfully detected with multiple targets at multiple wavelengths by using different fluorescently labeled antibodies.

Enhancing salt-induced gelation of egg yolk granules through pH-ultrasound combined treatment: A physicochemical and microstructural analysis

Salted duck eggs are a popular food product, but their high salt content and uneven salt distribution can reduce acceptability. This study investigated the effects of pH-high-intensity ultrasound combined treatment on the salt-induced gelation properties of egg yolk granules. The results showed that the pH5 + 150 W treatment group exhibited the best physical and gelation properties, with the smallest particle size (1597.33 nm), optimal dispersibility (PDI 0.29), and good stability. The gelation properties of this group also demonstrated excellent springiness (0.30 mm), cohesiveness (0.56), and gumminess (0.05 N). Furthermore, the pH5 + 150 W group had the highest water holding capacity of 97.42 % and relatively high hydrophobicity (173.39 μg). Notably, it also showed high oil exudation (2.83 %) and good sandiness (62.07 %). The pH5 + 150 W led to a significant redshift of the fluorescence peak at 335 nm and an enhancement of the peak intensity at 562 nm compared to the control group. Structural characterization revealed a more ordered protein structure and a uniform gel structure with enhanced electrostatic repulsion between oil droplets. Secondary structure analysis of the proteins showed a significant reduction in α-helix and β-sheet, while β-turn and random coil increased. In summary, the pH5 + 150 W treatment displayed the best gelation properties, providing theoretical guidance for enhancing the processing performance of yolk and expanding their application in the food industry.

Simulating High-Resolution Sun-Induced Chlorophyll Fluorescence Image of Three-Dimensional Canopy Based on Photon Mapping

The remote sensing of sun-induced chlorophyll fluorescence (SIF) is an emerging technique with immense potential for terrestrial vegetation sciences. However, the interpretation of fluorescence data is often hindered by the complexity of observed land surfaces. Therefore, advanced remote sensing models, particularly physically based simulations, are critical to accurately interpret SIF data. In this work, we propose a three-dimensional (3D) radiative transfer model that employs the Monte Carlo ray-tracing technique to simulate the excitation and transport of SIF within plant canopies. This physically based approach can quantify the various radiative processes contributing to the observed SIF signal with high fidelity. The model’s performance is rigorously evaluated by comparing the simulated SIF spectra and angular distributions to field measurements, as well as conducting systematic comparisons with an established radiative transfer model. The results demonstrate the proposed model’s ability to reliably reproduce the key spectral and angular characteristics of SIF, with the coefficient of determination (R2) exceeding 0.98 and root mean square error (RMSE) being less than 0.08 mW m−2 sr−1 nm−1 for both the red and far-red fluorescence peaks. Furthermore, the model’s versatile representation of canopy structures, enabled by the decoupling of radiation and geometry, is applied to study the impact of 3D structure on SIF patterns. This capability makes the proposed model a highly attractive tool for investigating SIF distributions in realistic, heterogeneous canopy environments.

Use of the 5P3/2→6P3/2 electric dipole forbidden transition in Rb as a non-perturbing probe of atom dynamics in an operating magneto-optical trap

Abstract Results of spectroscopy experiments using the $5P_{3/2} \to 6P_{3/2}$ electric dipole forbidden transition in cold rubidium atoms are presented. Production of this forbidden transition is detected by observing the emission of the $420 $ nm fluorescence photons that result from the decay of the $6P_{3/2} $ state into the ground state. The experiments are performed under the steady state operation conditions of a magneto-optical trap (MOT), and thus provide non-perturbing information on the atom-light system. The hyperfine structure of the $6P_{3/2}$ level is completely resolved, and the fluorescence peaks show the expected Autler-Townes (AT) splitting of the emission lines. This hyperfine structure is used to calibrate the frequency scale of all spectra recorded. A combination of this absolute frequency scale and an expression for the AT profile allows an absolute determination of the effective Rabi frequency and detuning of the MOT. The behavior of these AT doublets is studied as a function of frequency detuning and also as a function of the trapping light intensity.
The experiments also take full advantage of the strong polarization dependence of the relative intensities of the hyperfine fluorescence components.
This study results in a sensitive probe of the relative populations of the magnetic sublevel projections relative to the trapping magnetic field gradient.
An almost isotropic population distribution was found, but small deviations from isotropy could be determined with this electric dipole forbidden probe.

Photovoltaic Molecule-Based Phototheranostics With A-D-A Structure for Near-Infrared Fluorescence Imaging-Guided Synergetic Photodynamic and Photothermal Therapy of Tumors.

Phototheranostics with near-infrared fluorescence and reactive oxygen species generation ability and high photothermal conversion efficiency (PCE) plays a significant role in fluorescence imaging-guided synergetic photodynamic and photothermal therapy of tumors. Here, a star molecule in organic photovoltaic materials, NCBDT-4C with an A-D-A conjugated structure, was assembled with DSPE-PEG-NH2 to prepare water dispersive nanoparticles (NPs). The prepared NCBDT-4Cl NPs exhibited a maximum NIR absorption peak at 764 nm and a maximum fluorescence peak at 798 nm. These NPs could generate superoxide anion, singlet oxygen (1O2), and heat under 808 nm laser irradiation. The 1O2 generation quantum yield and PCE of the NPs were 37.5% and 53.6%, respectively. The combination of photodynamic and photothermal therapy of cancer was demonstrated invitro and invivo. This work presents the advanced application of organic photovoltaic materials in cancer phototherapy.

Opalescence and Fluorescence of 46 Resin-Based Composites Exposed to Ultraviolet Light

Identifying the boundary between the tooth and the resin-based composite (RBC) is difficult when replacing restorations. Ultraviolet (UV) light has been reported to assist the viewer by causing the RBC to fluoresce. Using a laboratory-grade fiberoptic spectrometer, 46 RBCs were exposed to UV light from the Woodpecker O-Star curing light. The opalescence and fluorescence were measured relative to a human tooth that contained just dentin and a tooth that contained both enamel and dentin. After these quantitative measurements, 10 RBCs with large differences in light emittance were compared qualitatively to assess their brightness when exposed to UV light compared to the dentin specimen and the specimen containing both enamel and dentin. It was found that, when exposed to UV light, some of the RBCs were less bright compared to the two samples of teeth used for comparison, but most were brighter; some were up to six times brighter. The filler appears to affect the opalescence peaks, while the resin appears to affect the fluorescence peaks. It was concluded that because RBCs emit very different levels of opalescence and fluorescence, UV light from the Woodpecker O-Star cannot be relied upon to detect all brands of RBC on the tooth. The opalescence and fluorescence can also be used to detect changes in the formulation of the RBC.

Adsorption and detection of praseodymium ion by ion-imprinted polymer with ultra-low sensitivity.

A novel kind of carbon dot (CD) was prepared by one-step hydrothermal microwave assisted method using L-tryptophan and L-tartaric acid as raw materials. Monodisperse poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) microspheres were utilized as the matrix, with praseodymium (Pr) ion (Pr3+) as the template, methacrylic acid as the functional monomer, and 5-amino-8-hydroxyquinoline (5-AHQ) acts as the ligand. A composite microsphere of ion-imprinted polymer (IIP) and CD (noted CD@IIP) was prepared by surface-initiated atom transfer radical polymerization (SI-ATRP). For comparison, IIP without CD (Pr-IIP) and non-imprinted polymer (NIP) were also prepared. Through static adsorption experiments, it was determined that the saturated adsorption amount of CD@IIP is 47.19mgg-1, that of Pr-IIP is 54.49mgg-1, while that of NIP is only 24.32mgg-1. Dynamic adsorption experiments showed that the equilibrium of three kinds of materials wasreached within 30min. Particularly, CD@IIP could emit two fluorescence peaks at 325nm and 421nm under ultraviolet irradiation, and exhibited excellent selectivity and fluorescence quenching effect on Pr3+. The fluorescence response of Pr3+ in the range 0-400μmol L-1 was determined by ratiometric fluorescence method, offering a two-stage model and robust linear regression coefficient. These results demonstrated that CD@IIP exhibited selective adsorption ability for Pr3+, and a sensitive, rapid and simple method for detection of Pr3+ was successfully developed.

In-Situ X-ray Diffraction/Fluorescence Analysis of Dy–Cu Electrochemical Alloying and Dealloying in Molten LiCl–KCl–DyCl3

Recycling spent Nd magnets is essential for maintaining a stable supply of rare earth (RE) elements prompting the development of a one-step recycling process using molten salt and alloy diaphragms. In this study, to investigate the mechanism of rapid alloy formation, an in-situ X-ray diffraction/fluorescence analysis of Dy–Cu electrochemical alloying and dealloying in molten LiCl–KCl–DyCl3 was performed. During the electrolysis, a diffraction peak corresponding to Cu was observed. In addition, X-ray fluorescence peaks of Dy were observed throughout the process. The area of the Dy X-ray fluorescence peak increased as the alloying progressed but remained relatively constant during the dealloying process. Compared with Dy–Ni alloying/dealloying, the areas of the fluorescence peaks were smaller. The results suggest a slower alloy formation rate with Cu than with Ni. Cross-sectional images show that the alloy formation rate is lower for Cu, which can be attributed to a larger crystal mismatch between the substrate and alloyed layer.

Cobalt oxyhydroxide nanoflakes enable ratiometric fluorescent assay of gallic acid

Gallic acid (GA) is widely used in beverages, food, and other fields as antioxidant. However, GA is slightly toxic and the accumulation of GA is harmful to human body. Therefore, it's vital to develop simple and sensitive detection methods for GA. In this work, a novel ratiometric fluorescent nanoprobe (named CoOOH/OPD/SiNPs) for the GA detection in different foods was designed and prepared. The fluorescence of silicon nanoparticles (SiNPs) at 443 nm would be quenched by cobalt oxyhydroxide (CoOOH) nanoflakes. o-phenylenediamine (OPD) would be oxidized to 2,3-diaminophenazine (DAP) by CoOOH nanoflakes that have peroxidase-like activity, which produces a new fluorescent peak at 556 nm. Meanwhile, SiNPs' fluorescence would be quenched through DAP due to inner filter effect (IFE). With the addition of GA, the reductive decomposition of CoOOH decreased DAP level, causing IFE being restrained. The concentration of GA indicates an excellent linear relationship with fluorescence ratio (F443/F556) in range of 0.4–12 μM (R2 = 0.9937) with 0.16 μM detection limit. This nanoprobe is applied to GA detection in water, tea leaves, fruits and nut fruits, which would be expected to act as a portable device for complex substances analysis.

Yellow Emissive Carbon Dots - A Robust Nanoprobe for Highly Sensitive Quantification of Jaundice Biomarker and Mitochondria Targeting in Cancer Cells.

The abnormally high level of bilirubin (BR) in biofluids (human serum and urine) indicates a high probability of jaundice and liver dysfunction. However, quantification of BR as the Jaundice biomarker is difficult due to the interference of various biomolecules in serum and urine. To address this issue, we developed a fluorescence-based detection strategy, for which yellow emissive carbon dots (YCDs) were produced from a one-step solvothermal process using phloroglucinol and thionin acetate as chemical precursors. The as-fabricated YCDs exhibited a strong fluorescence peak at the wavelength of 542 nm upon excitation at 390 nm. We used YCDs for detecting BR through the fluorescence turn-off mechanism, unveiling the excellent sensitivity in the linear range of 0.5-12.5 μM with a limit of detection (LOD) of 9.62 nM, which was far below the clinically relevant range. The analytical nanoprobe also offered excellent detection specificity for quantifying BR in real samples. Moreover, the biocompatible fluorescent nanoprobe was successfully employed to target mitochondria in live cancer cells. A colocalization study confirmed that YCDs possessed the ability to target mitochondria and overlapped completely with MitoTracker Red. The developed nanoprobe of YCDs turned out to be straightforward in their synthesis, noninvasive, and can be utilized for biomedical sensors to diagnose the onset of jaundice as well as for mitochondria targeting.

Design and synthesis of a 2,5-Diarylthiophene chromophore for enhanced near-infrared two-photon uncaging efficiency of calcium ions

The design and synthesis of two-photon-responsive chromophores have recently garnered significant attention owing to their potential applications in materials and life sciences. In this study, a novel π-conjugated system, 2-dimethylaminophenyl-5-nitrophenylthiophene derivatives, featuring a thiophene unit as the π-linker between the donor (NMe2C6H4–) and acceptor (NO2C6H4–) units was designed, synthesized, and applied for the development of two-photon-responsive chromophores as a photoremovable protecting group in the near-infrared region. Notably, the positional effect of the nitro group (NO2), meta versus para position, was observed in the uncaging process of benzoic acid. Additionally, while the para-isomer exhibited a single fluorescence peak, a dual emission was detected for the meta-isomer in polar solvents. The caged calcium ion (Ca2+) incorporating the newly synthesized thiophene unit exhibited a sizable two-photon absorption cross-section value (σ2 = 129 GM at 830 nm). Both one-photon and two-photon photoirradiation of caged calcium ions successfully released calcium ions, indicating the potential utility of 2,5-diarylthiophene derivatives in future biological studies.Graphical abstract

A europium (III) functionalized hydrogen-bonded organic framework for sensitively ratiometric fluorescent sensing of tetracycline.

As a kind of antibiotic, tetracycline (TC) might remain in animal blood and milk products during use, which poses a risk to humans after consumption. Therefore, a ratiometric fluorescence probe was proposed for the detection of TC, which was based on anEu3+ functionalized hydrogen-bonded organic framework (HOF). Since there are alarge number of N and O atoms in the skeleton of HOF, more Eu3+ could be loaded onto HOF by forming coordinate bonds, while preserving the fluorescence of luminol monomer in HOF. In the presence of TC, the fluorescence of luminol monomer was attenuated at 425nm due to inner filter effect (IFE), while TC selectively enhanced the fluorescence peak at 617nm of Eu3+ under the influence of antenna effect (AE). This highly sensitive probe could detect TC in the range of0.1-60μM and had a low limit ofdetection of 8.51nM. Besides, the HOF@Eu probe was able to detect TC in actual samples (milk and tap water) with good recoveries (95.09%-111.51%) and precision (R < 4.78%), indicating this probe has great application potential forthe detection of TC in food.

Asymmetricity in fluorescence peaks of a three level Λ-type quantum emitter placed near a spherical metal nanoparticle

Abstract A generalized master equation is derived here for a hybrid three level Λ-type quantum emitter-metal nanoparticle (MNP) system in the presence of strong external fields. With this new master equation, we show the spectral reshaping of the fluorescence peaks leading to asymmetric peak heights. This asymmetricity is attributed to dressed state-reservoir coupling and strong coherent fields. The coupling of reservoir with dressed states results in different sampling of local density of states (LDOS) of the vacuum field by dressed state transitions, giving different transition probabilities to each peak. We have further explored the directional features of the resonance fluorescence spectrum in the hybrid system. These observations of spectral reshaping in a three-level-MNP system opens new directions for studying tunable electromagnetically induced transparency utilizing ‘tailored vacuum’ in quantum plasmonics.

The effect of fluence rate and wavelength on the formation of protoporphyrin IX photoproducts

Photodynamic diagnosis and therapy (PDD and PDT) are emerging techniques for diagnosing and treating tumors and malignant diseases. Photoproducts of protoporphyrin IX (PpIX) used in PDD and PDT may be used in the diagnosis and treatment, making a detailed analysis of the photoproduct formation under various treatment and diagnosis conditions important.Spectroscopic and mass spectrometric analysis of photoproduct formation from PpIX dissolved in dimethyl sulfoxide were performed under commonly used irradiation conditions for PDD and PDT, i.e., wavelengths of 405 and 635 nm and fluence rates of 10 and 100 mW/cm2. Irradiation resulted in the formation of hydroxyaldehyde photoproduct (photoprotoporphyrin; Ppp) and formyl photoproduct (product II; Pp II) existing in different quantities with the irradiation wavelength and fluence rate. Ppp was dominant under 635 nm irradiation of PpIX, with a fluorescence peak at 673 nm and a protonated monoisotopic peak at m/z 595.3. PpIX irradiation with 405 nm yielded more Pp II, with a fluorescence peak at 654 nm. A higher photoproduct formation was observed at a low fluence rate for irradiation with 635 nm, while irradiation with 405 nm indicated a higher photoproduct formation at a higher fluence rate.The photoproduct formation with the irradiation conditions can be exploited for dosimetry estimation and may be used as an additional photosensitizer to improve the diagnostics and treatment efficacies of PDD and PDT. Differences in environmental conditions of the present study from that of a biological environment may result in a variation in the photoproduct formation rate and may limit their clinical utilization in PDD and PDT. Thus, further investigation of photoproduct formation rates in more complex biological environments, including in vivo, is necessary. However, the results obtained in this study will serve as a basis for understanding reaction processes in such biological environments.Graphical abstract