Peak Fluorescence Intensity Research Articles

Effects of microwave-vacuum pre-treatment with different power levels on the structural and emulsifying properties of lotus seed protein isolates

The present study investigated the changes in structural and emulsifying properties of lotus seed protein isolates (LSPIs) under different microwave-vacuum (MV) treatments. A decrease of fluorescence peak intensity with blue-shift of the fluorescence emission maximum indicated that MV treatment induced unfolding of LSPIs so that more hydrophobic residues were exposed. Raman spectra showed that the ordered secondary structures (α-helix, β-sheet) gradually converted into β-turns and random coils during 50–150 W MV treatment. Particle size distribution and atomic force microscope revealed that the amounts of small subunits increased when the LSPIs were modified by 50–100 W MV treatment. Emulsions prepared by 100-W-MV-LSPIs exhibited the optimal emulsifying ability with the smallest oil droplet sizes. Confocal laser scanning microscopy and analytical centrifugal analyzer further proved 50–100 W MV-treatment enhanced the flocculation and creaming stability. Our findings provide a certain theoretical foundation to apply MV technology for developing desirable LSPIs-stabilized emulsions.

Comments on EuroFlow standard operating procedures for instrument setup and compensation for BD FACS Canto II, Navios and BD FACS Lyric instruments

This commentary discusses particularities of application of the EuroFlow standardization of flow cytometric analyses on three different flow cytometers. The EuroFlow consortium developed a fully standardized approach for flow cytometric immunophenotyping of hematological malignancies and primary immunodeficiencies. Standardized instrument setup is an essential part of EuroFlow standardization. Initially, the EuroFlow Consortium developed and optimized a step-by-step standard operating procedure (SOP) to setup 8-color BD FACSCanto II flow cytometer (Canto), with the later inclusion of Navios (Beckman Coulter) and BD FACSLyric (Lyric). Those SOPs were developed to enable standardized and fully comparable fluorescence measurements in the three flow cytometers. In Canto and Navios, mean fluorescence intensity (MFI) of a reference peak of Rainbow beads calibration particles is used to set up photomultiplier (PMT) voltages for each detector channel in individual instruments to reach the same MFI across distinct instruments. In turn, a new feature of Lyric instruments allows to share collection of attributes that are used to place the positive population at the same position among instruments in the form of assays, as one of its components integrated in the Cytometer Setup and Tracking (CS&T) module. The EuroFlow Lyric assays thus allow for standardized acquisition of 8-color EuroFlow panels on Lyric without the need to setup the PMT voltages on the individual instruments manually.In summary, the standardized instrument setup developed by EuroFlow enables cross-platform inter- and intra-laboratory standardization of flow cytometric measurements. This commentary provides a perspective on the modifications of the standardized EuroFlow instrument setup of Canto, Navios and Lyric instruments that are described in detail in individual instrument-specfic SOPs available at the EuroFlow website.

P6314Left- versus Bi-Ventricular Assist Device-mediated anti-HLA alloantibody induction in bridge-to-transplantation patients

Abstract Background Presence of anti-Human Leukocyte Antigen (anti-HLA) alloantibodies (allosensitization) in a heart transplantation candidate impedes the chance of finding a compatible transplant. Left Ventricular Assist Devices (LVADs) have been shown to induce allosensitization. Purpose The purpose of this study is to characterize anti-HLA allosensitization in adult patients receiving left (LVAD) versus biventricular- (BiVAD) assist devices as bridge to transplantation (BTT). Methods This study retrospectively assessed anti-HLA antibody induction in all adult patients who have received either LVAD or BiVAD as BTT at our institution. Anti-HLA alloantibody screening was performed before, and at multiple time-points after VAD implantation. Anti-HLA antibody detection was performed with a cytotoxic panel-reactive antibody (PRA) method until 2003, enzyme-linked immunoassay (ELISA) method from 2003 to 2005 and SAB assays on the Luminex platform from 2005 to 2017. Sensitization was defined either as PRA >10%, or as peak anti-HLA antibody mean fluorescence intensity (MFI) values of more than 1000. Baseline characteristics and sensitization in the two patient groups were evaluated using descriptive statistics. Results Between 2003 and 2018, 154 patients were placed on VAD support at our institution as BTT. Sensitization data were available for 130 patients. Fifty five (36.6%) patients were supported with an LVAD (median age, 48 years, 26% female) and 95 (63.4%) with a BiVAD (median age, 45 years, 28% female). Twenty-five (45.4%) of the LVAD and 49 (51.2%) of the BiVAD patients were eventually transplanted (p=0.47) with an average time to transplantation 588 and 562 days respectively. Fifteen (27.2%) LVAD and 35 (36.8%) BiVAD patients died before transplantation (p=0.23) with an average time on VAD support before death 269 and 302 days respectively. Evidence of sensitization pre-VAD was found in 17.1% of the LVAD and 12.5% of the BiVAD patients (p=0.53); these percentages rose to 40.0% (p=0.001) and 43.7% (p=0.0001) respectively at 2 to 12 months post-VAD implantation. However, the post-VAD allosensitization status was not statistically different between the LVAD and the BiVAD group. Among the 25 LVAD patients who were transplanted 7 (30.4%) were sensitized immediately before transplantation, compared to 22 (46.8%) out of 49 BiVAD patients (p=0.16). Conclusion Both LVADs and BiVADs are a factor of de novo anti-HLA antibody development in adult patients after implantation. Sensitization pattern does not seem to differ between LVAD and BiVAD patients. Additionally, patients supported by LVAD or BiVAD have similar chances of finding a suitable donor heart.

The chemical fingerprint of solubilized organic matter from eroded soils and sediments

Organic matter (OM) transfers between solid and water phases are critical components of OM cycling in surface waters as they contribute to compositional differences between dissolved OM (DOM) and particulate OM (POM). However, fractionation effects during such phase changes are not well-characterized, especially during the release of soluble OM from sediments and eroded soils. Agricultural practices alter the magnitude and timing of OM export and constitute a major source of sediment through soil erosion. This study assessed the elemental, biomolecular, and optical characteristics of DOM solubilized from sediments and soils in an agricultural watershed of northern California to trace compositional changes during OM flow from mobilized soils in streams. Relative to mineral-bound OM, solubilized DOM was nitrogen-poor (more than doubled C:N ratios) and depleted in amino acids and lignin (three- to six-fold decrease in carbon-normalized yields). Distinct fractionation patterns of individual amino acids and lignin phenols led to a more acidic pool of solubilized DOM that appeared substantially more degraded than its source POM, with decreased degradation index (DI) values and more than doubled molar contributions of non-protein amino acids and processing ratio (PR) values. Lignin composition also greatly differed in solubilized DOM compared to mineral-bound OM, with cinnamyl:vanillyl phenol ratios up to six-fold lower in solubilized lignin than in particulate lignin. Solubilized DOM generally resembled stream DOM more than its source POM and was chemically distinguishable from DOM leached from plants. Absorption coefficients and fluorescence peak intensities were strongly correlated with solubilized DOM concentrations and composition, while optical parameters established to characterize DOM origin and reactivity such as spectral slope, fluorescence index, and carbon-specific fluorescence intensities suggested unique compositional traits for solubilized DOM compared to stream DOM. This study therefore documented strong fractionation patterns during solubilization, linking eroded soil OM and stream DOM and highlighting a pathway that can account for compositional differences between DOM and POM in surface waters. A new amino acid parameter, the Solubilization Index (SI), was defined to capture the effects of solubilization processes on OM composition. SI values in solubilized DOM were up to an order of magnitude higher than in its source POM and were similar to SI values in stream DOM. Because the SI is based on empirical behaviors of individual amino acids, each tied to mechanistic interpretations, the SI is demonstrating a strong potential for mechanistic-driven research on the extent of phase changes in streamwater DOM.

Synthesis and Crystallographic, Absorption and Emission Studies of 4-Pyridine Carboxamide of Zn(II) 4-Chlorophenylacetate.

A new zinc(II) complex, [Zn(CB)2(INA)2] (where CB is 4-chlorophenylacetate and INA is 4-pyridine carboxamide) was synthesized. The structure of the complex was characterized by elemental analysis, FT-IR spectroscopy and single-crystal X-ray diffraction technique. Besides, the thermal stability of the complex was investigated by TGA/DTA analysis method. Moreover, the optical absorption and the emission features of the complex were examined by using UV-Vis and fluorescence spectrophotometers, respectively. Furthermore, Density Functional Theory (DFT) calculations were carried out to support the experimental results. Accordingly, it was determined that the complex crystallized in a monoclinic system with space group Pc, a = 8.3329 (2) Å, b = 25.6530 (4) Å, c = 13.5048 (3) Å, α = 90°, β = 91.703 (3)° and γ = 90°. The complex consists two crystallographically independent molecules. In each molecule, the ZnII ion adopts a distorted trigonal pyramidal coordination formed by two O atoms from the two 4 chlorophenylacetate ligand and two N atoms of the two 4-pyridine carboxamide ligands. It was observed that the linear absorption spectra of the complex were similar to linear absorption spectra of the semiconductors. In addition, two emission peaks were observed in the fluorescence spectra which could be due to the formation of excimer and the interactions of the benzene and pyridine rings. The energy gap (ΔEgap = ELUMO - EHOMO) of the complex has been calculated as 3.712eV and this value is very close to the experimentally measured value (3.86eV). Therefore, because of higher fluorescence intensity of emission peak that was observed between 309 and 556nm wavelength besides other traits, the complex could potentially be used in the blue light OLED application by filtering of the emission peak around 710nm wavelength. Graphical Abstract It was reported synthesis and spectroscopic, structural and optical characterization of a new complex that is Zn(II) of 4-Chlorophenylacetate with isonicotinamide. The complex characterized by elemental analysis, Single crystal X-ray diffraction and FT-IR Spectroscopy. Thermal stabilities of the complex have also been investigated. The studying of the optical absorption and fluorescence spectra of the prepared complex is very important for the determination of the optical application areas. The fluorescence measurements showed that these materials are much suitable for application area of the detection of nitroaromatic explosives. In addition to the Density Functional Theory (DFT) calculations were carried out to support the experimental results. It was reported synthesis and spectroscopic, structural and optical characterization of a new complex that is Zn(II) of 4-Chlorophenylacetate with isonicotinamide. The complex characterized by elemental analysis, Single crystal X-ray diffraction and FT-IR Spectroscopy. Thermal stabilities of the complex have also been investigated. The studying of the optical absorption and fluorescence spectra of the prepared complex is very important for the determination of the optical application areas. In addition to the Density Functional Theory (DFT) calculations were carried out to support the experimental results.

Evidence of Increased Hydrophobicity and Dynamics inside the Tail Region of Glycolipid Self-Assemblies Using 2-n-Alkyl-Pyrene Derivatives to Probe Different Locations.

New designer biofluorophores are being increasingly used in the investigation of complex cellular processes. In this study, we utilized new derivatives of pyrene (Py), i.e., 2-n-alkyl-pyrenes (Py-C4 and Py-C8), in order to probe different regions inside the hydrophobic tail of n-dodecyl β-d-maltoside (βMal-C12) in two different phases (cubic ↔ lamellar). Although the sensitivity to the local environment is reduced compared to that of Py, attaching C4 and C8 at the 2-position of Py can provide a possible means to probe the local hydrophobicity in different parts of the tail region. The absence of excimer fluorescence and the ratio of the vibronic fluorescence peak intensities (I1/I3) in a lipid environment indicate the existence of Py as monomers in the hydrophobic region, similar to hydrophobic solvation, yet close to the headgroup region. When Py is replaced by Py-C4 and Py-C8, there is a small increase in hydrophobicity (reduction in I1/I3) as the Py moiety is pulled deeper inside the tail region of both cubic and lamellar phases. The larger space of the tail region in the lamellar phase is reflected as more local hydrophobicity measured by the probes which can penetrate deep inside, whereas the curved structure of the cubic phase limits the available space for the probes. Three fluorescence lifetime components were measured in lipid, indicating the heterogeneous nature of the hydrophobic region. In the lamellar phase, a large reduction in the average lifetime value, led by the long decay component, was measured for Py-C4 (reduction by 25%) and Py-C8 (45%) compared to that of the parent Py. This observation suggests the presence of a mechanism of interaction more collisional than static between the Py moiety and the tail region of the bilayer unit due to the ample space provided by the lamellar phase as the probe is buried deeper inside the hydrophobic region. A much smaller effect was observed in the cubic phase and was correlated with the tight environment around the probes, which stems from the increased curvature of the cubic phase. The current results provide a deeper understanding of the hydrophobic region during phase transition of lipid self-assembly which is important for better control during the process of membrane-protein crystallization.

S,N co-doped graphene quantum dots-induced ascorbic acid fluorescent sensor: Design, characterization and performance

In this work, new detection route for ascorbic acid was designed. First, highly luminescent sulfur and nitrogen doped graphene quantum dots (S,N-GQDs) were prepared via simple hydrothermal method using citric acid and thiourea as the C, N and S sources respectively. The prepared S,N-GQDs are characterized by XRD, HRTEM, FTIR, EDS and PL. Investigations showed that prepared S,N-GQDs have a good photostability and excitation-dependent emission fluorescence. Prepared S,N-GQDs showed maximum excitation wavelength and emission wavelength at 400 and 462 nm, respectively. In the following, prepared S,N-GQDs were applied as a photoluminescence probe for detection of ascorbic acid (AA). The designed sensor was based on “off-on” detection mode. The developed sensor had a linear response to AA over a concentration range of 10–500 μM with a detection limit of 1.2 μM. The regression equation is Y = 0.0014 X + 1.2036, where Y and X denote the fluorescence peak intensity and AA concentration, respectively.

Effect of introduction of TiO2 and GeO2 oxides on thermal stability and 2 μm luminescence properties of tellurite glasses

Abstract In this paper, Tm3+ doped pure tellurite glass, TiO2 modified tellurite glass and TiO2/GeO2 co-modified tellurite glasses were prepared. The effects of the introduction of TiO2 and GeO2 oxides on the thermal, structural, optical properties of tellurite glasses were compared and analyzed intensively. Besides, the Judd-Ofelt intensity parameters and absorption and emission cross sections were calculated. DTA curves indicated the thermal stability of pure tellurite glass enhance obviously by GeO2 modification. The introduction of TiO2 and GeO2 oxides in tellurite glasses arise a series of variation on the absorbance, luminescence peak position and fluorescence intensity which have been explained and analyzed in detail. Based on the analysis, the addition of TiO2 in tellurite glass contributes to the improvement of 2 μm fluorescence performance, and the introduction of GeO2 has great advantages in enhancing the thermal stability of glass.

Lentiviral Vector-Mediated Expression of Exoenzyme C3 Transferase Lowers Intraocular Pressure in Monkeys.

Primary open-angle glaucoma (POAG) is considered a lifelong disease characterized by optic nerve deterioration and visual field damage. Although the disease progression can usually be controlled by lowering the intraocular pressure (IOP), therapeutic effects of current approaches do not last long. Gene therapy could be a promising method for persistent treatment of the disease. Our previous study demonstrated that gene transfer of exoenzyme C3 transferase (C3) to the trabecular meshwork (TM) to inhibit Rho GTPase (Rho), the upstream signal molecule of Rho-associated kinase (ROCK), resulted in lowered IOP in normal rodent eyes. In the present study, we show that the lentiviral vector (LV)-mediated C3 expression inactivates RhoA in human TM cells by ADP ribosylation, resulting indisruption of the actin cytoskeleton and altered cell morphology. In addition, intracameral delivery of the C3 vector to monkey eyes leads to persistently lowered IOP without obvious signs of inflammation. This is the first report of using a vector to transduce the TM of an alive non-human primate with a gene that alters cellular machinery and physiology. Our results in non-human primates support that LV-mediated C3 expression in the TM may have therapeutic potential forglaucoma, the leading cause of irreversible blindness in humans.

The Impact of Exposed Surface Area on the Response of SWCNT Optical Sensors

Due to their distinct and advantageous fluorescence properties, semiconducting single-walled carbon nanotubes (SWCNTs) are being applied to a variety of optical sensing applications. Limitations in solubility and biocompatibility have been overcome by non-covalently functionalizing the surface of the SWCNT with wrappings using techniques that retain its inherent fluorescence. Though wrappings based on surfactants and single-stranded DNA (ssDNA) have been extensively studied for this purpose, they are limited by factors such as lack of selectivity and lower fluorescence quantum yield, respectively. In this study, we take advantage of the higher fluorescence emission of surfactant-coated SWCNTs and focus on new approaches that can tune their selectivity as sensors. Through the concomitant monitoring of both the fluorescence intensity and wavelength position of emission peaks, we demonstrate the ability to increase the selectivity of sensors based on surfactant-suspended SWCNTs while retaining their higher fluorescence intensity. These results provide not only a promising avenue for rationally designing SWCNT sensors, but also insight on the mechanisms governing the selectivity of existing SWCNT-based optical sensors.

Effects of ultrasonic treatment on the gel properties of microbial transglutaminase crosslinked soy, whey and soy-whey proteins.

This paper studied the influences of diverse ultrasonic power treatments on the physico-chemical properties of soy-whey mixed protein induced by microbial transglutaminase. Two groups of 15% (m/v) of protein solution-sole protein (as control group) and mixed protein were prepared and processed under different ultrasonic powers for 30min. After ultrasonic power treatments, gel properties were significantly increased: under 300W, the gel hardness of mixed protein reached a maximum of 998.9g, with its water binding capacity scoring a maximum of 87%. According to the analysis of fluorescence emission spectrum, the fluorescence intensity and maximum absorption peak had changed, for different ultrasonic power treatments had exposed more groups. The Fourier Transform Infrared Spectroscopy also suggested that ultrasonic power treatments could change the secondary structure of gel samples. The scanning electron microscope demonstrated that the network structure of mixed protein gel displayed more regular and uniform after ultrasonic treatments.

Molecular manganese catalyst anchored on Bi2MoO6 with enhanced photogenerated charges separation for efficient visible-light photoreduction of CO2

Metal–organic hybrid composites are considered stable photocatalysts that exhibit effective CO2 adsorption capability and high charge separation efficiency. Here, the reflux condensation method was used to synthesize organometallic complexes of 2,2-bipyridine-4,4-bisphosphonic acid tricarbonyl manganese bromide (MnP), which were then phosphate anchored onto Bi2MoO6 via a facile self-assembly method. The resulting Bi2MoO6/MnP (150:1) composites catalysts exhibited efficient photocatalytic reduction of CO2 under visible light. The photocatalysts were systematically characterized via XRD, SEM, TEM, BET analysis, FTIR and UV–Vis. Visible light catalytic reduction products were detected qualitatively and quantitatively by ion chromatography and gas chromatography. The results demonstrate that loaded MnP reveal unique C=O, C–C characteristic peak and a peak fluorescence intensity that is less than 50% before loading. Furthermore, a remarkable CO production of turnover number TONCO = 123 and methanol yield of 95 µmol g−1 were obtained at a reaction time of 8 h under optimal conditions. The results due to the MnP in the composites not only enhanced charge carrier extraction but also improved photocatalytic reduction CO2 performance. Overall, the Bi2MoO6/MnP composites exhibit good potential in the photocatalysts fields.

Fluorescently Labelled Myosin Regulatory Light Chains as Biosensors for Thick Filament Activation in Heart Muscle

Calcium binding to the actin-containing thin filaments has long been known to be the trigger for heart muscle contraction. The resulting change in the thin filament conformation allows myosin head domains from the neighboring thick filaments to attach to actin and drive force generation and filament sliding. There is growing interest, however, in the involvement of proteins of the thick filament in the regulation of cardiac muscle contractility. The myosin-associated regulatory light chains (RLC) form an integral part of the myosin head or motor domain and can control the availability of the heads for actin interaction. To develop an effective and targeted therapeutic strategy for heart failure, we have employed fluorescent probes on the RLC to detect structural changes in intact thick filaments in isolated cardiac myofibrils. We generated a series of single cysteine mutants of RLC by site directed mutagenesis and labelled these proteins with solvato-chromic fluorescent dyes. These labelled RLCs were exchanged into rat and bovine cardiac myofibrils, replacing ∼40% of the native RLCs. We recorded emission spectra from these myofibrils in rigor and relaxing conditions and observed significant spectral changes for some probes, with the peak intensity of fluorescence shifting towards shorter wavelength in the relaxed state. We conclude that biosensor-RLCs can be used to screen potential small molecule modulators of the regulatory state of the myosin-containing thick filaments. The robustness of this technique makes it suitable for scaling up for high throughput screens. These results also provide further insight into the role of RLC in thick filament-based regulation and cardiac muscle contractility.

Estimation of terrestrial humic-like substances in inland lakes based on the optical and fluorescence characteristics of chromophoric dissolved organic matter (CDOM) using OLCI images

Terrestrial humic-like substances (Peak C), the main constituent of chromophoric dissolved organic matter (CDOM), which is one of the optically active constituents present in water, is a good indicator of the ecological statuses of global aquatic ecosystems. In this study, the optical relationship between the absorption spectrum and the fluorescence spectrum of CDOM were investigated in a total of 168 samples collected from Lakes Taihu and Chaohu, and four components of the fluorescence spectrum were identified. There are significant positive correlations between the component arising from Peak C and the specific ultraviolet absorbance at 254 nm (SUVA), and the absorption coefficient of CDOM at 443 nm (a(443)), whereas the correlation between this component and the ratio of two absorption coefficients of CDOM (M) is negative. In addition, total nitrogen (TN), total phosphorus (TP), chlorophyll a and dissolved organic carbon (DOC) were shown to increase significantly with the increase in Peak C, highlighting the importance of the Peak C affecting the water quality in inland lakes. An optical algorithm was developed, which can be used to estimate the fluorescence intensity of Peak C based on Rrs(B6) and Rrs(B11) of the Ocean and Land Color Instrument (OLCI); the validation dataset showed that the mean absolute percentage error (MAPE) is 28% and the root mean square error (RMSE) is 0.13 QSU. This algorithm was successfully applied to OLCI images and used to analyze the distribution of Peak C in Lake Taihu. The resulting map indicated that the fluorescence intensity of Peak C was significantly higher near the lake entrance than in East Taihu, and the terrestrial input in the estuary area in the west is marked larger than other regions in Taihu Lake.

Fluorescence spectroscopy for assessing trihalomethane precursors removal by MIEX resin.

This study investigated the applicability of fluorescence excitation-emission matrix spectroscopy (EEMS) to assess total trihalomethane formation potentials (TTHMFPs) and the ability of magnetic ion exchange (MIEX®) resin to reduce TTHMFP. We treated a surface water and secondary wastewater effluent with MIEX mimicking full-scale operation by repeatedly exposing the same resin batch to additional feed water, with batches ranging from 500 to 5,000 resin bed volumes. Results showed that MIEX was more effective at removing or reducing ultraviolet absorbance (UVA254), dissolved organic carbon (DOC), and TTHMFP in surface water than in secondary effluent. The greater UVA254, DOC and TTHMFP removal for surface waters was explained by the stronger affinity of MIEX for terrestrial dissolved organic matter (DOM) compared to microbial DOM. Fluorescence EEMS results showed that the ratio between terrestrial and microbial fluorescent signals of DOM was significantly greater in surface water than in secondary effluent. Fluorescence surrogate parameters were strongly correlated with TTHMFP, namely, fluorescence intensity of humic-like peak C (R2 = 0.98, p < 0.01), protein-like peak T (R2 = 0.96, p < 0.01), and fulvic-like peak A (R2 = 0.87, p < 0.01). Correlations between fluorescence surrogate parameters and TTHMFP were substantially stronger than correlations between DOC and TTHMFP. Overall, the results indicate that fluorescent parameters extracted from EEMS data can be used as quick surrogate parameters to monitor TTHMFP for a diverse group of raw and MIEX-treated waters.

Energy transfer process between two laser compounds coumarin 334 &amp; rhodamine 590

In the current research the absorption and fluorescence spectrumof Coumarin (334) and Rhodamine (590) in ethanol solvent atdifferent concentration (10-3, 10-4, 10-5) M had been studied. Theabsorption intensity of these dyes increases as the Concentrationincrease in addition to that the spectrum was shifted towards thelonger wavelength (red shift). The energy transfer process has beeninvestigated after achievement this condition. The fluorescence peakintensity of donor molecule was decrease and its bandwidth willincreases on the contrary of the acceptor molecule its intensityincrease gradually and its bandwidth decreases as the acceptorconcentration increase.

Plasmonic-Ceria Nanoparticles as Fluorescence Intensity and Lifetime Quenching Optical Sensor.

Ceria nanoparticles have been recently used as an optical fluorescent material with visible emission under ultraviolet excitation, due to the formation of trivalent cerium ions with corresponding oxygen vacancies. This paper introduces the enhancement of both fluorescence emission and lifetime through adding gold nanoparticles. The reason is due to possible coupling between the plasmonic resonance of gold nanoparticles and the fluorescence emission of ceria that has been achieved, along with enhanced formation of trivalent cerium ions. Both factors lead to higher fluorescence intensity peaks and shorter fluorescence lifetimes. As an application, gold-ceria nanoparticles have been used as an optical sensing material for lead particles in aqueous media based on fluorescence quenching. Stern-Volmer constant of in-situ gold-ceria nanoparticles is found to be 2.424 M−1, with a relative intensity change of up to 40% at 0.2 g/L.

Mobile phone-based UV fluorescence microscopy for the identification of fungal pathogens.

Dermatophytes are fungi that cause infections in hair, skin, and nails. Potassium Hydroxide (KOH) microscopy is the most frequently used method for identifying dermatophytes. KOH helps in the visualization of the hyphae as it clears the debris present in the specimen but needs a trained eye for final diagnosis of the infection. Fluorescence microscopy using staining agents, such as calcofluor white (CFW) or blankophor, is a better method for identification of dermatophytes but is not used in clinics due to the cost and complexity of fluorescence microscopes. The objective of the present work is to develop a simple low-cost mobile phone-based device for the identification of fungal pathogens in skin samples. A fluorescence spectrometer was used to establish the excitation/emission peaks of fluorescence intensity of CFW and KOH and Methyl Cellulose, a surrogate of fungi used for system development. A transillumination microscopy prototype was fabricated using off-the-shelf components, 3D printing and a mobile phone. The system was optically characterized using contrast resolution targets and verified using fungi isolate samples. An isolate of Trichophyton (T) rubrum was grown for 10-14 days for formation of fungal colonies. The surface of a single colony was gently scraped with a sterile loop and transferred to a glass slide. CFW with KOH was added to the T. rubrum and covered with cover slip for microscopic examination. The images of T. rubrum obtained with the prototype device were compared to those obtained using a commercial microscope. The excitation/emission wavelength pair for CFW was found to be 370/430 nm. The proposed device design is a transillumination microscopy setup using a mobile phone. It consists of a 365 nm LED as the excitation source, a 3V battery to power the LED, a slide to hold the sample, a lens for magnification and a phone to capture and store the images of the sample. The fabricated prototype has a resolution of 70 to 99 µm, a 2% to 30% distortion, and 60% contrast value for well illuminated samples. Images of T. rubrum samples obtained under brightfield illumination clearly show the long septate hyphae of the dermatophyte. As expected, images of the same samples with CFW and KOH show blue fluorescence, which results from the binding of the CFW to the chitin and cellulose in the fungal hyphae. These images are similar to those obtained with a commercial microscope. The concept and design of a mobile phone-based fluorescence microscope to identify dermatophytes has been demonstrated in a prototype and laboratory samples. The concept and design offer a simple, low-cost, compact but robust method for identification of fungal pathogens. This method is shown to be feasible for detecting fluorescence accurately and imaging the fungal structure at a resolution of 100 µm or better. Lasers Surg. Med. 51:201-207, 2019. © 2018 Wiley Periodicals, Inc.

Research on thiamethoxam detection and ultraviolet degradation modeling based on fluorescence analysis

The detection and degradation of thiamethoxam by fluorescence spectrometry were researched in this paper. Firstly, the fluorescence spectrum of thiamethoxam was measured and analyzed by LS55 fluorescence spectrometer, and there was a distinct fluorescence peak at 345nm under the excitation of 200 nm. The concentration prediction model was established by using the least square fitting method. Secondly, the fluorescence spectrum of mixed solution between thiamethoxam and apple juice was studied, the prediction model function of thiamethoxam concentration in apple juice was also established, and the correlation coefficient was more than 0.99 which represented a linear relationship between thiamethoxam concentration and fluorescence intensity at 345nm. At last, the thiamethoxam degradation experiment was carried out based on ultraviolet. The degradation model function was established between the time of ultraviolet irradiation and the fluorescence intensity of the characteristic peak, and the degradation rate corresponding to different degradation time was calculated. The results showed that the degradation rate increased with the prolonging of ultraviolet irradiation time. The degradation rate was 35.57% after ultraviolet irradiation for 10 min and it can reach 97.39% after 32 min. The results have a reference value for the detection and degradation of thiamethoxam residues by fluorescence spectrometry.

Synthesis and Photoluminescence of Er3+ and Yb3+ Doped ZnS Nanocrystals

ZnS:Er/Yb nanocrystals were synthesized by a hydrothermal method using thioglycolic acid as a stabilizer. The crystalline phases, morphology, chemical bond states and photoluminescent properties of the nanoparticles were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoemission spectroscopy and fluorescence photometer. The results show that most prepared nanoparticles are spherical in shape with an average size of 5 nm, and have cubic zinc blende crystal structure. The emission spectrum of ZnS:Er/Yb nanocrystals excited at 270 nm displays three main peaks at 470, 530 and 580 nm, and the intensity of fluorescence peaks is the strongest for nanocrystals prepared at 120 °C. When ZnS: Er/Yb nanocrystals are excited at 980 nm, the emission peaks around 540 and 650 nm appear, associated with the 4F3/2→4I15/2 and 4F9/2→4I15/2 of Er3+ ions transitions, respectively.