Peak Fluorescence Intensity Research Articles

Isolation and characterization of dissolved organic matter fractions from antialgal products of Microcystis aeruginosa

An antialgal bacterium, Streptomyces sp. HJC-D1, was applied for the biodegradation of cyanobacterium Microcystis aeruginosa, and the isolation and characterization of dissolved organic matter (DOM) fractions in antialgal products were studied. Results showed the the growth of M. aeruginosa was significantly inhibited by the cell-free filtrate of Streptomyces sp. HJC-D1 with the growth inhibition of 86 ± 7 %. The antialgal products were divided using resin adsorbents into the hydrophilic fraction (HPI), hydrophobic acid (HPO-A), transphilic acid (TPI-A), hydrophobic neutral and transphilic neutral, and then the five fractions were analyzed by the 3-D fluorescence spectroscopy, gel permeation chromatography, and Fourier transform infrared spectroscopy. The results indicated that the HPI component was the most abundant DOM fraction in the antialgal products, and its concentration was increased with the increase of cell-free filtrate concentration. The fluorescence peak location and intensity analysis showed that the protein-, fulvic-, and humic-like substances were dominant in the HPI, HPO-A, and TPI-A fractions, and intensities of the relevant fluorescence peaks were stronger in the experimental groups than those of the control groups. It was also found that the number-average molecular weight of DOM fractions ranged from 245 to 1,452 g mol(-1), and thereinto organic acids such as HPO-A and TPI-A exhibited lower molecular weights.

Magnetic Ion Exchange (MIEX) Treatment of Surface Water, Groundwater, and Landfill Leachate Wastewater: Effect on Organic Matter Fluorescence

Dissolved organic matter (DOM) is increasing in many drinking water supplies, which can have adverse impacts on treatment. Magnetic ion exchange (MIEX) is an advanced treatment process that has been shown to effectively remove DOM from different water sources. DOM removal efficiency is typically determined through dissolved organic carbon (DOC) and ultraviolet absorbance (UVA) measurements, but these methods can be limited in the amount of information they provide on DOM. Fluorescence spectroscopy has been suggested as a more robust characterization technique for monitoring DOM, but there remain gaps in knowledge between DOM removal processes and fluorescence characterization of DOM. Accordingly, the goal of this research was to evaluate the impact of MIEX treatment on DOM fluorescence for diverse water sources. MIEX jar tests were conducted using surface water, synthetic water, groundwater, and landfill leachate wastewater, and analyzed for DOC, UVA, and fluorescence excitation-emission matrix (EEM). Fluorescence EEMs were used to determine fluorophore location, intensity, and fluorescence index. MIEX removal of DOC and UVA were strongly correlated with MIEX removal of peak fluorescence intensity across all water sources. Peak fluorescence location indicated that MIEX preferentially removed terrestrial DOM. Fluorescence is a promising tool for monitoring DOM removal efficiency by MIEX treatment.

Positive trends between salinity and chromophoric and fluorescent dissolved organic matter in a seasonally inverse estuary

Estuaries present high content of chromophoric and fluorescent dissolved organic matter (CDOM, FDOM) affecting the attenuation of ultraviolet and blue radiation. In temperate and tropical estuaries, the main CDOM source is riverine input that generally mixes conservatively with the oceanic waters leading to negative relationships between CDOM and salinity. In Mediterranean estuaries, riverine inputs are more limited or absent during the dry season producing a negative hydrological budget and, consequently, hypersalinity and an inverse circulation pattern. Much remains to be understood about CDOM and FDOM dynamics during rainy and dry periods in these last estuaries. In this study, we determined DOM absorbance and fluorescence in the Bay of Cádiz, Spain during a rainy (high riverine inputs) and dry (hypersaline conditions) period. We determined the absorption coefficients at 355 nm (a355) and acquired excitation–emission matrices (EEMs). The EEMs showed two fluorescence peaks associated with terrestrial humic-like components (peaks A and C), one peak considered to be a marine humic-like component (peak M), and two peaks considered to be amino acid-like components (peaks T and B). The a355 values ranged from 0.30 to 1.99 m−1 with the highest values during the dry season. From the rainy season to the dry season, the overall fluorescence intensity increased and fluorescent peaks M, B, and T increased by greater than two orders of magnitude, whereas the fluorescence intensities of peaks A and C changed less than one order of magnitude. Unlike temperate and tropical estuaries, the a355 values and fluorescence of the five peaks were positive and significantly related to salinity, but with different slopes. The inverse nature of the Bay of Cádiz during the dry season could be responsible for these positive trends between CDOM/FDOM and salinity. The slopes of the humic-like peaks A and C were lower than the a355 slope suggesting their preferential losses, likely due to photobleaching. By contrast, the slopes of the amino acid-like peaks B and T were higher than the a355 slope suggesting an in situ production of these fluorophores, likely due to diffusion from salt marsh and coastal sediments.

Feasibility Animal Study of Novel ICG Sentinel Node Detection Technique in Head and Neck Region

Objectives: Sentinel node biopsy (SNB) allows head and neck surgeons to avoid unnecessary neck dissection. The popular SNB method using radioisotope (RI) has some drawbacks, such as the strict legal regulations for RI use in Japan. Recently, the SNB technique using real time indocyanine green (ICG) fluorescence image has become prevalent in breast cancer testing. Some reports demonstrated improved detection sensitivity with this method. However, the major problem of ICG method is its quick migration through the lymphatic system, which results in a limited diagnostic time window and detection of downstream subsequent nodes. To overcome this problem, we modified the ICG detection method by making ICG-colloid and demonstrated the feasibility of this technique in a mouse model. Methods: ICG-colloid was formed by mixing ICG and phytate colloids, which are commercially available as a kit for 99mTc-radiocolloid. Twenty microliters of ICG or ICG-colloid was injected into the tongue of a nude mouse, and the fluorescent images were observed with time until 48Hrs after injection. The fluorescence intensity in detected SN was analyzed. Results: In ICG injected animals, SNs were detected soon after injection, and second echelon lymph nodes were detected after 30-60min. In ICG-colloid injected animals, SNs were also detected after 30-60 min, and no second echelon lymph node was detected. Peak fluorescence intensity was 6-12Hr in both animal groups. No SN was detected after 24Hr in ICG animals, whereas SNs were still detectable in ICG-colloid animals. Conclusions: SNB using ICG-colloid technique may have advantages of prolonged diagnostic time window and prevention of downstream subsequent node detection.

Preparation, characterization and luminescent properties of dense nano‐silica hybrids loaded with 1,8‐naphthalic anhydride

Novel luminescent dense nano-silica hybrid materials (DNSS) modified with different amounts of (3-aminopropyl)triethoxysilane (APTES) and 1,8-naphthalic anhydride (NA) were successfully synthesized via two steps combined with post-grafting methods. Powder X-ray diffraction (XRD), N2-sorption analysis, Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), photoluminescence (PL) spectroscopy and elemental analysis, as well as time-resolved decays were employed to characterize the resultant hybrid materials. The results revealed that luminescent organic molecules had been successfully loaded onto the amine-modified surface of nano-silica spheres. In addition, their fluorescence intensity and characteristic peak of emission spectra changed with increasing amount of APTES and NA additive. In particular, the characteristic peak showed a red shift from 390 to 450 nm, however, this was inconsistent with results calculated on the basis of the elemental analysis data, most probably because of the dispersion behaviors of NA molecules from the aggregating to the monolayer state. These observations demonstrated the existence of a quantum confinement effectiveness of NA-DNSS samples, and therefore a possible mechanism was put forward.

Optical signatures of dissolved organic matter in the watershed of a globally large river (Yangtze River, China)

Parallel factor analysis of fluorescence excitation emission matrices of surface water samples of a globally large river (Yangtze River, China) watershed identified three classes of fluorescent dissolved organic matter (FDOM) that had ex/em = 280/330 nm, 305/385 nm and 350/450 nm respectively, resembling “peak T”, “peak M” and “peak C” commonly identified in natural water, respectively. Peak T (a tyrosine/tryptophan-like FDOM) did not show correlations to peak M or C which were humic-like substances, while a positive correlation (r = 0.935, p < 0.001) was present between the natural log-transformed maximum fluorescence intensity (Fmax) of peaks T and M indicating a tight link during their production and processing. Fmax values (in Raman unit nm−1) normalized to dissolved organic carbon (DOC) concentration were low, varying in ranges 15.93–85.95, 29.83–83.54 and 19.73–51.05 × 10−5 nm−1 (μmol/L)−1 for peaks T, M and C, respectively, in line with the history of strong photobleaching of the water samples as indicated by fairly high absorption spectral slope ratios (0.75–1.53 with a mean 1.03). Intermediate fluorescence index (FI) (1.46–1.83 with a mean 1.61) and small specific absorption at 254 nm (0.64–1.93 with a mean 1.15 m−1 mg−1 L) of the water samples, indicated the presence of both aquatic microbial DOM (e.g. peak T) and soil DOM (e.g. peak C). Peak C could be substantially removed by UV-A (320–400 nm) irradiation, while peak M was slightly increased when a microbe-containing water was exposed to the same UV-A irradiation. Taken together, peak C was attributed to diffuse soil source while peak M was likely attributed to joint effects of microbial activities and solar irradiation on the chromophores in the sample.

A novel approach for the detection of early gastric cancer: Fluorescence spectroscopy of gastric juice

This study aimed to investigate the efficacy of fluorescence spectroscopy of gastric juice for early gastric cancer (EGC) screening. Gastric juice was collected from 101 participants who underwent endoscopy in the Outpatient Endoscopy Center of Peking University Third Hospital. The participants were divided into three groups: the normal mucosa or chronic non-atrophic gastritis (NM-CNAG) group (n = 35), advanced gastric cancer (AGC) group (n = 33) and EGC group (n = 33). Fluorescence spectroscopic analysis was performed in all the gastric juice samples and the maximum fluorescence intensity of the first peak (P1 FI) was measured. The mean fluorescence intensity of P1 FI of gastric juice in AGC (92.1 ± 10.7) and EGC (90.8 ± 12.0) groups was significantly higher than that in the NM-CNAG group (55.7 ± 7.5) (AGC vs NM-CNAG, P = 0.006 and EGC vs NM-CNAG, P = 0.015, respectively). The areas under the receiver operating characteristic curves for the detection of AGC and EGC were 0.681 (95% confidence interval [CI] 0.553-0.810, P = 0.010) and 0.655 (95% CI 0.522-0.787, P = 0.028). With the P1 FI of ≥47.7, the sensitivity, specificity and accuracy for detecting EGC were 69.7%, 57.1% and 63.2%, respectively. The enhancement of P1 FI of gastric juice occurs at the early stage of gastric cancer. Fluorescence spectroscopy of gastric juice may be used as a novel screening tool for the early detection of gastric cancer.

Energy Transfer Studies in Binary Dye Solution Mixture of Coumarin 440 + Coumarin 540 and its LifetimeCalculations

The sensitized fluorescence emission from the bimixture [Coumarin 440 (donor) + Coumarin 540 (acceptor)] has been measured as a function of dye concentration using a fluorescence spectrophotometer. The concentration of Coumarin 440 (donor) is kept constant at 5×10-5M while the concentration of Coumarin 540 (acceptor) is varied. The spectroscopic parameters for this bimixture have been calculated from the concentration dependence of peak fluorescence intensity curves. Also the data obtained from the Horiba JobinYvon Time Resolved Fluorescence Spectrophotometer was analyzed for the determination of lifetimes at various emission peaks. A comparative study between theoretically calculated lifetimes and experimentally obtained lifetimes shows a good agreement. The results indicate that the energy transfer process between unlike molecules can be studied by lifetime measurements (which could also be determined from the fluorescence emission spectral studies). Many attempts have been made in studies aimed to improve dye lasers efficiency and to extend their spectral range of operation. Energy transfer dye lasers (ETDL) have generated considerable interest as they are useful in obtaining enhanced laser output, wide tuning range, reduced concentration and pump threshold requirements and ultra-short pulse width in contrast to their single dye counterpart [1-7]. Energy Transfer Dye Lasers using numerous donor-acceptor dye pairs have been reported by various investigators duringthe last five decades. Fluorescence energy transfer is the transfer of the excited state energy from a donor (D) to acceptor (A) [8–19]. This transferoccurs without the appearance of photon and is primarily a resultof dipole–dipole interaction between the donor and the acceptor.The rate of energy transfer depends upon the extent of overlapof the emission spectrum of the donor with the absorptionspectrum of the acceptor, the relative orientation of the donorand acceptor transition dipoles and the distance between thesemolecules. The non-radiative energy transfer occurs as a result ofdipole–dipole coupling between the donor and the acceptor,anddoes not involve the emission and reabsorption of photons. In contrast to these trivial factorsnonradiative energy transfer depends upon the molecular detailsof donor–acceptor pairs.Non-radiative energy transfer is effective overdistance ranging of 50A°.The intervening of solvent or other macromoleculeshas little effect on the efficiency of the energy transfer, whichdepends primarily on the D–A distances[18].Dye lasers have some limitations as the dye solution used as an active medium absorbs energy from the excitation source in a very limited range and so the emission band also has these limitations. If a dye laser has to be used as an ideal source its spectral region needs to be extended. In order to extend the spectral region of operation mixtures of different dye solutions/dye molecules embedded in solid matrices arebeingused.The use of such energy transfer in dye lasers is also helpful in minimizing the photoquenching effects and thereby, increasing the laser efficiency. In the present studies the energy transfer mechanism has been investigated in the ethanol solution mixture, i.e. Coumarin 440 and Coumarin 540 from their absorption and emission spectra. The dependence of lifetimes of the dye molecules on their

Phase immiscibility induced enhanced fluorescence in spin-coated PVP/PPO polyblends

We report on the effect of phase immiscibility on the structure and optical properties of spin-coated polyvinylpyrrolidone (PVP) and polyphenylene oxide (PPO) polyblends using X-ray diffraction, IR absorption, optical absorption and florescence spectroscopic techniques. The broad diffraction halos in the X-ray diffraction patterns reveal the semi-crystalline nature for the synthesized polyblends. The change in q value for both the deconvoluted halos confirms the variation in the molecular interactions while the decrease in their fwhm values signify the enhancement in crystalline nature with the blending. The infrared absorption studies were used to elucidate the interaction of functional groups in the spin-coated polyblends. The position of three excitonic bands and the red shift in the optical absorption edge with the increase in the PPO content has been observed for these polyblends. The six time enhancement in fluorescence peak intensity in visible region (~500 nm) for immiscible blend (50/50) composition has been of importance for the design of low cost luminescent and photovoltaic devices.

Base Effects on Fluorescence and Surface-Enhanced Raman Scattering of Crystal Violet Adsorbed on Au Nanoparticles Surface

The Surface enhanced fluorescence (SEF) and Surface Enhanced Raman Scattering (SERS) of Au nanoparticle films deposited on Si and SiO2 substrates are presented. From the experimental results, it is concluded that the fluorescence peak intensity changes in a similar way with the Raman intensity for the various substrates. Both the fluorescence and the Raman intensity were much stronger on SiO2 substrate than on the Si substrate. That is due to the Crystal Violet (CV) adsorbed on the substrate having different refractive index effect the electrical field near the nanoparticles. The nanoparticle size effect on the Raman and fluorescence was also studied.

A dual channel optical detector for trace water chemodosimetry and imaging of live cells

A novel 3-5-dichlorosalicylaldehyde Schiff base chemodosimeter (compound 1) for water is designed and synthesized, and it works based on a water-triggered reaction of a Schiff base. Addition of trace amounts of water into 1 in various organic solvents leads to a fluorescence turn-on response and a simultaneous dual-channel signal modulation (both in the fluorescence and absorption spectra). Especially, 1 is found to be an outstanding fluorescence enhancement water sensor in methanol with an extremely low detection limit of 22 ppm. Consequently this probe can be utilized to detect trace water in commercial methanol. The quantitative detection of a wide range of water content is enhanced in THF and acetonitrile (0-35% v/v for THF and 0-20% v/v for acetonitrile), where the fluorescence peak intensity is nearly proportional to the amount of water added. Moreover, 1 can be used for monitoring pH through a novel ON-OFF-ON type signal modulation both in fluorescence and absorption spectra within a wide pH detection range. Thus, the chemodosimeter can not only be utilized to monitor the intracellular pH fluctuations, but also to accomplish simultaneous in situ staining of the cytosol and acidic organelles in two different channels, respectively.

Uptake of Gold Nanoparticles in Several Rat Organs after Intraperitoneal AdministrationIn Vivo: A Fluorescence Study

Background. The gold nanoparticles (GNPs) have potential applications in cancer diagnosis and therapy. In an attempt to characterise the potential toxicity or hazards of GNPs as a therapeutic or diagnostic tool, the fluorescence spectra in several rat organs in vivo were measured after intraperitoneal administration of GNPs. Methods. The experimental rats were divided into control and six groups (G1A, G1B, G2A, G2B, G3A, and G3B; G1: 20 nm; G2: 10 nm; G3: 50 nm; A: infusion of GNPs for 3 days; B: infusion of GNPs for 7 days). The fluorescence measurements were investigated in the liver, kidney, heart, and lung organs of rats after intraperitoneal administration of GNPs for periods of 3 and 7 days in vivo. Results. The 10 and 20 nm GNPs exhibited spherical morphology shape, while the 50 nm GNPs exhibited hexagonal shape. A sharp decrease in the fluorescence intensity induced with the larger 50 nm GNPs in the liver, kidney, heart, and lung organs of rats at the exposure duration of 3 and 7 days in vivo compared with the smaller 10 and 20 nm GNPs was observed. Conclusions. The decrease in fluorescence intensity may be attributed to occurrence of strong quenching, decrease in number and surface area of GNPs, and high clearance of GNPs via urine and bile. Moreover, decreasing size may lead to an exponential increase in surface area relative to volume, thus making GNPs surface more reactive on aggregation and to its surrounding biological components. The size, shape, surface area, number, and clearance of GNPs play a key role in toxicity and accumulation in the different rat organs. This study demonstrates that fluorescence peak intensity is particle size and exposure duration dependent. This study suggests that fluorescence intensity can be used as a useful tool for pointing to bioaccumulation and toxicity induced by GNPs in the different rat organs.

A Hg2+-mediated label-free fluorescent sensing strategy based on G-quadruplex formation for selective detection of glutathione and cysteine

A novel label-free fluorescent strategy for the detection of glutathione (GSH) and cysteine (Cys) is presented. The system consists of two single stranded DNA (ssDNA) with thymine-thymine (T-T) mismatches and used Hg(2+) as a mediator, and N-methyl mesoporphyrin IX (NMM) as the signal reporter. The assay is based on the competitive reaction of Hg(2+) with GSH/Cys and T-T mismatched double stranded DNA (dsDNA). In the absence of the target, two ssDNA containing T-T mismatches react with Hg(2+) to form a T-Hg(2+)-T dsDNA structure in the solution, which hampers the formation of a G-quadruplex structure. However, in the presence of the target, GSH/Cys reacts with Hg(2+) to keep DNA probes in a free single state, resulting in the effective formation of a G-quadruplex structure of the DNA probe (GP). Subsequently, due to the strong interaction between the G-quadruplex structure and NMM, fluorescence was greatly enhanced. This fluorescence strategy does not require any chemical modification, making the assay convenient and cost-effective. This method exhibited a linear relationship between peak fluorescence intensity and concentration of GSH in the range of 10-400 nM with a limit of detection (LOD) of 9.6 nM. A linear range for Cys detection was obtained in the concentration range of 10-500 nM with an LOD of 10 nM. Moreover, the proposed method worked well for the analysis of complex biological samples.

Cortical Indocyanine Green Videography for Quantification of Acute Hypoperfusion After Subarachnoid Hemorrhage

Acute neurological deficits after subarachnoid hemorrhage (SAH) correlate with outcome, and a phase of acute hypoperfusion was characterized recently. Indocyanine green (ICG) videography is an established intraoperative imaging technique with important descriptive potential. To analyze whether ICG can be used to analyze and confirm perfusion changes early after SAH. We prospectively enrolled 11 patients with acute SAH within the past 24 hours and 14 patients undergoing surgery for unruptured aneurysms. Cortical ICG videography was performed, and offline analysis included the arterial, parenchymal, and venous cortical compartment. Transit times, signal gradient, maximum of fluorescence intensity, and the area under the curve were calculated as surrogate markers for perfusion characteristics. Arterial, parenchymal, and venous transit times were comparable in both groups. The velocity of signal change in SAH patients was significantly lower in all 3 compartments (P < .001, P < .01, P < .001, respectively), as was the peak fluorescence intensity (P < .001). In SAH patients, fluorescence intensity did not vary between areas with and without diffuse cortical blood. Area under the curve analysis showed significantly lower values in SAH patients compared with the control group (P < .001). Cortical ICG videography and analysis are feasible during surgery. Patients early after SAH have a significantly lower velocity of signal change, lower peak of fluorescence intensity, and lower overall area under the curve, but similar transit times. This technique can be used to quantify perfusion alteration, in this case, acute SAH, and may be used as an adapted measurement tool for intraoperative therapy.

Fluorescence characteristics of dissolved organic matter during composting at low carbon/nitrogen ratios

We investigated the composting of swine manure at low carbon/nitrogen (C/N) ratios (about 13). The purpose was to elucidate organic matter transformation during composting by means of chemical and spectral methods. Swine manure was composted with two bulking agents (rice straw and leaves) at a ratio of 2:1 (manure:bulking agent; v:v) respectively. Low initial C/N ratios (about 13) did not prevent the swine manure from composting, which would greatly decrease the usage of bulking agent. A high organic matter mineralization rate was observed in the co-composting of straw and manure paired with a high maximum temperature and long thermophilic phase. Fluorescence excitation-emission matrix spectra were also used to monitor the component changes in the dissolved organic matter. Fluorescence parameters, including peak location, peak intensity, the ratio of peak intensity and fluorescence regional integration, were displayed and discussed as the maturity index. The fluorescence regional integration, showing higher correlation coefficient than the fluorescence intensity peaks, could be used as a valuable tool for assessing compost maturity.

A Novel Colorimetric and Fluorescent pH Sensor Derived from Iminocoumarin and Thiophene‐Carboxaldehyde

ABSTRACTA novel colorimetric and fluorescent pH sensor derived from iminocoumarin and thiophene‐carboxaldehyde was designed and synthesized. The structures of the dye and related compounds were characterized by IR, 1H NMR, 13C NMR, and mass spectra. Color change from green to yellow of the new sensor solution in ethanol–water with the decrease in the pH value from 7 to 2 was observed by the naked eye. Under acidic conditions, the intensity of the maximum fluorescence emission peak of the sensor increased gradually with the decrease in the acidity of the solution (the increase in the pH value from 2 to 7) and attained to the maximum value at about pH 6. Under basic conditions, the fluorescence intensity of the emission peak of the sensor did not exhibit a distinct change at pH ≤ 11.85, and the fluorescence was quenched at pH 13.36, concomitant with the green color of the solution turning pale. The sensor can be used as a fluorescent pH probe in the presence of common metal cations and anions without interference.

Use of three-dimensional excitation and emission matrix fluorescence spectroscopy for predicting the disinfection by-product formation potential of reclaimed water

This study was undertaken to demonstrate the feasibility of using three-dimensional excitation-emission matrix (3DEEM) fluorescence spectroscopy for the determination of chlorination disinfection by-product (DBP) precursors and the disinfection by-product formation potential (DBPFP) of reclaimed water samples. Two major DBP precursors were examined in this study, including humic acid (HA) and fulvic acid (FA). The 3DEEM fluorescence results obtained from various reclaimed water samples indicated that the reclaimed water samples were rich in fulvic acid-like substances that were associated with two main peaks (Ex/Em = 235–245/420–440 nm, and Ex/Em = 330–340/410–430 nm) in the fluorescence spectrum. The results also illustrated that the wavelength location of peak fluorescence intensity of a reclaimed water sample was independent of the influent water quality and the wastewater treatment process used in the reclamation plant. As a result, the peak fluorescence intensity and the wavelength location of the peak were used to identify the species of DBP precursors and their concentrations in the reclaimed water sample. Four regression models were then developed to relate the peak fluorescence intensity of the water sample to its DBPFP, including the formation potential of trihalomethane (THMFP) and the formation potential of haloacetic acid (HAAFP). The regression models were verified using the measured DBPFP results of a series of reclaimed water samples. It was found that the regression modeling results matched the measured DBPFP values well, with prediction errors below 10%. Therefore, the use of 3DEEM fluorescence spectroscopy together with the developed regression models in this study can provide a reliable and rapid tool for monitoring the quality of reclaimed water. Using this method, water quality could be monitored online, without utilizing the lengthy conventional DBPFP measurement.

Effect of natural organic matter (NOM) on Cu(II) adsorption by multi-walled carbon nanotubes: Relationship with NOM properties

The effect of natural organic matter (NOM) on Cu(II) adsorption by multi-walled carbon nanotubes (MWCNTs) was investigated. Particular attention was paid to the relationship between NOM properties and NOM adsorption and their effects on the Cu(II) adsorption by MWCNTs. The results showed that the NOM adsorption data were well fit to the Freundlich isotherm model, and the MWCNTs that had higher oxygen content had lower KF (Freundlich constants) values. The KF values for the different types of NOM varied greatly and were proportional to the aromatic carbon content, the specific ultraviolet absorbance at 275nm, and the TOC-normalized fluorescence intensity of the F3 peak at ∼460nm. In contrast, they had negative linear correlations with the absorbance ratios at 250nm and 365nm and the TOC-normalized fluorescence intensity of the F1 peak from 250nm to 300nm. The results indicated that π–π and hydrophobic interactions were the predominant NOM adsorption mechanisms by the MWCNTs. The Cu(II) adsorption by the MWCNTs increased with increasing NOM concentrations due to the complexing of Cu(II) with the adsorbed NOM. This was confirmed by XPS and FTIR spectra. The increased degree of Cu(II) adsorption was positively correlated with the carboxyl carbon content, carboxyl group content, and the polarity index of the NOM. The findings in this study highlight that the NOM characteristics are responsible for controlling the NOM adsorption and its effects on heavy metal sorption by MWCNTs.

A Receptor-targeted Fluorescent Radiopharmaceutical for Multireporter Sentinel Lymph Node Imaging

To determine the imaging and receptor-binding properties of a multireporter probe designed for sentinel lymph node (SLN) mapping via nuclear and fluorescence detection. The animal experiments were approved by the institutional animal care and use committee. A multireporter probe was synthesized by covalently attaching cyanine 7 (Cy7), a near-infrared cyanine dye, to tilmanocept, a radiopharmaceutical that binds to a receptor specific to recticuloendothelial cells. In vitro binding assays of technetium 99m (99mTc)-labeled Cy7 tilmanocept were conducted at 4°C by using receptor-bearing macrophages. Optical SLN imaging after foot pad administration was performed by using two molar doses of Cy7 tilmanocept. Six mice were injected with 0.11 nmol of 99mTc-labeled Cy7 tilmanocept (low-dose group); an additional six mice were injected with 31 nmol of 99mTc-labeled Cy7 tilmanocept (high-dose group) to saturate the receptor sites within the SLN. After 2.5 hours of imaging, the mice were euthanized, and the sentinel and distal lymph nodes were excised and assayed for radioactivity for calculation of SLN percentage of injected dose and extraction. Four mice were used as controls for autofluorescence. Standard optical imaging software was used to plot integrated fluorescence intensity against time for calculation of the SLN uptake rate constant and scaled peak intensity. Significance was calculated by using the Student t test. In vitro binding assays showed subnanomolar affinity (mean dissociation constant, 0.25 nmol/L±0.10 [standard deviation]). Fluorescence imaging showed a detection sensitivity of 1.6×10(3) counts·sec(-1)·μW(-1) per picomole of Cy7. All four imaging metrics (percentage of injected dose, SLN extraction, SLN uptake rate constant, and expected peak fluorescence intensity) exhibited higher values (P=.005 to P=.042) in the low-dose group than in the high-dose group; this finding was consistent with receptor-mediated image formation. The multireporter probe 99mTc-labeled Cy7 tilmanocept exhibits in vitro and in vivo receptor-binding properties for successful receptor-targeted SLN mapping with nuclear and optical imaging.

A quantitative diagnostic method for oral mucous precancerosis by Rose Bengal fluorescence spectroscopy

A novel in vivo fluorescence spectroscopic diagnostic method has been developed in an animal model to make a quantified precancer diagnosis. In the study, 40 golden hamsters were randomly divided into four groups (groups A, B, C, and D), with group A being the control group and the other three groups being inducted at different precancer stages. A 1% Rose Bengal (RB) solution was used for the fluorescence spectroscopic diagnosis. A parameter K defined as K = I(RB)/I(auto) was introduced to reflect the amount of RB in the tissue, where I(RB) and I(auto) represent the fluorescence peak intensity of the RB in the tissue and the autofluorescence intensity of tissue at 580 nm, respectively. The average K values of the four groups were calculated and statistically analyzed by analysis of variance (ANOVA), which revealed statistically significant differences within each group as well as between groups (p < 0.001). After analysis by Clementine 11.1 C&R Tree modeling (CART), the following diagnostic criteria were set: normal, K ≤ 8.91; simple hyperplasia, 8.91 < K ≤ 41.92; mild dysplasia, 41.92 < K ≤ 70.79; moderate and severe dysplasia, K >70.79. The sensitivity and specificity to detect precancerous lesions compared with scalpel biopsy were calculated. The results of this study showed that the spectrofluorometric method mediated by RB could accurately discriminate different precancer stages.