Plasmonic fluorescent nanocomposites are difficult to prepare due to strong quenching effects on fluorophores in the vicinity of noble metal nanoparticles such as gold (AuNPs). We successfully prepared plasmonic fluorescent nanocomposites of two cyanines (1 and 2) aggregating upon 2 – 40 nm AuNPs or streptavidin-conjugated 10 nm AuNPs. We used high throughput screening (HTS) for the first time to characterize the spectral properties, aggregation kinetics, aggregation density and photostability of the nanocomposites. Fluorescence from nanocomposites declined inversely with AuNPs size: 40 nm ≥ 20 nm > 10 nm > 5 nm > 2 nm. Sensitivity (limit of detection, LOD, 105 – 1011 AuNPs/mL), brightness of the nanocomposites and surface coverage of AuNPs by cyanine aggregates were all influenced by five factors: 1) AuNPs size; 2) cyanine type (1 or 2); 3) aggregate density; 4) distance between aggregates and AuNPs surface; and 5) streptavidin protein conjugation to AuNPs. We propose a model for plasmonic fluorescent nanocomposites based on these observations. Our plasmonic fluorescent nanocomposites have applications in chemical and biological assays.
A micro-flow reaction system was developed in which liquid–liquid interface was created based on the tube radial distribution of ternary mixed carrier solvents. The system was constructed from double capillary tubes having different inner diameters (100 and 250 μm i.d.). The smaller tube was inserted into the larger one through a T-type joint. The reaction of a protein with a fluorescence derivatizing reagent was adopted as a model. A water–acetonitrile mixture (3:1 volume ratio) including bovine serum albumin (hydrophilic) was delivered into the large tube from the inside through the small tube and an acetonitrile–ethyl acetate mixture (7:4 volume ratio) containing fluorescamine (hydrophobic) as a derivatizing reagent was delivered from the outside through the joint. Solutions were mixed through the double capillary tubes to promote ternary mixed carrier solvents (water–acetonitrile–ethyl acetate; 1:2:1 volume ratio). The liquid–liquid interface was created based on the tube radial distribution of ternary solvents in the larger tube. The derivatization reaction was performed in the larger, or reaction, tube in the micro-flow system. The fluorescence intensity of the fluorescamine-derivatized bovine serum albumin obtained by the system, which specifically included the kinetic liquid–liquid interface in the tube, was greater than that obtained through a batch reaction using a homogeneous solution of water–acetonitrile (1:2 volume ratio).
A low-energy, high-repetition-rate picosecond laser (40 μJ, 20 kHz, 258 nm) was used for multiphoton ionization (MPI) in gas chromatography/time-of-flight mass spectrometry to quantitatively determine dioxins (DXNs) and polycyclic aromatic hydrocarbons (PAHs). The sensitivity of the technique was compared with that obtained using a high-energy, low-repetition-rate femtosecond laser (86 μJ, 1 kHz, 261 nm). The limits of detection (LODs) for the picosecond laser were several femtograms for chlorinated DXNs with low numbers of chloro substituents, and were several times lower than values obtained using a femtosecond laser, although the LODs were increased, reaching values that were nearly identical to those for the femtosecond laser for octachlorodibenzo-p-dioxin (octaCDD) and octachlorodibenzofuran (octaCDF). The LODs were also measured for 16 PAHs specified by the United States Environmental Protection Agency; the values for half of these compounds were at sub-femtogram levels. The procedure was used to analyze a surface-water sample collected from a river.
Bladder cancer (BC) is one of the most common cancers and has a high mortality rate. However, both metabolite variations and metabolic pathways related to the pathogenic process of BC remain to be addressed, such results might contribute to early detection of the disease. 1H nuclear magnetic resonance (NMR)-based metabolomics was applied to identify differences of serum metabolic profiles among BC, calculi patients and healthy subjects. Serum metabolic profiles of BC patients are distinctly different from those of calculi and healthy subjects. Compared with those from healthy subjects, serum samples from BC patients show decreased levels of isoleucine/leucine, tyrosine, lactate, glycine, citrate, as well as increased levels of lipids and glucose. The results reveal disturbed metabolic pathways of aromatic amino acids, glycolysis and citrate cycle, as well as lipogenesis metabolism in BC patients. Our work will be of potential benefit to understanding the pathogenic process of BC and will offer valuable information for noninvasive diagnosis of the disease.
Spherical molecularly imprinted polymer particles for bisphenol A (BPA-MIP) were easily prepared by using a Y-junction microfluidic device. The sizes of the obtained BPA-MIP particles were found to be 86 μm with a narrow size distribution. The binding characteristics were investigated by drawing a binding isotherm to estimate the binding constant and by switching the polarity of solvents to examine the feasibility of use as a medium for affinity chromatography. When dichloromethane was used as a solvent, BPA was strongly bound to the spherical BPA-MIP particles based on hydrogen bond formation; after switching the solvent to methanol, BPA was eluted quantitatively due to the weakening of the hydrogen bonding, suggesting that the spherical BPA-MIP particles can be applied to affinity-type solid-phase extraction for BPA. As the present method can provide a diverse range of spherical MIPs without tedious procedures, MIP-based affinity media will be able to be more readily used as pretreatment and/or purification for various fields.
In the present work, we investigated the multielemental elution behavior of metal ions absorbed on iminodiacetic acid (IDA) chelating resin by using hydrogen peroxide (H2O2) as an eluent. As a result, V(V), Mo(VI), W(VI), Nb(V) and Ta(V) were efficiently eluted by H2O2. In contrast, other metal ions were rarely recovered. The oxidation states of V(V), Mo(VI), and W(VI) were not changed through the H2O2 eluting process, checked by X-ray photoelectron analysis. In addition, the UV-vis adsorption spectra and IR spectra of V(V), Mo(VI) and W(VI) in the H2O2 eluent suggested the formation of metal-peroxo complexes through H2O2 elution. The desorption of these metal ions from IDA functional groups is explained in term of destabilization along with the coordination of peroxo-ligands to the V(V)-, Mo(VI)- and W(VI)-IDA complexes, and a decrease in the adsorption capacity by electrostatic repulsion between dissociated carboxylic groups of IDA and the oxoanions in the neutral pH shown in 30 wt% H2O2. When this method was applied to the selective separation of V(V), Mo(VI) and W(VI) from other metals in an acid soluble fraction of fly-ash, 83.4 ± 2.5% of V(V), 88.1 ± 3.3% of Mo(VI), and 69.3 ± 5.4% of W(VI) were recovered in a 30 wt% H2O2 eluent.
Physicochemical properties such as a thermal behavior, ionic conductivity, viscosity and density, and acid-base properties of a new class of 2-hydroxyethylammonium-based protic ionic liquids (PILs) have been investigated. Thirty-six potential PILs were surveyed to find 32 salts with a melting point below 373 K. Among them, [(EtOH)nEt(3−n)NH+][TFS−] (Et, C2H5; n = 0 – 3) and [(EtOH)2EtNH+][X−] (X = TFS, trifluoromethanesulfonate; TFSA, bis(trifluoromethanesulfonyl)amide; NO3) were studied in terms of the Walden plots, molar volume and auto-protolysis reaction for effect of the number of 2-hydroxyethyl groups introduced in the cations and for dependence of the anion nature, respectively. With regard to [(EtOH)nEt(3−n)NH+][TFS−] (n = 0 – 3), the ion-ion interactions between cation-anion and cation-cation were enhanced with increasing the number of the 2-hydroxyethyl groups. In addition, the auto-protolysis constant Ks value for [(EtOH)2EtNH+][TFSA−] is smaller than that for TFS− based PIL, indicating that HTFSA behaves as a stronger acid than HTFS in the respective PIL. On the other hand, in [(EtOH)2EtNH+][NO3−], the emf jump was rather small, which suggests that the proton of HNO3 does not easily transfer to (EtOH)2EtN in the liquid state.
Dihydrolipoic acid (DHLA) modified gold nanoparticles (AuNPs) were used as a highly selective probe for the detection of prion proteins. We discovered that AuNPs undergo aggregation selectively in the presence of recombinant prion protein (rPrP), and such selective aggregation enhanced the resonance light scattering (RLS) intensity from AuNPs tremendously. Based on this phenomenon, we established a new assay for rPrP detection. This new assay is label-free, highly selective, and sensitive. The linear range for rPrP detection is from 2.0 × 10−10 to 2.0 × 10−8 mol L−1 with excellent discrimination against other interfering compounds, and the detection limit is 7 × 10−11 mol L−1. This assay has been successfully applied for rPrP detection in E. coli lysate, bovine serum samples and human plasma samples. Compared with other methods, the detection approach described here can achieve high selectivity and sensitivity without any complicated labeling or expensive instruments.
Understanding the chemical state of lead in fly ash generated from a waste thermal treatment is important, since the toxicity and solubility of the element depends on its chemical state. This study identified three potential methods for obtaining quantitative information regarding the chemical state of lead in fly ash: X-ray absorption near edge structure (XANES) analysis, extended X-ray absorption fine structure (EXAFS) analysis, and the sequential extraction procedure. The result of this procedure was strongly affected by the pH and sample matrix, and did not necessarily accurately reflect the chemical state. It was difficult to quantitatively examine the chemical species using only EXAFS. However, an XANES fitting enabled direct quantification of the chemical species. An XANES analysis showed that PbSiO3, PbCl2, or Pb2O(OH)2 was the predominant chemical species in fly ash. We concluded that multiple analyses should be compared multilaterally to improve the accuracy of the final analysis.
Titanium dioxide (TiO2) nanoparticles (NPs) are widely used as an important kind of biomaterials due to their large surface area, enhanced chemical reactivity and easy penetration into cells. Nano TiO2 with pure anatase phase was successfully prepared by solvothermal method. Its particle size was about 21 nm, while the larger specific surface area of TiO2 was 77.43 m2/g. The interaction of colloidal TiO2 with human serum albumin was studied by using absorption spectra and fluorescence spectra. The apparent binding constants (K) were 345.780 × 105, 4.376 × 105, 0.035 × 105 at 298, 303 and 308 K, respectively. In addition, the number of binding sites (n) was gradually decreased with the increase of temperature, which indicated that the quenching mechanism of albumin by colloidal TiO2 was static fluorescence quenching process. Based on fluorescence resonance energy transfer, the energy transfer efficiency (E) and critical transfer distance (r0) between donor (human serum albumin, HSA) and acceptor (colloidal TiO2) were calculated to be 0.862 and 6.244 nm, which suggested that non-radiative energy transfer occurred between TiO2 and HSA. Furthermore, the conformational changes of HSA were shown by synchronous fluorescence.
An ultrasensitive voltammetric sensor, a simply coated graphene-Na?on suspension on a glass carbon electrode surface, was fabricated and used to investigate the electrochemical behavior of theophylline as described in the present paper. The results indicated that this voltammetric sensor exhibited a special recognition capacity to determine theophylline as well as having high sensitivity due to the excellent characteristics of graphene and the adsorption action of Nafion for theophylline. Under the selected condition using differential pulse voltammetry, the response peak currents had a linear relationship with the theophylline concentrations in two ranges from 1.0 × 10−8 − 1.0 × 10−6 and 2.0 × 10−6 − 3.0 × 10−5 mol L−1 with a low detection limit of 6.0 × 10−9 mol L−1. Moreover, according to the results obtained in the analysis of theophylline in two standard samples, it demonstrated the applicability of present method into real sample determination.
Nickel microspheres were synthesized via a water-in-oil reverse nanoemulsion system using nickel nitrate as the nickel precursor and hydrazine hydrate as the reducing agent. The nanoemulsion was a triton X-100/cyclohexane/water ternary system. The surface morphology of the nickel microspheres was studied by scanning electron microscopy, which indicated that the microspheres had a nanoporous structure. The electrochemical behavior of the nanoporous nickel microspheres were studied in alkaline solution and were then employed to fabricate a modified carbon paste electrode in order to investigate the electrocatalytic oxidation of the drug acyclovir. The oxidation process involved, and its kinetics were investigated using cyclic voltammetry and chronoamperometry. The rate constant of the catalytic oxidation of acyclovir and the electron-transfer coefficient are reported. A sensitive, simple and time-saving amperometric procedure was developed for the analysis of acyclovir. The proposed amperometric method was also applied to determine acyclovir in tablets and topical cream.
This study investigated the effects of diabetic rats induced by streptozotocin (STZ) on acetone concentration emanating from the tail of a rat. Experiments were carried out with male Wistar rats (9 weeks of age, 220 – 250 g body weight). Glucose concentration in the blood was 10.8 ± 0.7 mmol/l for the control group and 39.6 ± 2.4 mmol/l for the diabetic group. β-Hydroxybutyrate concentration in blood was 218 ± 52 μmol/l for the control group and 1439 ± 101 μmol/l for the diabetic group. Both glucose and β-hydroxybutyrate concentrations in the blood of the diabetic group were significantly higher than those of the control group (p < 0.001). Skin gas acetone concentration emanated from rat tail was 124 ± 46 ppb for control and 1134 ± 417 ppb for diabetic. Skin gas acetone concentration emitted from the tail of a rat with diabetes was significantly higher than that from a rat in the control group (p < 0.001). The result indicates that skin acetone emanating from a rat tail is a useful parameter to use for insulin-dependent diabetes (type I).
A new chelating resin was synthesized by immobilizing 1-(2-thiazolylazo)-2-naphthol through the –N=N– group on Amberlite XAD-1180. The resin was used for the preconcentration of Cd(II), Co(II), Cu(II), Mn(II), Ni(II), and Pb(II) ions and their determination by flame atomic absorption spectrometry (FAAS). The influences of some analytical parameters, such as the pH, volume of the sample, flow rates of the sample and eluent, matrix components, amount of the resin, and amount and type of the eluent on the recovery, were investigated. Those metals retained on the resin at pH 8.5 were eluted with 25 mL of 2 mol L−1 HNO3. The sorption capacity of the resin was determined, except for Pb(II). The recoveries were found to be ≥95%, and the relative standard-deviation values were ≤4.3%. The detection limits were in the range of 0.1 – 3.6 μg L−1. For the accuracy of the method, the analysis of a certified reference material was performed. This method was applied to environmental water samples.
The concept of amplitude-modulated multiplexed flow analysis has been extended to the simultaneous determination of multiple analytes in a sample. A sample solution containing nitrite and nitrate ions is delivered from two channels, but the flow rates are varied at different frequencies. One of the channels has a reduction column for converting nitrate ions to nitrite ions. Downstream, the absorbance of the diazo-coupling product is monitored after the merging of both solutions with a Griess reagent. The signal is analyzed by a fast Fourier transform (FFT) in real time. From the thus-obtained amplitude, a μmol dm−3 level of the ions can be determined. The introduction of air bubbles is effective to reduce any axial dispersion, and hence to improve the sensitivity.
When the ternary mixed solvents of a water–hydrophilic/hydrophobic organic solvent mixture are delivered under microspace under laminar flow conditions, the solvent molecules are radially distributed in the microspace, and generate a major inner phase and a minor outer phase. We call this fluidic phenomenon as the tube radial distribution phenomenon (TRDP). In this paper, phase formation in the TRDP was collectively considered based on experimental data, such as the inner and outer phase formation in a microchannel under laminar flow conditions, the phase diagram for the ternary mixed solvents, the solvent-component ratios required for the TRDP, and the phase transformation in a batch vessel above atmospheric pressure, which were mainly reported in our previous papers. Furthermore, the formation of inner and outer phases in a capillary tube was simulated with the two-component solvents mixture model of water and ethyl acetate. Phase formations in capillary tubes were expressed through computer simulations.