Search

Eugenols (Eugs) such as eugenol (Eug), methyleugenol (MeEug), and linalool (Lin) in basil product are the main bioactive components of basil products and have a terminal double-bond. A sensitive HPLC-fluorescence method for Eugs derivatized with 4-(4,5-diphenyl-1H-imidazol-2-yl)iodobenzene (DIBI) was developed. Good separation of DIB-Eugs was achieved within 20 min on an Atlantis T3 column (50 × 2.1 mm i.d., 3 µm) with a mobile phase of methanol-water. The calibration curves obtained with Eug standards showed good linearities in the range of 0.1-50 µM (r ≥ 0.999). The limits of detection at a signal-to-noise ratio (S/N) = 3 for Eug, MeEug, and Lin were 1.0, 6.0, and 4.8 nM, respectively. The limits of quantitation (S/N = 10) of the Eugs were lower than 19.9 nM. The accuracies for the Eugs were within 96.8-104.6%. The intra- and inter-day precisions as relative standard deviations for the Eugs were less than 1.2 and 9.6% (n = 3). The recoveries of Eug, MeEug, and Lin were 99.0 ± 0.1, 98.0 ± 0.2, and 96.0 ± 0.4% (n = 3), respectively. The DIB-Eugs were confirmed to be stable for 2 h (90%) at room temperature and 24 h (95%) at 4 °C. These parameters of the proposed method were useful for the simultaneous determination of Eugs in basil products. Therefore, the developed method may be a powerful tool for the quality evaluation of dried commercially available basil products.

We have developed an HPLC-UV method for the determination of pyrroloquinoline quinone (PQQ), which utilizes a redox-based colorimetric reaction. In the proposed colorimetric reaction, the redox reaction between PQQ and dithiothreitol generates superoxide anion radicals that can convert 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyl-2H-tetrazolium chloride (INT) to formazan dye. After PQQ separation on an octadecyl silica column, it was mixed online with dithiothreitol and INT, and the formed formazan dye was monitored by absorbance at 490 nm. The detection limit (S/N = 3) of the proposed method was 7.6 nM (152 fmol/injection). The proposed method could selectively detect PQQ in food products without any clean-up procedures.

A new pulse UV irradiation-induced chemiluminescence (CL) determination method was developed for l-tyrosine using the luminol derivative L-012. The proposed method depends on the formation of reactive oxygen species (ROS) upon pulse UV irradiation of l-tyrosine; then, these ROS react with L-012 producing strong CL. The proposed method showed excellent sensitivity and ultraselectivity toward l-tyrosine. The mechanism of the developed CL method was studied using ROS scavengers, HPLC, and mass spectrometry. The method was linear for l-tyrosine in the range of 0.03-50 μM. Minor changes in the l-tyrosine structure, including hydroxylation, dehydroxylation, phosphorylation, or decarboxylation, were found to lead to a strong decrease in CL. Using the excellent selectivity of the proposed method for l-tyrosine, we have developed a CL assay for measuring alkaline phosphatase activity in the range of 0.02-15 U/L with the limit of detection (LOD) of 4 mU/L using the nonchemiluminescent

Myristicin [5-allyl-1‑methoxy-2,3-(methylenedioxy)benzene] is the major constituent of the seasoning nutmeg oil and powder. Sometimes myristicin is abused via its ingestion at high doses to cause hallucination. In these high doses, myristicin could cause severe adverse health effects, including convulsion, delirium, and palpitation. Hence there is a strong need for a sensitive method for its analysis, such as fluorescence determination. Myristicin has a very weak fluorescence and also lacks derivatizable groups like the carboxylic, hydroxyl, or amino group in its structure, which makes its fluorescence derivatization challenging. In this research, we developed a fluorescence labeling method for myristicin based on the Mizoroki-Heck coupling reaction of its terminal alkene with a fluorescent aryl iodide derivative, 4-(4,5-diphenyl-1H-imidazol-2-yl)iodobenzene (DIB-I). Then, we developed an HPLC fluorescence detection method for the determination of myristicin utilizing this labeling reaction. The developed method showed a good linear response for myristicin (r = 0.995) in the range of 0.01-10 µmol/L with excellent sensitivity down to the detection limit of 2.9 nmol/L (9.6 fmol/injection). Finally, the developed method could be successfully applied to determine myristicin content in nutmeg powder, oil samples, and human plasma with simple extraction methods and good recoveries ranging from 89.3 to 106%.

A sensitive and stable signal multiplied quinone-linked immunosorbent assay (Multi-QuLISA) was developed. In Multi-QuLISA, an oligomerized quinone linked to biotin, namely biotin-8mer-naphthoquinone (Bio8mer-NQ), is used as a signal-generating label. Bio8mer-NQ is formed from a dendrigraft poly-l-lysine generation 1 (DPLL G1), a controlled branched oligomer composed of eight lysine moieties with nine free amino groups as a backbone. One of the nine amino groups of DPLL G1 is attached to biotin moiety, while the other eight are attached to 1,2-naphthoquinone-4-sulfonate (NQS). Bio8mer-NQ labels a biotinylated detection antibody using avidin as a co-binder. Then, multi-quinones in Bio8mer-NQ undergo a redox cycle with dithiothreitol and luminol, generating strong chemiluminescence. Standard ELISA uses a label enzyme that suffers from vulnerability in different conditions and poor stability. Bio8mer-NQ showed better stability than the enzyme (biotin-HRP) under different drastic pH and temperature conditions, hydrolytic enzymes, etc. Furthermore, Bio8mer-NQ was used as both chemiluminescence and colorimetric label based on the redox cycle of quinone, and it had LODs of 1.5 and 6.5 nM, respectively. The method could detect biotinylated immunocomplex in an in-house designed immunoassay down to 0.2 nM, which is about 25 times more sensitive than biotin HRP. Eventually, Bio8mer-NQ was applied successfully in Multi-QuLISA for detecting β-casein with a sensitivity of 3.2 ng/mL, while the conventional ELISA had an LOD of 35 ng/mL. Overall, Bio8mer-NQ is a stable compound that could be used as an excellent replacement for the enzyme in immunoassay and can be used in both colorimetric and chemiluminescence assays with good sensitivity.

Summary Primary biliary cholangitis (PBC) is characterized by the presence of serum anti-mitochondrial autoantibodies (AMAs). To date, four antigens among the 2-oxo-acid dehydrogenase complex family, which commonly have lipoyl domains as an epitope, have been identified as AMA-corresponding antigens (AMA-antigens). It has recently been reported that AMAs react more strongly with certain chemically modified mimics than with the native lipoyl domains in AMA-antigens. Moreover, high concentrations of circulating immune complexes (ICs) in PBC patients have been reported. However, the existence of ICs formed by AMAs and their antigens has not been reported to date. We hypothesized that AMAs and their antigens formed ICs in PBC sera, and analyzed sera of PBC and four autoimmune diseases (Sjögren's syndrome, systemic lupus erythematosus, systemic scleroderma, and rheumatoid arthritis) using immune complexome analysis, in which ICs are separated from serum and are identified by nano-liquid chromatography-tandem mass spectrometry. To correctly assign MS/MS spectra to peptide sequences, we used a protein-search algorithm that including lipoylation and certain xenobiotic modifications. We found three AMA-antigens, the E2 subunit of the pyruvate dehydrogenase complex (PDC-E2), the E2 subunit of the 2-oxo-glutarate dehydrogenase complex (OGDC-E2) and dihydrolipoamide dehydrogenase binding protein (E3BP), by detecting peptides containing lipoylation and xenobiotic modifications from PBC sera. Although the lipoylated sites of these peptides were different from the well-known sites, abnormal lipoylation and xenobiotic modification may lead to production of AMAs and the formation ICs. Further investigation of the lipoylated sites, xenobiotic modifications, and IC formation will lead to deepen our understanding of PBC pathogenesis.

Copper (II) is one of the most important metal ions for the human body that act as a catalytic cofactor for many metalloenzymes and proteins, and its homeostasis disruption could lead to many neurological diseases. The reported probes for Cu (II) determination are mostly based on fluorescence quenching mechanism, which provides low precision and reliability. In the present work, a turn-on fluorescence probe, (Z)-1-[2-oxo-2-[2-[1-oxoaceanthrylen-2 (1H)-ylidene]hydrazinyl]ethyl]-pyridinium (OAHP), for highly selective detection of Cu

The long-wavelength fluorogenic derivatization method for aryl halides was developed based on stilbene formation by the Heck coupling reaction between aryl halides and vinylbenzenes in the presence of palladium(II) acetate as a catalyst. Fluorescent maximum wavelengths of the derivative obtained by the proposed reaction were 365 - 450 nm, which were 50 - 100 nm longer than those of the biphenyl derivatives formed with our previously developed fluorogenic derivatization method. Also,by the investigation using vinylbenzenes containing electron-donating or -withdrawing functional groups, it was found that an internal charge transfer system could contribute to extend the emission wavelength of the derivative. Furthermore, the proposed reaction was applied to develop a pre-column derivatization HPLC with fluorescence detection method for aryl bromides using 4-vinylanisole. p-Substituted aryl bromide derivatives (i.e., p-bromobenzonitrile, p-bromoanisole, bromobenzene, p-bromobenzoic acid ethyl ester, p-bromotoluene) were successfully detected within 40 min with the detection limit of 0.007 - 0.264 μM. Despite the short reaction time of 10 min, the reaction yields for p-bromoanisole and bromobenzene were good at 101 and 87%, respectively., Analytical sciences, 36(8), pp.997-1001; 2020

Antioxidants have gained marked attention owing to their ability to prevent the oxidation of biological components and to protect the body from reactive oxygen species, thereby maintaining human health. Thus, antioxidant-rich dietary supplements and natural foods can be effective against oxidative stress and can even act as chemopreventive agents. Therefore, a simple and rapid assay for evaluation of antioxidant capacity and assessment of their distribution profile in natural sources is vital. Herein, we report a rapid, innovative chemiluminescence (CL) platform for evaluation and visualization of antioxidant capacity. We found that intense and long-lasting CL was formed upon the redox reaction of quinones, e.g., menadione, with antioxidants, e.g., l-ascorbic acid, in the presence of luminol. The produced CL intensities were proportional to the antioxidants' concentrations with a detection limit of 0.18 μM for the model antioxidant, l-ascorbic acid. As the formed CL was long-lasting, it could be easily captured and detected with a charge-coupled device (CCD) camera. To evaluate the quantification ability of the CCD camera, we developed a smart and fast microplate-based assay based on photographing the generated CL with a cooled CCD camera. The photographed CL intensities were linearly proportional with the antioxidant concentrations, and then the method was applied for photographing multiple food sample extracts. Ultimately, we utilized our method for the distribution profiling of antioxidant capacity in food cut sections. Samples were dipped in luminol and then in quinone, followed by CCD camera photography, without the need for any pulverization/extraction procedure, giving precise antioxidant distribution information.

In this letter, an improved measurement method for power transistors is proposed to obtain drain-current characteristics as a function of drain-source voltage ( ${I}_{\text {d}}$ – ${V}_{\text {ds}}$ ) in high-voltage and high-current (HVHC) ranges. A simple double pulse test (DPT) is utilized in our previous method. However, the self-heating of the device under test (DUT) is not ignorable in the range of high ${I}_{\text {d}}$ . The improved test circuit is equipped with an additional transistor connected in parallel to DUT in order to prevent the flow of a large current into DUT before the measurement. When a trench-gate type SiC MOSFET (Metal-Oxide-Semiconductor Field-Effect-Transistor) is used as a DUT, the power loss of the DUT decreases by about 80%. The transient thermal analysis shows that the die temperature rise is suppressed by up to 10 °C in about 200 A ranges. The newly obtained ${I}_{\text {d}}$ – ${V}_{\text {ds}}$ characteristics are utilized to model the SiC trench MOSFET. The device model reproduces the measured switching waveforms very accurately.

The electrothermal cosimulation proposed in this paper accurately reproduces the power loss and the temperature of the silicon carbide (SiC) metal–oxide–semiconductor field-effect transistor ( mosfet ) dies assembled in a power module comprising a buck converter. The current–voltage characteristic of the body diode embedded in a SiC mosfet is not like that of an ideal diode because this characteristic depends on the negative gate–source voltage of the transistor. Our device model was, therefore, created to reflect this unique feature and the temperature dependence of the drain current for predicting the power loss of the mosfet . The simulation uses a look-up table to reduce the computation time. This yields accurate results for the power loss in a buck converter operating at switching frequencies ( f sw) ranging from 50 to 350 kHz. The f sw-dependent steady-state temperature of the SiC mosfet was reproduced well; it ranged from 60 °C to 140 °C. The maximum deviation between the measured and the simulated results was less than 3.0 W and 8 °C, respectively, for the power loss and the temperature of the dies.

Aldehydes are highly reactive carbonyl compounds that are widespread in the nature. Aldehydes are broadly distributed in the indoor and outdoor environment sourced from the industrial, restaurant, and motor vehicular exhausts. Besides, aldehydes are thought to be a major cause of the photochemical smog in the air. Aldehydes are also present in rainwater and the surface water due to their washing away from the atmosphere owing to their high-water solubility. In addition, microbial or photochemical degradation of organic chemicals leads to the formation of aldehydes in the surface water. Furthermore, chlorination and ozonation sterilization of drinking water lead to aldehydes’ formation. On the other hand, aldehydes could be formed during cooking upon high-temperature frying and also could be sourced from cigarette smoke and/or other combustion operations. Besides, aldehydes are present in wine and vegetable oils, and they are formed as by-products during deterioration, maturing, or microbial fermentation of food. Human exposure to aldehydes from the environment or food could bring many adverse health effects either acute or chronic ones. Aldehydes are highly reactive with biological molecules; thus, they are considered highly toxic. The aldehydes’ biochemical modification could lead to the disruption of biological functions, and consequently, cause many diseases. Thus, aldehyde monitoring in the surrounding environmental and food samples is vital to control the toxic aldehydes’ possible health risk on humans. Aldehydes’ different sources in the environment, molecular toxicity mechanisms, possible effects on human health, and recently developed analytical methods for determination and control of aldehydes in environmental and food samples will be summarized in this chapter.

A drain current model of AlN/GaN based ridge (GIT) HEMTs has been developed for source-field-plate structures. The generation mechanism and the geometry independent equations of the hole injection current are developed with Boltzmann Function. Because the current simulations show good agreements with the measurements in multi-geometries, the model can be applied to ridge HEMTs to design power supply circuits.

Synchronized bio-distribution of combination therapies has several merits such as synergistic effects and reduced side-effects. Co-delivery of a protein and small molecule drug using a single nanocarrier is challenging because they possess totally different characteristics. Herein, we report the development of sophisticated nanoparticles composed of lipids, calcium carbonate and RGD peptide ligands for the co-delivery of a protein and small molecule drug combination via a simple preparation method. A ‘one-step’ ethanol injection method was employed to prepare the highly organized nanoparticles. The nanoparticles exhibited a spherical shape with ca. 130?nm diameter, and clearly had an integrated lipid layer covering the periphery. As a ligand, an RGD-modified lipid was post-inserted into the nanoparticles, which was important to overcome the ‘PEG dilemma’. The pH-sensitivity of the targeted nanoparticles contributed to the efficient intracellular co-delivery of a protein and drug combination in Colon26 tumor cells, and noticeably improved their accumulation in the tumor region of xenograft mice. Synchronized bio-distribution of the protein and drug was achieved, which was the foundation for the synergistic effects of the combination. The targeting capability of the nanoparticles along with their pH-sensitive drug release and the synchronized bio-distribution of their cargos led to the significant antitumor activity of the SOD and paclitaxel combination in mice. This study provides novel information for the design and preparation of functionalized nanoparticles for the delivery of a protein/drug combination in vivo., Journal of Controlled Release, 302, pp.42-53; 2019

We developed high functionality and quality (HFQ) lipids for facile and rapid preparation of ligand-grafted PEGylated liposomes.Because HFQ lipids are designed to exhibit good water dispersibility, ligand-grafted PEGylated liposomes can be easily prepared using the post-insertion method. The aim of this study is to develop novel VTWTPQAWFQWV (VTW) peptide-HFQ lipid to target human glioma cells. In order to disperse in water, VTW-(SG)5-lipid derivatives containing various amino acid residues with different charges were synthesized. Based on our previous work, (SG)5, a serine-glycine repeated peptide with a discrete molecular weight, was used as a spacer between the VTW and lipid. Of the derivatives tested, VTW-K3-(SG)5-lipid with three lysine residues showed the highest dispersibility in water,and VTW-K3-(SG)5/PEGylated liposomes can be prepared using the post-insertion method. The sizes of PEGylated liposomes and VTW-K3-(SG)5/PEGylated liposomes were 69.5 ± 4.4 and 74.4 ± 5.0 nm, respectively.In addition, the zeta potentials of PEGylated liposomes and VTW-K3-(SG)5/PEGylated liposomes were ?2.7 ± 1.6 and ?1.3 ± 0.3 mV, respectively. We found that VTW-K3-(SG)5/PEGylated liposomes selectively associated with human glioma U251MG cells.We succeeded in developing water-dispersible VTW-K3-(SG)5-lipids for the preparation of VTW-grafted PEGylated liposomes for glioma cell targeting., Journal of Drug Delivery Science and Technology, 49, pp.668-673; 2019

A new fluorescence derivatization technique for the determination of the thyroid hormones, 3,3’,5-triiodo-L-thyronine (T3, triiodothyronine) and 3,3’,5,5’-tetraiodo-L-thyronine (T4, L-thyroxine), in human serum was developed based on the Sonogashira coupling reaction. This derivatization reaction was recently utilized by our research group as a promising solution for the derivatization of ortho-substituted aryl halides that suffer from steric hindrance. T3 and T4 possess amino groups that could be derivatized by many reagents; however, these reagents are not useful in the case of biological analysis as they could non-selectively react with many biogenic amines and amino acids. Thus, herein we aimed at labeling the iodo-phenyl group of T3 and T4 as a selective fluorescence labeling approach suitable for biological analysis. The fluorescent alkyne, 2-(4-ethynylphenyl)-4,5-diphenyl-1H-imidazole (DIB-ET), can label the ortho-substituted aryl halides T3 and T4 in the presence of palladium and copper as catalysts, overcoming the steric hindrance of ortho-substitution. Furthermore, the application of the proposed method for the selective analysis of T3 and T4 in biological samples was successfully performed even in the presence of numerous biological components. The formed fluorescent derivatives produced from the reaction of DIB-ET and T3 and T4 could be determined by an HPLC system with fluorescence detection. The proposed method was successfully applied for the selective and sensitive determination of T3 and T4 in human serum with the detection limits (S/N = 3) of 4.0 and 6.1 ng/mL and the recovery rate in the range of 84.3-92.1% and 81.3-84.9%, respectively. Therefore, the proposed method could be used as a new simple tool for the simultaneous determination of T3 and T4 in biological samples., Journal of Chromatography A, 1677, art. no. 463275; 2022

Enzyme-labeled immunoassays are widely used for trace analysis of clinically significant compounds owing to their high selectivity. However, utilizing an enzyme for labeling the antibody leads to many problems, including low reproducibility and inhibition of antigen-antibody immuno-reaction due to the enzymes’ instability and bulkiness, respectively. Hence, our research group has been using quinones as stable non-enzymatic tags for antibodies utilizing the redox cycle of quinones. Herein, we aimed to use the broadly available and cost-effective quinone, 1,2-naphthoquinone-4-sulfonate (NQS, Folin’s reagent), for signal tagging of immunoassays. NQS could bond with biotin in a relatively short time and without using a catalyst forming biotin-1,2-naphthoquinone (BT-NQ). The synthesized BT-NQ produces strong chemiluminescence or color upon mixing with reductant and luminol or tetrazolium salts, with sensitivity down to 7.7 nM and 49.0 nM, espectively. Next, BT-NQ was used for developing the first quinone-linked immunosorbent assay (QuLISA) through labeling biotinylated-detection antibodies using avidin and BT-NQ, and it was targeted to detect food allergen, β-casein using sandwich-immunoassay. Our method showed good linearity for determination of β-casein with good sensitivity down to 20.2 ng/mL. The results of our method were compared with ELISA kit results, and QuLISA showed good matching and higher sensitivity. Moreover, we applied Folin’s reagent for direct labeling of avidin, and the resulted compound possessed strong chemiluminescence originating from its quinone content. At last, we can conclude that the use of Folin’s reagent offered a simple, stable, sensitive, and cost-effective approach for la-beling immunoassays and direct chemiluminescence labeling of proteins., Sensors and Actuators B: Chemical, 368, art. no. 132167; 2022

Although benzofuran-2-boronic acid hardly emits fluorescence, it can be rapidly converted to a highly fluorescent benzofuran dimer after mixing with a palladium catalyst and amine. We found that a fluorescence enhancement accompanying dimerization was quantitatively promoted upon increasing the concentration of amine. In the present study, we developed a simple fluorescence assay for amines based on the promotive effect. As the result of a fluorescence measurement of the reaction mixture of 19 kinds of typical amines, it was found that tertiary amines including triethylamine (TEA) provided a significant fluorescence enhancement. Finally, the fluorogenic reaction could be applied to develop a high-throughput fluorescent microplate assay for TEA with the limit of detection (blank + 3SD) of 0.091 μM., Analytical Sciences, 37(10), pp. 1465-1467; 2021

This chapter presents the fundamentals and applications of green solvents as alternate environmentally friendly and safe solvents for extraction of radionuclides. At the beginning of the chapter, we outlined the definition, main sources, and uses of radionuclides. Then, we emphasized the main classes of green solvents for the extraction of radionuclides, namely; supercritical fluids and ionic liquids. The chemical and physical properties of each solvent class with various examples and different chelating agents utilized together with supercritical fluid extraction were discussed. The advantages of supercritical fluid extraction over classical techniques, as well as the advantages of using ionic liquids for improving the greenness of traditional techniques for radionuclide extraction were highlighted with many examples from the literature.

Summary Sjögren's syndrome (SS) is a chronic autoimmune disease that mainly damages the salivary and lacrimal glands. Immune complex (IC) formation triggers local inflammation through IC deposition and decreased antigen function. Some ICs can leak from the lesion and into the saliva, but no salivary ICs have been reported to date. We used immune complexome analysis to comprehensively identify antigens incorporated into IC (IC-antigens) in saliva samples from patients with SS (n = 9) or with xerostomia (n = 7). Neutrophil defensin 1 (67%), small proline-rich protein 2D (67%), myeloperoxidase (44%), neutrophil elastase (44%), cathepsin G (33%), nuclear mitotic apparatus 1 (33%) and phosphatidylinositol 4-phosphate 3-kinase C2 domain-containing subunit gamma (33%) were identified as new IC-antigens specifically and frequently detected in the saliva of SS patients. Of these, neutrophil defensin 1, myeloperoxidase, neutrophil elastase and cathepsin G are neutrophil intracellular proteins, which suggests that repeated destruction of neutrophils due to abnormal autoimmunity may be involved in the pathogenesis of SS. We also analyzed serum samples from three SS patients. There was little overlap of IC-antigens between two of the samples (fewer than 30% of the IC-antigens in the saliva samples), suggesting that many ICs are formed locally and independently of the circulation. In addition, we found that four SS-specific salivary antigens show sequence homology with several proteins of oral microbiomes but no antigen has homology with Epstein–Barr virus proteins. The homology between some IC-antigens and oral microbiome proteins may indicate the impact of oral infection on local autoimmunity through molecular mimicry theory.

This paper presents an experimental evaluation of the thermal couple impedance model of power modules (PMs), in which silicon carbide (SiC) metal-oxide-semiconductor field-effect-transistor (MOSFET) dies are implemented. The model considers the thermal cross-coupling effect, representing the temperature rise of a die due to power dissipations by the other dies in the same PM. We propose a characterization method to obtain the thermal couple impedance of the SiC MOSFET-based PMs for model accuracy. Simulations based on the proposed model accurately estimate the measured die temperature of three PMs with different die placements. The maximum error between measured and simulated die temperatures is within 8.1 °C in a wide and practical operation range from 70 °C to 200 °C. The thermal couple impedance model is helpful to design die placements of high-power PMs considering the thermal cross-coupling effect.

A drain current model of AlN/GaN based MIS-HEMTs and ridge (GIT) HEMTs has been developed for source-field-plate structures. Characteristic differences in these two structures are theoretically and experimentally analyzed with measurements of fabricated devices. For ridge HEMTs, hole injection current and leakage current of gate interface are focused on, whereas the MIS-HEMTs use a MOSFET gate modeling approach. Because the simulation results show good agreements with the measurements, one model can be applied to both MIS and ridge HEMTs to design power supply circuits.

Currently, LC-MS has various applications in different areas such as metabolomics, pharmacokinetics, and pathological studies. Yet, matrix effects resulting from co-existing constituents remain a major problem for LC-MS [or LC-tandem mass spectrometry (LC-MS/MS)]. Moreover, technical problems and instrumental drifts may lead to ion abundance variance. Thus, an internal standard (IS) is required to guarantee the accuracy and precision of the method. Because of their limited number, isotope-coded derivatization (ICD) has been recently introduced to overcome this problem. For ICD, a stable heavy isotope-coded moiety is used for labeling the standard or the control sample and the formed products can act as ISs. A light form of the reagent is used for labeling the sample. Then, both are mixed and analyzed by LC-MS(/MS). This strategy permits the identification of different unknown analytes including potential metabolites and disease biomarkers. All these attributes lead to persistent growth in the applications of ICD LC-MS(/MS) in various biomedical branches. In this article we review the ICD methods published in the last eight years for biomedical applications as well as briefly summarize other applications for environmental and food analyses as some of their used ICD reagents were further applied for analyzing biological specimens or have the potential for that.

Glyoxylic acid (GA) is the intermediate metabolite in various mammalian metabolic pathways. GA showed high reactivity towards formation of advanced glycation end-products (AGEs); the main cause of pathogenesis and complications of many diseases. The presented study aimed to detect GA in healthy and cardiovascular patients’ (CV) sera; however analysis of GA in biological fluid is a challenge and requires chemical derivatization. Hence, a new, highly sensitive, time saving and reproducible pre-column fluorescence derivatization procedure coupled with high performance liquid chromatography (HPLC) method was developed. The derivatization method was based on reaction of 2-aminobenzenthiol (2-ABT), a fluorogenic reagent, with GA in acidic medium to form highly fluorescent thiazine derivative (290 and 390 nm for excitation and emission wavelengths respectively). The fluorescent derivative was separated within 6 min on a reversed-phase ODS column using an isocratic elution with a mixture of methanol?water (70:30, v/v%). The proposed method parameters were optimized and the method was validated. A good linearity in the concentration range (0.05?5.0 μM) was obtained with detection limit (LOD) of 10 nM (200 fmol/injection), which is more sensitive than several previous methods. Moreover, the recovery results were within the range of 85.0?95.5 % and the intra- and inter-day precision results were ?3.5%. It should be emphasized that this method is the first one for monitoring of GA in CV patients; to investigate its role for diagnosis and monitoring the severity and complications of this disease in clinical laboratory., Journal of Chromatography B, 1143, art.no.122054; 2020

Accumulation of environmental contaminants that increased with the global amplified human activities has many harmful adverse effects on humans, animals, and the environment. Environmental pollutants include but not limited to heavy metals, pesticides, pathogens, toxins, and particulate matters. Consequently, the monitoring of environmental pollutants became a priority. For this aim, sensors have captivated the attention of many scientists in modern time by virtue of their eco-friendliness, cost-effectiveness, miniaturization ability, and rapidness.

Isotope-coded derivatization (ICD) is used as a promising alternative approach to isotope internal standards in order to overcome matrix effects caused by coexisting substances that often occur while analyzing metabolites by LC-MS/MS. ICD introduces two different mass tags to every analyte via the use of heavy and light forms of the derivatization reagents. Herein, we report the first ICD approach for aldehydes that uses commercially available reagents avoiding the need for expensive and tedious multisteps synthetic procedures. The method is based on the reaction of the safe and stable derivatizing agent, 9,10-phenanthrenequinone, and the cheap and commercially available ICD reagent, 14N/15N-ammonium acetate, with aldehydes followed by LC/ESI+-MS/MS. Multiple reaction monitoring is done at the transitions m/z [M + H]+ → m/z [Product ion A] and m/z [M + 2 + H]+ → m/z [Product ion A + 2] for 14N- and 15N-labeled analytes, respectively. Among lipid peroxidation products, 4-hydroxy-2-nonenal (HNE) and 4-hydro...

Aryl halides are a very important category of compounds that include many vital drugs and key industrial additives, such as clofibrate and bromobenzene, respectively. Due to their importance, our research group previously developed a novel fluorescence labeling approach for their analysis using a fluorescent aryl boronic acid as a reagent, based on the Suzuki coupling reaction. This coupling reaction was successfully applied for the determination of aryl halides in biological fluids; however, there was a limitation of low reactivity towards ortho-substituted aryl halides. In the present study, a novel fluorescence derivatization approach for aryl halides was developed using, 2-(4-ethynylphenyl)-4,5-diphenyl-1Himidazole (DIB-ET) as a fluorescent alkyne reagent, based on the Sonogashira coupling reaction. DIB-ET reacted with aryl bromides in the presence of palladium and copper as catalysts, yielding fluorescent derivatives that could be subsequently determined by an HPLC system with fluorescence detection. The detection limits (S/N = 3) for aryl bromides were in the range of 14 - 23 nM, which is 3.5 - 18-times more sensitive than our previously developed approach, Suzuki coupling derivatization. Moreover, in contrast to the previous technique, the reactivity of DIB-ET to orthosubstituted aryl bromides was almost equivalent to that of the para-substituted aryl bromides. Hence, by using this newly developed approach we could label the aryl halides with more sensitivity and reactivity. Finally, the proposed method was successfully applied for the selective determination of aryl bromides in human serum with good recovery (84.6 - 107%), which proves the ability of the developed method to determine occupational exposure to aryl halides., Analytical sciences, 34(10), pp.1183-1188; 2018

α-Dicarbonyl compounds (α-DCs) are very clinically important as they are considered as advanced glycation end products (AGEs) precursors and biomarkers for many chronic diseases such as diabetes and vascular diseases, in addition to their major role in progression of complications of such diseases. Aromatic aldehydes and ammonium acetate were productively used as a one-pot co-reagents for fluorogenic derivatization of α-DCs yielding fluorescent imidazole derivatives. Among the tried aromatic aldehydes, 4-carbomethoxybenzaldehyde yielded the products with best fluorescent characters. This approach for fluorogenic derivatization of α-DCs overcome the selectivity problem of the most commonly used derivatization reagent for α-DCs, α-diamino compounds, that can react unselectively with α-DCs and aldehydes. Separation of the formed imidazole derivatives of five α-DCs including glucosone, 3-deoxyglucosone, glyoxal, methyl glyoxal and dimethyl glyoxal together with ethylmethylglyoxal as an internal standard was carried out on an octyl column using a mobile phase consisted of methanol-water (15:85, v/v%) containing 0.2% formic acid with time programed flow, followed by fluorescence detection at excitation/emission wavelengths of 310/410 nm. The method showed excellent sensitivity for the targeted α-DCs with limits of detections ranging from 0.4 to 5.0 nM in human serum. Simple protein precipitation procedure was used for human serum treatment yielding very good recovery (91?105%) for the targeted α-DCs. The developed method was fully validated, then applied to the analysis of the five above mentioned clinically important α-DCs in serum samples of healthy, diabetic, rheumatic and cardiac disorders human volunteers. Due to the excellent analytical features of the developed method, including high selectivity and sensitivity, it was able to detect the pattern of the targeted α-DCs serum levels under the investigated different clinical conditions., Journal of Pharmaceutical and Biomedical Analysis, 158, pp.38-46; 2018

Oligoarginines (Rn) are becoming promising tools for the intracellular delivery of biologically active molecules. NuBCP-9, a peptide that induces apoptosis in B-cell lymphoma 2 (Bcl-2)-expressing cancer cells, has been reported to promote the uptake and non-specific cytotoxicity of R8, also called octaarginine. However, it is unknown whether a similar synergistic effect can be seen with other Rn. In this study, we conjugated NuBCP-9 with various Rn (n=8, 10, 12, 14) to investigate and compare their cellular uptake characteristics. In addition, their non-specific cytotoxicity and apoptosis-inducing abilities were evaluated. We found that NuBCP-9 conjugated with Rn enhanced cellular uptake mainly through clathrin-mediated endocytosis and macropinocytosis, and that the uptake pathways were not different from those used by unconjugated Rn. However, the cytotoxicity study showed that NuBCP-9-R12 and NuBCP-9-R14 conjugates enhanced nonspecific cytotoxicity. We found that NuBCP-9-R10 conjugate had the highest uptake efficiency and induced correspondingly high levels of apoptosis, while resulting in a tolerable degree of non-specific toxicity., Biological and Pharmaceutical Bulletin, 41(9), pp.1448-1455; 2018

This paper presents two novel measurement methods to characterize silicon carbide (SiC) MOSFET devices. The resulting data are utilized to significantly improve the extraction of a custom device model that can now accurately reproduce device switching behavior. First, we consider the $I_{\text{d}}- V_{\text{ds}}$ output characteristics of power devices such as SiC transistors. These are typically measured using traditional curve tracers, but the characterization of the high-voltage and high-current (HVHC) region is very challenging because of device power compliance and self-heating. In this paper, we introduce a measurement technique that overcomes self-heating and derives the HVHC region from switching waveforms. The switching transient characteristics of devices are used to determine drain current $(I_{\text{d}})$ as a function of drain–source voltage $(V_{\text{ds}})$ in the HVHC range. Second, we consider another challenging characterization area: measurement of nonlinear capacitances when device is turned on. These capacitance characteristics of on-state devices are important for correcting disagreements between simulations and measurements in turn-off switching transient waveforms and cannot be measured using a conventional capacitance-voltage meter. We introduce S-parameter measurements as an effective method to obtain the capacitance characteristics of both off-state devices and on-state devices. These novel measurement techniques have been applied to the modeling of a SiC device. The extracted device model, a modified version of the popular Angelov−GaN high-electron-mobility transistor model, shows significant improvement in terms of the accuracy of switching waveforms of devices over a wide range of operating conditions.

Liver transplantation is a life-saving procedure for many end-stage liver diseases; however, rejection after transplantation is still occurs in some recipients. The most common form of rejection is T cell-related acute cellular rejection (ACR). To understand the mechanism of rejection, it is necessary to identify immune targets. Since the development of B cell immunity depends upon concordant T cell immunity, we hypothesized that rejection-specific antigens in circulating immune complexes (CICs) may be present in the sera of recipients experiencing rejection, and as such, may be useful as diagnostic biomarkers for ACR. The purpose of this study was to investigate rejection-specific antigens in CICs (CIC-antigens) in serum of ACR patients. We applied immune complexome analysis, in which CICs are separated from whole serum and then subjected to direct tryptic digestion and identification of CIC-antigens by nano-liquid chromatography-tandem mass spectrometry, to sera of 32 living donor liver transplant recipients (10 recipients experienced ACR and the others did not experience). CIC-antigens were compared between rejection and non-rejection groups to elucidate those that were only detected in the rejection group. We identified 11 CIC-antigens that were only detected in patients who experienced rejection, 4 of which (thrombospondin-1, apolipoprotein E, apolipoprotein C-III, and complement factor H) were only detected during ACR.

Pre-column derivatization with fluorescence labeling reagents involves many problems including crowded chromatograms, possibility of the introduction of analytical errors, and poor selectivity. Herein we report a novel purification tag/fluorophore dual labeling approach based on a multi-component reaction to solve this major problem. Glyoxylic acid was recently identified as an early biomarker for diabetes, thus it was selected as a model analyte for our new dual labeling approach. Using the multi-component Petasis reaction, we could introduce a fluorophore (1-pyreneboronic acid, 1-PyBA) and a purification tag (taurine) to our target analyte (glyoxylic acid) in one step reaction. Using taurine as the amine reactant in Petasis reaction leads to the formation of a reaction product with a terminal sulfonic acid group which can be selectively retained on an anion exchange sorbent allowing excess fluorescent 1-PyBA reagent and its fluorescent decomposition products to be washed away. Then, quantification of the formed analyte-fluorophore-purification tag adduct was carried out by a simple isocratic HPLC-fluorescence detection method. The newly developed technique allowed highly selective, very rapid and efficient determination of glyoxylic acid in human serum eliminating endogenous components and excess reagent interference. Glyoxylic acid was determined in serum at a final concentration down to 30 nM (600 fmol/injection) with good recovery (87.0%), accuracy (? 2.2 to 9.2) and precision (%RSD ? 8.7)., Talanta, 180, pp.323-328; 2018

Aldehydes are toxic carbonyl compounds that are identified in various matrices surrounding us. For instance, aldehydes could be formed during the cooking and frying of foods which affects the food quality and safety. Derivatization is a must for the determination of aldehydes as they lack intrinsic chromophoric groups. 2,4-Dinitrophenyl hydrazine (DNPH) is the most used derivatizing reagent for aldehydes and the formed hydrazones could be determined by either HPLC-UV or LC-MS. However, UV detection is non-sensitive, and the MS equipment is expensive and not widely available. Thus, herein we report a smart chemiluminescence (CL) detection method for the DNPH aldehydes derivatives. These derivatives are supposed to possess photosensitization ability due to the presence of strong chromophoric structures; nitrobenzene and phenyl hydrazone. Upon their UV irradiation, singlet oxygen is found to be produced which then converts the DNPH-aldehyde derivative into hydroperoxide. Next, the hydroperoxide reacts with luminol in an alkaline medium producing a strong CL. An HPLC system with online UV irradiation and online reaction with luminol followed by CL detection was constructed and used for the determination of aldehydes after their derivatization with DNPH. The developed method showed excellent sensitivity with detection limits down to 1.5–18.5 nM. The achieved sensitivity is superior to that obtained by HPLC-UV and LC-MS detection methods for DNPH-aldehydes derivatives. Additionally, our approach is an chemiluminogenic where the DNPH reagent itself does not produce CL which is an excellent advantage. The method was applied successfully for the determination of aldehydes in canola oil samples using simple liquid-liquid extraction showing good recovery (87.0–106.0%), accuracy (87.2–106.6), and precision (RSD≤10.2%). After analysis of fresh and heated oil samples, it was demonstrated that heating of oil, even for short time, strongly elevated the level of their aldehydes' content. At last, it was found that the results of the analysis of aldehydes in oil samples using the proposed method perfectly matched those obtained by a reference LC-MS method.

Introduction Tanshinones are a major class of bioactive ingredients in the traditional herbal medicines, Danshen (Salvia miltiorrhiza). A sensitive and reliable determination method for tanshinones is useful to ensure the quality of Danshen. Objective To develop a sensitive and selective analytical method for tanshinones by high-performance liquid chromatography (HPLC) with fluorescence detection after pre-column derivatisation. Methodology The proposed method depends on derivatisation reaction of tanshinones with 4-carbomethoxybenzaldehyde and ammonium acetate forming intensely fluorescent imidazole derivative. Results The proposed method provided excellent sensitivity with the detection limits of 3.3 nM (66 fmol/injection), 3.2 nM (64 fmol/injection) and 2.0 nM (40 fmol/injection) for cryptotanshinone, tanshinone I and tanshinone IIA, respectively, without the necessity of complicated instrumentations. The developed method is successfully applied to quantify the contents of tanshinones in Danshen. Conclusion The developed method is the first analytical method for tanshinones by fluorescence detection. Since the derivatisation reaction is selective for the o-quinone structure of tanshinone, the developed method will become a suitable mean for the discovering of tanshinone type diterpenoids from herbal samples. Copyright © 2017 John Wiley & Sons, Ltd.

Benzofuran-2-boronic acid could be used as a fluorescent sensor for the detection of Pd2+ because it was rapidly converted to highly fluorescent derivative after mixing with Pd2+ under basic condition at room temperature. We found that dimerization of benzofuran was occurred to form fluorescent derivative by the catalytic activity of palladium. The fluorescence intensity at 360 nm increased with increasing the concentration of Pd2+. The excellent selectivity for Pd2+ was demonstrated among other metal ions. Based on this findings, we successfully applied benzofuran-2-boronic acid to develop a microplate-based assay for high-throughput measurement of Pd2+. The detection limit (blank + 3SD) for Pd2+ of the proposed assay was 9.8 nM.

A method for evaluating hydroxyl radical (・OH) scavenging activities using sequential injection analysis (SIA) with chemiluminescence (CL) detection was developed. In this system, CL was produced by the reaction of luminol with ・OH generated from the Fenton reaction. The scavenging activity was expressed as a diminution rate of the CL due to the scavenging of ・OH by a sample. The SIA system allows the automation of a series of experimental procedures including Fenton's reaction, scavenging of ・OH, and luminol CL reaction. The evaluation of scavenging activities in one sample (n = 3) was completed within 3.0 min. Relative standard deviations (n = 3) of scavenging activity with 700 μM L-ascorbic acid were 2.6% (intraday) and 3.7% (interday). The SIA-CL system was applied to measure ・OH scavenging activities of several antioxidants and pharmaceuticals., Analytical Sciences, 33(6), pp.697-701; 2017