A micro total bioassay system that mimics physiological processes was developed as a means of evaluating orally administered drugs. A new feature accounting for gastrointestinal digestion was added to the previous system, which consists of microintestine, microliver, and target components. The artificial micro-gastrointestinal tract employs synthetic digestive juices. The system could correctly assay the overall digestive properties of ingested anticancer agents, i.e., the stability during digestive processes, as well as intestinal absorption, hepatic metabolism, and bioactivity toward target cells.
The metabolism of anti-breast cancer drug, tamoxifen, in a single human hepatocellular carcinoma cell, HepG2, was directly monitored by a video-mass spectroscope. The cytoplasm, a vacuole or nucleus of the cell was directly sucked by a nano-spray tip under a video-microscope, and then was introduced into a mass spectrometer. Unchanged drug molecules were found in cytoplasm and a vacuole, but the metabolites were only found in the cytoplasm. This direct detection of drug metabolites in a live single cell is useful for speedy drug metabolism monitoring.
The present article reviews the use of polyethylene glycol (PEG) or polyoxyethylene (POE) as the stationary phase for the separation of inorganic anions in ion chromatography and discusses about the retention mechanisms involved in the separation of anions on the novel stationary phases. PEG permanently coated on a hydrophobic stationary phase retained anions in the partition mode and allowed us to use high-concentration eluents because the retention of anions increased with increasing eluent concentration for most of the eluents. This situation was convenient to determine trace anions contained in seawater samples without any disturbance due to matrices. Chemically bonded POE stationary phases retained not only anions but also cations. Anions were retained in the ion-exchange mode, although POE chains possess no ion exchange sites. The retention behavior suggested that eluent cations could be trapped among multiple POE chains via ion-dipole interaction, and that the trapped cations worked as the anion-exchange sites. Anions could be separated using crown ether, i.e., cyclic POE, as the eluent additive with a hydrophobic stationary phase, where analyte anions were retained via electrostatic interaction with the eluent cation trapped on the crown ether.
A stability-indicating reversed-phase liquid chromatography (RP-LC) method was validated for the assessment of recombinant human interleukin-11 (rhIL-11), based on the ICH guidelines. The method was carried out on a Jupiter C4 column (250 mm × 4.6 mm i.d.), maintained at 25°C. The mobile phase A consisted of 0.1% trifluoroacetic acid (TFA) and the mobile phase B was acetonitrile with 0.1% TFA, run at a flow rate of 1 mL/min, and using a photodiode array (PDA) detection at 214 nm. Separation was obtained with a retention time of 27.6 min, and was linear over the concentration range of 1 – 200 μg/mL (r2 = 0.9995). Specificity was established in degradation studies, which also showed that there was no interference of the excipients. The accuracy was 100.22% with bias lower than 1.25%. Moreover, the in vitro cytotoxicity test of the degraded products showed non-significant differences (p > 0.05). The method was applied to the assessment of rhIL-11 and related proteins in biopharmaceutical dosage forms, and the results were correlated to those of a bioassay.
Sel-P is considered to be the most important selenoprotein for evaluating the selenium (Se) status in the body. To isolate and determine Sel-P in plasma, we have developed an analytical method combining heparin affinity (AF) and size-exclusion column (SEC) high-performance liquid chromatography–inductively coupled plasma mass spectrometry (HPLC-ICPMS). We used this method to validate the adsorption efficiency of selenoproteins on a heparin AF column, and to then determine the Se concentrations incorporated in proteins in human and mouse plasma. The adsorption efficiency of Sel-P on a heparin column was more than 90% for both human and mouse plasma. Tandem AF and SEC separation proved to be useful for determining the Se concentrations incorporated in Sel-P in mouse plasma, but not in human plasma, because of nonspecific adsorption of plasma-extracellular glutathione peroxidase (eGPx) and albumin on the heparin AF column. Ultimately, we used the tandem AF and SEC separation method for mouse plasma and SEC separation alone for human plasma. The Se concentration incorporated in selenoproteins determined by our method showed good agreements with the total Se concentration determined following acid digestion.
A novel method for the selective determination of Fe(II) and Fe(III) in water using 2-nitroso-5-[N-n-propyl-N-(3-sulfopropyl)amino]phenol (PSAP) was developed. QAE-Sephadex anion exchanger packed in a flow-through cell was used as a medium not only for both the concentration and the spectrophotometric measurements of the Fe-PSAP complex, but also for reduction of the Fe(III)-PSAP complex. The PSAP complex of Fe(II) or Fe(III) was strongly adsorbed on the anion exchanger in a weakly acidic to weakly basic region, but the Fe(III) complex was readily and completely reduced to the Fe(II) complex only in a neutral to weakly alkaline region in the solid phase. These properties were utilized to determine the Fe(II) and total Fe concentration without the addition of any reducing agent. The detection limits (3σ) were 0.18 ng for Fe(II) and 0.18 ng for total Fe using a 3.2-cm3 sample solution. The present method is applicable to the determination of dissolved iron species present at μg dm−3 levels in natural water samples.
A new method for the determination of perchlorate in water and soil samples using on-line enrichment in a capillary zone electrophoresis–mass spectrometry is presented. The target analytes in the sample solutions were introduced into the capillary column by pressure-assisted electrokinetic injection (PAEKI) with the simultaneous application of –18 kV and +50 mbar external pressure to the sample vial at the capillary inlet for 4 min. The injected sample zone was flushed out with a running buffer and analyzed by a tandem mass spectrometer in a negative selected reaction monitoring mode. The influence of the matrix in both water and soil samples was eliminated by a clean-up step by passing the sample through Ba/Ag/H cartridges. The method showed good linearity in the dynamic range of 20 to 1000 ng/L, and achieved a detection limit of 18.7 ng/L for water samples and 3.3 ng/g for soil samples, respectively. The recovery of perchlorate in spiked samples, at three different levels, ranged over 79 – 127%. The method reproducibility was found to be 11% RSD for water samples and 7% RSD for soil samples. Perchlorate was found in 25 out of 28 water samples analyzed, with the levels ranging from 19.8 to 192 ng/L, and was not detected in the 10 soil samples analyzed.
In the present study, we aimed to develop a nucleic acid lateral-flow method for the rapid and sensitive detection of multiple bacteria that contaminate platelet concentrations (PCs). Polymerase chain reaction (PCR) amplicons were produced by a set of board-range primers that recognize the conserved region of bacteria 16S rDNA, followed by hybridization with both an FITC (fluorescein isothiocyanate)-labelled probe and biotin-labelled probe, and then a nucleic acid lateral-flow dipstick (LFD) assay. The LFD accurately identified 7 species of bacteria, but had no cross-reactivity with human genomic DNA. The limit of detection (LOD) of the LFD assay was as low as 101 copies/μL of 16S rDNA for plasmid. In the case of spiked PCs without enrichment, the detection limit of LFD for K. pneumonia was 5 CFU/mL, 6.5 × 104 CFU/mL for the S. epidermidis and 35 CFU/mL for P. aeruginosa.
Novel salicyl alcohol derivatives (H2Xnsal), 5-bromo-, 3,5-dibromo-, and 3,5-diiodosalicyl alcohol which were abbreviated to H2Brsal, H2Br2sal, and H2I2sal, respectively, were synthesized and used for the selective extraction of boric acid. Boric acid was extracted with each H2Xnsal into chlorobenzene containing trioctylmethylammonium chloride (TOMACl) as an ion-pair complex, TOMA·B(Xnsal)2, at a different pH range. The extraction constant (Kex) of boric acid was determined by the equilibrium analyses including the formation of hydrogen-bonded complex of each H2Xnsal with TOMACl in the organic phase. The Kex values obtained by salicyl alcohol (H2sal) and its derivatives were decreased in the order of H2I2sal ≥ H2Br2sal > H2Brsal > H2sal. The most powerful extractant, H2I2sal, was employed for the substoichiometric extraction of boric acid, which was extracted at pH 5 – 9 with a substoichiometric amount of TOMACl in the presence of an excess of H2I2sal. The present substoichiometric separation method combined with the stable isotope dilution analysis using inductively coupled plasma mass spectrometry (ICP-MS) could be successfully applied to the determination of boron in a reference material of high-analysis compound fertilizer (FAMIC-A-08) without any correction as to the isotopic abundance.
The voltammetric detection of phosphoproteins was developed using a gallium(III) acetylacetonate-modified carbon paste electrode. Because phosphate groups of the protein interacted with the gallium(III) ion, the protein was accumulated on the electrode surface. A hexaammine ruthenium(III) ion, which combined with the functional groups, was used to monitor the interaction. When phosvitin and hexaammine ruthenium(III) ions were incubated in 0.1 M acetate buffer (pH 3.2), a reduction peak of hexaammine ruthenium(III) ion at the electrode decreased as the concentration of the protein increased. In contrast, an increase in the peak current was observed with a plain carbon paste electrode. These results were caused by a competitive reaction of the phosphate groups with the hexaammine ruthenium(III) and gallium(III) ions. In the presence of α-, β- and κ-caseins, the electrode response decreased due to the order of the numbers of phosphate groups. This method could be applied to the sensing of phosphoproteins at the 10−10 M level.
The electrochemical reduction of 9,10-anthraquinone (AQ) was investigated in CH3CN in both the absence and presence of the hydrogen-bond and proton donating additives, CH3OH, CH(CF3)2OH, phenol, 4-methoxyphenol, 4-cyanophenol, 2,4,6-trichlorophenol, and benzoic acid (BA). Three clearly different types of electrochemical behavior were observed with increasing concentrations of the additives, and were simulated to analyze the reaction mechanisms. Type I was observed for weakly interacting additives, such as CH3OH, characterized by positive shifts of the two well-separated reduction waves, corresponding to the formation of AQ•− and AQ2−, with no loss of reversibility. The second wave shifted more strongly, and finally merged with the first. These behaviors are explained by the association of AQ2− with the additives via strong hydrogen-bonding. Type II is attributed to a reduction mechanism involving quantitative formation of strong hydrogen-bonded complexes of AQ2− with additives, such as CH(CF3)2OH, phenol and 4-methoxyphenol, showing a reversible or quasireversible two-electron reduction wave with increasing concentrations of the additives. The behavior of Type III, observed in the presence of strongly interacting additives, such as 2,4,6-trichlorophenol and BA, is characterized by a voltammogram composed of the 2-electorn cathodic and the broad anodic waves without keeping reversibility, facilitated by proton transfer in the hydrogen-bonded complexes, AQ•−-BA and AQ2−-BA. The effects of hydrogen-bonding and protonation on the electrochemistry of AQ have been systematically demonstrated in terms of the potentials and reaction pathways of the various species, which appear in quinone-hydroquinone systems.
A simple, rapid and sensitive electrochemiluminescence (ECL) sensor was proposed for direct measurements of methyl parathion (MP) based on the strong affinity of a nano zirconia particles (ZrO2 NPs) modified film on the electrode to the phosphoric group. ZrO2 NPs, which could provide a larger absorption area to immobilize organophosphorus, was firstly modified on the glassy carbon electrode surface to prepare the proposed ECL sensor (ZrO2/GC). Subsequently, the ZrO2/GC electrode was scanned from –0.8 to +0.6 V to obtain the background signal at 0.44 V in a luminol/KCl solution. Then, a certain concentration of MP was added to an aqueous solution for 240 s, which was absorbed onto the ZrO2/GC electrode surface. Moreover, the MP absorbed on the surface of the ZrO2/GC electrode enhanced the ECL signal of luminol in the luminol/KCl solution, which increased with the concentration of MP. As a result, a novel ECL sensor was obtained in a luminol/KCl solution. The MP was determined in the range of from 3.8 × 10−11 to 3.8 × 10−6 mol L−1, with a low detection limit of 1.27 × 10−11 mol L−1 (S/N = 3). The proposed ECL sensor performance for MP detection will open a new field in the application of rapid and screen detection of ultra-trace amounts of organ phosphorus pesticides (OPs) of vegetables used in farm markets.
Three novel hybrid materials have been synthesized by ligands: N-(2-vinylsulfanyl-ethylidene)-benzene-1,2-dimine (SBD), N-pyridin-2-ylmethylene-benzene-1,2-dimine (NBD) and N-furan-2-ylmethylene-benzene-1,2-dimine (OBD), covalently linking to multi-walled carbon nanotubes (MWCNTs). These MWCNT hybrid materials were used both as ionophores and as ion-to-electron transducers to construct Ag+ carbon paste electrodes. The resulting electrodes show higher selectivity to Ag+ than other cations tested. Among the three electrodes, the electrode based on SBD-g-MWCNTs with optimum composition shows the best performance to Ag+. It exhibits an excellent Nernstian response to Ag+ in the concentration range from 8.8 × 10−8 to 1.0 × 10−1 M with a detection limit of 6.3 × 10−8 M, and it can also be used over a wide pH range of 3.0 – 8.0 with a quick response time of 5 s. The response mechanism of the proposed electrode was also investigated by using AC impedance and UV-vis spectroscopy techniques.
Non-invasive Raman spectroscopy has been used in an increasing number of applications in recent years. However, in situations where surface signal is excessive, the acquired spectrum of probed sample suffers from surface interference in either conventional backscattering Raman or specially designed Raman methods. A computational method for Raman spectral recovery is required. Strong overlapping of Raman bands and intense fluorescence are the main obstacles that hinder the spectral recovery. In this paper, we present a modified version of an indirect hard modeling algorithm to extract the true Raman spectrum of the probed sample in a two-layer system. The proposed algorithm requires two spectra. By an iterative stepwise optimization, it models one spectrum as a combination of a scaling of the other spectrum, a polynomial baseline and the Raman peaks of the probed sample. It addresses the issue of Raman bands overlapping as well as intense fluorescence interference. The performance of the algorithm is evaluated on experimental Raman spectra. Comparative studies show that the proposed algorithm provides better results for Raman spectral recovery.
The electrodeposition of gold nanostructures increases the surface area of a biosensor, which brings an enhancement of the sensitivity by increasing the amount of analyte binding to the surface. To evaluate the relationship among the surface structure, the area and the analyte binding, we quantitatively analyzed them for quartz crystal microbalance (QCM) sensing by scanning electron microscopy and cyclic voltammetry measurements. The results indicate a several-times increase of analyte bindings, and also the limitation of the sensing performance.
In order to elucidate the role of desorption/ionization efficiency of peptides in MALDI-MS, we focused on peptides with disulfide bonds, which form a rigid tertiary structure. We synthesized seven sets of peptides with one disulfide bond (oxytocin, somatostatin, [Arg8]-vasopressin, [Arg8]-vasotocin, cortistatin, melanin-concentrating hormone, urotensin II-related peptide) and five sets of peptides with two disulfide bonds (tertiapin, α-conotoxin GI, α-conotoxin ImI, α-conotoxin MI and α-conotoxin SI). Each peptide set consisted of three peptides: the oxidized form (S-S type), the reduced form (SH type), and an internal standard peptide in which all cysteine residues were substituted with alanine residues. In the case of urotensin II-related peptide, tertiapin, α-conotoxin ImI and α-conotoxin MI, the reduced form showed higher desorption/ionization efficiency than the oxidized form. In contrast, the other peptides revealed higher desorption/ionization efficiency in the oxidized form relative to the reduced form. These results imply that a rigid structure of peptides formed by disulfide bonds does not correlate with desorption/ionization efficiency in MALDI-MS.
The application of matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) for pesticide analysis was demonstrated. Fifteen pesticides were chosen as the model pesticides and twenty-six MALDI matrices were screened for the most suitable matrix. Under the optimized conditions, the obtained limits of detections were lower than the maximum residue limit values stated with 12 pesticides out of 15 tested. The proposed methodology showed a good analytical performance in terms of rapid, good sensitivity and high throughput of the method as an alternative method for pesticide residues evaluation.
A simple and rapid reverse-phase high-performance liquid chromatographic (HPLC) method for the simultaneous separation and determination of erlotinib and its process-related impurities in bulk drugs has been developed. Five process-related impurities of erlotinib have been separated on an Inerstsil ODS-3V (C18) column and detected at 254 nm using a photo diode array (PDA). This HPLC method was successfully applied to the analysis of erlotinib bulk drug. The recoveries of erlotinib and process-related impurities were in the range of 92.86 – 106.23%, and found to be specific, precise and reliable for the determination of unreacted raw materials, intermediates in the reaction mixtures and bulk drugs.