Micro-channel chemiluminescence analysis using a peroxyoxalate reaction that works through liquid-liquid interface collapse under laminar-flow conditions.

An oxalate reagent-hydrogen peroxide-fluorescent compound chemiluminescence reaction, i.e., peroxyoxalate chemiluminescence, was introduced into micro-channel chemiluminescence analysis (MCCLA) to establish the concept of MCCLA through the direct observation of fluorescence and chemiluminescence using a fluorescence microscope-CCD camera and a microscope-CCD camera. It was confirmed from visual data that chemiluminescence in the MCCLA generated through the liquid-liquid interface collapsed during the course of molecular diffusion in the micro-channel. In addition, the visual data of chemiluminescence were transformed to line drawings on a computer to obtain chemiluminescence profiles. The chemiluminescence profiles were examined in detail at various flow rates and detection points; the relationship between the residence times and the chemiluminescence peak heights, or areas in the profiles, was easily represented as one smoothly changing reaction curve. Furthermore, the fluorescent compounds were detected with high sensitivity and good reproducibility in MCCLA by turning the syringe pumps on and off to produce determinable chemiluminescence signals; a photomultiplier tube was used as a detector. The chemiluminescence intensities in the signals of erythrosine, rhodamine B, Rose Bengal, fluorescein isothiocyanate, and eosin Y were examined; their intensities increased in this order, and eosin Y responded over the range of 1 x 10(-9) - 1 x 10(-6) M with a detection limit of 1 x 10(-9) M (S/N = 3). Introducing of the peroxyoxalate chemiluminescence reaction into MCCLA can extend the analysis system to the analysis of various types of sample and applications incorporating fluorescence labeling techniques.

Preparation of highly photosensitizing liposomes with fullerene-doped lipid bilayer using dispersion-controllable molecular exchange reactions.

Fullerene-containing liposomes with high photosensitization ability were prepared. Disaggregated fullerenes were efficiently injected into the bilayer of liposomes by a phototriggered molecular exchange reaction. These liposomes showed far higher photoreactivity than liposomes thermally produced by heating and microwave irradiation. This result indicates that control of self-aggregation of fullerene leads to a high quantum yield for the photoreaction because of the suppression of self-quenching of photoexcited fullerenes.

Development of an immune microanalysis system by use of peroxyoxalate chemiluminescence detection.

We developed an immune microanalysis system incorporating chemiluminescence detection, where the peroxyoxalate chemiluminescence (CL) detection using bis[4-nitro-2-(3,6,9-trioxadecyloxycarbonyl)phenyl]oxalate (TDPO)-hydrogen peroxide (H2O2)-fluorescein isothiocianate (FITC) reaction was newly adopted. The analysis system performed the following three processes on a microchip: immune reaction for high selectivity, electrophoresis for formation and transportation of the sample plug, and CL detection. The immune reaction was carried out using an antibody-immobilized glass bead. The glass bead was placed in one of the reservoirs in the microchip along with antigen (analyte) and a known amount of FITC-labeled antigen to set up a competitive immune reaction. The reactant after the immune reaction was fed electrophoretically into the intersection, resulting in a sample plug. The sample plug was then moved into another reservoir containing TDPO-H2O2 acetonitrile solution. At this point, CL detection was performed. The system described here was capable of determining human serum albumin or immunosuppressive acidic protein as a cancer marker in human serum.

Analysis of antioxidants using a capillary electrophoresis with chemiluminescence detection system.

We developed a capillary electrophoresis with chemiluminescence detection system using 2-methyl-6-p-methoxyphenylethynylimidazopyrazinone as a chemiluminescence reagent for determination of antioxidants of superoxide anions. 2-Methyl-6-p-methoxyphenylethynylimidazopyrazinone reacted with superoxide anions generated through the reaction of hypoxanthine and xanthine oxidase, and then emitted chemiluminescence. Suppression of the chemiluminescence in the presence of antioxidants for superoxide anions was introduced as a detection principle for antioxidants into the capillary electrophoresis with chemiluminescence detection system. After optimizing the analytical conditions, various antioxidants, such as superoxide dismutase, nitroblue tetrazolium, ascorbic acid, and catechin, were subjected to the present system. They gave negative peaks due to the quenching effect; the detection limits of superoxide dismutase, nitroblue tetrazolium, ascorbic acid, and catechin were 1, 100, 100, and 10 microM, respectively (S/N=2). A model sample consisting of superoxide dismutase and nitroblue tetrazolium was satisfactorily separated and detected within ca. 10 min. We also applied the present system to analysis of catechin in green tea as a real sample.

Migration behavior of isoluminol isothiocyanate-labeled alpha-amino acids in capillary electrophoresis with an absorption/chemiluminescence dual detection system.

In our previous study, we developed capillary electrophoresis with an ultraviolet absorption/chemiluminescence dual detection system. Here, to demonstrate one of the possible applications of the capable system as well as confirm the advantage, migration behavior of isoluminol isothiocyanate-labeled alpha-amino acids was examined in the capillary electrophoresis with a dual detection system. The labeled samples were first analyzed by absorption detection with an on-capillary, followed by chemiluminescence detection with an end-capillary. The system easily, rapidly, and simultaneously produced useful information concerning chemiluminescence quenching and amino group-labeling due to the presence of both absorption and chemiluminescence detections.

Enhancing effect of phenylboronic acid compounds and their interactions with the diol groups of saccharides in a capillary electrophoresis-chemiluminescence detection system.

In our previous study, we proposed molecular recognition of mono- and disaccharides making use of the interaction between their diol groups and p-iodophenylboronic acid in capillary electrophoresis with a chemiluminescence detection system. Here, to extend our knowledge of molecular recognition, we first examined the enhancing effects of four phenylboronic acid compounds other than p-iodophenylboronic acid i.e., 4-biphenylboronic acid, 4-octyloxyphenyl-boronic acid, 3-octyloxyphenylboronic acid, and 4-dodecyloxyphenylboronic acid, for luminol-hydrogen peroxide-horseradish peroxidase reaction in the capillary electrophoresis-chemiluminescence detection system. Only 4-biphenylboronic acid showed an enhancing effect similar to that of p-iodophenylboronic acid; the effect was determined over the range of 0.5-10 microM in this system. Second, we estimated the apparent stability constants between the diol groups of saccharides (1-methyl-D-glucoside, D-saccharose, and D-fructose) and the boronic acid moieties of the two enhancers, p-iodophenylboronic acid and 4-biphenylboronic acid. The apparent binding constants obtained here provided insight to confirm the principle of molecular recognition for the saccharides examined here.

Characterization of chemiluminescence from singlet oxygen under laminar flow conditions in a micro-channel and its quenching with beverages.

Singlet oxygen was generated by reaction of sodium hypochlorite and hydrogen peroxide in a micro-channel. The two reagent solutions were delivered into the micro-channel by a syringe pump, providing a laminar flow liquid-liquid interface. The chemiluminescence from the singlet oxygen was emitted in the collapse of the interface due to molecular diffusion under laminar flow conditions. The chemiluminescence intensity was observed continuously and stably for each combination of reagents fed into the micro-channel; while, in the normal batch-type reactor the chemiluminescence peaks from singlet oxygen were observed within ca. 5s. The features of the chemiluminescence emitted under laminar flow conditions were examined by changing the concentrations of sodium hypochlorite and hydrogen peroxide; the concentrations of 2.5mM sodium hypochlorite and 7.5mM hydrogen peroxide provided highest chemiluminescence intensities without bubble formation. Also, the effects of beverages, such as green tea, coffee, white wine, red wine, and sake (rice wine), on the chemiluminescence intensity as well as the concentrations of sodium hypochlorite and hydrogen peroxide were examined. The chemiluminescence intensities observed with addition of the beverages to the reagents decreased in the following orders; green tea>coffee>red wine>rice wine>white wine (being added to sodium hypochlorite); coffee>white wine>green tea>red wine>rice wine (being added to hydrogen peroxide). It was found that coffee decreased the chemiluminescence intensity (ca. 33% chemiluminescence decrease) without altering the concentrations of sodium hypochlorite or hydrogen peroxide. The cause of the decrease in chemiluminescence with coffee is discussed.

Compact polytetrafluoroethylene assembly-type capillary electrophoresis with chemiluminescence detection.

We have developed a compact polytetrafluoroethylene (PTFE) assembly-type capillary electrophoresis with chemiluminescence (CL) detection system. Luminol-microperoxidase-hydrogen peroxide chemiluminescence reaction was adopted. The device is rectangular in shape (60 mm x 40 mm x 30 mm) and includes three reservoirs (sample, migration buffer, and detection reservoirs) with electrodes. The detection reservoir includes an optical fiber to transport light at the capillary tip to a photomultiplier tube. Isoluminol isothiocyanate (ILITC) was analyzed as a model using this device with fused-silica or polytetrafluoroethylene capillary tubes 10 cm in length. We also used the sample reservoir as a reactor for an immune reaction between anti-human serum albumin immobilized on glass beads and isoluminol isothiocyanate-labeled human serum albumin. The present polytetrafluoroethylene assembly with the capillary tube was useful as a palm-sized analysis device for separation and detection, as well as a reactor.

Molecular recognition of mono- and disaccharides through interaction with p-iodophenylboronic acid in capillary electrophoresis with a chemiluminescence detection system.

Molecular recognition of mono- and disaccharides was performed making use of the interaction between their diol groups and p-iodophenylboronic acid in capillary electrophoresis (CE) with a chemiluminescence (CL) detection system. p-Iodophenylboronic acid acted as an enhancer for luminol-horseradish peroxidase-hydrogen peroxide CL reaction. p-Iodophenylboronic acid was injected as a sample into the present system to give a CL peak on the electropherogram. The CL intensities were examined using running buffers including mono- and disaccharides. The CL intensities with 1-methyl-D-glucoside, D-saccharose, D-maltose, D-glucose, and D-fructose decreased in this order. The decrease in CL intensity was based on the formation by p-iodophenylboronic acid of cyclic esters with mono- and disaccharides, particularly with those including cis-diol groups. That is, the decrease in CL intensity affected the specific complexation between p-iodophenylboronic acids and saccharides, leading to the molecular recognition of saccharides. We also report separation of a mixture of p-iodophenol and p-iodophenylboronic acid as well as estimation of the apparent binding constant between p-iodophenylboronic acid and saccharides taking advantage of their molecular recognition behavior.

Observation of the complex formation between Cu(II) and protein by capillary electrophoretic system incorporating an UV/CL dual detector.

We investigated the complex formation between Cu(II) and human serum albumin (HSA) through a biuret reaction by use of capillary electrophoretic system incorporating an ultra-violet absorption (UV) and chemiluminescence (CL) dual detector. Cu(II)-tartrate complex and Cu(II)-human serum albumin complex were detected by UV detection (282 nm) with on-capillary, followed by CL detection (luminol-hydrogen peroxide CL reaction) with end-capillary. We examined the effects of the reaction time and temperature on the UV and CL responses. On the basis of the obtained results we considered the Cu(II)-human serum albumin complex formation processes and its catalytic activity for the CL reaction. The system easily, rapidly, and simultaneously produced useful information concerning the complex formation of Cu(II) and human serum albumin due to the presence of the both detectors.

Chemiluminescence from singlet oxygen under laminar flow condition in a micro-channel.

Singlet oxygen was generated by reaction of sodium hypochlorite and hydrogen peroxide in a micro-channel. The two reagent solutions were delivered into the micro-channel by syringe pumps, providing a laminar flow. Such a laminar flow forms a liquid-liquid interface instantly in a micro-channel, and then the interface collapses gradually through molecular diffusion with the residence times. The chemiluminescence from the singlet oxygen was emitted in the course of the collapse of the interface under laminar flow condition. The chemiluminescence intensity was observed continuously and stably in the micro-channel as long as the reagents were fed into the channel. We examined the features of the chemiluminescence emitted in the micro-channel by changing the flow rates of reagents and the detection points in the micro-channel. The data obtained were considered along with the residence times and diffusion lengths. We also examined the effects of antioxidants, such as sodium azide, histidine, nitroblue tetrazolium, and 2-propanol on the chemiluminescence intensity.

Capillary electrophoretic system incorporating an UV/CL dual detector.

We developed a capillary electrophoretic system incorporating an ultra-violet absorption (UV)/chemiluminescence (CL) dual detector, taking advantage of the CL reaction of luminol-hydrogen peroxide and the batch-type CL detection cell. UV detection was carried out using the on-capillary method while CL detection was performed using the end-capillary method. Examination of isoluminol isothiocyanate (ILITC) as a model sample revealed two main peaks with UV detection and one main peak with CL detection. The first peak in the UV detection data corresponded to the main peak in the CL detection data. We then determined that the ILITC sample included natural ILITC as well as an impurity that had absorption behavior but did not have CL properties and labeling ability. Furthermore, the components of a mixture containing glycine, glycylglycine and glycylglycylglycine, all labeled with ILITC, were well separated and detected using the present system. The present system easily, rapidly, and simultaneously produces useful information due to the presence of both UV and CL detectors.

Capillary electrophoresis apparatus equipped with a bioluminescence detector using a batch- or flow-type detection cell.

We developed a capillary electrophoresis (CE) apparatus equipped with a batch- or flow-type bioluminescence (BL) detection cell. Firefly luciferin-luciferase BL reaction was used to analyze samples of nucleotides, such as ATP, dATP, ADP, GTP, UTP, CTP, ITP, and TTP. In the CE apparatus with the batch-type cell, ATP was detected at concentrations of 5-100 microM, while the other nucleotides were not detected at concentrations less than 500 microM. The electropherogram of ATP included two BL peaks; the latter peak showed peculiar broadening, which continued up to ca. 2.5 h. In the CE apparatus with the flow-type cell, ATP, dATP, and ADP were detected with single peaks with detection limits of 1, 75, and 100 microM, respectively. The other nucleotides, GTP, UTP, CTP, ITP, and TTP, were not detected at concentrations less than 0.5 mM. A mixture of 10 microM ATP and 100 microM dATP was examined using the CE apparatus with the flow-type BL detection cell. ATP and dATP were separated using running buffer at pH 10 containing 1 mM phenylboronic acid. The interaction between ATP and phenylboronic acid delayed the migration time of ATP.

Development of a micro total analysis system incorporating chemiluminescence detection and application to detection of cancer markers.

We developed a micro total analysis system (mu-TAS) incorporating chemiluminescence detection, in which the chemiluminescence reaction of isoluminol isothiocyanato (ILITC) (as a chemiluminescence reagent for labeling)-microperoxidase (as a catalyst)-hydrogen peroxide (as an oxidant) was adopted. The analysis system performed the following three processes on a microchip: immune reaction for high selectivity, electrophoresis for formation and transportation of the sample plug, and chemiluminescence detection for high sensitivity. The three processes were compactly integrated onto the microchip to give the mu-TAS. The microchip contained two microchannels that crossed at an intersection, while the ends of the microchannels accessed four reservoirs. As the first process, the immune reaction was performed using an antibody-immobilized glass bead. The glass bead was placed in one of the reservoirs along with antigen (analyte) and a known amount of ILITC-labeled antigen to set up a competitive immune reaction. For electrophoresis, as the second process, the reactant after the immune reaction was fed electrophoretically into the intersection resulting in a sample plug. The sample plug was then moved into another reservoir containing hydrogen peroxide solution. At this point, chemiluminescence detection was performed as the third process: the labeled antigen mixed with the hydrogen peroxide and the catalyst included in the migration buffer to produce chemiluminescence. Chemiluminescence was detected by a photomultiplier tube located under the reservoir. The mu-TAS described here was capable of determining, with high selectivity and sensitivity, human serum albumin or immunosuppressive acidic protein as a cancer marker in human serum.

Simultaneous operation of plural separation modes in capillary electrophoresis with a chemiluminescence detector possessing a micro-space area for reaction/detection.

Analysis of alpha-amino acids, proteins, and phenolic compounds was simultaneously performed using three capillaries in capillary electrophoresis with chemiluminescence detection, taking advantage of the micro-space area for reaction/detection at the tip of the capillary. The three capillaries included usual, polymer-containing, and sodium docley sulfate (SDS)-containing migration buffers for separation. The eluted samples from the capillaries, which were inserted into the chemiluminescence detection cell, were mixed with chemiluminescence reagent at the tips of the capillaries to generate visible light. The specific micro-space area for reaction/detection at the tips of the capillaries enabled the simultaneous operation of the three separation modes in the present system.

Direct detection of biomolecules in a capillary electrophoresis-chemiluminescence detection system.

Direct detection of biomolecules, such as alpha-amino acids, peptides, and proteins, was accomplished using a capillary electrophoresis-chemiluminescence detection system, in which a luminol-hydrogen peroxide-Cu(II)-catalyzed chemiluminescence reaction was utilized. Biomolecules migrated in the capillary, where they mixed with luminol and the Cu(II) catalyst included in the running buffer. The capillary outlet was inserted into a batch-type chemiluminescence detection cell with hydrogen peroxide-supplemented electrolyte solution. Chemiluminescence was observed at the tip of the capillary outlet. The chemiluminescence peak from biomolecules appeared due to the enhancement of Cu(II) catalytic activity for luminol-hydrogen peroxide chemiluminescence. The Cu(II) was more catalytically active when it interacted with biomolecules forming Cu(II)-biomolecule complexes. In this study, biomolecules were directly separated and detected in a capillary electrophoresis-chemiluminescence detection system. Twenty alpha-amino acids, 4 peptides, and 11 proteins were examined. Most of them were detected with satisfactory CL intensity response. Glutamic acid, an alpha-amino acid, was detected at concentrations ranging from 2.0 x 10(-7) to 1.2 x 10(-5) M with a detection limit (S/N = 3) of 1.0 x 10(-7) M (0.6 fmol). Glycylglycine, a peptide, was detected at concentrations ranging from 1.7 x 10(-7) to 1.2 x 10(-5) M with a detection limit (S/N = 3) of 1.7 x 10(-7) M (0.9 fmol). Hemoglobin, a heme protein, in which the heme structure was independently catalytically active, was detected at concentrations ranging from 1.2 x 10(-7) to 1.0 x 10(-5) M with a detection limit (S/N = 3) of 1.2 x 10(-7) M (0.6 fmol). Representative mixtures of alpha-amino acids and peptides were well detected with superior separation.

Preparation of an iminodiacetic acid-modified capillary and its performance in capillary liquid chromatography and immobilized metal chelate affinity capillary electrophoresis.

We prepared iminodiacetic acid (IDA)-modified and Cu(II)-IDA-modified capillaries through polymerization of N-(vinylbenzylimino) diacetic acid. The fundamental performance of these capillaries was examined in capillary liquid chromatography (LC) and immobilized metal chelate affinity capillary electrophoresis (IMACE). Copper(II), cobalt(II), and hematin were detected at different retention times by means of capillary LC with a chemiluminescence detector, during which the IDA-modified capillary was used. The difference in the retention times was attributed to the difference in the interaction between metal ions or complex and IDA moieties on the inner wall of the capillary. In addition, human serum albumin (HSA) and human serum gamma-globulin (HgammaG) were separated and detected using IMACE with an absorption detector, during which the Cu(II)-IDA-modified capillary was used. The separation of HSA and HgammaG was achieved through the interaction between proteins and Cu(II) chelate moieties on the inner wall of this capillary.

Capillary electrophoresis-chemiluminescence detection system equipped with a consecutive sample-injection device.

We have developed a consecutive sample-injection device for capillary electrophoresis, which comprises one four-way cock, two syringe pumps, and an interface part taking advantage of two three-way Teflon joints. Sample introduction into the capillary is made hydrodynamically by pressure, caused by the flow of the sample solution at the tip of the capillary inlet. We combined the injection device with a capillary electrophoresis-chemiluminescence detection system. A mixture solution of N-(4-aminobutyl)-N-ethylisoluminol, isoluminol isothiocyanate, and luminol was analyzed as a model sample by the present system. The sample solution was consecutively injected and detected with about a 230 s interval. The present capillary electrophoresis-chemiluminescence detection system with the consecutive sample injection device features easy and rapid operation, an inexpensive apparatus, high sensitivity, as well as consecutive analysis.

Simultaneous analysis of plural samples in a CE-CL detector possessing micro-space area for reaction/detection.

Plural samples were simultaneously analyzed in a capillary electrophoresis (CE)-chemiluminescence (CL) detector system, taking advantage of a micro-space area for reaction/detection at the tip of the capillary. The CL reaction of 1,10-phenanthroline and hydrogen peroxide was adopted and a Cu(II) sample was used as a model. Three different length capillaries were inserted into a flow-type CL detection cell made of a Teflon tube. Three samples migrated in the corresponding capillaries at the same time and mixed with the CL reagent at the tip of capillary to produce CL. The simultaneous analysis of plural samples in the present system supported the possibility that a real sample could be determined more easily, rapidly, and precisely with the calibration curve.

Development of ultra-micro flow analysis with chemiluminescence detector.

We proposed to combine an ultra-micro flow analysis instrument using the fused-silica capillary and the CL detector. The CL reaction of luminol and hydrogen peroxide was adopted and the batch-type CL detection cell was used. Luminol and isoluminol-labeled protein as a model were sensitively and reproducibly detected with very small amounts of quantitative reagents. The analyses were repeated at least 100 times without any treatments such as washing capillaries or exchanging the hydrogen peroxide solution. The present system successfully promoted the miniaturization, simplification, and sensitization of the analytical system.