Molecularly imprinted polymers for solid-phase extraction.
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Journal Article↗
Biomedical subjects
Jun Haginaka
Publications and source records attributed to Jun Haginaka.
Determination of bisphenol A in environmental water at ultra-low level by high-performance liquid chromatography with an effective on-line pretreatment device.
We have developed a simple HPLC method for the microanalysis of bisphenol A (BPA), which is often contained in environmental water and is known as an endocrine disrupter. HPLC coupled with electrochemical detection requires a simpler procedure of pretreatment compared to GC-MS. In this study, we analyzed BPA using molecularly imprinted polymer as an on-line pretreatment device. This polymer has molecular recognition sites and provides specific selectivity in extraction process. Due to this effect, the detection limit obtained with this HPLC was 0.36 ng/l. This method applied to environmental water and purified water samples containing 2-70 ng/l of BPA successfully. Furthermore, UV detection was performed in some actual analyses.
Benzhydryl Compounds↗
Peroxynitrite-mediated oxidative modification of low-density lipoprotein by aqueous extracts of cigarette smoke and the preventive effect of fluvastatin.
Cigarette smoking is known to promote atherosclerosis, possibly through enhanced oxidative stress. The aim of the present study was to elucidate the possible involvement of peroxynitrite in oxidative modification of low-density lipoprotein (LDL) induced by aqueous extract of cigarette smoke (CSE) and the preventive effect of fluvastain, a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor with antioxidative activity, in vitro and in vivo. Modification of LDL was monitored by LDL subfraction analysis using anion-exchange HPLC, TBARS formation and 3-nitrotyrosine production. Incubation of LDL with CSE caused a marked increase in oxidative modification of LDL and nitration of tyrosine residues in the apolipoprotein B. These modifications were prevented by treatment with fluvastatin as well as Vitamin E in a concentration-related manner. Fluvastatin was equal to or more effective than Vitamin E for preventing protein nitration, but weaker for preventing oxidative modification. When CSE was injected daily into the ear vein of Watanabe heritable hyperlipidemic rabbits for 5 months, both oxidative modification and nitration of the plasma LDL noticeably occurred. These changes induced by CSE could be effectively prevented by the simultaneous oral administration of fluvastatin (10 and 30 mg/kg) or Vitamin E (150 mg/kg). Fluvastatin prevented the LDL nitration more effectively than Vitamin E. These results suggest that peroxynitrite in CSE is involved in oxidative modification of LDL and that fluvastatin can efficiently prevent LDL modification by scavenging peroxynitrite. Fluvastatin may be potentially beneficial to hypercholesterolemic patients with oxidative stress such as smoking.
Animals↗
HPLC retention behavior of poly-aromatic-hydrocarbons on aminopropyl silica gels modified with Cu(II)- and Ni(II)-phthalocyanine derivatives in non-polar eluent.
A comparative study was conducted to elucidate the mechanism underlying the separation of poly-aromatic-hydrocarbons (PAHs) and related compounds thereof on a column packed with silica gels modified with Ni(II)- or Cu(II)-phthalocyanine derivatives (PCS) (Ni- or Cu-PCS(D) column) and commercially available PYE and NPE columns with a non-polar eluent, such as n-hexane. It has been revealed that the dominant interaction responsible to the separation of PAHs on the Cu-PCS(D) and the PYE columns with n-hexane is the pi-pi interaction; however, in the separation of PAHs having 4 rings such as pyrene on the Ni-PCS(D) column, participation of pi-d interaction was indicated. The predominant role of pi-pi interaction in the separation of PAHs of less than three rings on the Ni-PCS(D) column was demonstrated using anthracene. All the columns possessed planar recognition ability and were estimated to be potentially useful in the separation and the analysis of PAHs.
Anthracenes↗
Coloration of phenothiazines with metal-containing drugs.
We studied the color change of phenothiazines and metal-containing drugs after compound formation, followed by use of FT-Raman spectrocopy to observe any structural changes in them. When 6 phenothiazines (thioridazine hydrochloride, prochlorperazine maleate, levomepromazine maleate, chlorpromazine phenolphthalinate, fluphenazine maleate and perphenazine fendiate) formed compounds with natural aluminum silicate, the color change was accompanied by a shift of FT-Raman signals. These changes could be attributed to the structural changes of phenothiazines. This present observation can be then used in advance to avoid coloration of phenothiazines during preparative procedures with metal-containing drugs such as antacids.
Aluminum Silicates↗
Chiral separations by capillary electrophoresis using proteins as chiral selectors.
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Acrylic Resins↗
Improved detectability with a polymer-based trapping device in rapid HPLC analysis for ultra-low levels of bisphenol A (BPA) in environmental samples.
A new high-performance liquid chromatography (HPLC) method has been developed to detect ultra-low concentrations of bisphenol-A (BPA) (below 1 ng/L (ppt)) using column switching electrochemical detection (ECD). The results were superior to those obtained from manual pretreatment procedure with membrane stationary phase. BPA is inherently ubiquitous in the environment, including tools and solvents used for its analysis; to obtain meaningful results, therefore, the concentration of the overall BPA contamination must be below the detection limit for BPA using the analytical system. Therefore, purified water for preparing the standard BPA solution must be filtered with a hydrophobic membrane to suppress BPA background levels of contamination. In addition, we investigated methods for effectively preserving environmental water containing BPA. The addition of a small amount of ethylenediaminetetraacetic acid (EDTA) provided good recovery even after overnight storage. By employing these precautionary measures and procedures to reduce BPA contamination from the analytical procedure, we could accurately determine l(-10) ppt of BPA in environmental water samples using a column switching HPLC system.
Benzhydryl Compounds↗
Uniformly sized molecularly imprinted polymers: their applications to chiral separation and bioanalysis.
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Chromatography, High Pressure Liquid↗
Chiral resolution of derivatized amino acids using uniformly sized molecularly imprinted polymers in hydro-organic mobile phases.
Uniformly sized molecularly imprinted polymers (MIPs) for Boc-L-Trp were prepared using ethylene glycol dimethacrylate (EDMA) as the cross-linker, and methacylic acid (MAA) and/or 4-vinylpyridine (4-VPY) as the functional monomers or without use of a functional monomer. The MIPs prepared were evaluated using acetonitrile or a mixture of phosphate buffer and acetonitrile as the mobile phase. The Boc-L-Trp-imprinted EDMA polymers can recognize Boc-L-Trp by its molecular shape, and can thus afford the enantioseparation of Boc-Trp. Besides the molecular shape recognition, the hydrophobic interactions with the polymer backbones as well as the hydrogen-bonding interactions of Boc-L-Trp with carboxyl and pyridyl groups in the polymers should work for the retention and recognition of Boc-L-Trp on the imprinted MAA- co-EDMA and 4-VPY- co-EDMA polymers, respectively, in the hydro-organic mobile phase. The hydrogen-bonding interactions seem to become dominant when only acetonitrile is used as the mobile phase. The Boc-L-Trp-imprinted 4-VPY- co-EDMA polymers gave the highest retentivity and enantioselectivity for Boc-Trp among the MIPs prepared. However, the simultaneous use of MAA and 4-VPY was not effective for the enantioseparation of Boc-Trp in a hydro-organic mobile phase. Furthermore, the baseline separation of Boc-Trp enantiomers was attained within 10 min on the Boc-L-Trp-imprinted 4-VPY- co-EDMA polymers under the optimized HPLC conditions.
Acetonitriles↗
Uniformly sized molecularly imprinted polymers for bisphenol A and beta-estradiol: retention and molecular recognition properties in hydro-organic mobile phases.
Uniformly sized molecularly imprinted polymers (MIPs) for bisphenol A (BPA) have been prepared using ethylene glycol dimethacrylate (EDMA) as a cross-linker and methacrylic acid, 2-diethylaminoethyl methacrylate or 4-vinylpyridine (4-VPY) as a functional monomer or without use of a functional monomer. The MIPs obtained for BPA were evaluated using a mixture of phosphate buffer (or water) and acetonitrile or only acetonitrile as the mobile phase. Among the MIPs prepared, that using 4-VPY showed the highest retentivity and selectivity for BPA. The highest selectivity factor, which is defined as the ratio of the retention factors (k) on the molecularly imprinted and non-imprinted polymers, k(imprinted)/k(non-imprinted), was 9.4 for BPA on the BPA-imprinted 4-VPY-co-EDMA polymers, while that for beta-estradiol on the beta-estradiol-imprinted 4-VPY-co-EDMA polymers was 2.4. The differences in the selectivity factors between BPA and beta-estradiol on the respective MIPs could be ascribable to differences in the number of interaction sites. It is plausible that the phenol groups of BPA could interact with two pyridyl groups of the MIP by hydrogen bonding interactions, while there is only one such site for beta-estradiol. Furthermore, the results suggest that hydrophobic and hydrogen bonding interactions can play an important role in the retention and recognition of BPA and beta-estradiol in the hydro-organic mobile phase, while hydrogen bonding interactions seem to be useful for the retention and recognition when acetonitrile is used as the mobile phase.
Benzhydryl Compounds↗
A possible purification method of DNAs' fragments from humic matters in soil extracts using novel stimulus responsive polymer adsorbent.
Novel stimulus responsive, uniformly sized polymer-based adsorbent was prepared for a possible purification method of DNAs from humic matters in soil extracts. The prepared polymer adsorbent has a pair of anion exchangeable and cation exchangeable polymeric selectors, which are reversibly responded by the changes of column temperature as well as pH of mobile phase. At pH 5, DNAs and humic matters were completely adsorbed on the polymer adsorbent at room temperature, while up to 90% of the adsorbed DNAs were released and recovered at 70 degrees C with no release of adsorbed humic matters. Cleaning up of the polymer adsorbent could be performed by washing the adsorbed humic matters with alkaline mobile phase (pH 9) to recover those and realize repeatable use of the adsorbent.
Adsorption↗
Separation of basic drug enantiomers by capillary electrophoresis using chicken alpha1-acid glycoprotein: insight into chiral recognition mechanism.
Recombinant chicken alpha(1)-acid glycoprotein (alpha(1)-AGP) was prepared by the Escherichia coli expression system and completely deglycosylated alpha(1)-AGP (cd-alpha(1)-AGP) was obtained by treatments of native alpha(1)-AGP with a mixture of endoglycosidase and N-glycosidase. The average molecular masses of chicken alpha(1)-AGP, cd-alpha(1)-AGP and recombinant alpha(1)-AGP were estimated to be about 29 200, 21 700 and 20 700, respectively, by matrix-assisted laser desorption-time of flight-mass spectrometry. We compared the chiral recognition ability of chicken alpha(1)-AGP, cd-alpha(1)-AGP and recombinant alpha(1)-AGP using them as chiral selectors in capillary electrophoresis. The chicken alpha(1)-AGP showed higher resolution for eperisone, pindolol and tolperisone than cd-alpha(1)-AGP or recombinant alpha(1)-AGP. Recombinant alpha(1)-AGP still showed chiral recognition for three basic drugs tested. By addition of propranolol as a competitor in the separation solution in CE, no enantioseparations of three basic drugs were observed with chicken alpha(1)-AGP, cd-alpha(1)-AGP or recombinant alpha(1)-AGP. These results reveal that the protein domain of the chicken alpha(1)-AGP is responsible for the chiral recognition ability, and that the chiral recognition site(s) for basic drugs exists on the protein domain.
Animals↗
Restricted access media-molecularly imprinted polymer for propranolol and its application to direct injection analysis of beta-blockers in biological fluids.
A restricted access media-molecularly imprinted polymer (RAM-MIP) for propranolol (PRP) has been prepared for direct injection analysis of beta-blockers in biological fluids. First, the MIP for PRP was prepared using methacrylic acid and ethylene glycol dimethacrylate as the functional monomer and cross-linker, respectively, by a multi-step swelling and polymerization method. Next, a 1:1 mixture of glycerol monomethacrylate and glycerol dimethacrylate was used for hydrophilic surface modification, and added directly to the MIP for PRP after 4 h from the start of polymerization. Then further polymerization was carried out for 20 h. The obtained RAM-MIP for PRP showed excellent molecular recognition ability for PRP, good ones for alprenolol (ALP) and pindolol, and fair ones for other beta-blockers. The RAM-MIP was applied for direct injection analysis of ALP enantiomers in a rat plasma sample by a column-switching HPLC system using a beta-cyclodextrin phenylcarbamate-bonded silica column as the analytical column. The calibration graph, constructed from peak area versus each ALP enantiomer concentration, was linear with a correlation coefficient of > 0.999 over the concentration ranges of 12.5-250 ng ml(-1). The limit of quantitation was 12.5 ng ml(-1) with a 50 microl injection. This method could be applicable for the assay of ALP enantiomers at the therapeutic plasma levels, and have wide applicability for the assay of beta-blockers in biological fluids.
Adrenergic beta-Antagonists↗
Highly stereoselective, uniformly sized molecularly imprinted polymers for cinchona alkaloids in hydro-organic mobile phases.
Highly stereoselective, uniformly sized molecularly imprinted polymers (MIPs) for cinchona alkaloids, cinchonine (CN) and cinchonidine (CD), were prepared using methacrylic acid (MAA) as a functional monomer and ethylene glycol dimethacrylate (EDMA) as a cross-linker. The MIPs were evaluated using a mixture of phosphate buffer and acetonitrile as the mobile phase. The CN- and CD-imprinted MAA-co-EDMA polymers can recognize the respective template molecule more than the other diastereomer, and afford an excellent diastereomer separation of CN and CD. In addition, the MIPs gave diastereomer separations of structurally related compounds, quinidine and quinine. The retentive and stereoselective properties of those compounds on the MIPs suggest that electrostatic and hydrophobic interactions can work to recognize these compounds. Furthermore, thermodynamic studies reveal that the entropy-driven effect is significant at mobile-phase pH 5.4, while the enthalpy-driven interactions seem to be dominant at mobile-phase pH 9.6.
Chromatography, High Pressure Liquid↗
Preparation of uniformly sized molecularly imprinted polymers for phenolic compounds and their application to the assay of bisphenol A in river water.
Uniformly sized molecularly imprinted polymers, which can recognize bisphenol A (BPA), have been prepared by a multi-step swelling and polymerization method using BPA or a structurally related analogue of BPA [p-t-octylphenol (OP) or p-t-butylphenol (BP)] as the template molecule, 4-vinylpyridine as the functional monomer, and ethylene glycol dimethacrylate as the cross-linker. The BP-imprinted polymer showed higher molecular recognition ability for BPA than the OP-imprinted polymer. The BPA- and BP-imprinted polymers were applied for the assay of a trace amount of BPA in river water using column-switching HPLC with fluorescence detection: A BPA-imprinted polymer was used for removal of BPA from the pretreatment eluent as the trap column, and a BP-imprinted polymer was used for selective pretreatment and enrichment of BPA in river water as the pretreatment column. The calibration graph, constructed from peak area data plotted versus BPA concentration, was linear with a correlation coefficient of >0.999 in the concentration ranges of 25-1000 ppt. The limit of quantitation was 25 ppt with a 5-ml injection. The column-switching HPLC system was successfully applied for the assay of BPA in river water.
Benzhydryl Compounds↗
Assay methods of modified lipoproteins in plasma.
Modified lipoproteins, especially oxidatively modified low-density lipoprotein (Ox-LDL), are present in the plasma of patients with atherosclerosis and related diseases. The modification of LDL is believed to play an important role in the development of atherosclerosis. Thus, measurement of plasma Ox-LDL is essential not only for investigating its relevance to atherosclerotic diseases, but also for diagnosis. Chromatographic methods are effective for indirectly measuring the oxidatively modified state of LDL or directly measuring the modified LDL. Indirect determination can be done by estimating the LDL subfraction, LDL particle size, oxidized amino acids in apolipoprotein B, lipid hydroperoxide or F(2)-isoprostane in LDL. Direct determination of the modified LDL in plasma can be done with chromatographic methods such as anion-exchange chromatography and size-exclusion chromatography. Other methods for estimating the modified state of LDL include electromigration methods such as agarose gel, polyacrylamide gradient gel and capillary electrophoresis. Recently, enzyme-linked immunosorbent assay methods of malondialdehyde (MDA)-LDL and autoantibodies against Ox-LDL have been developed to assess Ox-LDL in plasma. This review article summarizes the detection and assay methods of modified lipoproteins in plasma.
Arteriosclerosis↗
Displacement and nonlinear chromatographic techniques in the investigation of interaction of noncompetitive inhibitors with an immobilized alpha3beta4 nicotinic acetylcholine receptor liquid chromatographic stationary phase.
A liquid chromatographic column containing immobilized alpha3beta4 nicotinic acetylcholine receptors (alpha3beta4-nAChRs) has been used to determine the equilibrium association constants (Ka), desorption rate constants (kd), and adsorption rate constants (ka) for the noncompetitive inhibitors: mecamylamine, ketamine, bupropion, and dextromethorphan. Displacement chromatography, with mecamylamine as the displacer, was used to verify that the four compounds bound to the same site on the immobilized alpha3beta4-nAChRs. Nonlinear chromatographic techniques were then utilized to calculate the Ka, ka, and kd values associated with the formation of the noncompetitive inhibitor-alpha3beta4-nAChR complexes. The ka values determined in this study ranged from 19.7 to 10.5 microM(-1) sec(-1), with a relative order of mecamylamine > dextromethorphan > or = ketamine > bupropion. The kd values determined in this study indicated that dextromethorphan-induced inhibition should produce a longer recovery time than the other three NCIs. This was consistent with results from a previous in vitro study. The data from this study indicate that the immobilized alpha3beta4-nAChR column and nonlinear chromatography can be used in the study of NCIs at the alpha3beta4-nAChR.
Chromatography, Liquid↗
Protein domain of chicken alpha(1)-acid glycoprotein is responsible for chiral recognition.
Ovoglycoprotein from chicken egg whites (OGCHI) has been used as a chiral selector to separate drug enantiomers. However, neither the amino acid sequence of OGCHI nor the responsible part for the chiral recognition (protein domain or sugar moiety) has yet to be determined. First, we isolated a cDNA clone encoding OGCHI, and clarified the amino acid sequence of OGCHI, which consists of 203 amino acids including a predictable signal peptide of 20 amino acids. The mature OGCHI shows 31-32% identities to rabbit and human alpha(1)-acid glycoproteins (alpha(1)-AGPs). Thus, OGCHI should be the chicken alpha(1)-AGP. Second, the recombinant chicken alpha(1)-AGP was prepared by the Escherichia coli expression system, and its chiral recognition ability was confirmed by capillary electrophoresis. Since proteins expressed in E. coli are not modified by any sugar moieties, this result shows that the protein domain of the chicken alpha(1)-AGP is responsible for the chiral recognition.
Amino Acid Sequence↗