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Biomedical subjects

Börje Sellergren

Publications and source records attributed to Börje Sellergren.

At least 19 recordsLinked to original sources
PubMed2007

Direct extraction of penicillin G and derivatives from aqueous samples using a stoichiometrically imprinted polymer.

A molecularly imprinted polymer (MIP) prepared using penicillin G procaine salt as the template (PENGp) and a stoichiometric quantity of urea-based functional monomer to target the single oxyanionic species in the template molecule has been applied to the development of a molecularly imprinted solid-phase extraction (MISPE) procedure for the selective preconcentration of beta-lactam antibiotics (BLAs) from environmental water samples. Various parameters affecting the extraction efficiency of the polymer have been evaluated to achieve the selective preconcentration of the antibiotics from aqueous samples and to reduce nonspecific interactions. This resulted in an MISPE-HPLC method allowing the direct extraction of the analytes from the sample matrix with a selective wash using just 10% (v/v) organic solvent. On the basis of UV detection only, the method showed good recoveries and precision, ranging between 93% and 100% (RSD 3.8-8.9%, n = 3) for tap water and between 90% and 100% (RSD 4.2-9.1%, n = 3) for river water fortified with 30 or 60 microg L-1 (50 mL samples) penicillin G, penicillin V, nafcillin, oxacillin, cloxacillin, and dicloxacillin, suggesting that this MIP can be successfully applied to the direct preconcentration of BLAs in environmental water samples.

Chromatography, High Pressure Liquid↗
PubMed2006

Polymeric receptors for the recognition of folic acid and related compounds via substructure imprinting.

A range of 2-acrylamidopyridines, showing subtle differences in solution binding toward carboxylic acids, has been investigated as functional monomers in molecular imprinting. Imprinting of N-Z-L-glutamic acid with one such monomer is shown to be effective in the creation of a molecularly imprinted polymer (MIP) with recognition properties for its template and also for larger molecules containing glutamic acid residues. In comparison to a MIP prepared via a more "traditional" approach, the new polymeric receptors exhibit reduced nonspecific binding. The new receptors are compared with previously reported urea-based receptors targeting the glutamic acid residue and receptors targeting the pteridine substructure of folic acid.

Acrylamides↗
PubMed2005

Molecularly imprinted polymers grafted to flow through poly(trimethylolpropane trimethacrylate) monoliths for capillary-based solid-phase extraction.

Monolithic molecularly imprinted polymers (mMIPs) have been synthesized in a novel way using a trimethylolpropane trimethacrylate core material photo-polymerized in situ in a 100 microm I.D. UV-transparent capillary and further photo-grafted to create specific cavities in the grafted layer. This polymerization technique allows the imprints to be directly created on the surface of the material using a minimum amount of template. Three different anaesthetics of similar structures (bupivacaine, mepivacaine and S-ropivacaine) were used as model target molecules to synthesize sample enrichment media. Hence, various mMIPs have been prepared and evaluated on a micro-system against each analyte in order to test the retention properties and cross-selectivities of the materials. The retention factors were determined and compared with the non-imprinted reference column (mNIP), yielding high imprinting factors together with good selectivity factors between the three analytes. A study with a pure enantiomeric target was carried out to assess the degree of stereo-specific imprinting for injection of racemic mixtures. Finally, one column was imprinted with an equimolar mixture of all three anaesthetics to provide further comprehension of the retention mechanism and accredit the possibility of using the material as a sample enrichment entity. Scanning electron microscopy (SEM), nitrogen absorption/desorption (BET) and mercury intrusion porosimetry were used to characterize the monolith and the mMIPs properties. Nuclear magnetic resonance (NMR) has been used to assess the similarities between the mMIP and mNIP.

Amides↗
PubMed2005

Analysis of the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol in urine by extraction on a molecularly imprinted polymer column and liquid chromatography/atmospheric pressure ionization tandem mass spectrometry.

The tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) is present in the urine of tobacco users and, at lower concentrations, in the urine of nonsmokers exposed to secondhand smoke. NNAL is a valuable biomarker of human exposure to the carcinogenic nitrosamines in tobacco and tobacco smoke, but its presence at low concentrations in urine requires sensitive and often complex analytic procedures. In this report, we describe the development of an efficient method for the analysis of NNAL in human urine using liquid chromatography/atmospheric pressure ionization tandem mass spectrometry (LC/MS/MS) combined with a novel sample cleanup based on a molecularly imprinted polymer (MIP) column developed specifically for this assay. Our results suggest that this combination of MIP column extraction and LC/MS/MS can provide a sensitive and relatively simple analytical method suitable for application to epidemiologic investigations of health risks associated with the exposure to tobacco smoke or SHS in both smokers and nonsmokers.

Calibration↗
PubMed2005

Molecularly imprinted polymers: a bridge to advanced drug delivery.

Specific molecular recognition is a fundamental requirement of living systems on which processes as diverse as neural transmittance, respiration, immune defence, cellular differentiation and nutrition rely. It is therefore not surprising that scientists have invested huge amounts of time and effort into harnessing, and more recently mimicking, biological function. A number of synthetic approaches have been developed and one of the most promising of these is molecular imprinting. Molecular imprinted polymers have routinely been used, as robust and effective synthetic molecular receptors, in a diverse range of technologies. But it is perhaps in the area of drug delivery, in particular 'intelligent drug release' and 'magic bullet' drug targeting, that significant future opportunities lie.

Biomimetic Materials↗
PubMed2005

Improved imide receptors by imprinting using pyrimidine-based fluorescent reporter monomers.

[reaction: see text] Optically responsive receptors toward imides based on 6-substituted 2,4-bis(acrylamido)pyrimidines are presented. The monomers were readily prepared in good yield. Solution binding to 1-benzyluracil (BU) monitored by 1H NMR appeared lower than a previously reported pyridine-based monomer. However, as indicated by 1H NMR and IR spectral investigations, the association strength was demonstrated to be "masked" by dimerization of the pyrimidine-based monomer units. Thus, from dilution experiments, a dimerization constant of 731 M(-1) was estimated for the pyrimidine-based monomer 2,4-bis(acrylamido)-6-piperidinopyrimidine whereas for the pyridine-based monomer 2,6-bis(acrylamido)pyridine, no self-association was observed. This precluded an accurate determination of the binding constant for BU to the former monomer whereas for the latter a binding constant of 757 M(-1) was measured. Despite the strong self-association, the novel monomer was shown to lead to enhanced imprinting effects when compared to imprinted polymers prepared analogously, but using the pyridine-based monomer as the recognition element. This was attributed to a higher intrinsic binding affinity exhibited by the pyrimidine based host monomer vis a vis the guest and the existence in the former of more than one interaction site for the guest. The monomers exhibited fluorescence emission informative of the mode of monomer incorporation in the polymer and the presence of guest species. Thus, the fluorescence was rapidly and selectively quenched upon template addition, with the degree of quenching correlating with binding affinity and the amount of template bound to the polymer.

Journal Article↗
PubMed2005

Urea host monomers for stoichiometric molecular imprinting of oxyanions.

A series of urea-based vinyl monomers was synthesized and investigated for their ability to function as polymerizable hosts for the molecular imprinting of N-Z-D- or L-glutamic acid in polar media (DMSO or DMF). The monomers were synthesized in one step from a polymerizable isocyanate and a nonpolymerizable amine or vice versa, with yields typically over 70%. Prior to polymerization their solution binding properties vis-a-vis tetrabutylammonium benzoate in DMSO were investigated by 1H NMR, UV-vis and fluorescence monitored titrations. The affinities of the urea monomers for benzoate depended upon the substitution pattern of the urea, with all diaryl ureas exhibiting high affinity. EDMA-based imprinted polymers prepared in DMF or DMSO against Z-D-(or L)-glutamic acid using 2 equiv of the urea monomer and 2 equiv of base were able to recognize the imprinted dianion as well as larger molecules containing the glutamic acid substructure. The affinity, reflected in liquid chromatography retention data, correlated with the solution binding properties of the corresponding monomers.

Anions↗
PubMed2004

Approaches to imprinted stationary phases for affinity capillary electrochromatography.

The combination of two highly attractive technologies in analytical chemistry, namely molecular imprinting and capillary electrochromatography, is reviewed. Molecular imprinting represents an approach to incorporate affinity binding sites for one or a class of target molecules in network polymers whereas capillary electrochromatography is a technique that profits from the high separation efficiency of electrodriven separations and the high selectivity and capacity available with liquid chromatography. The review discusses and compares the various approaches taken, to combine these concepts aiming at robust, reproducible and easily available capillary-based affinity separation media.

Chromatography, Micellar Electrokinetic Capillary↗
PubMed2004

Odd-even chain length-dependent order in pH-switchable self-assembled layers.

The reversible self-assembly of a series of bipolar amphiphiles, alpha,omega-bis(3- or 4-amidinophenoxy)alkanes (chain length n = 5-12), on mercaptoalkanoic acid-functionalized gold surfaces (chain length n = 10, 11, 14, 15) has been studied by in-situ ellipsometry, IR reflection absorption spectroscopy (IRAS), and atomic force microscopy (AFM). The layer order, amphiphile orientation, and tendency to form bilayers depends on the position of the amidine substituent, the alkyl chain length of both the amidine amphiphile and the underlying acid self-assembled monolayer (SAM), and whether the amidine alkyl chain contained an even or odd number of methylene groups. Thus, para-substituted bisbenzamidines containing more than six methylene groups (n>6) and with an odd number (n = 7, 9, 11) tended to form bilayered structures, whereas those containing an even number formed monolayers when adsorbed on SAMs of the long-chain acids (n = 14, 15). This behavior also correlated with the average tilt angle of the benzene moieties of the amphiphiles, as estimated by IRAS. The odd-numbered chains gave lower tilt angles than the even-numbered ones, and a possible model that accounts for these results is proposed. IRAS also revealed a higher order of the odd-numbered chains and an increasing hydrogen-bonding contribution with increasing chain length. Additional evidence for the proposed bilayered assemblies and their reversibility was obtained by AFM. Images obtained from the assembly of decamidine on a SAM of mercaptohexadecanoic acid in a pH 9 borate buffer revealed domains of similar size to that of the underlying acid SAM (20-30 nm), but less densely packed. By acidifying the solution, the second layer was destabilized and a very smooth layer with few defects appeared. Further acidification to pH 3 also destabilized the first layer.

Journal Article↗
PubMed2004

Peptide recognition via hierarchical imprinting.

Silica particles containing immobilised peptidic templates have been used for the generation of hierarchically imprinted polymers. The pores of the silica mould were filled with a mixture of monomers/initiator and polymerised, followed by dissolution of the silica template. This method leaves behind imprinted polymers with binding sites located at the surface, which are capable of recognising larger molecules with the same immobilised epitope. All the products resulting from solid-phase synthesis of peptides were characterised by elemental analysis, FT-IR spectroscopy and fluorescence microscopy. The hierarchically imprinted polymers generated from these products were characterised by elemental analysis, FT-IR spectroscopy, fluorescence microscopy, scanning electron microscopy (SEM) and nitrogen adsorption, providing evidence concerning the reproducibility of each step. The chromatographic properties of the materials have been investigated and the advantages of the immobilisation method have been proven. The materials exhibit selectivity for their templates and other structurally related dipeptides. Furthermore, the polymers proved to be capable of recognising larger peptides containing the immobilised sequence.

Adsorption↗
PubMed2004

Screening of oxazepine indole enantiomers by means of high performance liquid chromatography with imprinted polymer stationary phase.

Chromatographic enantiomer separations of different oxazepine indole derivatives were performed using a molecularly imprinted polymer. A 5aR,12R,13S-trans-6,6-dimethyl-12,13-dihydro-6H-5a, 1 3-methanoindolo[2,1-b][1,3]naphthoxazepine-12-carboxamide enantiomerderivative was used as a template and the resultant polymer has shown enantiomer recognition for series of template related compounds. The mechanistic description of the chiral discrimination process is scrutinised, comparing the discrimination between the different conformations and substituents of the oxazepine indoles.

Chromatography, High Pressure Liquid↗
PubMed2003

Water-compatible molecularly imprinted polymers obtained via high-throughput synthesis and experimental design.

A technique allowing high-throughput synthesis and evaluation of molecularly imprinted polymer sorbents at a reduced scale (mini-MIPs) was developed and used for the optimization of MIPs for use in pure aqueous environments. The technique incorporated a 4-port liquid-handling robot for the rapid dispensing of monomers, templates, solvents and initiator into the reaction vessels of a 96-well plate. A library of 80 polymers, each ca. 50 mg, could thus be prepared in 24 h. The MIP rebinding capacity and selectivity could be rapidly assessed in the batch mode by quantifying nonbound fractions in parallel using a UV monochromator plate reader. This allowed a complete evaluation of the binding characteristics of an 80 polymer library in approximately 1 week. With the objective of optimizing a polymer imprinted with the local anaesthetic Bupivacaine for use in pure aqueous systems, a polymer library was prepared by varying the original poly(MAA-co-EDMA) MIP composition. The variable factors were the added amount of the hydrophilic comonomer, 2-hydroxyethyl methacrylate (HEMA), the cross-linking ratio, and the porogen. This optimization resulted in polymers showing high imprinting factors (IF = K(MIP)/K(NIP)) in water as a result, mainly, of reduced binding to the nonimprinted polymer. Normal scale batches of these materials showed strong retention of the template and low nonspecific binding when assessed as chromatographic stationary phases using pure phosphate buffer, pH 7.4, as mobile phase, by equilibrium batch rebinding experiments and as sorbents for extractions of the analyte from blood plasma samples.

Journal Article↗
PubMed2003

A substructure approach toward polymeric receptors targeting dihydrofolate reductase inhibitors. 2. Molecularly imprinted polymers against Z-l-glutamic acid showing affinity for larger molecules.

The preparation of a molecularly imprinted polymer against N-Z-L-glutamic acid using a novel bis-urea functional monomer is described. The polymer exhibits affinity for the template over N-Z-protected aspartic acid and glycine and, further, is capable of binding larger molecules, e.g., the anti-cancer drug methotrexate, containing the glutamate substructure.

Enzyme Inhibitors↗
PubMed2003

Molecularly imprinted polymer films grafted from porous or nonporous silica: novel affinity stationary phases in capillary electrochromatography.

Molecularly imprinted composite materials were evaluated as chiral stationary phases in capillary electrochromatography (CEC). These consisted of spherical silica particles of different sizes and of different porosities, containing a surface-immobilized layer of molecularly imprinted polymer (MIP) targeted to bind L-phenylalanine anilide. Fused silica capillaries were packed over a length of 8.5 cm, using a pneumate amplification pump, and the stationary phase thus obtained was tested with respect to its electrochromatographic performance. The electroendosmotic flow (EOF) mobility was evaluated with respect to the content of grafted polymer, as well as the ionic strength and the acetonitrile content of the electrolyte. Moreover, the influence of the layer thickness and of the stationary phase porosity on the performance and on the sample load capacity was investigated. The packings exhibited different relative efficiencies for the two enantiomers. The results were discussed in terms of differencies in accessibility to the binding sites of the packings and of the mechanism of EOF generation. In the wide context of the different approaches so far proposed for MIP stationary phases in CEC, these materials can be a good alternative, worthy of further development and application, not restricted to chiral separations.

Electrophoresis, Capillary↗
PubMed2002

Extraction of clenbuterol from calf urine using a molecularly imprinted polymer followed by quantitation by high-performance liquid chromatography with UV detection.

A method for the extraction of clenbuterol from calf urine samples using a molecularly imprinted polymer (MIP) has been developed. The aim was that the final extracts from the MIP should allow quantitation of clenbuterol down to 0.5 ng/mL urine using HPLC with UV detection. The MIP was produced using brombuterol as a template and the selectivity of the MIP, for clenbuterol, was tested against a non-imprinted polymer (produced without template) and was found to be high. After loading of 5 mL diluted centrifuged urine, selective binding was established in acetonitrile-acetic acid (98:2). For further elution of interferences, 0.5 M ammonium acetate buffer pH 5 and 70% acetonitrile in water was used. Clenbuterol was eluted using 1% trifluoroacetic acid in methanol, which was evaporated and reconstituted in buffer. Results from the HPLC analyses showed that the extraction of clenbuterol using MIP is linear in the range 0.5-100 ng/mL with good precision (4.3% for 0.6 ng/mL and 2.1% for 6.0 ng/mL) and accuracy (96.7% for 0.6 ng/mL and 96.7% for 6.0 ng/mL). The recoveries were 75%. The results show that the method offers a selectivity and sensitivity that make the quantitation of 0.5 ng clenbuterol/mL urine by HPLC-UV possible and a competitive alternative to state-of-the-art routine analytical methods.

Adrenergic alpha-Agonists↗