Biomedical subjects
H S Andersson
Publications and source records attributed to H S Andersson.
Crown ethers as a tool for the preparation of molecularly imprinted polymers.
Molecularly imprinted polymers have been prepared against aniline and a bis-aniline compound, making use of a crown ether (18-crown-6) to solubilize the monomer-template complexes. Subsequent chromatographic rebinding studies in the absence of crown ether revealed regioselectivity for the templates in the respective polymers. This study indicates that crown ethers can be potentially useful in conjunction with molecular imprinting to solubilize and imprint organic solvent-insoluble compounds.
Spectroscopic studies of the molecular imprinting self-assembly process.
A method for the rapid estimation of the extent of complex formation in molecular imprinting prepolymerization mixtures is described. By the use of a UV spectroscopy titration procedure, apparent binding constants for such self-assembly processes have been obtained. This method was used for comparison of the interactions between a dipeptide template (N-acetyl-L-phenylalaninyl-L-tryptophanyl methyl ester) and the functional monomer methacrylic acid, and the monomer analogues acetic acid and trifluoroacetic acid. The importance of template-monomer association during the molecular imprinting prepolymerization phase is discussed with respect to the systems studied.
Novel chiral recognition elements for molecularly imprinted polymer preparation.
The use of a novel chiral functional monomer system in molecular imprinting protocols is described. The monomer, dibenzyl (2R,3R)-O-monoacryloyl tartrate, possesses a hydroxyl moiety which can be used to direct template-functional monomer interactions during molecular imprinting polymerization. This system simultaneously positions benzyl ester-protected carboxyl groups in close proximity to the template, which upon deprotection yield recognition sites with stronger ligand-binding capacities. Furthermore, the inherent chirality of the monomer engenders the polymer with an inbuilt preference for a given stereoisomer. Application of the system to the molecular imprinting of the cinchonidine alkaloids (+)-cinchonine and (-)-cinchonidine yielded stereoselective polymers. The effect of imprinting (+)-cinchonine produced a polymer which more than reversed the inherent chiral selectivity of the chiral monomer residues present in the matrix.
The rational use of hydrophobic effect-based recognition in molecularly imprinted polymers.
A novel molecularly imprinted polymer (MIP) system selective for D-phenylalanine is described where polymerization is performed in aqueous solution. The unique polymer system comprises a hydrophobic moiety-selective functional monomer, polymerizable beta-cyclodextrin, an electrostatic interacting functional monomer, 2-acryloylamido-2-methylpropane sulfonic acid (AMPSA), and the crosslinking agent N,N'-diacryloylpiperazine. Chromatographic evaluation of polymer-ligand recognition characteristics demonstrated ligand selectivity by the MIP and that optimal recognition was achieved through a balance of hydrophobic and electrostatic ligand-polymer interactions, indicating that recognition in these systems is regulated by enthalpy-entropy compensation. The imprinting effect was shown to be sufficient to reverse the inherent selectivity of cyclodextrin for L-phenylalanine.
Theophylline molecularly imprinted polymer dissociation kinetics: a novel sustained release drug dosage mechanism.
The template release kinetics of theophylline molecularly imprinted polymers has been examined with a view to determining their potential as a controlled release drug dosage form. The basis for the ligand selectivity of these polymers has been shown through the demonstration of pre-polymerization template-monomer complexation and HPLC studies of the product polymer ligand selectivities. The release kinetics shows a dependence upon template loading and pH. Small differences in release characteristics between imprinted and non-imprinted (reference) polymers have been observed.
Study of the nature of recognition in molecularly imprinted polymers.
In the present study molecularly imprinted polymers (MIPs) were prepared against a series of structurally related compounds containing various numbers of pyridyl groups. The goal, to increase understanding of the mechanisms of recognition in MIPs, was achieved by comparing the patterns of retention of the imprinted compounds on the different MIPs when related to a blank (non-imprinted) polymer in a high performance liquid chromatography system. Furthermore, frontal analysis was carried out on three polymers: a blank, a pyridine-imprinted and a 4,4'-bipyridyl-imprinted polymer, to evaluate the number (Bt), average specificity and strength (dissociation constant; Kdiss) of the recognition sites. The Kdiss values of pyridine on the different polymers were in the range 0.10-0.12 M, and the amount of imprinted binding sites (Bt) 0.10-0.12 mmol/g. Kdiss values of 4,4'-bipyridyl were approximately 0.06 M, with Bt values equal to the above, except for in the anti-4,4'-bipyridyl polymer where the Kdiss was determined to be 0.02 M and Bt 0.07 mmol/g. From the results it can be concluded that multiple additive weak interactions dominate the recognition of the template molecules in these imprinted polymers.