Biomedical subjects

M Metalová

Publications and source records attributed to M Metalová.

4 recordsLinked to original sources

PubMed1997

New radiopaque polyHEMA-based hydrogel particles.

New iodine-containing polymeric hydrogel particles were prepared by suspension radical copolymerization of 2-hydroxyethyl methacrylate (HEMA), 3-(methacryloylamidoacetamido)-2,4,6-triiodobenzoic acid (MABA) and ethylene dimethacrylate (EDMA) in an aqueous medium using azobisisobutyronitrile as an initiator and magnesium hydroxide as a suspension stabilizer. To impart porosity to the product, cyclohexanol and 1-dodecanol were added as inert diluents to the polymerization mixture. Particles containing 27 wt % iodine produced radiopacity sufficient to observe a clearly visible X-ray image. The equilibrium swelling behavior of the particles in water was characterized. Swelling of the particles dramatically increased by converting the acid groups of MABA into their Na+ form. The more MABA the copolymer particle contain, the higher is their swelling in the Na+ form.

Biocompatible Materials↗

PubMed1990

Degradation of N5-(2-hydroxyethyl)-L-glutamine and L-glutamic acid homopolymers and copolymers by papain.

The rate of degradation of poly[N5-(2-hydroxyethyl)-L-glutamine] (PHEG), poly(L-glutamic acid) (PGA) and poly[HEG-co-GA] random copolymers by papain was measured in the pH range 4.0-7.5, employing the gel permeation chromatography method. The effect of the degree of ionization on the polymer conformation was measured by circular dichroism (c.d.). PHEG, which is uncharged, had a random coil conformation and an almost constant degradation rate within the whole pH interval. The ionization of PGA increased with increasing pH and was accompanied by conformational transition from helix to random coil. The hydrolysis of PGA by papain depended on pH with the optimum at about pH 5, indicating that both the high content of helix (at pH less than 5) and increasing charge density (at pH greater than 5), decreased the degradation rate. Contrary to PGA, pH profiles of the degradation rate of poly[HEG-co-GA] copolymers are monotonous and do not decrease at pH less than 5. In the copolymers the HEG residues act as a helix breaker and limit the formation of helical conformation. The role of structural features of a macromolecular substrate, i.e. the charge, helical conformation and the nature of amino acid residues, in the interaction between enzyme and polymer is discussed.

Chromatography, Gel↗

PubMed1987

Hydrogels in endovascular embolization. III. Radiopaque spherical particles, their preparation and properties.

The synthesis and properties of spherical radiopaque hydrogel particles designed for endovascular occlusion are reported. These particles were prepared by the hydroxyl acylation of low crosslinked poly (2-hydroxyethyl methacrylate) beads with a nontoxic radiopaque compound based on triiodobenzoic acid, without affecting their properties which are advantages in medical practice. The effect of the iodine content on the size of dry and swollen particles is discussed. It has been found that an iodine content of about 25-30 wt% is desirable in order to obtain an easily recognizable X-ray image. These particles make the immediate control of embolus application easy and enable periodical inspection of the polymer to check the successful blockage of the vessel. They also open up the method of endovascular occlusion to further improvement.

Contrast Media↗

PubMed1982

A high-molecular mass derivative of trypsin-kallikrein inhibitor for potential medical use. II. Study of inhibitory activity.

Three derivatives of poly[alpha-N beta-(2-hydroxyethyl)-DL-asparagine, beta-N alpha-(2-hydroxyethyl)-DL-asparagine] were used as soluble carrier polymers for binding the trypsin-kallikrein inhibitor (TKI). In addition to the parent polymer an anionic derivative with 19.2 mol of carboxyl groups/100 mol of residues and a hydrophobized derivative with 18.0 mol of butyl groups/100 mol of residues were also used. All carriers contained 6.6 mol of 2-(4-aminobenzamido)ethyl residues/100 mol which were used for the binding after diazotation. All derivatives retained a high inhibitory activity toward trypsin and chymotrypsin whereas the effect on kallikrein was substantially reduced. The kinetic constants were estimated under the simplifying assumption, that classical kinetic equations for the enzyme-inhibitor interaction may be applied. The equilibrium dissociation constants (5 X 10(-9) mol/l) and association rate constants (1 X 10(5) l X mol-1 X s-1) with respect to trypsin are unaffected by the two chemical modifications of the carrier. The increase in the equilibrium dissociation constant (compared to native TKI) is probably a result of the decreasing strength of the enzyme-inhibitor complex rather than a manifestation of reduced rate of diffusion of the enzyme to the active center of the polymer-bound inhibitor.

Chymotrypsin↗