Biomedical subjects

G B Sukhorukov

Publications and source records attributed to G B Sukhorukov.

11 recordsLinked to original sources

PubMed2006

Layer-by-layer coating of degradable microgels for pulsed drug delivery.

Recently, we reported on "self-rupturing" microcapsules which consist of a biodegradable dextran-based microgel surrounded by a polyelectrolyte membrane. Degradation of the microgel increases the swelling pressure in the microcapsules which, when sufficiently high, ruptures the surrounding polyelectrolyte membrane. The membrane surrounding the microgels is deposited using the layer-by-layer (LbL) technique, which is based on the alternate adsorption of oppositely charged polyelectrolytes onto a charged substrate. In this paper, we characterize with confocal microscopy, electrophoretic mobility, scanning electron microscopy and atomic force microscopy in detail the deposition and the properties of the LbL coatings on the dextran microgels. We show that by fine-tuning the properties of both the microgel core and the LbL membrane the swelling pressure which is evoked by the degradation of the microgel is indeed able to rupture the surrounding LbL membrane. Further, we show that the application of an LbL coating on the surface of the microgels dramatically lowers the burst release from the microcapsules and results in massive release at the time the microcapsules rupture.

Delayed-Action Preparations↗

PubMed2003

Inclusion of proteins into polyelectrolyte microparticles by alternative adsorption of polyelectrolytes on protein aggregates.

A new method of protein immobilization into polyelectrolyte microparticles by alternative adsorption of the oppositely charged polyelectrolytes on the aggregates obtained by salting out of protein is proposed. The model protein alpha-chymotrypsin (ChT) was included in the polyelectrolyte microparticles obtained by various number of polyelectrolyte adsorption steps (from 1 to 11). The main parameters of ChT inclusion into microparticles were calculated. Scanning electron and optical microscopy were used for characterization of morphology and determination of particle size which was from 1 to 10 micro m in most cases. It was shown that the size and shape of protein-containing particles and protein aggregates used as a matrix were similar. Change in ChT enzymatic activity during entrapment into polyelectrolyte particles and activity of released protein were studied. The effect of pH on release of incorporated proteins was investigated; it was shown that change in pH and the number of polyelectrolyte adsorption steps allows protein release to be manipulated.

Adsorption↗

PubMed2002

Artificial cell based on lipid hollow polyelectrolyte microcapsules: channel reconstruction and membrane potential measurement.

A new model system as an artificial cell based on hollow polyelectrolyte microcapsules (HPM), fabricated by step-wise adsorption of polyelectrolytes and phospholipids, was proposed. To demonstrate the feasibility of the functioning of HPM coated with lipid layers as a model biosystem, the membrane permeability for ions and the channel reconstruction were examined by measuring the membrane potential as one of the most important cell parameters. The membrane potential was measured by confocal microscopy using the potentiometric fluorescent dye tetramethylrhodamine ethyl ester perchlorate (TMRE). The influence of the lipid composition (phosphatidylcholine--DPPC-HPM, phosphatidylcholine/phosphatidic acid 9/1-(DPPC/DPPA)-HPM) and metal cations (Na+, K+, Ca2+) on the membrane potential was shown. Addition of DPPA was found to lead to an increase of the negative membrane potential value. To investigate the ion-transport activity of the lipid-HPM, the ion channel-forming peptides valinomycin and gramicidin were used. The selectivity of the valinomycin and gramicidin channels for K+ and for K+, and Na+ ions, respectively, and the tolerance for Ca2+ ions is evidence that lipid-HPM functions as an artificial cell.

Biomimetic Materials↗

PubMed2001

Encapsulation of proteins by layer-by-layer adsorption of polyelectrolytes onto protein aggregates: factors regulating the protein release.

A novel method of protein encapsulation is proposed. Preformed protein aggregates are covered with polyelectrolyte layers by means of layer-by-layer adsorption. The polyelectrolyte membrane prevents protein leakage out of the capsule. Using chymotrypsin as a model enzyme the capsule wall selective permeability was demonstrated for substrates and inhibitors of different molecular weight and solubility.

Adsorption↗

PubMed1997

Protein architecture: assembly of ordered films by means of alternated adsorption of oppositely charged macromolecules.

Methods of making molecularly ordered protein films are reviewed with special reference to the recently developed technique of protein multilayer assembly by alternated adsorption of opposite-charge polyions. This method has been applied for linear and branched polyions, DNA, polynucleotides, proteins, viruses and clay nanoplates. This provides good prospects for biomolecular architecture. Quartz crystal microbalance, X-ray and neutron reflectivity, scanning electron microscopy, atomic force microscopy and UV-absorbance data are used to analyze the film structure. Multilayer buildup by alternation of polyions and 16 different charged proteins is discussed. In most cases, enzymes in the films retained their activity. Protein/ceramic nanoplates consisting of alternated montmorillonite clay and glucose oxidase layers electrostatically linked by polycations were also assembled. Protein layers can be arranged according to specific biological activity. Consecutive enzymic reactions were performed in anisotropic protein layers prepared with precise control of distances between the active layers (1-50 nm). Film superlattices containing ordered layers of more than one protein were constructed using myoglobin, lysozyme, peroxidase, glucoamylase, glucose oxidase and catalase. Glucoamylase, glucose oxidase/peroxidase catalyze the starch-glucose-H2020 reaction. The reaction products and nonreacting starch were separated by filtration when the substrate solution passed through the multienzyme films assembled on a filter. Formation of alternate outermost layers (of opposite charge or opposite specificity) at every adsorption cycle is the key point of the layer-by-layer assembly. Multilayers were obtained by alternated adsorption of concanavalin A and glycogen (or streptavidin and biotinylated polylysine) were designed using their biospecific interaction. Protein films are of extreme interest as novel biologically active materials.

Adsorption↗

PubMed1996

Multilayer films containing immobilized nucleic acids. Their structure and possibilities in biosensor applications.

Langmuir-Blodgett (LB) and film technologies based on electrostatic attraction self-assembly (SA) are shown to be useful for immobilization of nucleic acids (DNA, polynucleotides) onto solid supports in sensor devices. The nucleic acids were immobilized in complexes with cationic surfactants (for LB) and polycations (for SA). Infrared spectral studies showed that DNA unfolds in multilayer LB films with octadecylamine and conserves its double helical structure in the LB films with dioctadecyldimethylammonium and in the SA films with polyallylamine, polyethylenimine and poly-L-lysine. Atomic groups and the types of interactions determining the complex formation of these films have been identified. The hydration of LB and SA films was studied to find out binding sites of water molecules and to evaluate the flexibility of nucleic acid compounds in the multilayer films. The possibilities of biosensor applications of these LB and SA films were monitored on binding of specific reagents for DNA by DNA-containing films and mononucleotides by a complementary single-stranded polynucleotide immobilized on a positively charged solid support.

Biosensing Techniques↗

PubMedDate not supplied

Microencapsulation by means of step-wise adsorption of polyelectrolytes.

Step-wise adsorption of polyelectrolytes is used for the fabrication of micro- and nanocapsules with determined size, capsule wall composition and thickness. The capsule walls made of polyelectrolyte multilayers exclude high molecular weight compounds. Assembling of lipid layers onto these polyelectrolyte capsules prevents the permeation of small dyes. Encapsulation of magnetite nanoparticles is demonstrated and the features of these novel capsules are discussed.

Adsorption↗

PubMedDate not supplied

[Lactate dehydrogenase in an interpolyelectrolyte complex. Function and stability].

A new method for encapsulating enzymes by multilayer polyelectrolyte coating is proposed. The method consists in a stepwise adsorption of polyelectrolytes from solution onto protein aggregates formed by salting out the proteins in highly concentrated salt solutions. Polystyrene sulfonate and fluorescence-labeled polyalylamine were used for capsule formation. The size of lactate dehydrogenase aggregates covered by four layer pairs of electrolytes was 1-5 microns, as indicated by fluorescence microscopy. The catalytic characteristics and stability of pig muscle lactate dehydrogenase (EC 1.1.1.13) incapsulated in multilayer electrolyte complex obtained by this method were studied. It was found that the affinity of the substrate pyruvate for the enzyme in the polyelectrolyte complex (K(M)) did not essentially change as compared with the free enzyme. Incapsulated lactate dehydrogenase showed the following features that distinguish it from the free form: (1) the lifetime in diluted solutions increases from 30 min (without capsules) to 1-2 days (in capsules); (2) a higher stability to basic denaturation (up to pH 10); and (3) the absence of substrate inhibition of enzyme in the polyelectrolyte complex. The changes in the catalytic characteristics of incapsulated lactate dehydrogenase are discussed in terms of an increase in effective pK values of amino acid perturbed by polyelectrolyte coating of enzyme.

Animals↗

PubMedDate not supplied

[Conformation and molecular and ionic transformations of polycytidylic acid immobilized in multilayer Langmuir and polyelectrolyte films].

Multilayer films of complexes of polycytidylic acid with dioctadecyldimetylammonium were obtained by the Langmuir-Blodgett method (LB films), and complexes of poly(C) with polycations (poly-L-lysisne, polyethyleneimine, polyallylamine) were obtained by the method of alternate adsorption (polyionic assembly) from solutions of oppositely charged polyelectrolytes on the solid carrier (SA films). It was shown that poly(C) exists in SA films in a single-stranded state irrespective of whether in the starting solution it occurred in the single-stranded nonprotonated or double-stranded protonated conformation. Conversely, in the LB film poly(C) preferred to be in a double protonated conformation. UV-spectra of water-insoluble LB and SA films at different pH values of surrounding water medium were investigated. Proton titration curves of poly(C) immobilized in LB films were obtained. The analysis of the shape of titration curves showed that the molecular-ionic transformation of poly(C) in LB films is accompanied by both the conformational transition of the polynucleotide and the molecular rearrangement in the whole film. Poly(C) was found to transform from the double- to single-stranded state and vice versa in the "deprotonation-protonation" cycle of LB film due to cooperative release/binding of hydrogen ions by cytosine bases. In contrast, poly(C) "protonation-deprotonation" in SA films occurred without conformational transitions of the polynucleotide. As opposed to poly(C) in solution a rather big hysteresis of forward and back titration curves was found for both types of multilayer films, indicating molecular rearrangements in films. The reason for the structural transformations of poly(C) upon fabrication of LB or SA films and the mechanism of molecular ionic transformations of poly(C) in films are discussed in terms of a simple model of ion exchange. An assumption about the nature of structural transformations of LB and SA films during their protonation-deprotonation is put forward.

Electrolytes↗

PubMedDate not supplied

[Preparation and study of Langmuir films of nucleic acid and octadecylamine complexes].

Formation conditions of langmuir films of nucleic acids (DNA and poly-U)-octadecylamine complexes are determined. Successive transfer of the monolayers of these complexes from the aqueous subphase surface to solid substances (quartz, silicon) is carried out. The structure of multilayer langmuir films of nucleic acid-octadecylamine complexes is studied by small angle X-ray scattering, ellipsometry and UV-spectroscopy. The produced films are shown to have high lamellar orderliness with the multilayer structure period D = 57.0 A. A scheme of the realized structure of these films is proposed in which the nucleic acids are located between octadecylamine bilayers. A suggestion is discussed based on similar results for poly-U and DNA containing langmuir films concerning possible untwisting of double helical DNA in the langmuir film of octadecylamine, as well as biological significance of the discovered phenomena.

Amines↗

PubMedDate not supplied

[The dual stabilizing and destabilizing effect of decylamine on DNA structure and stability].

The influence of decylamine on DNA structure and stability has been studied from the changes in UV-spectra and UV-melting curves. It was found that at low concentrations, the aliphatic amine stabilizes the double helix while at high concentrations, on the contrary, the amine disturbs it. The interaction of aliphatic amine with DNA results in a sharp increase in the heterogeneity of thermostability of different sites of the double helix. The stabilizing effect of aliphatic amines is connected with a decrease in repealing between negatively charged sugar-phosphate chains of the double helix, while the destabilizing effect is the result of displacement of intramolecular base-base hydrogen bonds by intermolecular base-amine H-bonds. The biological significance of the dual, stabilizing and destabilizing effects of aliphatic amines on DNA helix is shown.

Amines↗