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Biomedical subjects

A L Klibanov

Publications and source records attributed to A L Klibanov.

51 records · Page 3Linked to original sources
PubMed1985

Binding of antibodies in liposomes to extracellular matrix antigens.

We have incorporated antibodies against fibronectin or laminin into liposomes and studied their interaction with insoluble forms of these antigens. The antibodies, after modification by palmitoylchloride, were incorporated into the lipid bilayer by the cholate dialysis method. The antibodies in the liposomes recognized their specific antigen with little reaction to the alternative attachment protein or to albumin (less than 2%). The binding of antibody-containing liposomes to insoluble antigen was inhibited by soluble antibodies to the respective antigens but not by antibodies to other antigens. The affinity constant of the liposome-antibody complex with the antigen was estimated at 1-10 X 10(-9) M liposomes. Thus, antibodies in liposomes retain their reactivity and specificity, and the reaction constant is comparable to that observed for immune complexes.

Animals↗
PubMed1985

[The use of the cationic detergent dodecyltrimethylammonium bromide for the isolation of influenza virus glycoproteins with subsequent integration of the protein into liposome membrane].

Glycoproteins were isolated from influenza virus with the use of cationic detergent dodecyltrimethylammoniumbromide and attached to preformed liposomes. Liposomal vesicles, thus, acquired their ability for hemagglutination and lysis of chicken erythrocytes. The possibility of using these liposomes for transfer of alien agents into eucaryotic cells is discussed.

Detergents↗
PubMed1981

Incorporation of chemically modified proteins into liposomes.

Enzymes, not anchored into bilayers of membranes like trypsin, alpha-chymotrypsin, and carboxypeptidase A are chemically modified by acylation with fatty acids chlorides. This treatment renders these proteins hydrophobic so that they can combine with the phospholipid membrane of liposomes. This report deals with the incorporation of modified enzymes into liposomes prepared by different methods.

Acylation↗
PubMed1981

[Use of phosphatidylinositol as a hydrophobic anchor for protein binding with liposomes].

For binding of proteins with the membranes of liposomes, natural lipid phosphatidylinozite was proposed. First, it was activated by periodate, then in incubation with protein in alkaline medium the binding between the modifier and the protein was covalent. Liposomes with the bound protein are obtained by dialysis detergent removal. In binding of the pattern protein alpha-chymotripsin with liposomes from egg phosphatidylcholine there was reached the binding of 2,4 . 10(-3) M of protein per mole of the lipid. 70% of the enzyme immobilized on liposomes was observed to completely retain its affinity to pancreatic tripsin inhibitor. Thermostability of the immobilized enzyme was studied.

Chymotrypsin↗
PubMed1980

Incorporation of hydrophilic protein modified with hydrophobic agent into liposome membrane.

The hydrophilic protein-enzyme, alpha-chymotrypsin, can be bound to the liposomal membrane after the preliminary increase in hydrophobicity induced by acylation of protein amino groups with palmitic chloroanhydride. The efficacy of binding depends on the degree of modification. The bound enzyme almost completely preserves its catalytic properties and the ability to interact with a high molecular weight inhibitor. Binding can be performed during both the process of liposome formation and the incubation of a modified enzyme with preformed liposomes. According to ESR and fluorescence spectroscopy, the hydrophobic tail of the modified enzyme is incorporated into the membrane and the protein globule is located on the surface of the membrane. Protein incorportation causes an increase in the amorphous nature of the membrane, and the bound protein is not as mobile as the free protein. The approach discussed can be useful in binding soluble hydrophilic proteins to artificial membranes.

Chymotrypsin↗
PubMedDate not supplied

Targeted ultrasound contrast agent for molecular imaging of inflammation in high-shear flow.

Targeted ultrasound contrast materials (gas-filled microbubbles carrying ligands to endothelial selectins or integrins) have been investigated as potential molecular imaging agents. Such microbubbles normally exhibit good targeting capability at the slower flow conditions. However, in the conditions of vigorous flow, binding may be limited. Here, we describe a microbubble capable of efficient binding to targets both in slow and fast flow (exceeding 4 dyne/cm(2) wall shear stress) using a clustered polymeric form of the fast-binding selectin ligand sialyl Lewis(X). Microbubbles were prepared from decafluorobutane gas and stabilized with a monolayer of phosphatidylcholine, PEG stearate and biotin-PEG-lipid. Biotinylated PSLe(x) (sialyl Lewis(X) polyacrylamide) or biotinylated anti-P-selectin antibody (RB40.34) was attached to microbubbles via a streptavidin bridge. In a parallel plate flow chamber targeted adhesion model, PSLe(x) bubbles demonstrated specific adhesion, retention and slow rolling on P-selectin-coated plates. Efficiency of firm targeted adhesion to a P-selectin surface (140 molecules/microm(2)) was comparable for antibody-carrying bubbles and PSLe(x)-targeted bubbles at 0.68 dyne/cm(2) shear stress. At fast flow (4.45 dyne/cm(2)), PSLe(x)-targeted bubbles maintained their ability to bind, while antibody-mediated targeting dropped more than 20-fold. At lower surface density of P-selectin (7 molecules/microm(2)), targeting via PSLe(x) was more efficient than via antibody under all the flow conditions tested. Negative control casein-coated plates did not retain bubbles in the range of flow conditions studied. To confirm echogenicity, targeted PSLe(x)-bubbles were visualized on P-selectin-coated polystyrene plates by ultrasound imaging with a clinical scanner operated in pulse inversion mode; control plates lacking targeted bubbles did not show significant acoustic backscatter. In vivo, in a murine model of inflammation in the femoral vein setting, targeting efficacy of intravenously administered PSLe(x)-microbubbles was comparable with targeting mediated by anti-P-selectin antibody, and significantly exceeded the accumulation of non-targeted control bubbles. In the inflamed femoral artery setting, PSLe(x)-mediated microbubble targeting was superior to antibody-mediated targeting.

Acrylic Resins↗
PubMedDate not supplied

Succinylated polylysine as a possible link between an antibody molecule and deferoxamine.

Modification of antibodies with chelating polymers may be helpful for radioimmunoimaging, radioimmunotherapy, and NMR tomography. Succinylated polylysine was activated with carbodiimide/N-hydroxysulfosuccinimide in dimethyl sulfoxide and isolated as a dry solid. Sulfosuccinimide-esterified polymer was used for the two-stage coupling of an amino-containing chelating agent (deferoxamine) to monoclonal R11D10 (IgG) or its Fab fragment. Conjugates were separated from free components by using gel-chromatography and anion-exchange chromatography. Antibody-coupling efficiency and the loss of its immunoreactivity upon modification have been studied for polymers with different deferoxamine content. Specific binding of 67Ga to the corresponding antigen via the conjugate has been demonstrated.

Antibodies, Monoclonal↗
PubMedDate not supplied

Terminal-modified polylysine-based chelating polymers: highly efficient coupling to antibody with minimal loss in immunoreactivity.

A method is suggested for the preparation of chelating polymers containing a single terminal reactive group capable of interaction with proteins. These polymers were synthesized from N-CBZ-polylysine and DTPA and contain a terminal SH or pyridyldisulfide group. A polymer molecule with MW 13,500 is able to carry up to 40 DTPA residues. Polymers easily and quantitatively bind with antibodies (Fab fragments of antimyosin antibodies R11D10) with minimal effect on antibody immunoreactivity as revealed in ELISA assay and in direct immunoanalysis. Conjugates prepared can chelate radioactive metal ions reaching very high specific radioactivity (greater than 1 mCi 111In/10 micrograms of protein). Perspectives for their application are discussed.

Antibodies↗
PubMedDate not supplied

Selectin ligands promote ultrasound contrast agent adhesion under shear flow.

Contrast-enhanced ultrasound imaging has shown promise in the field of molecular imaging. This technique relies upon the adhesion of ultrasound contrast agent (UCA) to targeted molecular markers of disease. This is accomplished by coating the surface of the contrast agent with a ligand that specifically binds to the intended molecular marker. Most UCA particles remain in the blood space, and their retention is influenced by the forces imposed by blood flow. For a UCA bound to a molecular target on the vascular endothelium, blood flow imposes a dislodging force that counteracts retention. Additionally, contrast agent adhesion to the molecular marker requires rapid binding kinetics, especially in rapid blood flow. The ability of a ligand:target bond complex to mediate fast adhesion and withstand dislodging force is necessary for efficient ultrasound-based molecular imaging. In the current study, we describe a flow-based adhesion assay which, combined with a novel automated tracking algorithm, enables quick determination of the ability of a targeting ligand to mediate effective contrast agent adhesion. This system was used to explore the adhesion of UCA targeted to the proinflammatory endothelial protein P-selectin via four targeting ligands, which revealed several interesting adhesive behaviors. Contrast agents targeted with glycoconjugate ligands modeled on P-selectin glycoprotein ligand 1 exhibited primarily unstable or transient adhesion, while UCA targeted with an anti-P-selectin monoclonal antibody exhibited primarily firm adhesion, although the efficiency with which these agents were recruited to the target surface was relatively low.

Adhesiveness↗
PubMedDate not supplied

Liposomal diamidine (imidocarb): preparation and animal studies.

Diamidine (imidocarb, 3,3'-di-imidasolin-2-yl carbonylide dihydrochloride), a babesicidal drug, was encapsulated in liposomes to reduce the toxicity of the drug and to increase its therapeutic index. Liposomes were prepared from the mixture of egg yolk phosphatidyl choline and cholesterol (1:1 molar ratio) by a reverse-phase evaporation technique. Liposomes used in the study were of diameter 1.5-2.5 microns and contained 53 mg/ml (0.125 M) of diamidine. Animal tests were performed in three animal species. The LD50 values of the liposome-encapsulated diamidine administered intravenously and intramuscularly in inbred white mice were 52 and 6000 mg/kg, respectively. The overall decrease in acute toxicity compared to that for free drug amounted to 50-fold. At a dose of 30-80 mg/kg the loposomal diamidine was satisfactorily tolerated by sheep and horses, while free diamidine is lethal to these animals at 10 mg/kg. The liposome-encapsulated diamidine had no effect on metabolic functions of the liver. After four i.m. injections of the liposomal diamidine at a dose of 30 mg/kg we observed a 10% increase in haemoglobin content and an elevation in erythrocyte count in the blood of Babesia equi-infected horses. This indicates a therapeutic effect of the liposomal form of the drug.

Animals↗
PubMedDate not supplied

[A method of fluorescence immunoassay with temporal resolution and the use of europium label and polymeric complexon].

Recently developed solid-phase immunofluorescent assay with temporal distinction involved a newly produced procedure for binding of of the boron group label with antibodies via modified polymer, which is able to bind with antibodies across the avidin bridge. The assay developed is more simple than the widely used procedures, it exhibits high sensitivity being superior as compared with a corresponding immunoenzyme assay by a decimal order.

Animals↗