PubMed Health⌕ Search

Biomedical subjects

R Kravtzoff

Publications and source records attributed to R Kravtzoff.

12 recordsLinked to original sources
PubMed2000

Proofs of the structure of lipid coated nanoparticles (SMBV) used as drug carriers.

PURPOSE: Supramolecular Biovectors (SMBV) consist of cross-linked cationic nanoparticles surrounded by a lipid membrane. The purpose was to study the structure of the lipid membrane and to characterise its interaction with the nanoparticles in order to differentiate SMBV from other polymer/lipid associations. METHODS: The interaction of lipids with the nanoparticle surface was studied using zeta potential. Fluorescence Energy Transfer (FET) and Fluorescence Microscopy. SMBV were compared to liposomes and mixtures nanoparticles/liposomes. Finally the structure of SMBV was visualised by Electron Microscopy. RESULTS: Zeta potential measurements showed that lipids on SMBV had a pronounced shielding effect on the surface charge. This was not the case for mixtures of nanoparticles and liposomes. FET experiments confirmed these results indicating that, for SMBV, the lipids are much closer to the nanoparticle surface. SMBV Fluorescence microscopy on model microparticles showed a lipid crown on SMBV that was confirmed by electron microscopy on SMBV nanoparticles. CONCLUSIONS: Results show that in case of SMBV lipids are strongly adsorbed on the polysaccharide core surface probably due to ionic/hydrophobic interactions. The resulting supramolecular structure is a spherical cationic polysaccharide particle surrounded by a phospholipid/cholesterol layer.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1998

SupraMolecular BioVectors (SMBV) improve antisense inhibition of erbB-2 expression.

New therapeutic strategies are now being developed against adenocarcinoma associated with erbB-2 amplification, particularly by inhibiting p185erbB-2 expression. Antisense oligodeoxynucleotides seem promising for this purpose as long as they are efficiently protected against degradation and targeted into the cells. We present antisense oligonucleotide carriers, the supramolecular biovectors (SMBVs), for which we have already demonstrated the ability to improve both cellular uptake and protection of oligodeoxynucleotide. The present work demonstrates that SMBVs elicit a specific and non-toxic action of antisense compounds in a cell model, irrespective of their sensitivity to nucleases. This is a major point, considering the specificity problems associated with the use of nuclease-resistant phosphorothioate oligodeoxynucleotide. SMBVs improve antisense efficiency of oligodeoxynucleotide designed against p185erbB-2, with a complete growth arrest of SK-Br-3, human adenocarcinoma mammary cells that overexpress p185erbB-2 and no effect on MCF-7 cells that normally express p185erbB-2. The comparison of SMBVs with DOTAP reveals the statistically higher efficiency of SMBVs, which allows the antisense inhibition of p185erbB-2 expression in 65-75% of SK-Br-3 cells (P < 0.05). The efficiency and controlled synthesis of SMBVs underline their potentialities as oligodeoxynucleotide carriers for in vivo experiments.

Cell Division↗
PubMed1997

Improved oligonucleotide uptake and stability by a new drug carrier, the SupraMolecular Bio Vector (SMBV).

Antisense oligodeoxynucleotides are potential therapeutic agents, but their development is still limited by both a poor cellular uptake and a high degradation rate in biological media. The strategy that we propose to face these problems is to use small synthetic carriers, around 30 nm diameter, the SupraMolecular Bio Vectors (SMBV). We used positively charged SMBV and settled the ionic incorporation of negatively charged oligonucleotides into these carriers. A minimal leakage of 10% of total incorporated oligonucleotides was then measured during two months. Both protection and uptake of oligonucleotides were then analyzed. On the one hand, we showed that the incorporation of oligonucleotides into the selected SMBV allows to significantly increase, 8 times, their half-life, in cell growth medium. On the other hand, the internalization of the SMBV, into cells, by an endosomal pathway has been characterized. The essential point is that the SMBV uptake elicits the simultaneous oligonucleotide uptake. The oligonucleotide amount that goes through cells within 5 h can be up to 30 times higher than for free oligonucleotides and the fraction of oligonucleotides that is present in the cytosol is increased up to 10 fold after incorporation into the SMBV. This study demonstrates the ability of SMBV to improve oligonucleotide cellular behaviour.

Animals↗
PubMed1996

Improved pharmacodynamics of L-asparaginase-loaded in human red blood cells.

To evaluate the modification of pharmacodynamic parameters induced by the administration of L-asparaginase loaded into red blood cells, 13 patients received a single dose of L-asparaginase internalised into the carrier. The enzyme was loaded using a reversible lysis-resealing process. The dose per patient ranged from 30 to 200 i.u. kg-1. Considerable heterogeneity occurred between patients. the level of L-asparaginase circulating after 24 h represented 47% of the total injected dose as compared to 74.8% for red blood cells (RBCs). However, the half-life of the enzyme remaining in the circulation was very similar to that of the RBC carrier, i.e. 29 days and 27 days, respectively, compared with 8-24 h for the free enzyme. Sustained elimination of plasma L-asparagine occurred, the duration of which was dependent on the injected dose. A single injection of 30.i.u.kg-1 was sufficient to eliminate plasma L-asparagine over 10 days. With 150-200 IU.kg-1 the elimination period was extended to 50 days. These data show that the use of RBCs as carriers of L-asparaginase greatly improves the pharmacodynamic parameters of the drug.

Adolescent↗
PubMed1996

Tolerance evaluation of L-asparaginase loaded in red blood cells.

OBJECTIVE: A pilot clinical study was conducted to evaluate the toxicity of a single dose of L-asparaginase loaded in red blood cells (RBCs). METHODS: Thirteen patients received a single dose of L-asparaginase in the range 30-200 i.u.kg-1. The enzyme was loaded in one autologous blood unit using a lysis-resealing process. A control population of 33 patients receiving L-asparaginase intravenously were tested in parallel. IgG, IgM and IgE class anti-L-asparaginase antibodies were detected using specific radioimmunoassays. RESULTS: L-Asparaginase pharmacodynamic parameters may be greatly improved by administration of the drug after internalisation in RBCs as compared to intravenous injection of free drug. The drug elimination was prolonged and similar to that of circulating carrier. After one injection of 30 i.u.kg-1, plasma L-asparagine was eliminated in 10 days and this was extended to 50 days for 150-200 i.u.kg-1. The drug was well tolerated and only transient variations were observed for some of the biological parameters measured. We did not reach the maximum tolerable dose (MTD) of L-asparaginase loaded in RBCs. No significant clinical toxicity was detected. In particular, no immune adverse effects were observed. CONCLUSION: This study opens new perspectives for the clinical utilisation of L-asparaginase. This mode of administration of the drug is able to improve pharmacodynamic parameters and enzymic efficacy and to increase the general tolerance of the treatment.

Adolescent↗
PubMed1994

Density gradient separation of L-asparaginase-loaded human erythrocytes.

L-Asparaginase has been encapsulated in human red blood cells using a hypotonic dialysis process. Erythrocytes loaded with L-Asparaginase were separated into eight fractions using a discontinuous Percoll density gradient. A minor cell subpopulation of low density cells and a major subpopulation of denser erythrocytes was obtained after hypotonic dialysis treatment, in both the absence or presence of L-Asparaginase. The encapsulated L-Asparaginase activity per resealed erythrocyte was higher in low-density cells and decreased progressively with increasing in cellular density.

Asparaginase↗
PubMed1991

[HLA B27 phenotyping using flow cytometry].

Results of typing for HLA B27 antigens of 106 patients in whole blood with a FITC monoclonal anti HLA B27 antibody and analysis by flow cytometry are compared to the results obtained by the classical microlymphocytoxicity test. By flow cytometry analysis, there are not false negative result, but, because of cross reactions of the used monoclonal antibody with other specificities of the CREG B7 group, false positive result may be encountered. The flow cytometry analysis for typing HLA B27 antigens using a monoclonal antibody can be a good screening technique: so it's rapid and moreover the negative results can be accepted. The positive results must be confirmed.

Antibodies, Monoclonal↗
PubMed1990

Erythrocytes as carriers for L-asparaginase. Methodological and mouse in-vivo studies.

L-Asparaginase has been encapsulated in Swiss mouse or human erythrocytes by hypotonic haemolysis followed by isotonic resealing and reannealing. The details of incorporation and properties of carrier erythrocytes are presented. When L-asparaginase loaded into 51Cr-labelled erythrocytes, was infused intravenously, the same half-life was found for asparaginase and 51Cr. In addition, L-asparaginase loaded into erythrocytes was much more effective in eliminating plasma asparagine compared with the same dose of free L-asparaginase injected in solution, during a sustained period (14 days).

Animals↗
PubMed1990

Several aspects of red blood cell engineering: potential therapeutic applications.

Erythrocytes can be used to entrap drugs, enzymes or other molecules with active properties, with various encapsulation procedures. The method of internalization we are using includes an hypotonic dialysis step. Carrier erythrocytes survival depends on the dialysis process and the carried molecule. Research has led us to perform preclinical trials on animals for several drugs and enzyme therapies and for the improvement of oxyphoric capacity of erythrocytes. There exist many potential clinical applications for each kind of internalized molecules.

Animals↗