Biomedical subjects

S Margel

Publications and source records attributed to S Margel.

At least 19 recordsLinked to original sources

PubMed2005

Glial cell line-derived neurotrophic factor-conjugated nanoparticles suppress acquisition of cocaine self-administration in rats.

The neurotrophic factor glial cell line-derived neurotrophic factor (GDNF) may have therapeutic potential for preventing and treating cocaine addiction. Previously, we found that transplantation of a GDNF-expressing astrocyte cell line into the striatum and nucleus accumbens attenuates cocaine-seeking behavior in Sprague-Dawley rats. However, as a potential treatment for humans, cell transplantation presents several technical and ethical complications. Nanoparticulate systems are a safe and effective method for introducing exogenous compounds into the brain. Therefore, we examined the effect of GDNF-conjugated nanoparticles microinjected into the striatum and nucleus accumbens on cocaine self-administration in rats. GDNF-conjugated nanoparticles blocked the acquisition of cocaine self-administration compared to control treatments. Furthermore, a cocaine dose response demonstrated that decreased lever response in rats that received GDNF-conjugated nanoparticles persisted after substitution with different cocaine doses. This effect is not due to a non-specific disruption of locomotor or operant behavior, as seen following a water operant task. The current study is one of the first demonstrations that drug-conjugated nanoparticles may be effective in treating brain disorders. These findings suggest that GDNF-conjugated nanoparticles may serve as a novel potential treatment for drug addiction.

Animals↗

PubMed2001

Mobility measurements of immunomagnetically labeled cells allow quantitation of secondary antibody binding amplification.

Magnetic cell separation methods commonly utilize paramagnetic materials conjugated to antibodies that target specific cell surface molecules. The amount of magnetic material bound to a cell is directly proportional to the magnetophoretic mobility of that cell. A mathematical model has been developed which characterizes the fundamental parameters controlling the amount of magnetic material bound, and thus, the magnetophoretic mobility of an immunomagnetically labeled cell. In characterization of the paramagnetic labeling, one of the parameters of interest is the increase in magnetophoretic mobility due to the secondary antibody binding to multiple epitopes on the primary antibody, referred to as the "secondary antibody binding amplification," Psi. Secondary antibody-binding amplification has been investigated and quantitated by comparing the mobilities of lymphocytes directly labeled with anti-CD4 MACS (Miltenyi Biotec, Auburn, CA) magnetic nanoparticle antibody with the mobilities of lymphocytes from the same sample labeled with two different indirect antibody-labeling schemes. Each indirect labeling scheme incorporated a primary mouse anti-CD4 FITC antibody that provides both FITC and mouse-specific binding sites for two different secondary antibody-magnetic nanoparticle conjugates: either anti-FITC MACS magnetic nanoparticle antibody or anti-mouse MACS magnetic nanoparticle antibody. The magnetophoretic mobilities of the immunomagnetically labeled cells were obtained using Cell Tracking Velocimetry (CTV). The results indicate that an average of 3.4 anti-FITC MACS magnetic nanoparticle antibodies bind to each primary CD4 FITC antibody, Psi(1,2f) = 3.4 +/- 0.33, and that approximately one, Psi(1,2m) = 0.98 +/- 0.081, anti-mouse MACS magnetic nanoparticle antibody binds to each primary mouse CD4 FITC antibody on a CD4 positive lymphocyte. These results have provided a better understanding of the antibody-binding mechanisms used in paramagnetic cell labeling for magnetic cell separation.

Antigen-Antibody Reactions↗

PubMed2001

Polymer support for exonucleolytic sequencing.

Different kinds of particles were investigated for their potential use as supports for exonucleolytic sequence analysis. Composite beads composed of an unreactive polystyrene "core" and a "shell" of functionalized silica nanoparticles were found to best fulfill the various prerequisites. The biotin/streptavidin system was used for attachment of DNA to composite beads of 6 microm diameter. Applying M13 ssDNA in extremely high dilution (approximately 1 molecule versus 100 beads) with internal fluorescent labels, only a small fraction of beads was found to be associated with fluorescent entities, which likely correspond to a very small number of bound DNA molecules per particle. For better selection and transfer of DNA-containing beads into microstructures for exonuclease degradation the loading experiments were repeated with composite beads of 2.3 microm diameter. In this case a covalent bond was formed between carboxylate-functionalized beads and amino-terminated oligonucleotides, which were detected through external labelling with fluorescent nanoparticles interacting with biotinylated segments of the complementary strand.

Biotin↗

PubMed2000

The use of magnetite-doped polymeric microspheres in calibrating cell tracking velocimetry.

Continuous magnetic separation, in which there is no accumulation of mass in the system, is an inherently dynamic process, requiring advanced knowledge of the separable species for optimal instrument operation. By determining cell magnetization in a well-defined field, we may predict the cell trajectory behavior in the well-characterized field environments of our continuous separators. Magnetization is determined by tracking the migration of particles with a technique known as cell tracking velocimetry (CTV). The validation of CTV requires calibration against an external standard. Furthermore, such a standard, devoid of the variations and instabilities of biological systems, is needed to reference the method against day-to-day shifts or trends. To this end, a method of synthesizing monodisperse, magnetite-doped polymeric microspheres has been developed. Five sets of microspheres differing in their content of magnetite, and each of approximately 2.7 microm diameter, are investigated. An average gradient of 0.18 T/mm induces magnetic microsphere velocities ranging from 0.45 to 420 microns/s in the CTV device. The velocities enable calculation of the microsphere magnetization. Magnetometer measurements permit the determination of magnetization at a flux density comparable to that of the CTV magnet's analysis region, 1.57 T. A comparison of the results of the CTV and magnetometer measurements shows good agreement.

Cells, Cultured↗

PubMed2000

Study of magnetic particles pulse-injected into an annular SPLITT-like channel inside a quadrupole magnetic field.

Advantages of the continuous magnetic flow sorting for biomedical applications over current, batch-wise magnetic separations include high throughput and a potential for scale-up operations. A continuous magnetic sorting process has been developed based on the quadrupole magnetic field centered on an annular flow channel. The performance of the sorter has been described using the conceptual framework of split-flow thin (SPLITT) fractionation, a derivative of field-flow fractionation (FFF). To eliminate the variability inherent in working with a heterogenous cell population, we developed a set of monodisperse magnetic microspheres of a characteristic magnetization, and a magnetophoretic mobility, similar to those of the cells labeled with a magnetic colloid. The theory of the magnetic sorting process has been tested by injecting a suspension of the magnetic beads into the carrier fluid flowing through the sorter and by comparing the theoretical and experimental recovery versus total flow-rate profiles. The position of the recovery maxima along the total flow-rate axis was a function of the average bead magnetophoretic mobility and the magnetic field intensity. The theory has correctly predicted the position of the peak maxima on the total flow-rate axis and the dependence on the bead mobility and the field intensity, but has not correctly predicted the peak heights. The differences between the calculated and the measured peak heights were a function of the total flow-rate through the system, indicating a fluid-mechanical origin of the deviations from the theory (such as expected of the lift force effects in the system). The well-controlled elution studies using the monodisperse magnetic beads, and the SPLITT theory, provided us with a firm basis for the future sorter evaluation using cell mixtures.

Magnetics↗

PubMed1994

Synthesis, characterization, and use of immobilized polyacrolein microspheres in diagnostics: a model determination of alpha 1-antitrypsin in human serum.

Polyacrolein microspheres covalently coupled onto solid surfaces, e.g., glass, silicon crystals, and polystyrene, have been prepared and characterized. These surfaces were synthesized by derivatization of the substrate surfaces with SiCl3(CH2)3CN or Si(OEt)3-(CH2)4NH2. The terminal nitrile groups were then reduced to primary amine groups. Polyacrolein microspheres of various diameters (0.08 and 0.4 microns) were then covalently bound in a monolayer structure to the modified surfaces. This binding of the microspheres to the derivatized surfaces is achieved via polyvalent Schiff-base bonds formed by the interaction between aldehyde groups of the microspheres and omega-primary amine groups of the modified surfaces. Residual amine groups were blocked with acetic acid N-hydroxysuccinimide ester. The residual aldehyde groups of the immobilized microspheres can then be used for covalent binding of amino ligands, e.g., proteins, in a single step and at physiological pH (or any other desired pH). The potential use of the immobilized polyacrolein microsphere surfaces for diagnostics has been demonstrated by determination of alpha 1-antitrypsin in human serum with trypsin bound to the immobilized microspheres. The comparison between this new method for the determination of alpha 1-antitrypsin and the routine methods is discussed.

Acrolein↗

PubMed1994

Body distribution of 75Se-radiolabeled silica nanoparticles covalently coated with omega-functionalized surfactants after intravenous injection in rats.

Silica nanoparticles, radiolabeled with 75Selenium were coated with 14 types of omega-functionalized surfactants covalently bound to the particle surface. The particles were suspended in phosphate buffered saline (PBS) and injected intravenously via the tail vein of Wistar rats. The animals were sacrificed after 5 different time points (30 min, 2 h, 6 h, 24 h, and 7 d), and two samples of each organ and two blood samples were weighed into vials. The radioactivity of each sample was measured in a LKB-Wallac CliniGamma counter. Coated silica nanoparticles accumulated in the liver at much lower levels than other colloidal drug carriers after short time periods (30 min). The liver accumulation increased after longer time periods due to a natural redistribution process. Surface modification by increasing the hydrophilicity and thickness of coating yielded higher and longer persisting concentrations in the intestine, blood, and the muscles. Initially increased lung concentrations were decreasing with time, probably due to migration of the alveolar phagocytes.

Animals↗

PubMed1993

Peptide, protein, and cellular interactions with self-assembled monolayer model surfaces.

Model biomaterial surfaces with well defined chemistry were prepared from close-packed alkyltrichlorosilane monolayers on polished silicon and glass. The outermost molecular groups which come in direct contact with the biological environment were varied across a wide range of oxidation states by employing -CF3, -CH3, -CO2CH3, and -CH2OH terminal functionalities. Characterization by contact angles, surface spectroscopy, and ellipsometry verified that these model surfaces could be repeatedly prepared with good consistency for routine use to study biomolecule adsorption onto model surfaces. Adhesion of canine endothelial cells and the adsorption of proteins (human serum albumin and human fibrinogen) as well as series of synthetic defined oligopeptides to these model surfaces have been studied. Endothelial cells attachment and growth were in the rank order of: -CH2OH > -CO2Me > -CH3 > -CF3. The peptides were comprised of different alternating sequences of lysine, leucine, and tryptophan residues. These structural differences imparted different amphiphilic characters that led to measurable differences in the adsorption of these peptides to liquid-vapor interfaces. The adsorption to model surfaces was studied using ESCA, radiometry, and concentration-dependent contact angles. ESCA and radiometry measured irreversible biomolecules adsorption whereas the contact angle method measured steady-state adsorption. Radiometric results were inconsistent with ESCA, possibly due to artifacts associated with protein radiolabeling.

Adsorption↗

PubMed1989

Affinity separation with polyaldehyde microsphere beads.

Agarose polyaldehyde microsphere beads were prepared by encapsulating polyaldehyde microspheres of various diameters, e.g., polyacrolein or polyglutaraldehyde microspheres, within agarose beads. Amino ligands such as proteins or drugs can be bound covalently to the beads in a single step at physiological pH. The binding capacity of the beads towards various amino ligands is inversely related to the diameter of the microspheres encapsulated in the agarose matrix. Different reagents, e.g., bovine serum albumin, ethanolamine and hydroxylamine, were studied as blocking reagents of the free aldehyde groups. Blocking the remaining aldehyde groups after coupling the amino ligands to the beads is essential for increasing or retaining the reactivity of the ligands conjugated to the beads. Among the reagent studied, hydroxylamine was found to be the most suitable blocking reagent of the free aldehyde groups of beads conjugated with proteins. The extent of leakage of amino ligands bound to the agarose-polyaldehyde microsphere beads was studied as a function of the pH of aqueous solutions of the beads. At physiological pH the leakage was negligible. At acid pH, leakage of ligands containing several primary amine groups, e.g., proteins, was insignificant. However, significant leakage was detected for ligands containing a single amino group. The leakage of proteins bound to the agarose-polyaldehyde microsphere beads was found to be much less than the leakage of the same proteins bound to agarose beads through the cyanogen bromide activation method.

Aldehydes↗

PubMed1988

Removal of breast cancer cells by soybean agglutinin in an experimental model for purging human marrow.

Soybean agglutinin (SBA) was used as a differential reagent to achieve selective elimination of human breast cancer cells (T-47D cell line) from human marrow contaminated with tumor cells. Two successive cycles of direct agglutination by soluble SBA resulted in depletion of 3.5 logs of tumor cells as determined by radiolabeling, whereas removal of more than 4 logs of tumor cells was demonstrated by a clonogenic bioassay. A more convenient procedure for tumor purge involved the use of SBA bound to either polyglutaraldehyde magnetic beads or to commercial polystyrene magnetic beads. After one cycle of magnetic separation, 2 to 3.5 logs of tumor cells were removed. A second separation cycle using fresh magnetic beads improved depletion to more than 4 logs. Neither of these purging procedures affected the hematopoietic potential of granuloid-macrophage colony-forming unit cells. We suggest the use of SBA bound to magnetic beads as a convenient tool for effective ex vivo purging of marrow aspirates contaminated with metastatic breast cancer cells in patients with advanced disease. A similar procedure is applicable for all SBA-positive neoplasms.

Agglutination↗

PubMed1987

Specific removal of paraquat by hemoperfusion through antiparaquat conjugated agarose-polyacrolein microsphere beads.

A novel specific adsorbent for removal of paraquat from blood has been developed. Immobilized antiparaquat antibodies provide the specificity and high affinity of the adsorbent. The antibodies were raised in rabbits and goats immunized with an analogue of paraquat, conjugated to bovine serum albumin (BSA). Specific antiparaquat antibodies were isolated from the animals' sera by affinity chromatography. The antibodies were polyvalently bound to crosslinked agarose-polyacrolein microsphere beads (APAMB). Antiparaquat conjugated beads (APB) were used as packing material in a hemoperfusion column for detoxification of paraquat and were compared to activated charcoal. In vitro and in vivo experiments showed specific and enhanced rate of removal of paraquat from plasma and blood by using APB. Minimal alteration of the formed elements and plasma constituents of the blood was observed.

Animals↗

PubMed1987

Treatment of adverse digitalis effects by hemoperfusion through columns with antidigoxin antibodies bound to agarose polyacrolein microsphere beads.

Ten patients with an array of moderate to severe adverse effects resulting from digitalis were effectively treated by hemoperfusion through small columns which contained antidigoxin antibodies bound to polyacrolein microspheres in agarose macrospheres (APAMB). The procedure was well tolerated. There was no detectable damage to formed blood elements and no changes in electrolytes, liver enzymes, or other related biochemical parameters. Despite some theoretic considerations to the contrary, the removal of a relatively small load of digoxin resulted in amelioration of the clinical symptoms and ECG abnormalities associated with digitalis. No rebound phenomena of intoxication or posthemoperfusion increase in digoxin serum levels were noted over the subsequent 5 to 6 days. A further increase in the capacity of the columns may render this method a safe and convenient emergency procedure for patients with digitalis toxicity.

Acrolein↗

PubMed1987

Digitalis hemoperfusion: increase of column binding capacity by pretreatment with ouabain.

Extracorporeal hemoperfusion through polyacrolein microsphere beads (APAMB) attached to antidigoxin antibodies is an effective treatment of digitalis intoxication. In order to increase the binding capacity of the APAMB columns the active sites of the antidigoxin antibodies were protected by ouabain during the binding to the microbeads. This brought about an 11-18 percent increase in digoxin binding capacity of the columns. It was also found that binding capacity does not increase with the rise of antibody concentration beyond a certain limit. Protection of antibody binding sites and determination of optimal concentration are, therefore necessary steps during preparation of antibody based hemoperfusion columns.

Acrolein↗

PubMed1987

Purging breast cancer cells in preparation for autologous bone marrow transplantation.

Mixtures of the T-47D human breast cancer cell line and normal human bone marrow cells were used for studying a new approach for purging epithelial tumor cells for autologous bone marrow transplantation (BMT) in breast cancer. Breast cancer cell line T-47D cells were shown to bind soybean agglutinin (SBA) in a specific fashion that could be blocked by D-galactose. Tumor cells were effectively purged by both SBA agglutination and depletion of cells bound to magnetic beads (0.7-5.0 micron) covalently linked to SBA. A depletion of 3-4 orders of magnitude of tumor cells was consistently accomplished by combining one step of agglutination followed by one cycle of SBA-magnetic bead depletion. Neither procedure affects stem cell recovery. We suggest that effective purging of breast cancer cells can be accomplished using SBA for autologous BMT in patients with advanced breast cancer.

Agglutination↗

PubMed1986

Specific hemoperfusion through agarose acrobeads.

Agarose acrobeads were produced by encapsulating polyacrolein microspheres (acrobeads) of 0.2 micron average diameter within an agarose matrix. Crosslinked agarose acrobeads of diameters ranging from 0.5 to 0.8 mm were found to be optimal spheres for specific hemoperfusion purposes. Agarose provides the biocompatibility and mechanical strength of the agarose acrobeads. Acrobeads contain a high aldehyde-group content through which various amino ligands, i.e., proteins, antigens, antibodies, enzymes, and so on, can be covalently bound in a single step under physiological pH (or other pH). Thus, antibodies, antigens, or toxic materials may be directly removed from whole blood by hemoperfusion. During in vitro and in vivo hemoperfusion trials, the content of erythrocytes, leukocytes, and thrombocytes was essentially unaltered. Likewise, a battery of the soluble blood components (Cl-, K+, Na+, Ca2+, PO3/4-), total proteins, albumin, and C'4 component of the complement cascade, as well as the enzymes SGOT, LDH, and alkaline phosphatase, remained constant within narrow limits during the hemoperfusion procedure. The chemical and physical structure of the beads is stable; neither acrolein nor bead fragments were detected in hemoperfusion trials. Similarly, leakage of antibody bound to the agarose acrobeads into the blood is insignificant. Thus far, we have demonstrated the efficacy of the crosslinked agarose acrobeads for extracorporeal removal of "unwanted" substances from whole blood in the following systems: (a) removal of specific antigens (digoxin or paraquat removal with antidigoxin or antiparaquat antibodies bound to the acrobeads, respectively), (b) removal of specific antibody (antiBSA) removal with BSA bound to the beads), (c) removal of immune complexes (BSA-antiBSA complex removal with C1q bound to acrobeads), and (d) removal of specific metals (removal of iron with deferoxamine bound to the agarose acrobeads).

Animals↗

PubMed1986

Depletion of human lymphocytes from peripheral blood and bone marrow by affinity ligands conjugated to agarose-polyacrolein microsphere beads.

Protein-A or goat anti-mouse-Ig (GAMIg) covalently bound to agarose-polyacrolein microsphere beads (APAMB) were employed for the removal of T cells from human peripheral blood leukocytes (PBL) and bone marrow (BM). The cell suspensions were treated with a monoclonal anti-T cell antibody (Leu-1) or monoclonal antilymphocyte antibody (CAMPATH-1) and passed through the conjugated APAMB columns. Cell separation efficacy was determined by assaying the number and function of T cells in the final cell preparation in comparison with a sample of unseparated cells. The number of cells that form rosettes (E-RFC) with sheep red blood cells (SRBC) in a sample of PBL treated with anti-Leu-1 antibodies and subsequently passed once through GAMIg-conjugated APAMB dropped from a range of 41.5-86.0% to a range of 1.6-13.3%. The in vitro response to concanavalin-A (Con-A) dropped to a range of 0.7-27.2% (GAMIg) and a range of 1.2-21.8% (protein-A column) of the response of untreated PBL. Treatment with CAMPATH-1 antibody and passage through a protein-A-conjugated APAMB reduced E-RFC from a range of 55.6-57.4% to a range of 3.2-3.9% and abolished the Con-A induced proliferative responsiveness to background levels. Treatment of BM cells with CAMPATH-1 and passage of the cells through either GAMIg or protein-A conjugated APAMB columns resulted in reduction of E-RFC from a range of 12.4-17.7% to a range of 0-1% and from a range of 17.7-19% to a range of 1.6-3.2%, respectively. Viability of BM precursors, determined by the CFU-GM assay in semisolid medium, was not affected by these cell separation procedures. The data suggest that protein-A or GAMIg-conjugated APAMB columns may be a useful tool for separation of BM cell suspensions into specific cell subsets that can be defined by monoclonal antibodies.

Acrolein↗

PubMed1986

Polyacrolein microspheres as a new solid phase for radioimmunoassay.

Polyacrolein (PA) microspheres contain reactive aldehyde groups through which ligands containing primary amino groups such as proteins and drugs can be covalently bound in a single step at physiological pH. Antibodies against cyclic-AMP, digoxin and rabbit serum were thus coupled to PA microspheres. The immuno-microspheres were kept in suspension or freeze-dried, with insignificant decrease in their binding capacity. The conjugates were used in the respective radioimmunoassay (RIA) systems to facilitate the separation of the free and the antibody-bound 125I ligands, in comparison with precipitation of Protein A of Staphylococcus aureus. Cyclic-AMP was assayed using PA microspheres coupled either with the primary antibody or with anti-rabbit serum as a secondary antibody, in a buffer system, in chick plasma, in urine and in media in which avian dispersed kidney cells had been stimulated by various agents. The results obtained using the immuno-microspheres and the bacterial separation methods were indistinguishable. Other 125I-ligands, such as digoxin in buffer system or thyroxine and triiodothyronine in chick plasma, were assayed in the picogram range. Owing to the solubility of non crosslinked microspheres conjugates in toluene-based scintillation fluids, both the free and the bound fractions could be counted when using 3H-ligands. Corticosterone was assayed using this technique.

Acrolein↗

PubMed1985

Therapy of digoxin intoxication in dogs by specific hemoperfusion through agarose polyacrolein microsphere beads-antidigoxin antibodies.

The usefulness of a new biocompatible, specific immunosorbent, Agarose-Polyacrolein Microsphere Beads--Antidigoxin antibodies (APAMB-AD) for hemoperfusive removal of digoxin in digoxin intoxicated dogs is described. The sorbent contains antidigoxin antibodies covalently bound to polyacrolein microspheres, 0.2 micron in diameter. Thousands of microspheres are matrix-encapsulated in cross-linked agarose to form beads 500 to 800 micron in diameter. The sorbent removes digoxin specifically, leaving other components of the blood intact, in contrast to the nonspecific sorbents (charcoal and ion exchange resins) currently in use. Digoxin-intoxicated dogs looked ill, vomited, and their ECGs showed malignant arrhythmias which were reversed during the first hour of hemoperfusion. By 2 hours of hemoperfusion, the ECG tracings returned to the preintoxication state. Up to 27% of the total body digoxin burden was removed. The sorbent is biocompatible. Neither the formed elements nor a battery of the routinely assayed soluble components of the blood or complement (C'4) were altered significantly during the hemoperfusion trials. The dogs tolerated the hemoperfusion well and all survived the intoxication. Nonhemoperfused dogs or dogs whose blood was hemoperfused through beads lacking antidigoxin did not survive the digoxin intoxication.

Acrolein↗