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Biomedical subjects

F Chouinard

Publications and source records attributed to F Chouinard.

7 recordsLinked to original sources
PubMed2001

Characterization of cytohesin-1 monoclonal antibodies: expression in neutrophils and during granulocytic maturation of HL-60 cells.

ADP-ribosylation factors (Arf) are small GTP-binding proteins involved in vesicular transport and the activation of phospholipase D (PLD). The conversion of Arf-GDP to Arf-GTP is promoted in vivo by guanine nucleotide exchange factors such as ARNO or cytohesin-1. In order to examine the expression of ARNO and cytohesin-1 in human granulocytes, we generated specific polyclonal and monoclonal antibodies (mAbs). We also overexpressed GFP-ARNO and GFP-cytohesin-1 in RBL-2H3 cells to characterize the specificity and the ability of cytohesin-1 mAbs to immunoprecipitate cytohesin-1. Among the hybridomas secreting cytohesin-1 mAbs, only the clones 2E11, 1E4, 3C8, 6F5, 4C7, 7A3 and 8F7 were found to be specific for cytohesin-1. Furthermore, mAb 2E11 immunoprecipitated GFP-cytohesin-1 but not GFP-ARNO under native conditions. In contrast, mAbs 5D8, 4C3, 2G8, 6G11, 4C3, 6D4, 7B4 and 6F8 detected both cytohesin-1 and ARNO as monitored by immunoblotting. Although mAb 6G11 detected both proteins, this antibody immunoprecipitated GFP-ARNO but not GFP-cytohesin-1 under native conditions. Another antibody, mAb 10A12, also selectively immunoprecipitated GFP-ARNO under native conditions, but the epitope recognized by this mAb is unlikely to be linear as no signal was obtained by immunoblotting. Immunoprecipitation with a cytohesin-1 polyclonal antibody and blotting with cytohesin-1 specific mAbs revealed that cytohesin-1 is highly expressed in neutrophils. Cytohesin-1 can be detected in HL-60 cells but the endogenous protein levels were low in undifferentiated cells. Using the specific cytohesin-1 mAb 2E11 we observed a marked increase in levels of cytohesin-1 expression during dibutyryl-cyclic AMP-induced granulocytic differentiation of HL-60 cells. These data suggest that cytohesin-1, which may have important functions in neutrophil physiology, can be useful as a potential marker for granulocytic differentiation.

Antibodies, Monoclonal↗
PubMed2001

Enzymatic degradation of cross-linked high amylose starch tablets and its effect on in vitro release of sodium diclofenac.

The influence of several physicochemical parameters on enzymatic hydrolysis and the in vitro release of sodium diclofenac (SDic) from cross-linked high amylose starch (Contramid) (CLA) tablets was evaluated. These parameters included pH, ionic strength of the medium, enzyme concentration, compression force and incorporation of gel-forming polymers such as hydroxypropyl methylcellulose (HPMC), poly(ethylene oxide) (PEO) and poly(vinyl alcohol) into the tablet. Pure CLA tablets were incubated in phosphate buffer (pH 6.8) containing alpha-amylase and the extent of enzymatic erosion was determined by gravimetry. Release of SDic from CLA tablets, in the presence of alpha-amylase, was measured using a USP type III dissolution apparatus. For low alpha-amylase concentrations (<2250 IU/l), the drug release was mainly diffusion-controlled. At higher alpha-amylase concentrations (>4500 IU/l) both diffusion and erosion contributed to the release of SDic. The hydrolysis kinetics of CLA tablets by alpha-amylase was biphasic. During the first phase (2-4 h), the hydrolysis rate was hyperbolically related to the alpha-amylase concentration but was practically alpha-amylase concentration-independent during the second phase. Enzymatic erosion and drug release kinetics appear to be relatively independent of ionic strength, pre-incubation time in simulated gastric fluid, and compression force of the tablets (6-34 kN). Incorporation of HPMC or PEO into the tablet resulted in a significant decrease of both tablet erosion and drug release rates.

Amylose↗
PubMed1998

Cross-linked high amylose starch for controlled release of drugs: recent advances.

Cross-linked high amylose starches have been developed as excipients for the formulation of controlled-release solid dosage forms for the oral delivery of drugs. Advantages of this new class of excipients include cost-effectiveness, readily accessible industrial manufacturing technology, high active ingredient core loading and the possibility of achieving a quasi zero-order release for most drugs. In addition to the latter, other features distinguish cross-linked high amylose starches from other excipients used to prepare hydrophilic matrices. Among these are the absence of erosion, the limited swelling and the fact that increasing cross-linking degrees results in increased water uptake rate, drug release rate and equilibrium swelling. Thus the goal of the present study was to gain some insights into the mechanism of drug release control by matrices of cross-linked high amylose starch. Water transport kinetics and dimensional changes were studied in matrices placed in water at 37 degrees C by an image analysis technique. The results show that in the first 5 min, a gel layer is formed at the surface of the tablet, after which the gel front seems to halt its progression toward the center of the tablet. Water continues to diffuse through the front and to invade the core. As a consequence, this latter swells, with a predominance for radial swelling. Equilibrium swelling is reached over 3 days, when the water concentration in the tablet becomes homogeneous and the whole tablet gelifies. Solid-state 13C-NMR were acquired on cross-linked high amylose starch powders, tablets and hydrated tablets with varying cross-linking degrees. They show a predominance of the V-type single helix arrangement of amylose in the dry state irrespective of the cross-linking degree. Upon hydration, the homologues with a low cross-linking degrees show a transition from the V to the B-type double helix arrangement. It is therefore hypothesized that the capacity of amylose to undergo the V to B transition is an important factor in controlling water transport and drug release rate. Finally applications to different drugs are reviewed briefly. They illustrate the versatility of this technology as generic versions of zero order OROS drug (Efidac) and Fickian release conventional matrices (Voltaren SR) were developed and successfully tested in pilot clinical studies to be bioequivalent to the references. These studies further showed that cross-linked high amylose starch matrices have the lowest inter-subject variability among the systems tested and show a total absence of food effect.

Administration, Oral↗
PubMed1994

Poly(alkylcyanoacrylate) nanocapsules: physicochemical characterization and mechanism of formation.

Nanocapsules of poly(isobutylcyanoacrylate) and poly(isohexylcyanoacrylate) were prepared by addition of the monomer to an organic phase and subsequent mixing of the organic phase to an aqueous phase containing poloxamer 188, 238 or 407. Gel permeation chromatography indicated that in contrast to literature reports, polymerization occurred in the organic phase and nanocapsules were obtained by interfacial precipitation of the polymer without any significant change of the molecular weight. Addition of SO2 to the organic phase before the introduction of the monomer allowed preparation of nanocapsules with a lower molecular weight. Nanospheres were prepared in a similar way albeit using an organic phase that was completely miscible within the aqueous phase so that solid spheres were obtained. Density gradient centrifugation revealed that nanocapsules had a density intermediate between nanospheres and an emulsion prepared in the same way without addition of monomer to the organic phase. Further, the process used to prepare nanocapsules had a high yield since no oil droplets or nanospheres were obtained by this process. Zeta potential of the nanocapsules and spheres was found to be related to the molecular weight of the polymer: values as high as approximately -42 mV were obtained for low molecular weight nanocapsules (MW approximately 1000) compared to approximately -10mV for the emulsion and the high molecular weight nanocapsules (MW approximately 100,000). Surface charge of the nanocapsules and molecular weight of their polymeric wall conditioned the adsorption capacity of poloxamers. Moreover, the highest adsorption was measured with the most hydrophobic poloxamer. These observations agree with previous work conducted on hydrophobic surfaces.

Adsorption↗
PubMed1991

Biodegradable nanospheres containing phthalocyanines and naphthalocyanines for targeted photodynamic tumor therapy.

Preparation methods of cyanoacrylic nanocapsules or nanoparticles containing phthalocyanines and naphthalocyanines are described. Nanocapsules were obtained by interfacial polymerization in an oil-in-water emulsion. Drug encapsulation efficiency depended upon drug concentration, ethanol concentration, and phthalocyanine sulfonation degree and reached 100% in some cases. Nanocapsules size ranged from 150 to 250 nm and varied with phthalocyanine sulfonation degree and pH of the aqueous phase. Nanoparticles were prepared by the addition of monomer to an aqueous phase containing hydrophilic phthalocyanine derivatives. Depending upon the pH, sizes ranged from 10 to 380 nm. Drug binding was between 75 and 80%. These new preparations could prove useful in the photodynamic treatment of tumors.

Biodegradation, Environmental↗
PubMedDate not supplied

Association of cyclosporin to isohexylcyanoacrylate nanospheres and subsequent release in human plasma in vitro.

Polyisohexylcyanoacrylate nanocapsules containing cyclosporin were prepared by mixing in a 1:2 ratio an oil/ethanol solution of monomer and drug with an aqueous phase. Drug nanoencapsulation rate was controlled by its partition coefficient between the inner (organic) and outer (aqueous) phases. Thus highest encapsulation yields (88 per cent) were achieved by reducing cyclosporin solubility in the aqueous phase, i.e. by reducing ethanol concentration under reduced pressure, achieving a 3-fold volume reduction. Due to the relative insolubility of cyclosporin in water, no drug was released from the nanocapsules during storage in this injectable vehicle. Upon a 1/5 dilution in human plasma at 37 degrees C in vitro around 40 per cent of the initially encapsulated cyclosporin diffused quickly out of the capsules and an equilibrium was reached, the drug being most likely dissolved in the fatty compartment of the plasma such as lipoproteins, etc. This release mechanism is different from plain polymeric nanoparticles. Indeed, in this case the drug was released in two phases: an initial burst (around 60 per cent) of adsorbed drug as a result of the dilution, followed by a slow release (around 20 per cent over 3 h) which is likely to result from the progressive enzymatic erosion of the polymer. The initial burst was markedly more pronounced (around 80 per cent) when nanoparticle suspensions were evaporated to 1/3 of their initial volume under reduced pressure. Finally, experiments performed at 0 degree C allowed a reduction of the fraction released immediately from both types of nanospheres, probably because of a reduced solubility in plasma. In the case of nanoparticles the second phase of slow release is also inhibited at 0 degree C, in agreement with an enzymatically controlled release mechanism.

Capsules↗