Interactions between energetic heavy ions and biodegradable polymers. Application to macrophages culture on membranes

Doctorat en sciences naturelles appliquées - UCL, 199

Modifications induced by swift heavy ions in poly(hydroxybutyrate-hydroxyvalerate) (PHB/HV) and poly(epsilon-caprolactone) (PCL) films. Part 1. Thermal behaviour and molecular mass modifications

Modifications induced by different energetic heavy ions in poly(epsilon -caprolactone) (PCL) and poly(hydroxybutyrate-hydroxyvalerate) (PHB/HV) have been investigated by the differential scanning calorimetry (DSC) and steric exclusion chromatography (SEC). A certain dose of damages, depending mainly on the charge and mass of the ion and on the intensity of irradiation, has to be overcome in order to detect any effect on PHB/HV. Actually, at a given intensity of irradiation, superior to 10(10) ions/cm(2), the level of damage intensity increased with the increase in charge and mass of the ion. Moreover, according to the SEC results, there seems to be a critical mass and/or charge threshold above which the dominant type of damages changes. As a matter of fact, high-density irradiation with Ar9+ and Kr15+ resulted mainly in chain scission whereas cross-linking was dominant when irradiating the polymer with Xe24+ and Pb56+. Th, irradiation of PCL in the conditions studied did not modify significantly the values of the melting point, the crystallisation temperature and the molecular masses of the system studied. The main effect of the irradiation detected by the DSC is the cross-linking of the polymer chains. (C) 2000 Elsevier Science B.V. All rights reserved

Modifications induced by swift heavy ions on poly(hydroxybutyrate-hydroxyvalerate) (PHB/HV) and poly(epsilon-caprolactone) (PCL). Part 2. Radicals characterization

Modifications induced by different energetic heavy ions (Ar-40(9+), Kr-80(15+), Xe-129(24+), Pb-208(53+) and Pb-20(56+)) on poly(epsilon -caprolactone) (PCL) and poly(hydroxybutyrate-hydroxyvalerate) (PHB/HV) have been investigated by electron spin resonance (ESR). Indeed, film irradiation by heavy ions leads to, among other phenomena, the formation of radicals in the ion tracks. Thanks to ESR, it is possible to detect these radicals and to identify them or at least to characterize them by following the evolution of the radical signal as a function of parameters, like temperature, or the kinetic of disappearance of the radical species at ambient temperature in vacuum or ambient atmosphere. This study confirmed the generation of radicals by the irradiation of PHB/HV samples with energetic heavy ions reported in the literature. The study on PCL was not pursued after a few preliminary studies, revealing the presence of an ESR signal in the nonirradiated sample. Electronic stopping power has a major influence on radical decrease at ambient temperature. The ion used for the irradiation did not modify very much the radical signal and the evolution of the radicalar signal intensity with temperature. Different reasoning and experiments revealed that the glass transition temperature is a key temperature above which irreversible recombinations of the most stable radicals take place. A simulation study indicated that the most stable radical produced was probably a tertiary radical formed by the stabilization of the secondary radical resulting from the abstraction of a highly mobile hydrogen adjacent to the carbonyl. (C) 2000 Elsevier Science B.V. All rights reserved

Adsorption of albumin, collagen, and fibronectin on the surface of poly(hydroxybutyrate-hydroxyvalerate) (PHB/HV) and of poly (epsilon-caprolactone) (PCL) films modified by an alkaline hydrolysis and of poly(ethylene terephtalate) (PET) track-etched membranes.

The effect of alkaline hydrolysis on several surface properties of poly(hydroxybutyrate-hydroxyvalerate) (92/8) (PHB/HV) and poly(epsilon-caprolactone) (PCL) films and of poly(ethylene terephtalate) (PET) track-etched membranes have been characterized, as well as the adsorption of three proteins normally encountered by mammalian cells in vivo, namely albumin, collagen, and fibronectin. The water contact angle decreases and the number of -COOH functions accessible to a chemical reaction at the surface of PCL increases with alkaline hydrolysis. Analysis by atomic force microscopy pictures reveals a change in surface morphology. The modifications of surface properties are correlated with a two times increase of the adsorption of three radiolabelled proteins. The hydrolysis results in a slight increase in the water contact angle of one face of the PHB/HV film and a sharp increase in the number of -COOH functions. Important morphology changes are also induced. The adsorption of the radiolabelled proteins is almost 100 times higher on the hydrolyzed polymer than on the native surface. The increase in hydrophilicity of different PET batches correlates to an increase in the number of -COOH functions. Nevertheless, the surface chemical composition and rugosity are constant and no significant difference in the amount of radiolabelled fibronectin adsorbed on the different surfaces is detectable. In conclusion, the effect of hydrolysis on the surface properties of each of the polyesters studied as well as the proteins adsorption on the different surfaces are different. The results strongly support the hypothesis that, in the system studied, parameters other than hydrophilicity influence protein adsorption: the main parameters that might play a role are the total surface area accessible to the proteins, as well as the surface chemical composition

Encapsulation of amphotericin B in poly(ethylene glycol)-block-poly(epsilon-caprolactone-co-trimethylenecarbonate) polymeric micelles.

The aim of this work was to evaluate the potential of self-assembling poly(ethyleneglycol)(750)-block-poly(epsilon-caprolactone-co-trimethylenecarbonate)(4500) 50/50 copolymers (PEG-p(CL-co-TMC)) to solubilize amphotericin B in polymeric micelles and to disaggregate the drug to the less toxic monomeric form. Amphotericin B was encapsulated in the micelles upon dilution of a mixture of the liquid polymer and the drug in water. Its solubility was increased by two orders of magnitude depending on polymer concentration. The aggregation state of amphotericin B was decreased by PEG-p(CL-co-TMC). The preparation method and the loading of the polymeric micelles influenced it. The antifungal activity of the drug was reduced by encapsulation in the polymeric micelles whereas the onset of amphotericin B-induced hemolysis was delayed. PEG-p(CL-co-TMC) micelles could be an easy method for amphotericin B encapsulation

Use of a radial-flow cell for the cleanability assessment of solid surfaces.

peer reviewe

Cleanability assessment of model solid surfaces with a radial-flow cell

The cleanability of several model solid substrates (glass, stainless steel, polystyrene and polytetrafluoroethylene-PTFE) was studied with a radial-flow cell. Two soiling methods were used to mimic splashing with oil; a thin layer chromatography sprayer giving a narrower and more reproducible oil droplet size distribution was preferred. Glass was the most cleanable substrate, a result which may be consistent with the presence of a swelling gel-like layer at the surface. For the other substrates, the mechanical action exerted by the fluid played a major role in oil removal; however the detergent seemed to intervene after about 5-10 min, facilitating cleaning of PTFE. Oil droplet removal took place only at high wall shear stress, in zones where flow conditions where not well controlled making it impossible to evaluate the wall shear stresses needed for oil droplet removal. Evaluation of cleanability by using the radial-flow cell is restricted to variations of wall shear stresses in a range below 3 N m(-2). (C) 2007 Elsevier B.V. All rights reserved

Spontaneously self-assembled micelles from poly(ethylene glycol)-b-poly(epsilon-caprolactone-co-trimethylene carbonate) for drug solubilization

Di-block copolymers composed of polyethylene glycol (PEG) and a second block of (co)polyesters of F-caprolactone (CL) and/or trimethylene carbonate (TMC) were synthesized and characterized. Tin octoate was used as catalyst and polymerization were completed over a period of 24h with high conversion (> 95%). Self-assembling properties in water were evaluated. All di-block copolymers behave similarly except when PCL served as the second block. Stable crew-cut micelles of about 20 nm were obtained by direct dissolution of the liquid di-block copolymers in water at room temperature. When PCL was present as the second block, no solubilization occurred. Drug encapsulation of poorly water-soluble drugs belonging to biopharmaceutics classification system (BCS) class 11 (ketoprofen and furosemide) was evaluated. Experimental solubility for these two drugs shows a significant enhancement such that a maximum value of 23.4 mg/ml was obtained for ketoprofen in a 10% w/v micellar solution as compared to 0.14 mg in water. In the case of furosemide, the solubility increased from 0.04 mg/ml in water to about 3.2 mg/ml in a 10% w/v micellar solution. Enzymatic degradation of di-block copolymers was also studied in the presence of Pseudomonas lipase in a phosphate buffer solution (pH 7.4). Results indicated rapid degradation of copolymers containing relatively higher amounts of CL compared to TMC suggesting the potential in vivo degradation

Interactions between a biodegradable polymer, poly(hydroxybutyrate-hydroxyvalerate), proteins and macrophages

The effect of the chemical and morphological modifications of the surface of poly(hydroxybutyrate-hydroxyvalerate) (92/8) (PHB/HV) films induced by an alkaline hydrolysis on the adsorption of three proteins known to modify cell behavior, namely albumin, collagen and fibronectin and on the adhesion and proliferation of monocytes-macrophages of the J774 cell line, has been studied. Before treatment, the water contact angle theta of the face that went through a corona pretreatment was higher than the other one. It increases with hydrolysis to equal the value of theta angle of the other face after 2 hours. The XPS analysis revealed that all the impurities present on the native material have been eliminated after hydrolysis leading to a similar chemical composition on both faces. The surface concentrations of -COOH functions accessible to [H-3]-lysine increases sharply with the duration of hydrolysis. The sharpest increase is observed at the very beginning of hydrolysis. The surface morphology of the polymer is also modified by hydrolysis. The adsorption of the three proteins increases when the polymer is hydrolyzed as well as the adhesion and proliferation of the monocytes-macrophages, no matter which protein was adsorbed. There are some evidence suggesting that the protein conformation is different on both substrates. Collagen has a drastic repulsive effect on the cells on the native polymer but this repulsive effect disappeared on the hydrolysed one. Accordingly, it clearly appears that it is possible to modulate the biocompatibility of PHB/HV by either chemical hydrolysis or protein adsorption