Biomedical subjects

J P Benoit

Publications and source records attributed to J P Benoit.

At least 19 recordsLinked to original sources

PubMed2006

Evaluation of pegylated lipid nanocapsules versus complement system activation and macrophage uptake.

This work consisted in defining the in vitro behavior of pegylated lipid nanocapsules (LNC) toward the immune system. LNC were composed of an oily core surrounded by a shell of lecithin and polyethylene glycol (PEG) known to decrease the recognition of nanoparticles by the immune system. The "stealth" properties were evaluated by measuring complement activation (CH50 technique and crossed-immunoelectrophoresis (C3 cleavage)) and macrophage uptake. These experiments were performed on 20-, 50-, and 100-nm LNC before and after dialysis. A high density of PEG at the surface led to very low complement activation by LNC with a slight effect of size. This size effect, associated to a dialysis effect in macrophage uptake, was due to differences in density and flexibility of PEG chains related to LNC curvature radius. Thanks to a high density, 660-Da PEG provided LNC a steric stabilization and a protective effect versus complement protein opsonization, but this protection decreased with the increase of LNC size, especially versus macrophage uptake.

Animals↗

PubMed2006

Development and characterization of interleukin-18-loaded biodegradable microspheres.

Immunostimulation represents a promising approach designed to specifically eradicate malignant cells. Since glioma tumour cells hole up in the central nervous system (CNS) in a particularly inauspicious milieu to antitumour immune reactions we here propose a new strategy to revert the properties of this microenvironment by administering an antitumour cytokine into the CNS tumour itself. Thus, biodegradable poly(D,L-lactide-co-glycolide) (PLGA) sustained-release microspheres for stereotaxic implantation loaded with interleukin-18 (IL-18), that is known to exert antitumour activity and trigger immune cell-mediated cytotoxicity, were developed. Different tests for assessing IL-18 bioactivity were set-up and evaluated. A specific bioassay was considered as the most reliable test. The stability and integrity of IL-18 was then verified during the encapsulation process. Consequently, two procedures of IL-18 encapsulation in PLGA microparticles (W/O/W and S/O/W) were investigated. As determined by radiolabelling studies using 125I-IL-18 and a continuous flow system, the in vitro release profile of IL-18 was optimum with S/O/W method with a moderate burst effect and a subsequent progressive discharge of 16.5+/-8.4 ng/day during the next 21 days against 6.1+/-4.2 ng/day with the W/O/W method. Considering analytical testing of IL-18 together with its preserved biological activity after release from microspheres, amounts of the active cytokine obtained with S/O/W method were relevant to plan in vivo evaluation to validate the therapeutic strategy.

Absorbable Implants↗

PubMed2006

In vitro investigation of lipid implants as a controlled release system for interleukin-18.

Operating on the inductive and effective phases of an anti-tumor immune response and uncovering pivotal functions that may reduce cancer cell growth, interleukin-18 (IL-18) appears to be an attractive candidate for the sustained local adjuvant immunotherapeutic treatment of brain gliomas. The objective of this work was to develop IL-18 loaded lipid implants as a controlled delivery system. For the preparation of protein loaded triglyceride matrix material, a solid-in-oil (s/o) dispersion technique was chosen for which protein particles in the micrometer range were first prepared by co-lyophilization with polyethylene glycol (PEG). Implants of 1 mm diameter, 1.8 mm height and 1.8 mg weight were manufactured by compression of the powder mixture in a specially designed powder compacting tool. The in vitro release behavior of 125I-Bolton-Hunter-radiolabeled IL-18 was assessed in a continuous-flow system. A cell culture assay was established for the determination of bioactivity of released IL-18. Implants showed a continuous release of 10-100 ng IL-18 per day for 12 days. A progressive integrity loss was observed with ongoing release, which would be related to protein degradation during incubation. The initially released fraction proved complete retention of bioactivity, indicating that the manufacturing procedure had no detrimental effects on protein stability.

Animals↗

PubMed2006

Effects of the type of release medium on drug release from PLGA-based microparticles: experiment and theory.

The major objectives of the present study were: (i) to prepare 5-fluorouracil (5-FU)-loaded, poly(lactic-co-glycolic acid) (PLGA)-based microparticles, which can be used for the treatment of brain tumors, (ii) to study the effects of the type of release medium on the resulting drug release kinetics, and (iii) to get further insight into the underlying drug release mechanisms. Spherical microparticles were prepared by a solvent extraction method and characterized using different techniques, including size exclusion chromatography (SEC), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and particle size analysis before and upon exposure to various release media. Interestingly, very different drug release patterns (including mono-, bi- and tri-phasic ones) were observed, depending on the pH, osmolarity and temperature of the release medium. An adequate mathematical theory was used to quantitatively describe the experimentally measured 5-FU release patterns. The model considers the limited solubility of the drug, polymer degradation as well as drug diffusion and allowed to determine system and release medium specific parameters, such as the diffusion coefficient of the drug. In particular, the pH and temperature of the release medium were found to be of major importance for the resulting release patterns. Based on the obtained knowledge the selection of an appropriate release medium for in vitro tests simulating in vivo conditions can be facilitated, and "stress tests" can be developed allowing to get rapid feedback on the release characteristics of a specific batch.

Antimetabolites, Antineoplastic↗

PubMed2006

Paclitaxel-loaded microparticles and implants for the treatment of brain cancer: preparation and physicochemical characterization.

The aim of this study was to prepare different types of paclitaxel-loaded, PLGA-based microparticles and lipidic implants, which can directly be injected into the brain tissue. Releasing the drug in a time-controlled manner over several weeks, these systems are intended to optimize the treatment of brain tumors. The latter is particularly difficult because of the blood-brain barrier (BBB), hindering most drugs to reach the target tissue upon systemic administration. Especially paclitaxel (being effective for the treatment of ovarian, breast, lung and other cancers) is not able to cross the BBB to a notable extent since it is a substrate of the efflux transporter P-glycoprotein. Both, biodegradable microparticles as well as small, cylindrical, glycerol tripalmitate-based implants (which can be injected using standard needles) were prepared with different paclitaxel loadings. The effects of several formulation and processing parameters on the resulting drug release kinetics were investigated in phosphate buffer pH 7.4 as well as in a diethylnicotinamide (DENA)/phosphate buffer mixture. Using DSC, SEM, SEC and optical microscopy deeper insight into the underlying drug release mechanisms could be gained. The presence of DENA in the release medium significantly increased the solubility of paclitaxel, accelerated PLGA degradation, increased the mobility of the polymer and drug molecules and fundamentally altered the geometry of the systems, resulting in increased paclitaxel release rates.

Antineoplastic Agents, Phytogenic↗

PubMed2006

Novel composite core-shell nanoparticles as busulfan carriers.

This study presents a method for the design of novel composite core-shell nanoparticles able to encapsulate busulfan, a crystalline drug. They were obtained by co-precipitation of mixtures of poly(isobutylcyanoacrylate) (PIBCA) and of a diblock copolymer, poly(epsilon-caprolactone)-poly(ethylene glycol) (PCL-PEG), in different mass ratios. The nanoparticle size, morphology and surface charge were assessed. The chemical composition of the top layers was determined by X-ray photo-electron spectroscopy (XPS). (3)H-labelled busulfan was used in order to determine the drug loading efficiency and the in vitro drug release by liquid scintillation counting. Physico-chemical techniques such as Zeta potential determination and XPS analysis provided evidence about a preferential surface distribution of the PCL-PEG polymer. Therefore, composite nanoparticles have a "core-shell"-type structure, where the "core" is essentially formed by the PIBCA polymer and the "shell" by the PCL-PEG copolymer. The use of PIBCA to form the core of the nanoparticles leads to a 2-4 fold drug loading increase, in comparison to the single PCL-PEG nanoparticles. In addition, the complement activation results showed a significant difference between the composite nanoparticles and the single PIBCA nanoparticles, thus demonstrating that PEG at the surface of the nanoparticles reduced the complement consumption. The PIBCA:PCL-PEG composite nanoparticles prepared using the new co-precipitation method here described represent an original approach for busulfan administration.

Antineoplastic Agents, Alkylating↗

PubMed2005

Development of new polymer-based particulate systems for anti-glioma vaccination.

Biodegradable and biocompatible microspheres represent a promising alternative to conventional adjuvants for anti-tumour vaccination. Focusing on glioma, we developed two poly(D,L-lactide-co-glycolide) (PLGA)-based particulate systems presenting tumour antigens associated with plasma membranes or with cell lysates. Glioma cell fractions were prepared for adsorption onto poly-D-lysine (PDL)-coated PLGA microspheres formulated using a double-emulsion procedure. Adsorption was followed by (125)I-radiolabelling, Western blot and confocal laser scanning microscopy. Only a panel (34%) of the proteins isolated from both cell fractions adsorbed onto PDL-coated PLGA microspheres. The integrity of the epitopes after loading was preserved, as shown by identification of plasma membrane and cytoplasmic markers. Finally, one of the major potential advantages of those particulate systems resides in the fact they not only serve as injectable adjuvant matrices presenting tumour antigens to antigen presenting cells, but also as potential reservoirs for controlled delivery of active immunostimulant molecules.

Animals↗

PubMed2005

Pharmacologically active microcarriers: a tool for cell therapy.

To overcome certain problems encountered in cell therapy, particularly cell survival, lack of cell differentiation and integration in the host tissue, we developed pharmacologically active microcarriers (PAM). These biodegradable particles made with poly(D,L-lactic-co-glycolic acid) (PLGA) and coated with adhesion molecules may serve as a support for cell culture and may be used as cell carriers presenting a controlled delivery of active protein. They can thus support the survival and differentiation of the transported cells as well as their microenvironment. To develop this tool, nerve growth factor (NGF)-releasing PAM, conveying PC12 cells, were produced and characterized. Indeed, these cells have the ability to differentiate into sympathetic-like neurons after adhering to a substrate, in the presence of NGF, and can then release large amounts of dopamine. Certain parameters such as the size of the microcarriers, the conditions enabling the coating of the microparticles and the subsequent adhesion of cells were thus studied to produce optimized PAM.

Animals↗

PubMed2005

Description and technical pitfalls of a hepatoma model and of intra-arterial injection of radiolabelled lipiodol in the rat.

Intra-arterial metabolic radiotherapy (using lipiodol labelled with iodine-131 or rhenium-188) is a therapeutic approach that can be used for the treatment of hepatocellular carcinomas (HCC). We propose a detailed description of the tumoral model using the N1-S1 cell line as well as a technique for intra-arterial injection of radiolabelled lipiodol in order to undertake preclinical studies necessary for the evaluation of a new molecule. We also report the principal technical pitfalls that were faced. The speed of injection of the tumoral cells is a key factor in the tumoral induction since slow injections lead to a tumoral induction rate of 36.3% compared with 76.6% (P<0.01) when using very slow injections. This parameter should thus be controlled carefully during the subcapsular injection of the tumoral cells. In addition, when injecting radiolabelled lipiodol, anaesthesia should not be performed with isoflurane since this leads to a reduction in tumoral uptake. Indeed, we found a 'tumour/healthy liver' uptake ratio of only 2.1+/-0.7 with isoflurane as against 4.4+/-2.6 (P<0.05) when anaesthesia was carried out by intraperitoneal injection of ketamine. Lastly, we show that the tumour size has an influence on the tumoral uptake of radiolabelled lipiodol; therefore, this parameter must also be carefully controlled.

Anesthetics↗

PubMed2005

Combining polymeric devices and stem cells for the treatment of neurological disorders: a promising therapeutic approach.

Cell therapy will probably become a major therapeutic strategy for neuronal disorders in the coming years. Nevertheless, due to poor survival of grafted cells and limited differentiation and integration in the host tissue, certain ameliorations must be envisaged. To address these difficulties, several strategies have been developed and among them, two methods seem particularly promising : in situ controlled drug delivery and implantation of cells adhered on biomaterial-based scaffolds. Indeed, the ability of drugs, such as growth factors, to regulate neuronal survival and/or plasticity infers the use of these molecules to treat neurodegeneration associated with human diseases. Moreover, the synthesis of cell scaffolds which mimic the extra-cellular matrix can help guide morphogenesis and tissue repair. Furthermore, cells can be cultivated on these matrices that may eventually make graft therapy a more practical approach for the treatment of neurological diseases. Nevertheless, for those two encouraging approaches multiple parameters have to be considered, such as the drug targeting strategy, but also the physical and morphological characteristics of the scaffold and the type of cells to be conveyed. This review thus focuses on those two promising strategies and also on their possible association to improve stem cell therapy of neurodegenerative disorders. Indeed, tissue replacement by grafting cells within or adhered onto drug delivering biomaterial-based devices, has recently been reported and seems to be very promising.

Animals↗

PubMed2004

Effect of the size of biodegradable microparticles on drug release: experiment and theory.

The aim of this study was to investigate the effect of the size of biodegradable microparticles (monolithic dispersions) on the release rate of an incorporated drug in a quantitative way. 5-Fluorouracil-loaded, poly(lactic-co-glycolic acid)-based microparticles were prepared with a solid-in-oil-in-water solvent extraction technique. In vitro drug release from different-sized particle fractions was measured in phosphate buffer pH 7.4. Differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and size exclusion chromatography (SEC) were used to monitor the degradation behavior of the polymer and morphological changes of the microparticles upon exposure to the release medium. Based on these experimental results, an appropriate mathematical theory was identified and used to get further insight into the underlying physical and chemical processes, which are involved in the control of drug release. Interestingly, the relative as well as the absolute release rate of the drug increased with increasing microparticle radius, despite of the increasing diffusion pathways. SEC, DSC and SEM analysis revealed that the degradation behavior of the matrix forming polymer was not significantly affected by the size of the devices and that autocatalytic effects do not seem to play a major role. Importantly, the initial drug loading significantly increased with increasing radius of the drug delivery system. Thus, large microparticles became more porous during drug release than small microparticles, leading to higher apparent diffusivities and drug transport rates. This effect overcompensated the effect of the increasing diffusion pathways with increasing microparticle radius, resulting in increased drug release rates with increasing device dimension. The applied mathematical model, considering drug diffusion with non-constant diffusivities (to account for polymer degradation) was able to quantitatively describe the observed drug release patterns. Importantly, an exponential relationship could be established between the diffusion coefficient and the initial loading of the drug. Based on this dependency, it was possible to predict the resulting drug release kinetics for arbitrary microparticle sizes in a quantitative way.

Biotransformation↗

PubMed2004

Pitfalls in the detection of lipid vectors in neural cell culture and in brain tissue.

Lipid particles (liposomes and lipid-coated microbubbles) are currently studied as vectors for drug delivery to the central nervous system. The visualization of these particles is usually based on their labeling with a lipophilic fluorescent dye (3,3'-dioctadecycloxacarbocyanine perchlorate) or staining with Oil Red O. The purpose of this article was to highlight the difficulties and pitfalls encountered with the use of these techniques in the detection of lipid particles in neural cell cultures and in brain tissue. In vitro and in vivo studies were conducted on different neural cell cultures (rat and human tumors, microglial cells) and animal models of brain lesion (lipopolysaccharide and quinolinic acid-induced lesion, induced brain tumor). The cells or brain slices were observed with optical microscopy after staining with Oil Red O, fluorescent microscopy, or scanning electron microscopy. Intra and extracytoplasmic lipid particles (stained with Oil Red O or autofluorescent or visualized by scanning electron microscopy) were naturally found in the cells and tissues studied. Intracytoplasmic lipid microparticles were present in tumoral and microglial cells. These lipid microparticles were also observed with some extracytoplasmic lipid droplets in the induced brain lesions. These images could be misinterpreted as lipid vectors if the cells or animals would have been treated with such a vector.

Animals↗

PubMed2004

In vivo evaluation of pharmacologically active microcarriers releasing nerve growth factor and conveying PC12 cells.

Cell therapy will probably become a major therapeutic strategy in the coming years. Nevertheless, few cells survive transplantation when employed as a treatment for neuronal disorders. To address this problem, we have developed a new tool, the pharmacologically active microcarriers (PAM). PAM are biocompatible and biodegradable microparticles coated with cell adhesion molecules, conveying cells on their surface and presenting a controlled delivery of growth factor. Thus, the combined effect of growth factor and coating influences the transported cells by promoting their survival and differentiation and favoring their integration in the host tissue after their complete degradation. Furthermore, the released factor may also influence the microenvironment. In this study, we evaluated their efficacy using nerve growth factor (NGF)-releasing PAM and PC12 cells, in a Parkinson's disease paradigm. After implantation of NGF-releasing or unloaded PAM conveying PC12 cells, or PC12 cells alone, we studied cell survival, differentiation, and apoptosis, as well as behavior of the treated rats. We observed that the NGF-releasing PAM coated with two synthetic peptides (poly-D-lysine and fibronectin-like) induced PC12 cell differentiation and reduced cell death and proliferation. Moreover, the animals receiving this implant presented an improved amphetamine-induced rotational behavior. These findings indicate that PAM could be a promising strategy for cell therapy of neurological diseases and could be employed in other situations with fetal cell transplants or with stem cells.

Amphetamines↗

PubMed2003

Implantable drug-releasing biodegradable microspheres for local treatment of brain glioma.

Our group have developed a new method of drug delivery into the brain using implantable biodegradable microspheres. In this mini-review, we describe the development, preclinical studies and clinical trials involving 5-fluorouracil-releasing microspheres for interstitial radiosensitization of malignant glioma. Future developments concerning these microspheres for treatment of brain tumors are presented.

Adolescent↗

PubMed2003

Biocompatibility of implantable synthetic polymeric drug carriers: focus on brain biocompatibility.

Numerous polymeric biomaterials are implanted each year in human bodies. Among them, drug delivery devices are potent novel powerful therapeutics for diseases which lack efficient treatments. Controlled release systems are in direct and sustained contact with the tissues, and some of them degrade in situ. Thus, both the material itself and its degradation products must be devoid of toxicity. The knowledge and understanding of the criteria and mechanisms determining the biocompatibility of biomaterials are therefore of great importance. The classical tissue response to a foreign material leads to the encapsulation of the implant, which may impair the drug diffusion in the surrounding tissue and/or cause implant failure. This tissue response depends on different factors, especially on the implantation site. Indeed, several organs possess a particular immunological status, which may reduce the inflammatory and immune reactions. Among them, the central nervous system is of particular interest, since many pathologies still need curative treatments. This review describes the classical foreign body reaction and exposes the particularities of the central nervous system response. The recent in vivo biocompatibility studies of implanted synthetic polymeric drug carriers are summarized in order to illustrate the behavior of different classes of polymers and the methodologies used to evaluate their tolerance.

Acute-Phase Reaction↗

PubMed2003

Mathematical modeling of drug release from bioerodible microparticles: effect of gamma-irradiation.

Bioerodible polymers used in controlled drug delivery systems, such as poly(lactic-co-glycolic acid) (PLGA) undergo radiolytic degradation during gamma-irradiation. In spite of the considerable practical importance, yet only little knowledge is available on the consequences of this sterilization method on the resulting drug release patterns in a quantitative way. The major objectives of the present study were: (i) to monitor the effects of different gamma-irradiation doses on the physicochemical properties of drug-free and drug-loaded, PLGA-based microparticles; (ii) to analyze the obtained experimental results using adequate mathematical models; (iii) to get further insight into the occurring physical and chemical phenomena; and (iv) to relate the applied gamma-irradiation dose in a quantitative way to the resulting drug release rate. 5-Fluorouracil-loaded, PLGA-based microparticles were prepared with an oil-in-water solvent extraction method and exposed to gamma-irradiation doses ranging from 0 to 33 kGy. Size exclusion chromatography, differential scanning calorimetry, scanning electron microscopy, particle size analysis, determination of the actual drug loading and in vitro drug release kinetics were used to study the effects of the gamma-irradiation dose on the physicochemical properties of the microparticles. Two mathematical models-a simplified and a more comprehensive one-were used to analyze the experimental results. The simplified model considers drug diffusion based on Fick's second law for spherical geometry and a Higuchi-like pseudo-steady-state approach. The complex model combines Monte Carlo simulations (describing polymer erosion) with partial differential equations quantifying drug diffusion with time-, position- and direction-dependent diffusivities. Interestingly, exponential relationships between the gamma-irradiation dose and the initial drug diffusivity within the microparticles could be established. Based on this knowledge both models were used to predict the resulting drug release kinetics as a function of the gamma-irradiation dose. Importantly, the theoretical predictions were confirmed by experimental results.

Dose-Response Relationship, Radiation↗

PubMed2002

Microencapsulation of protein particles within lipids using a novel supercritical fluid process.

Solvent-free microparticles, loaded with a model protein (bovine serum albumin: BSA) have been produced using a novel coating process based on supercritical (SC) fluid technology. Coating material consists of either trimyristin (Dynasan114) or Gelucire50-02, two lipidic compounds having a high melting point. Microparticles were characterized as regards their morphology, protein content and in vitro release profile. A discontinuous coating made of crystalline micro-needles was obtained using Dynasan114. It led to particles with an initial burst release of about 70% in 30 min at 37 degrees C. However, a prolonged release of the protein has been achieved over a 24 h period from particles coated with Gelucire50-02, which produces a more homogeneous, film-forming coating. Furthermore, it was shown that BSA does not undergo any degradation after SCCO2 treatment under the SC conditions used in the coating process.

Carbon Dioxide↗

PubMed2002

Development and characterization of solid lipid nanoparticles loaded with magnetite.

This paper describes the preparation of colloidal lipid particles containing magnetite from warm emulsions. A two step method was used to obtain the nanoparticles: (i) formulation of a transparent phase by heating a O/W emulsion (aqueous surfactant solution melted with a lipid phase, containing the ethyl oleate and soybean lecithin) in which modified lipophilic magnetite is incorporated, and (ii) preparation of the nanoparticles by dispersing the warm transparent phase in cold water (7 degrees C) under mechanical stirring. The latter method gives spherical nanoparticles of a mean size of 62 nm measured by Photon Correlation Spectroscopy and Transmission Electronic Microscopy. The magnetite entrapment efficiency was determined by use of a magnetophoretic sedimentation method.

Colloids↗