Protein release profiles and morphology of biodegradable microcapsules containing an oily core.

The protein release profiles and the morphology of poly(D,L-lactide-co-glycolide) (PLG) and poly(epsilon-caprolactone) (PCL) microcapsules were investigated. The microcapsules were prepared by the (oil(1)-in-oil2)-in-water emulsion solvent evaporation method using bovine serum albumin (BSA) as a model protein. The internal and external morphologies of the microcapsules were examined using a light microscope, scanning electron microscope and a laser scanning confocal microscope. A Coulter counter was used to determine particle size and particle size distribution. Protein quantitation and molecular integrity were performed by the bicinchoninic acid protein assay micro-method and SDS-PAGE, respectively. Microcapsules with a polymeric wall surrounding an oily core containing the protein were formed. The encapsulation efficiency (39-96%) for PLG and (13-90%) for PCL increased with polymer molecular weight and particle volume mean diameter (Vmd). Vmd ranged from 87-128 to 42-157 microm for PLG and PCL, respectively. The protein release profile for PLG microcapsules was either continuous or irregularly pulsatile depending on particle morphology and was completed after cavity breakdown. However, that of PCL microcapsules was essentially irregularly pulsatile and was completed after a longer period of time without cavity breakdown but with significant swelling. There was no detectable cleavage of the protein during 6 months storage of PLG and PCL microcapsules at 4 degrees C. Furthermore, insignificant degradation of protein occurred during in vitro release from PCL microcapsules. In contrast, significant degradation occurred in PLG microcapsules. This approach to microencapsulation of a protein may be promising for the controlled delivery of protein vaccines, and the oil core may enhance the immunogenicity of some weak subunit vaccine candidates.

Protein-loaded poly(epsilon-caprolactone) microparticles. I. Optimization of the preparation by (water-in-oil)-in water emulsion solvent evaporation.

The aim of this work was to optimize protein entrapment in pure poly(epsilon-caprolactone) (PCL) microparticles (MP) using the (water-in-oil)-in water solvent evaporation technique and bovine serum albumin (BSA) as drug model. Therefore, the preparative variables such as polymer solvent, protein/polymer ratio, polymer molecular weight, internal aqueous/organic phases ratio, organic/external aqueous phase ratio, and nature of the emulsifier were evaluated on microparticle characteristics such as BSA entrapment, entrapment efficiency, size and morphology. The in vitro release profiles of BSA from such MP in two different media with or without sodium dodecyl sulphate (SDS) were investigated. In optimum conditions, smooth and spherical pure PCL MP with high encapsulation efficiency (50.29 +/- 5.01%) were prepared. The release profiles of BSA in the release media were significantly different and faster in the presence of SDS. Moreover, they exhibited a relatively low burst effect after 24h (<30%) followed by a continuous release over 28 days. Due to PCL's numerous desirable characteristics, such MP could be an exciting alternative for the controlled release of proteinaceous compounds.

Protein-loaded poly(epsilon-caprolactone) microparticles. II. Muramyl dipeptide for oral controlled release of adjuvant.

This work investigated the means for the efficient encapsulation of muramyl dipeptide (MDP) in poly(epsilon-caprolactone) (PCL) microparticles (MP) by a solvent evaporation method in order to optimize the effect of the adjuvant for oral immunization. Therefore, the influence of MDP concentration in the inner aqueous phase was evaluated on MP characteristics such as size, morphology, drug entrapment, entrapment efficiency and the eventual interactions of MDP with co-entrapped model antigen, bovine serum albumin (BSA). The process of manufacturing produced a high entrapment efficiency of MDP (63.58 +/- 0.40%) without altering its integrity, as shown by chromatogram peaks analysis of a and beta anomers. The crystallinity of the polymer was dramatically increased (+24.6%) either with or without MDP loading but the entrapment of BSA reduced this crystallinity suggesting BSA-PCL interaction. These MP were resistant to simulated gastric fluid and exhibited a continuous BSA release. Moreover, their average diameter (<10 microm) combined with their high hydrophobicity make of this delivery system an exciting alternative for enhanced oral immunization.

In vivo evaluation of sixteen plant extracts on mice inoculated with Trypanosoma brucei gambiense.

After examination of the drugs used by traditional practitioners in Côte d'lvoire, nine formulas prescribed in the treatment of African human trypanosomiasis (AHT) were selected for investigation. These formulas made use of 40 plants, 16 of which were studied because of their properties, as described in the literature, and their frequent use by practitioners. The plant extracts were administered, after maceration or decoction, either orally or intraperitoneally to Swiss mice that had previously been inoculated with Trypanosoma brucei gambiense (Tbg), strain MHOM/Cl/81/Dal 083. The parasitaemia in each mouse was followed for three consecutive days and compared with that in control mice, which had been given either a saline solution (SS: negative control) or well-known drugs (melarsoprol, difluoromethylornithine, and pentamidine: positive control). Our investigations led to the following conclusions. (a) None of the plant extracts revealed trypanocidal or trypanostatic activity relative to SS controls (P > 0.05). In fact, the mice that received the extracts died on the third day after inoculation, with 0% survival and an average parasitaemia of 10.8 +/- 2 x 10(7) trypanosomes/ml. (b) The treated positive controls, relative to SS, showed 100% survival and no parasitaemia (P < 0.05). Melarsoprol appeared to be active when given orally at a dose of 3.6 mg/kg body weight twice a day for 3 days. This method of testing the sensitivity of trypanosomes to plant extracts is easy and inexpensive, and could be applied to other areas of research on tropical diseases.