Dissolution Characteristics of Benzoic Acid and Salicylic Acid Mixtures in Reactive Media

The dissolution rates of mixtures of the two acids, benzoic acid and salicylic acid were determined in a phosphate buffered medium. Dissolution properties from compressed discs under sink conditions were essentially linear. Plots of dissolution rate versus compact composition deviated from the two component models for both non-interacting and interacting components. Dissolution rates, particularly for benzoic acid at intermediate weight fractions, were lower than predicted by the theory for two non-interacting components. These lower than expected rates were explained in terms of the physicochemical changes occurring in the microenvironment at the solid liquid interface.     

Characterisation of Biodegradable Microspheres Containing Dehydro-Iso-Androsterone

Poly-DL-lactide (PLA) and poly-DL-lactide-co-glycolide (DL-PGA) micromatrices (PharmazomesTM) containing dehydro-isoandrosterone (DHEA), a weak androgen, were prepared by a solvent evaporation process. Micromatrices with increasing drug loading as well as increasing polymer molecular weight were prepared. The morphology of these systems depended on the drug loading, the polymer molecular weight and polymer composition. Increasing the drug loading or polymer molecular weight resulted in increasingly irregular microparticles being formed. DSC thermograms did not reveal the presence of crystalline DHEA in micromatrices containing 10 to 50% DHEA loading. However crystalline DHEA was observed in microspheres heated to above the glass transition temperature of the polymer. Xray analysis of 30% DHEA micromatrices established the presence of crystalline DHEA in the micromatrices. The percent release of DHEA from the micromatrices, into 40% ethanol at 37°C, increased with increasing DHEA loading. The dissolution of DHEA from drug-polymer compressed discs of constant surface area was proportional to the square root of time indicating matrix controlled release.     

Influence of Parathyroid Hormone-Loaded PLGA Nanoparticles in Porous Scaffolds for Bone Regeneration

Biodegradable poly(lactide-co-glycolide) (PLGA) nanoparticles, containing human parathyroid hormone (PTH (1–34)), prepared by a modified double emulsion-solvent diffusion-evaporation method, were incorporated in porous freeze-dried chitosan-gelatin (CH-G) scaffolds. The PTH-loaded nanoparticles (NPTH) were characterised in terms of morphology, size, protein loading, release kinetics and in vitro assessment of biological activity of released PTH and cytocompatibility studies against clonal human osteoblast (hFOB) cells. Structural integrity of incorporated and released PTH from nanoparticles was found to be intact by using Tris-tricine SDS-PAGE. In vitro PTH release kinetics from PLGA nanoparticles were characterised by a burst release followed by a slow release phase for 3–4 weeks. The released PTH was biologically active as evidenced by the stimulated release of cyclic AMP from hFOB cells as well as increased mineralisation studies. Both in vitro and cell studies demonstrated that the PTH bioactivity was maintained during the fabrication of PLGA nanoparticles and upon release. Finally, a content of 33.3% w/w NPTHs was incorporated in CH-G scaffolds, showing an intermittent release during the first 10 days and, followed by a controlled release over 28 days of observation time. The increased expression of Alkaline Phosphatase levels on hFOB cells further confirmed the activity of intermittently released PTH from scaffolds.     

Influence of formulation variables on the morphology of biodegradable microparticles prepared by spray drying

The preparation of microparticles of the biodegradable poly-DL-lactide (PLA) and polylactide-co-glycolide (PLGA) polymers using spray-drying technology was studied. Formulation parameters investigated include polymer type, polymer molecular weight, polymer concentration, and viscosity. Microparticles were characterized using electron microscopy, particle size analysis, and gel permeation chromatography. Kinematic viscosity was determined for each of the sprayed polymer solutions. Polymer molecular weight and polymer concentration were found to be important parameters when preparing PLA and PLGA microparticles using spray-drying technology.