Pharmaceutical microparticle engineering with electrospraying: the role of mixed solvent systems in particle formation and characteristics.

Microparticles of Celecoxib, dispersed in a matrix of poly(lactic-co-glycolic acid) (PLGA), were prepared by electrospraying using different solvent mixtures to investigate the influence upon particle formation and the resulting particle characteristics. Mixtures consisting of a good solvent, acetone, and an anti-solvent, methanol, for PLGA were studied in different ratios. Properties of the spraying solutions were examined and the resulting microparticles were characterized with regard to size, morphology, porosity, solid state form, surface chemistry and drug release. Particle formation was strongly influenced by the polymer molecular conformation during droplet formation and by the anti-solvent concentration during droplet drying. A strong correlation was found between particle morphology and the solubility of the polymer in the solvent mixtures. The lack of chain entanglements in droplets containing anti-solvent resulted in compact polymer conformation and grain-like particle morphology. Further, the early precipitation of polymer and low chain interaction with increasing content of anti-solvent resulted in surface enrichment of drug (from 10 and 20% up to 41 and 57% respectively), also demonstrated by the increasingly higher drug release rates. The results demonstrate the importance of solvent composition in particle preparation and indicate potential for exploiting this dependence to improve pharmaceutical particle design and performance.

Release profile and characteristics of electrosprayed particles for oral delivery of a practically insoluble drug.

Poly(lactic-co-glycolic acid) (PLGA) microspheres containing celecoxib were prepared via electrospraying, and the influence of three processing parameters namely flow rate, solute concentration and drug loading, on the physico-chemical properties of the particles and the drug-release profile was studied. Microspheres with diameters between 2 and 8 µm were produced and a near-monodisperse size distribution was achieved (polydispersivity indices of 6-12%). Further, the inner structure of the particles showed that the internal porosity of the particles increased with increasing solvent concentration. X-ray powder diffraction (XRPD) analysis indicated that the drug was amorphous and remained stable after eight months of storage. Drug release was studied in USP 2 (United States Pharmacopeia Dissolution Apparatus 2) dissolution chambers, and differences in release profiles were observed depending on the parametric values. Changes in release rate were found to be directly related to the influence of the studied parameters on particle size and porosity. The results indicate that electrospraying is an attractive technique for producing drug-loaded microspheres that can be tailored towards an intended drug-delivery application. Compared with the more conventional spray-drying process, it provides better control of particle characteristics and less aggregation during particle formation. In particular, this study demonstrated its suitability for preparing capsules in which the drug is molecularly dispersed and released in a sustained manner to facilitate improved bioavailability.

Preparation of microspheres containing low solubility drug compound by electrohydrodynamic spraying.

Micro- and nanoparticle formulations are widely used to improve the bioavailability of low solubility drugs. In this study, electrospraying is introduced as a method for producing drug-loaded microspheres at ambient conditions. PLGA microspheres containing celecoxib, a low solubility drug, were prepared with the objective of producing near-monodisperse microspheres with the drug in a stable amorphous form. We found that it is possible to produce near-monodisperse celecoxib-loaded PLGA microspheres at different polymer:drug ratios. The microspheres produced were in the size range 1-5 µm depending on the polymer:drug ratio and had smooth surfaces. Thermal analysis further indicates that celecoxib is present in an amorphous form inside the microspheres. Drug dissolution studies showed an initial burst release followed by a period of sustained release with the dissolution curve depending on the polymer:drug ratio. Electrospraying is thus a promising method for producing amorphous microspheres of low solubility drugs such as celecoxib. The microsphere properties may be further optimized to achieve an appropriate dissolution profile with the aim of increasing oral bioavailability of low solubility drugs.

Quantitative risk modelling for new pharmaceutical compounds.

The process of discovering and developing new drugs is long, costly and risk-laden. Faced with a wealth of newly discovered compounds, industrial scientists need to target resources carefully to discern the key attributes of a drug candidate and to make informed decisions. Here, we describe a quantitative approach to modelling the risk associated with drug development as a tool for scenario analysis concerning the probability of success of a compound as a potential pharmaceutical agent. We bring together the three strands of manufacture, clinical effectiveness and financial returns. This approach involves the application of a Bayesian Network. A simulation model is demonstrated with an implementation in MS Excel using the modelling engine Crystal Ball.