The application of electrostatic dry powder deposition technology to coat drug-eluting stents

Purpose: A novel methodology has been introduced to effectively coat intravascular stents with sirolimus-loaded polymeric microparticles. Methods: Dry powders of the microparticulate formulation, consisting of non-erodible polymers, were produced by a supercritical, aerosol, solvent extraction system (ASES). A design of experiment (DOE) approach was conducted on the independent variables, such as organic/CO2 phase volume ratio, polymer weight and stirring-rate, while regression analysis was utilized to interpret the influence of all operational parameters on the dependent variable of particle size. The dry powders, so formed, entered an electric field created by corona charging and were sprayed on the earthed metal stent. Furthermore, the thermal stability of sirolimus was investigated to define the optimum conditions for fusion to the metal surfaces. Results: The electrostatic dry powder deposition technology (EDPDT) was used on the metal strut followed by fusion to produce uniform, reproducible and accurate coatings. The coated stents exhibited sustained release profiles over 25 days, similar to commercial products. EDPDT-coated stents displayed significant reduced platelet adhesion. Conclusions: EDPDT appeared to be a robust accurate and reproducible technology to coat eluting stents.

The effect of ownership structure, country governance, and financial development on the capital structure of unlisted eastern European firms

This paper investigates the determinants of capital structure for a sample of 20,713 unlisted firms from 11 eastern European countries over the period 1994-2004. We employ usual firm-specific financial variables as well as country-specific variables that describe the degrees of governance structure and financial development of each country. Using regression analysis, our results indicate that firm ownership concentration and country governance structure are insignificant explanatory variables to the degree of leverage of the firms in our sample. On the other hand, indicators of country financial development are robust determinants of capital structure. However, the marginal explanatory power of country-specific variables is small. We conclude that firm-specific characteristics are decisive in capital structure.