In vitro evaluation of thiomer microparticles for nasal drug delivery

The purpose of the present study was to compare two preparation methods concerning the development of a thiomer (polycarbophil-cysteine; PCP-Cys)-based microparticulate delivery system for nasal drug administration. Microparticles were prepared either by emulsification solvent evaporation technique or via mechanical micronization. Resulting microparticles were characterized and compared concerning their inherent properties and the permeation enhancing effect of PCP-Cys in combination with the permeation mediator glutathione (GSH) was investigated on freshly excised bovine nasal mucosa. Additionally, the effect of PCP-Cys on the ciliary beat frequency (CBF) of human nasal epithelial cells was evaluated in vitro. Results demonstrated that microparticles of both preparation types were mainly of spherical structure displaying particle diameter up to 100 μm. Particles prepared by mechanical micronization showed a comparatively higher drug load compared to those produced via the emulsification solvent evaporation technique. In addition, controlled drug release of the incorporated model compounds sodium fluorescein (NaFlu) and FITC-dextran (FD 4) was achieved from these particles. The mucosal transport of NaFlu and FD 4 was increased 1.70-fold and 2.64-fold, respectively, in the presence of the PCP-Cys/GSH system. Furthermore, no ciliotoxic effect could be observed for thiolated polycarbophil. Due to these results polycarbophil- cysteine-based microparticles prepared either way seem to be a safe and promising tool in the field of nasal drug delivery