Single and Double Emulsion Manufacturing Techniques of an Amphiphilic Drug in PLGA Nanoparticles: Formulations of Mithramycin and Bioactivity

Formulation of hydrophilic compounds in nanoparticles is problematic due to their escape to the external aqueous phase. The certain amphiphilic nature of mithramycin, utilized clinically in cancer, makes its incorporation into nanoparticles an interesting challenge, elucidating the formulation factors of amphiphilics in nanoparticles. We hypothesized that mithramycin nanoparticles could provide more effective therapy of restenosis due to its antiproliferating and potential monocyte inhibition properties. The nanoprecipitation technique (designed for lipophilic compounds) was found preferable, with better encapsulation efficiency, than the emulsification solvent diffusion (ESD) technique (79.3 +/- 3.1% and 40.8 +/- 1.1%, respectively). The double emulsion solvent diffusion (DESD) method, designed for hydrophilic compounds, yielded similar encapsulation efficiency (80%). Nanoparticles size was, 110 +/- 36, 130 +/- 30, and 160 +/- 31 nm, ESD, nanoprecipitation, and DESD techniques, respectively. Mithramycin solution and in nanoparticles significantly inhibited RAW264 macrophages and smooth muscle cells in a dose-dependent relationship, and reduced the number of circulating monocytes in rabbits. However, no inhibition of restenosis was obtained in the rat carotid model following Lv. administration of mithramycin nanoparticles. It can be concluded that PLGA-based polymeric nanoparticles of mithramycin can be formulated by techniques suitable for lipophilic/hydrophilic compounds. The ineffectiveness in the rat restenosis model is probably due to the short depletion period of circulating monocytes and lack of arterial targeting. (C) 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:1452-1462, 2009