Nanoparticles of a polyelectrolyte-fatty acid complex: carriers for Q(10) and triiodothyronine

Poly(ethylene imine) (PEI) was used for the complexation of dodecanoic acid (C12) resulting in a poly(ethylene imine) dodecanoate complex (PEI-C12) wi th a lamellar nanostructure and a repeat unit of 2.9 nm. PEI-C12 was doped with coenzyme Q(10) and the hormone triiodothyronine as typical hydrophobic and pharmacological active compounds, respectively. The PEI-C12 acts as a guest matrix that dissolves both molecules up to weight uptakes of about 20 % (w/w) and 15% (w/w), respectively, both without crystallization. Agglomer ate-free dispersions of core-shell type nanoparticles were developed. Ratio s of PEI to C12 of 2:1 or higher were found to be suitable for this purpose . The particles exhibit hydrodynamic diameters in the range of 80-150 nm, w hich depend on the preparation conditions. Each particle consists of a rela tively compact core surrounded by a diffuse corona. PEI-C12 forms the core, while non-complexed PEI acts as a cationic-active dispersing agent. It was found that the nanoparticles show high xi potentials (approximate to +40 m V) and are stable in NaCl solutions at concentrations of up to 0.3 mol l(-1 ). The stabilization of the nanoparticles results from a combination of ion ic and steric contributions. A variation of the pH value was used to activa te the dissolution of the particles. The PEI-C12 nanoparticles may have pot ential as carriers for hydrophobic drugs. (C) 2001 Published by Elsevier Sc ience BM