ACRYLIC-ACID COPOLYMER NANOPARTICLES FOR DRUG DELIVERY .1. CHARACTERIZATION OF THE SURFACE-PROPERTIES RELEVANT FOR INVIVO ORGAN DISTRIBUTION

Copolymer nanoparticles of acrylic acid, acrylamide, acrylic acid butyl ester and methacrylic acid methyl ester with increasing acrylic acid content were produced by emulsion polymerization. The particles were characterized in terms of parameters relevant for in vivo organ distribution: particle size and distribution, particle charge (zeta-potential) and surface hydrophobicity. The increase in the acrylic acid content could not be correlated with the resulting particle sizes and produced no detectable effect on the zeta-potential. However, the degree of hydrophobicity of the particle surface could be distinctly reduced. The particles were polydisperse with regard to the degree of surface hydrophobicity. Subpopulations differing in the degree of hydrophobicity were detected by hydrophobic interaction chromatography (HIC). However, the reduction in surface hydrophobicity was not regarded as sufficiently large to prevent uptake by the reticuloendothelial system after intravenous injection.