Formation of a lanthanoid complex shell on a nanoparticulate wax core

Carboxylate-rich lanthanide complexes were employed as anion counterions to the cationic surfactant cethyltrimethylammonium (CTA) and assembled to form a shell around emulsifying wax nanoparticles. The anionic complexes consisted of lanthanide ions coordinated by the ligand DOTA-tetrahomoserine (DhS). In combination with CTA the complexes formed a surfactant system (CTA)[LnDhS] (Ln = Eu, Gd) with the nonpolar tail of CTA embedded in an emulsifying wax (EW) nanoparticle core. The DhS units were then crosslinked with divinylsulfone to form a shell around the EW core. Fluorescence and NMR data on the Eu complex were consistent with the formation of a stable polymeric shell around the wax core template. These results illustrate a general method that exploits electrostatic interactions to assemble capsules around solid lipid nanoparticles. Preliminary relaxivity measurements were carried out on particles with Gd-containing shells.