Nanostructured polyelectrolyte multilayer drug delivery systems for bone metastasis prevention.

Polyelectrolyte multilayers (PEM) are well established nanoarchitectures with numerous potential applications, in particular as biomaterial coatings. They may exhibit specific biological properties in terms of controlled cell activation or local drug delivery. Here, in a new approach for bone metastasis prevention, we employed poly-l-lysine covalently grafted with beta-cyclodextrin as a polycationic vector (PLL-CD) for the antitumor bisphosphonate drug risedronate (RIS). Molar ratio for maximum loading of the PLL-CD vector with RIS was determined by Raman microspectroscopy. The efficacy of RIS at inhibiting cancer cell invasion in vitro was strongly enhanced upon complexation, whatever PLL-CD:RIS complexes were in solution or embedded into PEM nanoarchitectures. Complexes in solution also clearly prevented cancer-induced bone metastasis in animals. Incorporation of the complexes into PEM nanoarchitectures covering bone implants appears of interest for in situ prevention of bone metastasis after ablation.