Proofs of the structure of lipid coated nanoparticles (SMBV™) used as drug carriers

Purpose. Supramolecular Biovectors (SMBV(TM)) consist of cross-linked cationic nanoparticles surrounded by a lipid membrane. The purpose was to study the structure of the lipid membrane and to characterise its interaction with the nanoparticles in order to differentiate SMBV(TM) from other polymer/lipid associations. Methods. The interaction of lipids with the nanoparticle surface was studied using zeta potential, Fluorescence Energy Transfer (FET) and Fluorescence Microscopy. SMBV(TM) were compared to liposomes and mixtures nanoparticles/liposomes. Finally the structure of SMBV(TM) was visualised by Electron Microscopy. Results. Zeta potential measurements showed that lipids on SMBV(TM) had a pronounced shielding effect on the surface charge. This was not the case for mixtures of nanoparticles and liposomes. FET experiments confirmed these results indicating that, for SMBV(TM), the lipids are much closer to the nanoparticle surface. SMBV(TM) Fluorescence microscopy on model microparticles showed a lipid crown on SMBV(TM) that was confirmed by electron microscopy on SMBV(TM) nanoparticles. Conclusions. Results show that in case of SMBV(TM) lipids are strongly adsorbed on the polysaccharide core surface probably due to ionic/hydrophobic interactions. The resulting supramolecular structure is a spherical cationic polysaccharide particle surrounded by a phospholipid/cholesterol layer.