Layer-by-layer self-assembly of polymeric multi-layers on solid lipid nanoparticles: A comparative study via dynamic light scattering, transmission electron microscope, atomic force microscope and quartz crystal microbalance with dissipation

SLN or solid lipid nanoparticles were suggested as advantageous alternatives to liposomes and other colloidal carriers for hydrophobic drug delivery, yet with limited loading capabilities and diminished tunable release profiles, especially for hydrophilic proteins and peptides. Thus, we proposed formulating core-shell nanocapsules: coating SLN cores with alternate layers of natural polyelectrolytes via the layer-by-layer self-assembly approach based on electrostatic interactions. In the present work, tricaprin-based SLN were simply produced, a bi-layered shell constructed and step-wise characterization carried out by DLS, TEM and AFM. To further gain an understanding, we employed quartz crystal microbalance with dissipation (QCM-D) to monitor and compare, the build-up, in real time. Findings reveal that alginate-chitosan ([AL-CH]) and hyaluronan-chitosan ([HA-CH]) layers were successfully deposited on SLN. QCM-D provided further evidence that polyelectrolyte shells range ̃40-60 nm in thickness with differences attributed to dissimilar growth regimens in both systems. A viscous yet compact and rigid structure was formed in the AL-based system while a floppy and spongy multi-layer was formed with HA. To the best of our knowledge, this is the first report depicting the formation and characterization of polyelectrolyte multi-layers on SLN and analyzing structural properties of core-shell colloids on a gold surface by QCM-D tool.