Hierarchically built hyaluronan nano-platelets have symmetrical hexagonal shape, flattened surfaces and controlled size.

Most of nanomaterials composed of hyaluronic acid (HA) used for drug targeting are spherical. In this investigation, we suggest that the morphology of HA nanomaterials could be considered as a new parameter to control their interactions with cells. However, designing nanomaterials with elongated morphology and controlled size is still challenging. The aim of this study was to design and to characterize non-spherical HA nanomaterials with flat surfaces and to highlight main parameters controlling the size. Nanoparticles were formed by mixing HA hydrophobically-modified with palmitoyl groups (PA-HA) and α-cyclodextrin in water. These particles, called nano-platelets, had symmetrical hexagonal shape, flattened surfaces and were 9-fold larger than thick. Small nano-platelets with well-defined shape were obtained with low PA-HA degree of substitution, by adding 5 wt% of α-cyclodextrin solution for a fixed concentration of PA-HA (1 wt%) (569 nm) and for long stirring periods (735-538 nm for 72-168 h). PA-HA was successfully conjugated to a near-infrared fluorescent probe suitable for in vitro and in vivo experiments without nano-platelet size and surface charge modification. This is the first report showing the design of non-spherical and flattened HA nano-platelets that could be used to study the impact of nanomaterial shape on molecular interactions with cells.