Investigation on Mechanisms of Glycopeptide Nanoparticles for Drug Delivery across the Blood-Brain Barrier

AimsNano-neuroscience, based on the use polymeric nanoparticles (NPs), is representing an emerging field of research for achieving an effective therapy for neurodegenerative diseases. In particular, poly-lactide-co-glycolide (PLGA) glyco-heptapetide-conjugated NPs (g7-NPs) were shown to be able to cross the Blood-Brain Barrier (BBB). However, the in vivo mechanisms of the BBB crossing of this kind of NPs has not been investigated until now. This paper aimed to develop a deep investigation on the mechanism of BBB crossing of the modified NPs.Materials and MethodsLoperamide (LOP) and Rhodamine-123 (Rh-123) (model drugs unable to cross the BBB) were loaded into NPs, composed of a mixture of poly-lactide-co-glycolide (PLGA), differently modified with g7 or with a random sequence of the same aminoamids (random-g7). To study brain targeting of these model drugs, loaded NPs were administered via tail vein in rats in order to perform both pharmacological studies and biodistribution analysis along with fluorescent, confocal and electron microscopy analysis, in order to achieve NPs BBB crossing mechanism. Computational analysis on the conformation of the g7- and random-g7-NPs of the NPs surface was also developed. Results Only LOP delivered to the brain with g7-NPs created a high central analgesia, corresponding to the 14% of the injected dose, data confirmed by biodistribution studies. Electron photomicrographs showed the ability of g7-NPs in crossing the BBB as evidenced by several endocytotic vesicles and macropinocytotic processes. The computational analysis on g7 and random-g7 showed a different conformation (linear versus globular), thus suggesting a different interaction with the BBB. ConclusionTaken together, these evidences suggested that g7-NPs BBB crossing is owing to a multiple-pathway, mainly membrane-membrane interaction and macropinocytosis-like mechanisms. The results of the computational analysis showed the Biousian structure of the g7 peptide, on the contrary of random-g7 peptide (globular conformation), suggesting that this difference is pivotal in explaining the BBB crossing and to allow to hypothesize the mechanism of BBB crossing by g7-NPs.