Nanotechnology and Central Nervous System Drug Delivery

In line with the overall increase in knowledge and nanotechnologies, surface engineering of nano-sized carriers is now representing the cutting edge of nanomedicine, leading to the production of selectively targeted therapies based on targeted nanocarriers. In fact, achieving nanocarriers able to be stable in the blood-stream, to protect the drug from metabolism and to promote a long-lasting release of the drug is still a pivotal pre-requisite for nanomedicine, but it is now to be considered as “not enough”. Active targeting to specific pathological cells is now the challenge of pharmaceutical nanotechnologists, who are facing with difficulties in colloidal chemistry and most of all in the characterization of the engineered nanocarriers from a technological and physiological points of view. As an example, the application of nanotechnology to brain-related disorders, called nanoneuromedicine, is surely representing one of the most stimulating challenge as well as one the most difficult due to the presence of biological barriers (BBB) and the great variability in BBB permeability depending on the chosen disease. Encouraging results have been obtained demonstrating the possibility of targeting the CNS up to an important percentage of brain localization. In this contest, polymeric nanoparticles (NPs) and liposomes (LPs) were formulated and specifically engineered to cross the BBB and arrive to CNS and proposed to encapsulate some drugs able to rescue from neurodegeneration, to the CNS. Our attention point on the use of polymeric nanoparticles engineered on surface by a selective ligand able to promote the NPs crossing of BBB. In fact, preliminary studies demonstrated the ability of new targeted polymeric poly-lactide-co-glycolide (PLGA) NPs modified with a short peptide (H2N-Gly-L-Phe-D-Thr-Gly-L-Phe-L-Leu-L-Ser(O-β-D-Glucose)-CONH2 (g7-NPs) to create BBB interaction and trigger an efficacious BBB crossing delivering of active. In particular, several in vivo biodistribution studies and pharmacological proof-of-evidence of brain delivery of model drugs (not able by themselves to reach the brain) demonstrated the ability of g7-NPs to create BBB interaction and trigger an efficacious BBB crossing. A total biodistibution of g7-NPs, obtained after i.v. administration in rats, evidenced a strong and significant localization of the g7-NPs into CNS in a quantity about two orders of magnitude greater (10-15%) than that found with the other known NP drug carriers. More recently, the g7-NP BBB crossing mechanism was investigated, pointing out an interaction between g7-NPs and BBB and endocytosis/macropinocytosis pathways for BBB crossing. Same results were pointed out also in vitro on neurons/glia cell coltures, evidencing the endocytotic pathways as g7-NPs cell entrance as well as the assessing of the safety of g7-NPs not creating any damage to cells even at high doses. Notwithstanding these outputs, it is our opinion that in order to obtain a real update of neurological disorders’ therapy based on innovative and non invasive protocols (i.e. nanomedicine), a team work is strongly needed. The interdisciplinar competences and skills of all the experts in Neuro-diseases and Nano-Technology (from neurobiologists to neurophysiologist, from nanotechnologists to physicians) must be shared, discussed, considered and applied, thus opening the pave to new vistas in treatments and most of all for the correct development of the research.