Nanotechnology has brought new possibilities in the development of various delivery systems such as systemic CNS delivery. Nanotechnology has been applied in the production ofmaterials, devices, and electronic biosensors with sizes ranging from low to high nanometers. Nanotechnology-based products are being extensively used in clinics, drug delivery, and diagnosis [50]. Nanocarriers are designed for specific targeting of therapeutic agents to specific tissues and organs while also minimizing exposure of healthy tissues to toxic insults. Poorly distributed drugs can be easily loaded into a nanocarrier, and can thus deliver therapeutic concentrations into the brain. Nanoparticles being small in size pass through BBB capillaries and diffuse into the target tissues, releasing the loaded drug directly at the site of action [51].

Despite the advances and breakthroughs, nanotechnology-based strategies and approaches are not very effective in treating CNS disorders including GBM, HIV, and Alzheimer disease. Keeping in mind the dearth of currently available therapies for such debilitating disorders, targeting of drugs to the CNS will be the mainstay for the future development of nanotechnology-based therapeutics. Functionalization of nanocarriers will perhaps be the foremost step toward nanoscale CNS drug delivery systems.

Nanocarriers are colloidal systems in which the drug is either entrapped within the colloidal matrix of the nanoparticle or coated on the particle surface via conjugation or adsorption. Various nanocarriers have been developed and examined for delivery and diagnostic purposes such as polymeric, lipid-based, magnetic, and dendritic nanocarriers [52]. Other types of nanocarriers include micelles, nanogels, nanoemulsions, nanosuspensions, and ceramic as well as metal-based nanocarriers [53,54].

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