Evaluation of Nanomaterials as Effective Carriers Targeted to Traverse Blood–Brain Barrier for Theragnostics of Neurodegenerative Diseases: An Overview

The human brain is a vital organ that governs and performs various meticulous tasks. So, it is even more important to safeguard these brain cells from attacks arising from internal and external sources. The body has an inbuilt defense mechanism where a barrier has been created that acts as a shield for the blood flowing to brain cells and thereby provides safety against the intrusion of detrimental substances. Despite this blood–brain barrier, the in-built defense mechanism gets breached and leads to neurodegenerative disorders like Alzheimer’s disease that are lethal to the brain cells. The treatments for these disorders are very limited as the barrier blocks the drug molecules from entering the brain. Another important aspect is that the treatment techniques are mostly invasive that can damage the blood–brain barrier, causing cognitive deficits. Emphasis has been given to the use of non-invasive techniques such as convection-enhanced diffusion and focused ultrasound, but still, the damage to tissues cannot be completely ruled out. Thus, there is a need to address this issue. Nano-carriers provide an option as these are designed in such a manner that they can mimic the delivery of minerals required for the brain to traverse the drug molecule through the blood–brain barrier. As a result, a high concentration of drugs in the target tissue can be released efficiently by carrier systems. This review paper provides an overview of various materials that serve as nano-carriers and penetrate the membrane to facilitate the release of drugs. Graphical Abstract