NANOSTRUCTURES AS DRUG DELIVERY VEHICLE FOR BRAIN AND AS A SCAFFOLD FOR TISSUE ENGINEERING

The brain, administrator of the whole body is a delicate and soft organ of the body that
controls and regulates most of our abilities to think, see, feel, hear, and much more. The
administrator has very tight security unlike other organs called the blood-brain barrier
(BBB) which allows only limited things to enter the brain. The protection (BBB) is full
of a series of defences that helps to protect the brain from most of the internal and
external threats. The presence of these protections, most importantly BBB, also offers
difficulties to treat any disease condition in the brain. But, the advancement in
neuroscience and drug delivery research has accorded many possible ways to bypass,
open, or cross this barrier to treat brain diseases effectively including cancer.
BBB is provided with a layer of endothelial cells which also cover the outer layer of all
other organs and blood vessels in the body. Generally, this endothelial cell layer has
gaps to allow passage of different important materials including nutrients and
medicines through the layer. But, in the case of brain, these gaps are covered and
blocked with proteins that restrict and controls the passage of materials through the
layer. For example, necessary items like glucose, insulin and oxygen are allowed while
toxins, bacteria and most of medicines are not allowed.
Brain cancer is a rapidly expanding disease affecting a large population and is the 10th
dominant cause of mortality. The survival rate for brain cancer
patients after starting the treatment with radiation and chemotherapy is less than a year. Treatment of brain cancer with chemotherapeutics is very limited due to the presence of BBB and therefore their restricted entry to the brain. Strategies
acquired to deliver chemotherapeutic drugs to brain include both invasive and noninvasive
techniques. Invasive technique includes chemical or osmotic opening of BBB while
non-invasive technique includes enhanced transcellular transport by modifying the drug
to increase their lipid solubility, inhibition of efflux transporters, use of chimeric
peptides, trojan horse approach, intranasal delivery and use of transport or carrier
systems.The non-invasive carrier system-based strategy utilises delivery of drugs to brain
tumors using nano-sized particle systems and this strategy found to have significant
potential in improved therapy of brain disorders. Nanoparticle delivery systems can
camouflage their cargoes to the brain and can provide sustained release of therapeutic
molecules inside the brain resulting in a longer half-life, protection against
environmental conditions, and reduced toxicities. Studies comprising direct as well as
intravenous administration of nanoparticles loaded with therapeutic agents into the
brain have shown promise in the treatment of brain cancers. But, complex synthesis procedures, low biocompatibility and
biodegradability, and toxicity problems of nanoparticle delivery systems have raised
concerns for their clinical development.