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.