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

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