Actually "Gold" happens to be a boring metal in chemistry point of view. But when we zoom into it's nano size scale, it will be far more interesting. This nano particle is similar to the size of the virus. The surface can be modified when it comes in this size. By the help of sulfur atoms, making a covalent bond of certain types of drugs with the gold nanoparticle helps in curing of certain neurological conditions.
Till now, it has been very challenging for the drug developers and engineers for making a drug that can traverse the Blood-brain barrier. When talking about this gold-nano particle, it offers a non-invasive and a very rapid way of delivering the drug to the brain via. aerosol nasal spray route.
So, What is this "BBB" ?
Fig: Blood Brain Barrier (credit)
BBB means is "Blood Brain Barrier". Maximum, it surrounds the blood vessels present in the brain. It acts as a barrier or a compact door between the flowing blood stream and extracellular space of the brain. It only allows certain substances like oxygen, water and small lipid-soluble substances to pass through it.On the other hand, it prevents certain toxins and pathogens from entering the brain which happens to be a kind of barrier for the dangerous substances from blood to brain.
Talking about the composition, arranged in a tight junction are the endothelial cells which is the interior surface of the blood capillaries. The space between the endothelial cells make some blood-born substances through it which can sometimes cause inflammation in the surrounding tissues. However, they are tightly fused making a tight junction and restricting the diffusion across the blood capillaries. Astrocytes on the other side is attached with the endothelial cells by the help of astrocytic end-feet. This play a critical role in formation as well as maintenance and regulation of the blood brain barrier.
Some part of the brain such as circumvemtricular organs lying in the ventricles of brain lacks blood brain barrier. These organs need some access to the bloodstream for the function to occur. Not only this, the posterior pituitary also lacks BBB as the hormones have to travel through the bloodstream for particular function to occur.
Blood Brain Barrier prevents the toxins in entering to the brain via bloodstream. Not only this, it also prevents various drugs in reaching the brain just like the cancer cell killing drugs.
For the brain to work properly, it should be working in the stable environments even of the body has some fluctuations.
When delivering the drugs to brain via injections, there has been some risk in causing damage to the tissue. Not only this, distribution of the drugs from certain point of injection is also poor compared to the other site of injection. This potential of using the nano-particles as a medium in delivering drug has been effective with less risk conditions. This nano-particles are delivered through the nose with the help of olfactory medium.
Nose to Brain Drug Delivery :
As you all know, nose has some cranial nerve I fibres, called as "Olfactory Nerve". The Nose to brain approach provides a greater pathway in delivering the drugs via this Olfactory nerve, trigeminal nerves.
The more interesting part is that, it by-passes the BLOOD BRAIN BARRIER.
Fig: Drug delivery by Nose to Brain (credit)
Considered as the excellent alternative approach, non-invasive, practical and very safe to use. This treatment can be considered in treating certain neurological condition as well as minimizing the side effects. It acts as the shortest and most easiest route to the brain. The olfactory nerve route directly delivers drug to the brain tissue whereas, the trigeminal pathway deliver to the cerebro-spinal fluid.
Gold nano-particles acts as a material for the drug delivery. They are easily synthesized and customized and also the bioavailabitlity of these is long-lasting. The nose has the olfactory mucosa which on medications absorbed through the mucosa and enter directly to the Cerebro-spinal fluid. This is the nose brain pathway which can offer a rapid and direct delivery of the drug to the brain.
Nowdays, varieties of lipid based, polymeric and carbon are used for targeting certain organs as a purpose for the delivery of drug. This gold nano-particles has emerged in this study cases. This particles are much flexible, inert in nature containing large surface area. Even of it's small size, it has a very good bio-compatibility. Even of <10nm size of this particle can cross the blood brain barrier.
The test was performed in the invertebrate locust; Schistocerca americana which has similar kind of Blood-brain barrier compared with the humans. When the drug is projected to it's antenna, it acts similar like humans, reaching the Brain bypassing blood-brain barrier. This insect has a vary well developed olfactory system which helps to give the best result output.
So, what did we see on Lucust's brain when the gold nano-particles were projected to the Locust's antenna ?
Fig: A] Shows the pathway of the Olfactory system B] Section of Lucust's antenna and brain after Gold-nano particle aerosol delivery (fluroscence staining) C] Electrone Microscopy confirms depositions of gold nano-particles in the brain (credit)
As long as the drug is exposed, the more deposition of the particles occurs in the brain. Using the fluroscent markers tag with the gold nano-particles helped in the tracking of the drug. The drug passed through the antenna, crossed the Blood brain barrier and suffused the brain tissue.
Neurological functions as well as any physical functions were not harmed or affected. Even the electrophysical response of the olfactory neurons were normal as usual before and after the experiments.
Conclusively, the Blood brain barrier acts as a barrier for certain harmful substances. When any treatment is performed, there should be invasive treatment but now, the gold-nano particles has helped by the non-invasive technique and there will be less risk and quick response time of the drug.
Reference :
Daniel, M.-C. & Astruc, D. Gold nanoparticles: assembly, supramolecular chemistry, quantum-size-related properties, and applications toward biology, catalysis, and nanotechnology.
Banks, W. A. From blood-brain barrier to blood-brain interface: new opportunities for CNS drug delivery.
Medical News; Nanoparticles delivery
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