Nanomedicine: Drugs can be made 'smarter'


Packaging small-molecule drugs into nanoparticles improves their bio-availability, bio-compatibility and safety profiles. Multifunctional particles carrying large drug payloads for targeted transport, immune evasion and favourable drug release kinetics at the target site, require a certain minimum size usually 30-300 nm diameter, so are nanoparticles. Targeting particles to a disease site can signal the presence of the disease site, block a function there, or deliver a drug to it. Targeted nanocarriers must navigate through blood-tissue barriers, varying in strength between organs and highest in the brain, to reach target cells. They must enter target cells to contact cytoplasmic targets; specific endocytotic and transcytotic transport mechanisms can be used as Trojan horses to ferry nanoparticles across cellular barriers. Specific ligands to cell surface receptors, antibodies and antibody fragments, and aptamers can all access such transport mechanisms to ferry nanoparticles to their targets. Gold nanoparticles are spheres made of gold atoms having a diameter of only few billionths of a metre which can be coated with a biological protein and combined with drugs to enable the treatment to travel through the body and reach the affected area. The nanoparticles can 'adsorb' (hold on its surface) drugs which would otherwise become insoluble or quickly degrade in the blood stream, and due to their small size they can overcome biological barriers such as membranes, skin and the small intestine which would usually prevent the drug from reaching its target. The technology is already used in real world applications such as pregnancy tests - where gold nanoparticles decorated with an antibody against the hormone present in the urine of pregnant women is added to the 'positive' strip so it reacts with the nanoparticles to turn the stick red - but is not yet widely used in drug development. Gold nanoparticles are a vital tool in new drug development and drug delivery systems. This method might help to design nanomedicines that do not need extensive chemical modification of a protein drug or a nano-carrier and therefore can be developed more easily and faster.



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