Nanoparticles are the colloidal particles having diameter smaller than 100 nm that behaves as a whole unit in terms of its transport and properties. Nanoparticles are about of ten nm to 1,000 nm in size and widely used in different applications such as drug delivery and to pass organ barriers such as blood brain barrier.

Nanoparticles are of different types : Liposomes, Dendrimer, polymeric micelles, nanocapsule, nanosphere and solid lipid nanoparticles. Because of their unique properties nanoparticles like quantum dots, gold colloids, nanobars, nanoshells, dendrimers have been used in therapeutics, bioengineering and drug discovery. Here we will discuss some examples of the nanoparticles :

Liposomes : Liposomes exhibits number of advantages in terms of biocompability, amphiliphic character and ease of surface modification rendering it a suitable candidate delivery system for the biotech drugs. Liposomes have been used successfully in the field of medicine, biology and biochemistry, As these alter pharmacokinetics profile of loaded drugs to a great extent especially in case of proteins and peptides and can be easily modified by surface attachments of polyethylene glycols unites ( PEG ) making it as stealth liposomes and thus increase its circulation half life.

Nanocrystals : Nanocrystals are made up of around hundreds or thousands of molecules that combine in a crystalline form, composed of pure drug with only thin coating comprised of surfactant or combination of surfactants. Poorly soluble drugs and its problems like reduced bioavailability and improper adsorption pattern may be resolved by formulation of nanocrystals. These nanocrystals are favorably serving as delivery systems for drugs like amphoterin B, tacrolimus etc.

Solid Lipid Nanoparticles : These are developed through combination of advantages from different carrier systems like liposomes and polymeric nanoparticles. Solid lipid nanoparticles are made up of solid lipid matrix where the drug is normally incorporated with an average diameter of 1 ┬Ám. these particles are used for the gene transfer.

Polymeric Nanoparticles : Polymeric nanoparticles consists of biodegradable polymer represents a significant improvement over traditional oral and intravenous methods of administration in terms of efficiency and effectiveness. These nanoparticles increase the stability of any volatile pharmaceutical agents and these are easily and cheaply fabricated in large quantities. Polymeric nanoparticles have made ideal candidates for cancer therapy, delivery of vaccines, contraceptives and delivery of targeted antibiotics.

Dendrimers : These are the polymers made up of highly branched macromolecules whose size and shape can be precisely controlled. Dendrimers are fabricated from monomers using either convergent or divergent step growth polymerization. The unique properties of dendrimers like well defined structure, monodispersity of size, surface functionalization capability and stability make them attractive drug carrier molecules. Drug molecules can be incorporated into dendrimers via complexation or encapsulation. These are used for both drug and gene delivery as a carrier for penicillin and for the use in anticancer therapy.

Metal Structures : Metal nanoshells are fabricated by using methods involving templating of thin metal shell around a core metal shell around a core material such as silica nanoparticles. Typical metals include gold, silver, platinum and palladium.

Carbon Structures :
These are hollow carbon based cage like architectures also known as buckyballs. Common configuration includes single, multiwalls nanotubes and CO 60 fullerenes. These may be used as vaccine delivery structures, transfer of DNA indicates potential use as a gene delivery tool. Tissue selective targeting and intracellular targeting of mitochondria have been shown with use of fullerene structures.

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