Nano drugs or nano medicine is the medical application of nanotechnology. As defined by the Royal Society and Royal Academy of Engineering, “nanoscience” is the study of phenomena and manipulation of materials at atomic, molecular, and macromolecular scales, where the properties differ significantly from those at a larger scale; and “nanotechnologies” are the design, characterization, production, and application of structures, devices, and systems by controlling shape and size at the nanometer scale. In recent years, great progress was achieved in making drugs own the characteristics of targeted and controlled release via nanotechnologies. Nano drug is an important product of the rapidly developing nanotechnologies in biology and medicine field. The drug is usually made from natural polymer material. The main advantage is that it can effectively improve stability of clinical drug, improve patients’ drug absorption capacity, and thus effectively improve targeting of drugs and drugs nature, which can effectively extend action time of drug, then effectively improve clinical effect of the drug and minimize toxic and side effects of the drug.
Types of Nano-Structures
Polymeric nanoparticles: Polymeric nanoparticles (colloidal solid particles with a size range of 10 to 1000nm) have a matrix architecture composed of biodegradable and biocompatible polymers of synthetic or natural origin.
Liposomes: Liposomes are closed spherical vesicles consisting of a lipid bilayer that encapsulates an aqueous phase in which drugs can be stored. The liposome diameter varies from 400 nm to 2.5 μm.
Dendrimers: Dendrimers are nano-sized, radially symmetric molecules with well-defined, homogeneous, and monodisperse structure consisting of tree-like arms or branches. The particle size range is between 1 to 100nm although their sizes are mostly less than 10nm.
Solid lipid nanocarriers: Solid lipid nanoparticles (with a size range of 50 and 1000nm) are a new generation of colloidal drug carrier systems and consist of surfactant-stabilized lipids that are solid both at room and body temperatures. Solid lipid nanoparticles are promising drug carriers for systemic circulations as well as local applications.
Nanocapsules: Nanocapsules are spherical hollow structures in which the drug is confined in the cavity and is surrounded by a polymer membrane. Sizes between 50 and 300nm are preferred for drug delivery and they may be filled with oil which can dissolve lipophilic drugs.
Nanoemulsions: Nanoemulsions (submicron emulsions) are another novel drug delivery forms. They are single-phase and thermodynamically stable isotropic systems that consist of emulsified oil, and water and amphiphilic molecules. The diameter of the emulsion globule (droplet) reaches approximately 20–500 nm, although usually this diameter is from 100 to 500 nm.
Metallic nanoparticles: Metallic nanoparticles include iron oxide, gold, silver, gadolinium, and nickel which have been studied for targeted cellular delivery. Gold exhibits favourable optical and chemical properties at the nanoscale for biomedical imaging and therapeutic applications.
Carbon nanomaterials: These include carbon nanotubes and fullerenes. Fullerenes are carbon allotrope made up of 60 or more carbon atoms with a polygonal structure. Nanotubes have been used for their high electrical conductivity and excellent strength.
Drug delivery: Drug delivery and related pharmaceutical development in the context of nanomedicine should be viewed as science and technology of nanometer scale complex systems (10–1000 nm).The primary goals for research of nano-bio-technologies in drug delivery include:
Effects of particle size and surface coating: It has been found that the size of the nanoparticles plays a key role in their adhesion to and interaction with the biological cells. The possible mechanisms for the particles to pass through the gastrointestinal (and other physiological) barriers could be (1) paracellular passage—need small size (<50 nm); (2) For absorption by intestinal particles size<500 nm and (3) lymphatic uptake particle size should be <5 μm.
The Safety Of Nano-Drug: With increased R&D work on nano drug delivery, emerge concerns about the safety of the nanotechnologies in humans. Some of the nanomaterials are biodegradable while some are not; furthermore, the side effects of the by-products present a huge concern.
Yang studied the distribution and toxicity of silicon nanoparticles in vivo. When silica nanoparticles suspension injected in mice , after 96 h, electron microscopy result showed that silica nanoparticles distributed in the brain, liver, heart, spleen, lung, kidney, stomach, intestines, prostate, testis and other organs, and found a large quantity of silica nanoparticles had enter into the cell nucleus of liver and a small amount that cell nucleus of brain. But some scholars also believe that when the particle size reduced to a certain degree, the substance and material that original have non-toxic or low toxic begin to appear toxicity or toxicity significantly strengthened.
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