Nanoparticles refer to any particles with a dimension in the range of 1-100 nm. Let's consider the size of a water is about 0.3 nm, while the size of most viruses is about 20-400 nm and that of mammalian cells is about 104 n .
Achieving the size of a nanoparticle depends on its manufacturing process. And, there are two approaches. One is a top down method, wherein an external force is applied to break down a solid into fine particles. Another one is the bottom-up method, wherein atoms or tiny molecules are assembled into nanoparticles, via atomic transformations or molecular condensation.
Nanoparticles have a high surface-to-volume ratio, compared to larger particles with the same composition, and consequently they have a high surface energy, and unique mechanical, thermal, electrical, magnetic, and optical behaviors. Further, by modifying their surface properties by altering or adding functional groups, nanoparticles can be applied to different unique biological or other applications or achieve desired physical functionalities, such as re-dispersibility. (1)
There are different types of nanoparticles, and they are as follows; (a) Polymeric nanoparticles - solid polymeric matrices, (b) Liposomes - vesicles of a phospholipid bilayer, (c) Mesoporous silica - a solid framework with a porous structure, (d) micelles - vesicles of a surfactant layer, (e) Quantum dots - semiconductor particles, (f) Dendrimers - highly branched, star-shaped macromolecules. They have 3 components, namely central core, interior dendritic structure and exterior surface with functional surface groups. (1)
Reference
(1) Mingzhen Zhang and Didier Merlin, Nanoparticle-based oral drug delivery systems targeting the colon for treatment of ulcerative colitis, Inflamm Bowel Dis. 2018 Jul; 245(7): 1401-1415.
