ABSTRACT
Polymer microparticle (often a microsphere): A polymer particle of any shape with an equivalent diameter approximately from 0.1 to 100 µm. Polymer nanoparticle (often a polymeric nanosphere): A polymer particle of any shape with an equivalent diameter from a few to a hundred nanometers. In the literature this definition is not strictly held and sometimes particles up to 1000 nm are still called nanoparticles (see Chapter 5). Polymer gel: A gel consisting of a polymer solution in a liquid solvent in which a three-dimensional structure has been formed.
