Nanoparticle Concentration as an Important Parameter for Characterization of Dispersion and Its Applications in Biomedicine.

Currently, there are problems to standardize methods for determining the concentration of nanoparticles and creation of etalon materials for calibrating measured concentrations. Accurate determination of nanoparticle concentration is necessary to assess the maximum dose of administered nanotherapeutics for diagnostics and therapy in vivo, to determine the order of reaction in enzymatic nanoreactors. In addition, this parameter determines biological effects, such as the formation of a protein corona on the outer surface of nanoparticles that precedes nanoparticles' absorption and internalization in cells. This review discusses the most common methods for determining the concentration of nanoparticles based on direct visualization, using microscopy, light absorption or light scattering, direct counting of nanoparticles, and gravimetry. Results may differ from one method to the other. Thus, the use of a combination of several methods provides more reliable results. The advantages, disadvantages and ways to improve accuracy of results are also presented. [ABSTRACT FROM AUTHOR]