Particle size and surface charge are key parameters of nanoparticles (NPs), especially therapeutic NPs, to influence the kinetics in vivo and interaction with the cellular and biological membranes and decide the efficacy for biological systems. Characterization of nanomaterials including both nanoparticles and micelles has therefore been a major issue in nanomedicine research to develop well-defined nano-formulations with focus on therapeutic goals. Dynamic light scattering (DLS) and zeta potential (ZP) measurements are widely accepted techniques for proper determination of the particle size and surface charge of therapeutic NPs. These have so far been easy, simple, and reproducible tools. However, there are challenges to interpret and systematically analyze data effectively due to lack of adequate understanding of the principles involved and impeccable background for operation of the system along with competence of sample preparation and characterization and so on. This review addresses the issues with focus on the fundamental principles involved in the techniques of DLS and ZP. The ultimate goal has been development of knowledge–base with a view to better analyzing and interpreting results for evaluation of hydrodynamic size, diffusion, inter particular interactions and stability of colloidal systems based on surface charge of therapeutic NPs. پرونده مقاله