In a number of biomedical applications it is important to detect the amount of entities such as biomolecules or gold NPs that are bound to “core” nanoparticles (liposomes, exosomes or solid nanoparticles). However, the present measurement techniques are unable to accurately determine this number as well as the particle-to-particle variation. In this project, sensitive measurements of the size, intensity and zeta-potential of single nanoparticles will be carried out to enable precise measurements of the amount of bound gold nanoparticles or biomolecules. It will be investigated how the binding of gold nanoparticles or biomolecules affects the hydrodynamic size and zeta-potential of the core particles. And different optical and electrophoresis techniques will be developed to improve the measurement sensitivity. These sensitive measurements will then be applied, firstly, to novel applications of drug delivery and disease diagnostics being investigated at Ghent University, in which it is desired to know the amount of gold nanoparticles per liposome or exosome, and secondly to biosensing, in which it is desired to know the amount of target biomolecules bound to functionalized nanoparticles. In this way the project may lead to earlier diagnosis of diseases and better health care.