  Comprehensive characterization of nanomaterials for medical applications is a
challenging and complex task due to the multitude of parameters which need to
be taken into consideration in a broad range of conditions. Routine methods
such as dynamic light scattering or nanoparticle tracking analysis provide some
insight into the physicochemical properties of particle dispersions. For
nanomedicine applications the information they supply can be of limited use.
For this reason, there is a need for new methodologies and instruments that can
provide additional data on nanoparticle properties such as their interactions
with surfaces. Nanophotonic force microscopy has been shown as a viable method
for measuring the force between surfaces and individual particles in the
nano-size range. Here we outline a further application of this technique to
measure the size of single particles and based on these measurement build the
distribution of a sample. We demonstrate its efficacy by comparing the size
distribution obtained with nanophotonic force microscopy to established
instruments, such as dynamic light scattering and differential centrifugal
sedimentation. Our results were in good agreement to those observed with all
other instruments. Furthermore, we demonstrate that the methodology developed
in this work can be used to study complex particle mixtures and the surface
alteration of materials. For all cases studied, we were able to obtain both the
size and the interaction potential of the particles with a surface in a single
measurement.
