Measurement of the Density of Polymeric Nanoparticulate Drug Carriers by Isopycnic Centrifugation

The development of polymer nanoparticles as drug carriers requires numerous steps including several in vitro evaluations in cell cultures and biocompatibility. To perform these experiments, it is crucial to express the particle concentration as the number of particles per volume unit or as the particle surface area. Calculation of these suspension characteristics can be perfomed knowing the size and the density of the nanoparticles as well as the polymer concentration. While particle size and polymer concentration are parameters being determined routinely, this study proposes to measure the density of the nanoparticle drug carriers by isopycnic centrifugation using linear sucrose gradients. The method was found to be very reproducible and it presents the advantage of being applied on a small sample of nanoparticles.