Macrophage Cellular Adaptation, Localization and Imaging of Different Size Polystyrene Particles

Several studies have tackled the evaluation of the biocompatibility of nanomaterials in cell and tissue. Nonetheless to date, a quantitative technique for the assessment of the total intracellular nanocarrier dose administered has not been introduced. In this paper we develop two rapid and sensitive assays for the measurement of internalised nanomaterials in macrophages to be applied as vehicular carriers for drug delivery and contrast imaging applications. Five commercially available polystyrene particles with different diameters (from 20 to 1000 nm) were used and imaged by using a 3dimensional confocal imaging techniques. The two proposed assays are: “volumetric” assay which evaluate the spherical volume of internalised particles and 2) “max-flat” assay which evaluate the total differential area between cells and internalised particles. These two assays were then compared to a reference method. Among these three assays, the “max-flat” assay was found to be the most reliable and accurate to quantify and investigate the total content of internalised nanomaterials. The “max-flat” assay also allowed for a 3dimensional subcellular investigation of the adaptation and localisation mechanisms between cytoskeleton and internalised materials, which may help to further increase the selectivity and delivery of active and passive biopolymers. Therefore, we believe that the here presented assays could become a useful tool to address many biomaterials questions, especially where the key issue is the quantitative assessment of dose effect issues related to the size-dependence response of nanomaterials.