NPs have emerged as important players in current research in modern medicine. The literature suggest that NPs should no longer be viewed only as simple carriers for biomedical applications, but can also play an active role in mediating biological effects. In this study we evaluated different type of NPs that, once entered the cells, approach the nucleus and induce alteration in its size. Confocal images of fixed cells (L929, A549, HeLa) were acquired along a plane on the Z axis corresponding to the cell mid-height and nuclei dimension was calculated with ImageJ software.

Starting from 1 up to 8 hrs of NPs exposure, the nucleus dimension increases from 12 to 17 % compared to the untreated cells (p<0.001). This result seems not to be related to cytoskeleton alteration since Cytochalasin D treatment causes a 13% reduction of the nucleus size and no effect was observed after nocodazole incubation. When we focus on NPs whose trafficking is microtubule but not actin-myosin dependent, nocodazole prevents variation in nuclear dimension, suggesting that NPs trafficking is a prerequisite for the increase of nuclear size.

These results may support the idea of a mechanical connections between plasmamembrane, cytoskeletal filaments, and nucleoplasm and the findings that the nuclear envelope may act as a mechanosensor (Jaalouk DE, 2009) such as intracellular deformations NPs-induced could alter chromatin conformation and modulate access to transcription factors or machinery.