Fluorescence images of intracellular physical traces of red fluorescence MNPs and the expression of GFP in PK15 cells with time.

Abstract

<p>A) 2 h, MNPs move though the cell membrane. B) 6 h, most MNPs are in the cytoplasm. C) 12 h, MNPs transfer from the cytoplasm to the nucleus. D) 18 h, most MNPs are inside the nucleus. E) 24 h, cells express GFP and MNPs shift back to the cytoplasm. F) and G) 36–48 h, MNPs gradually excrete out the cells and release in culture medium. H) 72 h, most MNPs escape from cells (scale bar  = 50 µm).</p