Fig. 5

Gene expression levels of autophagy markers induced by NPs as measured by qRT-PCR. a Quantification of mRNA expressed after exposure to NPs for 1, 3, 6, 24, and 48 h. Immediately after NPs are added, Beclin-1 was expressed at 1 h and tended to decrease slowly. b LC3-α increased until 3 h with no difference after 6 h. c LC3-β increased at 1 h and gradually decreased thereafter. d p62 expression levels decreased for the duration of the experiment. e ATG5 displayed the highest expression in autophagosomes. f STX17 showed higher after 6 h. The effect of magnetic and iron oxide-based PCS NPs on the development of exosomes. g After the incubation of the NPs with the MSCs, internalization by the magnet was confirmed by FACS. A large number of NPs were introduced into the cell by the magnet at 1 h. A similar number of NPs were introduced at 24 h in the absence of the magnet (−) as at 6 h with the magnet (+). h PLGA-PEI PCS NPs internalized in MVBs. It is possible that as the inflow of NPs increased, the generation of exosomes had also increased, resulting in the release of exosomes together with the undissolved NPs. When MSCs were treated with PCS NPs and magnets were active for 1 h, exosomes combined with NPs were generated. The amount of “PCS + exosome” increased at concentrations of 5, 10, and 20 μg/mL, with higher levels after 24 h. i Number of exosomes generated from cells, image analysis quantification. Without the magnet, the number of exosomes released in response to 5, 10, and 20 μg/mL PLGA-PEI PCS NPs was ~ 2.56 × 10⁷, 5.26 × 10⁷, and 5.7 × 10⁷, respectively. With the magnet, the numbers were ~ 7.86 × 10⁷, 1.6 × 10⁸, and 1.93 × 10⁸ exosomes released in response to 5, 10, and 20 μg/mL PCS NPs, respectively