Immuno-silent polymer capsules encapsulating nanoparticles for bioimaging applications.

PEGylated polymer capsules encapsulating LaVO:Tb, GdVO:Tb, GdO:Tb, GdF:Tb, YVO:Tb and iron oxide nanoparticles are promising new fluorescence, magnetic and magnetofluorescence imaging agents. Recently, we have reported their in vitro and in vivo level toxicity profiles which show the non-toxic nature of these polymer capsules encapsulating nanoparticles. However, prior to clinical use, it is essential to ensure that these agents are unlikely to activate immune responses. Herein, we investigated the immunocompatibility of polymer capsules with dendritic cells (DCs), macrophages (MOs), and major antigen presenting cell (APC) subsets required for the activation of innate and adaptive immunity. The capsules were efficiently internalized by both DCs and MOs in vitro. Importantly, despite the presence of intracellular capsules, there was no significant impact on the viability of the cells. We studied the impact of different capsules on the cytokine profiles of the DCs and MOs, which is known to be important for the polarization of T-cell immunity. None of the capsules elicited a change in cytokine secretion from the DCs. Furthermore, the capsules did not alter the polarization of either M1 or M2 MO subsets as determined by the balance of IL-12 and IL-10 secretion. These data support the notion that PEGylated polymer capsules loaded with nanoparticles have the potential to remain immunologically silent as they do not activate APCs nor do they hinder the response of DCs or MOs to pathogen activating signals. These systems, therefore, exhibit promising characteristics for bioimaging applications.