Immuno-silent polymer capsules encapsulating nanoparticles for bioimaging applications

PEGylated polymer capsules encapsulating LaVO4:Tb3+, GdVO4:Tb3+, Gd2O3:Tb3+, GdF3:Tb3+, YVO4:Tb3+ and iron oxide nanoparticles are promising new fluorescence, magnetic and magnetofluorescence imaging agents. Recently, we have reported the in vitro and in vivo level toxicity profile which shows the non-toxic nature of 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 immuno-compatibility of polymer capsules with dendritic cells (DC) and macrophages (MO), major antigen presenting cell (APC) subsets required for activation of innate and adaptive immunity. Capsules were efficiently internalized by both DC and MO in vitro. Importantly, despite the presence of intracellular capsules, there was no significant impact on the viability of cells. We studied the impact of different capsules on the cytokine profile of DC and MO, known to be important for the polarization of T-cell immunity. None of the capsules elicited change in cytokine secretion from DC. Furthermore, 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 APC and neither do they hinder the response of DC or MO to pathogen activating signals. These systems, therefore, exhibit promising characteristics for bioimaging applications. KEYWORDS: PEGylated polymer capsules, M1 and M2 macrophages, dendritic cells, immune respons