Preparation of polymeric Janus particles for stimulation of immune cells
Biomaterials
Final Report Abstract
In summary, we evaluated 4 types of OVA NPs varying in size and crosslinking density on BMDC processing and T cell proliferation. OVA NPs were fabricated by EHD co-jetting with varying crosslinker (NHS-PEG-NHS) amounts: (1) 10% 2k NHS-PEG-NHS, (2) 30% 2k NHS- PEG-NHS, (3) 50% 2k NHS-PEG-NHS, and (4) 5% 20k NHS-PEG-NHS. Formulations (1)-(3) yielded NPs of ~85 nm dry size, while (4) resulted in ~175 nm dry size. SEM imaging showed that the jetted PNPs are of spherical shape and monodisperse. OVA NPs were further characterized by DLS, AFM force-distance measurements, and SANS. We found that the amount of crosslinking affected swelling (water uptake), particle elasticity, and mesh size. SANS data showed that the amount of added crosslinker directly affected the network density. NP swelling increased with decreasing crosslinking, a phenomenon which was previously observed for hydrogels. The particle stiffness (Young’s modulus) increased with increasing crosslinking density. This has consequences on cellular uptake. We found that uptake of OVA NPs by BMDCs was affected by the crosslinker density, with less-crosslinked NPs resulting in higher cellular uptake. Particle-treated BMCDs were shown to promote antigen cross-presentation and crosspriming of CD8α+ T cells. Less-crosslinked OVA NPs showed higher proliferation rates than highly crosslinked ones. We attributed this to their higher uptake by BMDCs and facilitated internal cell processing due to lower network density. Finally, we conducted an in vivo prime-boost immunization experiment. While 5% and 10% crosslinked OVA NPs showed similar cellular uptake and T cell proliferation in vitro, the 5% OVA NPs elicited weak immune responses in vivo; we believe that their larger size (500nm) may cause them to get stuck at the injection site. For 10%, 30% and 50% crosslinked OVA NPs, less-crosslinked NPs exhibited greater cellular and humoral immune responses than highly crosslinked ones. For all particle groups, two-dose immunization significantly improved CD8α+ T cell responses. In summary, crosslinked OVA NPs were successfully internalized by BMDCs and elicited antigen specific cellular and humoral immune responses after subcutaneous injections in mice.
