The importance of nanoparticle coating structural design in the development of nanovaccines

Homogeneity/dis-homogeneity of the NP surface may deeply influence the formation of the protein corona (serum proteins that recognize and bind the surface of a NP). In fact, innate immunity may intercept NPs whose coating mimic Pathogen Associated Molecular Patterns (PAMPs) or Damage Associated Molecular Patterns (DAMPs), leading to Antigen Presenting Cells (APCs) targeting via Pattern Recognition Receptors (PRRs) or complement receptors (CRs), and immune maturation. Knowing this, in collaboration with Prof. Roberto Fiammengo and PhD Ander Eguskiza Bilbao (University of Verona) we decided to characterize the effect of different types of - COOH or -OH terminated poly (ethylene-glycol) (PEG) coatings, that differ in length and charge, with the aim of finding candidates for the design of an anti-cancer NV. First, we discovered that the best candidates in terms of immune recognition and uptake by APCs are two negative and homogeneous coating made by -COOH terminated PEG with ~12 units or 4 units of ethylene glycol called respectively 100PEG and 100EG. In particular, 100EG is the most internalized NPs by both human and mouse primary macrophages and dendritic cells in vitro. 100PEG and 100EG where then functionalized with tumor associated mucin 1 (MUC1) generating two NVs candidate called PEG MUC1 and EG MUC1. MUC1, a tumor- associated antigen, differently expressed and glycosylated in several tumors, is a promising immunogen for the immunotherapy against cancer. After the in vitro characterization of the two NV candidates, we found that the uptake of EG MUC1 is significantly lower than the internalization of PEG MUC1 in the human model (24h). On the other hand, for the mouse model, the pattern of internalization is exactly the opposite at 24h of incubation; EG MUC1 is captured massively more than PEG MUC1. Therefore, we moved in vivo. PEG MUC1 induces a higher antibody titer in immunized mice compared to EG MUC1. All this evidence allows to assess that just changing the length and the charge of a polymer it is possible to achieve different cellular targets and to design NPs for different biomedical applications. Moreover, MUC1 is confirmed to be a promising antigen for a proper immunization against cancer cells