Changing Surface Polyethylene Glycol Architecture Affects Elongated Nanoparticle Penetration into Multicellular Tumor Spheroids

Modular nanoconjugates present opportunities to explore the interactions of anisotropic nanoparticles (NPs) in biological environments. To promote colloidal stability and biocompatibility, most NPs designed for biomedical applications are coated with polyethylene glycol (PEG) brushes. However, concerns have been raised about the immunogenicity of PEG, even though new evidence has suggested that differences in PEG architecture (i.e., branching) can change how NPs with surface-grafted PEGs interact with different biological environments. In particular, poly(oligoethyleneglycol methacrylate) (POEGMA) has been shown to have useful antifouling properties without triggering PEG-associated immunogenicity. Nevertheless, these observations have not resulted in useful relationships between PEG structure and its biological activity, as there have been few direct comparisons of these polymers in biological systems. The following data compares the penetration of three rod-like NPs with narrow size distributions (Ln = 170 nm, wn = 12 nm) using tumor spheroids as a model.