Nanoparticles are instantly modified once injected in the bloodstream because of their interaction with the blood components. The adsorption of proteins and their layering onto nanoparticle surfaces has been called the ‘protein corona’ and has been postulated as a determinant factor for the pharmacological, toxicological and therapeutic profile of NPs. This dynamic process of protein adsorption has been extensively studied following in vitro incubation of many different nanoparticles with plasma proteins. However, the formation of protein corona under dynamic, in vivo conditions remains largely unexplored.
In our recently published study1, we attempted to offer for the first time a comprehensive comparison between the protein coronas that formed in vitro and in vivo on clinically established, PEGylated liposome systems of nanoscale dimensions and to determine the corona impact on their cellular internalisation. Bare (non-PEGylated) and antibody-targeted versions of the same liposome composition were investigated, to determine the ability of surface PEGylation to suppress protein adsorption, as well as the effect of the protein corona on the targeting (binding and internalisation) capability of liposomes within mammalian cell cultures. The formation of in vivo protein corona was determined after the recovery of the liposomes from the blood circulation of CD-1 mice 10 minutes post-injection. In comparison, in vitro protein corona was formed by the incubation of liposomes in CD-1 mouse plasma.
Overall, this study revealed that the molecular complexity of the in vivo protein corona formed on clinically-developed liposomes cannot be adequately predicted by their in vitro plasma incubations. Even though the total amount of protein attached on circulating liposomes correlated with that observed from in vitro incubations, the variety of molecular species in the in vivo corona were considerably wider. Such complexity can lead to sharply different structural characteristics of the in vivo corona compared to that forming in vitro. A network of linear fibrillary structures constituted the in vitro protein corona, whereas the in vivo corona had a different morphology and did not appear to coat the liposome surface entirely. Despite the substantial differences observed in the composition and morphology between the in vitro and in vivo formed protein coronas, both restricted cellular internalization and compromised the targeting capability of MoAb-conjugated liposomes.
Significant progress has been made towards understanding the principles and mechanism of protein corona formation and self-assembly, yet the effect of ‘protein corona’ formation on nanoparticles pharmacology is far from being well understood. We anticipate that this work will provide impetus for many more studies needed to reveal the characteristics of the in vivo protein coronas on different NP types and their impact on the overall biological profile of these nanoparticles.
- Hadjidemetriou, M.; Al-Ahmady, Z.; Mazza, M.; Collins, R. F.; Dawson, K.; Kostarelos, K., In Vivo Biomolecule Corona around Blood-Circulating, Clinically Used and Antibody-Targeted Lipid Bilayer Nanoscale Vesicles. ACS nano 2015. http://pubs.acs.org/doi/abs/10.1021/acsnano.5b03300