Unbiased Identification of the Liposome Protein Corona using Photoaffinity-based Chemoproteomics

Protein adsorption to the surface
of a nanoparticle can fundamentally
alter the character, behavior, and fate of a nanoparticle in vivo.
Current methods to capture the protein corona rely on physical separation
techniques and are unable to resolve key, individual protein–nanoparticle
interactions. As a result, the precise link between the “synthetic”
and the “biological” identity of a nanoparticle remains
unclear. Herein, we report an unbiased photoaffinity-based approach
to capture, characterize, and quantify the protein corona of liposomes
in their native state. Compared to conventional methods, our photoaffinity
approach reveals markedly different interacting proteins as well as
reduced total protein binding to liposome surfaces. Identified proteins
do not follow protein abundancy patterns of human serum, as has been
generally reported, but are instead dominated by soluble apolipoproteins–endogenous
serum proteins that have evolved to recognize the lipidic surface
of circulating lipoproteins. We believe our findings are the most
accurate characterization of a liposome’s biological identity
but, more fundamentally, reveal liposome–protein binding is,
in many cases, significantly less complex than previously thought.