Label-free quantitative analysis for studying the interactions between nanoparticles and plasma proteins.

A shotgun proteomics approach was used to compare human plasma protein binding capability with cationic liposomes, DNA-cationic lipid complexes (lipoplexes), and lipid-polycation-DNA (LPD) complexes. Nano-high-performance liquid chromatography coupled with a high-resolution LTQ Orbitrap XL mass spectrometer was used to characterize and compare their protein corona. Spectral counting and area under curve methods were used to perform label-free quantification. Substantial qualitative and quantitative differences were found among proteins bound to the three different systems investigated. Protein variety found on lipoplexes and LPD complexes was richer than that found on cationic liposomes. There were also significant differences between the amounts of protein. Such results could help in the design of gene-delivery systems, because some proteins could be more selectively bound rather than others, and their bio-distribution could be driven in vivo for more efficient and effective gene therapy.