Proteomics reveals time-dependent protein corona changes in the intracellular pathway

The intracellular protein corona has not been fully investigated in the field of nanotechnology-biology (nano-bio) interactions. To effectively understand intracellular protein corona formation and dynamics, we established a workflow to isolate the intracellular protein corona at different uptake times of two nanoparticles - magnetic hydroxyethyl starch nanoparticles (HES-NPs) and magnetic human serum albumin nanocapsules (HSA-NCs). We performed label-free quantitative LC-MS proteomics to analyze the composition of the intracellular protein corona and correlated our findings with results from conventional methods for intracellular trafficking of nanocarriers, such as flow cytometry, transmission electron microscopy (TEM), and confocal microscopy (cLSM). We determined the evolution of the intracellular protein corona. At different time stages the protein corona of the HES-NPs with a slower uptake changed, but there were fewer changes in that of the HSA-NCs with a more rapid uptake. We identified proteins that are involved in macropinocytosis (RAC1, ASAP2) as well as caveolin. This was confirmed by blocking experiments and by TEM studies. The investigated nanocarrier predominantly trafficked from early endosomes as determined by RAB5 identification in proteomics and in cLSM to late endosomes/lysosomes (RAB7, LAMP1, cathepsin K and HSP 90-beta) We further demonstrated differences between nanoparticles with slower and faster uptake kinetics and determined the associated proteome at different time points. Analysis of the intracellular protein corona provides us with effective data to examine the intracellular trafficking of nanocarriers used in efficient drug delivery and intracellular applications. STATEMENT OF SIGNIFICANCE: Many research papers focus on the protein corona on nanoparticles formed in biological fluids, but there are hardly any articles dealing with proteins that come in contact with nanoparticles inside cells. The "intracellular protein corona" studied here is a far more complex and highly demanding field. Most nanocarriers are designed to be taken up into cells. Given this, we chose two different nanocarriers to reveal changes in the proteins in dendritic cells during contact at specific times. Further studies will allow us to examine molecular target proteins using these methods. Our research is a significant addition towards the goal of understanding and thus improving the efficacy of drug nanocarriers.