Effect of polyethyleneglycol (PEG) chain length on the bio–nano-interactions between PEGylated lipid nanoparticles and biological fluids: from nanostructure to uptake in cancer cells

TLDR

When nanoparticles enter physiological fluids, adsorbed proteins form a corona that includes opsonins, leading to rapid clearance by phagocytes, and PEGylation is the most effective strategy to prevent this. The study aimed to balance anti‑opsonization with cellular uptake by testing PEGylated multi‑component liposomes of varying PEG chain lengths for delivery to prostate cancer cells. PEG chains grafted onto the liposome surface provide steric hindrance that limits protein adsorption, yet longer chains diminish cellular uptake; the authors used nanoLC‑MS/MS to characterize the corona, revealing that apolipoproteins dominate and that increasing PEG length reduces their binding, and leveraged this corona to target PC3 cells via SR‑B1. Confocal microscopy and flow cytometry showed that MC‑PEG2k achieved the best balance between reduced opsonization and efficient uptake, making it a promising candidate for in‑vivo prostate cancer therapy.

Abstract

When nanoparticles (NPs) enter a physiological environment, medium components compete for binding to the NP surface leading to formation of a rich protein shell known as the "protein corona". Unfortunately, opsonins are also adsorbed. These proteins are immediately recognized by the phagocyte system with rapid clearance of the NPs from the bloodstream. Polyethyleneglycol (PEG) coating of NPs (PEGylation) is the most efficient anti-opsonization strategy. Linear chains of PEG, grafted onto the NP surface, are able to create steric hindrance, resulting in a significant inhibition of protein adsorption and less recognition by macrophages. However, excessive PEGylation can lead to a strong inhibition of cellular uptake and less efficient binding with protein targets, reducing the potential of the delivery system. To reach a compromise in this regard we employed a multi-component (MC) lipid system with uncommon properties of cell uptake and endosomal escape and increasing length of PEG chains. Nano liquid chromatography coupled with tandem mass spectrometry (nanoLC-MS/MS) analysis allowed us to accurately determine the corona composition showing that apolipoproteins are the most abundant class in the corona and that increasing the PEG length reduced the protein adsorption and the liposomal surface affinity for apolipoproteins. Due to the abundance of apolipoproteins, we exploited the "protein corona effect" to deliver cationic liposome–human plasma complexes to human prostate cancer PC3 cells that express a high level of scavenger receptor class B type 1 in order to evaluate the cellular uptake efficiency of the systems used. Combining laser scanning confocal microscopy with flow cytometry analysis in PC3 cells we demonstrated that MC-PEG2k is the best compromise between an anti-opsonization strategy and active targeting and could be a promising candidate to treat prostate cancer in vivo.