PEG-lipid shedding and biodistribution are shaped by nanocarrier morphology and lipid chemistry

Targeting moieties are often attached to nanocarriers (NCs) using poly(ethylene glycol)-lipids (PEG-lipids) to direct uptake to target cells and organs. However, nanoparticles (NPs) can interact with proteins during systemic circulation, causing PEG-lipids to dissociate or "shed," which limits targeting efficiency. Here, we investigate how lipid chemistry and poly(ethylene glycol)-b-poly(propylene sulfide) (PEG-PPS) NC morphology affect PEG-lipid shedding. We conjugated one fluorophore to the NC and another to the PEG-lipid to track shedding over time. By coupling Förster resonance energy transfer (FRET) and total internal reflection fluorescence microscopy (TIRF) with biological systems, we found that PEG-lipids with stable anchors shed slowly and are consistent across NC morphologies. In contrast, weakly anchored PEG-lipids exhibit morphology-dependent shedding and biodistribution in vivo . These findings underscore how PEG-lipids can have different biodistribution from their NCs, highlighting the importance of this phenomenon in the design of new targeted nanomedicines.