LAUSR

&NA; Sterosomes (STEs), a new and promising non‐phospholipidic liposome platform based on palmitic acid (PA) and cholesterol (Chol) mixtures, need to have polyethylene glycol (PEG) chains grafted to their surface in order to obtain long‐circulating nanocarriers in the blood stream. A post‐insertion method was chosen to achieve this modification. The post‐insertion process of PEG‐modified distearoylphosphoethanolamine (DSPE‐PEG) was monitored using the zeta potential value of STEs. Various conditions including PEG chain length and the DSPE‐PEG/PA‐Chol ratio, were explored. Zeta potential of STEs changed from about −40 mV for non‐modified STEs to values close to 0 mV by the end of the process, i.e. for PEG‐modified STEs. The kinetics of DSPE‐PEG insertion and the stability of the resulting PEG‐modified STEs were not considerably influenced, within the investigated range, by changes in PEG chain lengths and in DSPE‐PEG/PA‐Chol proportion. The post‐insertion of PEG chains reduced in vitro complement activation as well as in vitro macrophage uptake compared to the non‐modified STEs. Moreover, longer blood circulation time in mice was established for PEG‐modified STEs intravenously injected compared to non‐modified STEs. These results establish that post‐insertion process of PEG chains to STEs is a promising strategy for developing long‐term circulating drug delivery nanocarriers. Graphical abstract Figure. No caption available.