Regarding the role and function of PEG in liposome structure I can mention the following section from the Citation which appears underneath:

5.2. Long-circulating stealth liposomes and nanoliposomes

Intravenously injected conventional vesicles are mostly eliminated from the blood

circulation, after opsonization, by the cells of the immune system that are mainly present in the liver and spleen [60]. Opsonization is the process by which liposomes are marked for ingestion and elimination by the macrophages and phagocytes. Inclusion of certain polymers (e.g., polyethylene glycol (PEG), polyhydroxyethyl L-asparagine (PHEA), etc.), or incorporation of glycolipids (e.g., monosialoganglioside) into liposomes and nanoliposomes, prevent opsonization and result in sterically stabilized vesicles [61-63]. These carrier systems

have several advantages over conventional liposome formulations including reduced recognition and uptake by MPS / RES, extended circulation half-lives and dose-independent pharmacokinetics [62, 63].

From:

Mozafari, M. R., Torkaman, S., Karamouzian, F. M., Rasti, B., & Baral, B. (2021). Antimicrobial applications of nanoliposome encapsulated silver nanoparticles: A potential strategy to overcome bacterial resistance. Current Nanoscience, 17(1), 26-40.

size and distribution, surface charge, and the method of the formulation process.

hiii,

Actually we aim to prepare steric and electrostatic stability with using PEG.