Used extensively in the formulation of liposomes and lipid nanoparticles for drug delivery, particularly in targeted therapies. The PEGylated structure enhances circulation time by reducing immune system clearance, allowing nanoparticles to accumulate preferentially in tumor tissues via the EPR (enhanced permeability and retention) effect. The terminal carboxylic acid group enables covalent conjugation to targeting ligands such as antibodies, peptides, or proteins, enabling site-specific delivery. Commonly employed in cancer therapeutics, mRNA vaccines, and diagnostic imaging agents due to its stability and biocompatibility. Also used in surface functionalization of nanocarriers to improve solubility and prevent aggregation in biological fluids.