Phospholipid-PEG-Biotin (MW 2000), a biotin-labeled phospholipid PEG derivative, is designed for modifying the surfaces of liposomes, cells, and pancreatic islets intended for cell transplantation. This compound integrates the properties of three distinct components: phospholipids, which are lipids featuring a hydrophilic "head" and two hydrophobic "tails"; PEG, a low-toxicity, water-soluble, hydrophilic polymer; and biotin, an enzyme co-factor utilized in protein labeling [1].