HO-PEG-COOH is widely used in biomedical and pharmaceutical research due to its biocompatibility and functional groups. It is commonly employed in drug delivery systems to enhance the solubility and stability of therapeutic agents. The hydroxyl group allows for further conjugation with targeting molecules, while the carboxylic acid group enables coupling with drugs or other bioactive compounds. This chemical is also utilized in the development of hydrogels and biomaterials for tissue engineering, where it provides a hydrophilic and flexible matrix. Additionally, HO-PEG-COOH is used in surface modification to improve the biocompatibility of medical devices and nanoparticles, reducing immune responses and increasing circulation time in the body. Its versatility makes it a valuable tool in creating advanced therapeutic and diagnostic platforms.