COOH-PEG-COOH is widely used in biomedical and pharmaceutical applications due to its biocompatibility and ability to modify surfaces. It is commonly employed as a linker or spacer molecule in drug delivery systems, enabling the conjugation of therapeutic agents to nanoparticles or other carriers. This enhances the solubility, stability, and circulation time of drugs in the body. Additionally, it is utilized in the development of hydrogels for tissue engineering, where it provides a scaffold for cell growth and regeneration. In bioconjugation, it serves as a crosslinker to attach proteins, peptides, or other biomolecules, facilitating targeted delivery and improved functionality in diagnostic and therapeutic applications. Its hydrophilic nature also makes it suitable for surface modification to reduce non-specific interactions in biosensors and medical devices.