Azido-PEG12-acid is widely used in bioconjugation and chemical biology due to its reactive azide group and hydrophilic PEG spacer. The azide group allows for efficient click chemistry reactions, particularly copper-catalyzed azide-alkyne cycloaddition (CuAAC), enabling the attachment of biomolecules, polymers, or other functional groups. The PEG12 spacer enhances solubility, reduces steric hindrance, and improves biocompatibility, making it suitable for modifying peptides, proteins, or nanoparticles. It is commonly applied in drug delivery systems, where it facilitates the targeted attachment of therapeutic agents. Additionally, it is utilized in surface functionalization for biosensors and diagnostic tools, enabling precise and stable immobilization of biomolecules. Its versatility also extends to the development of hydrogels and biomaterials for tissue engineering, where it aids in creating crosslinked networks with controlled properties.