Thiol-PEG3-acid is widely used in bioconjugation and surface modification due to its reactive thiol group and hydrophilic polyethylene glycol (PEG) spacer. It is commonly employed to functionalize nanoparticles, proteins, and peptides, enhancing their solubility, stability, and biocompatibility. The thiol group allows for specific attachment to gold surfaces or maleimide-functionalized molecules, making it valuable in biosensor development and drug delivery systems. Additionally, it is utilized in the creation of crosslinked hydrogels for tissue engineering and controlled release applications. Its PEG chain helps reduce immunogenicity and prolong circulation time in biological systems, making it a key component in therapeutic and diagnostic platforms.