Thiol-PEG7-COOH is a bifunctional polyethylene glycol derivative composed of three structural components: the terminal thiol group (-SH) provides strong nucleophilicity and can covalently bind to groups such as maleimides and active esters; the PEG7 chain imparts molecular flexibility and water solubility while reducing immunogenicity; and the carboxyl group (-COOH) enables functional modification through amidation or esterification reactions. The production process typically involves a two-step method: first, introducing the thiol group to the end of the PEG chain via esterification, then introducing the carboxyl group using reagents such as chloroacetic acid, followed by purification to obtain a high-purity product (>95%). This compound is widely used in the construction of nanomedicine drug carriers, protein surface modification, and biosensor development. For example, it can be immobilized on nanoparticle surfaces through thiol-gold interactions or coupled with antibodies via its carboxyl group to achieve targeted delivery, holding significant value in the field of biomedicine.