Carboxy-PEG-sulfonic acid is a compound that belongs to the class of polyethylene glycol (PEG) derivatives. It is a water-soluble polymer that contains carboxyl and sulfonic acid functional groups. This compound has become increasingly popular in pharmaceutical research and development due to its unique properties and applications. Carboxy-PEG-sulfonic acid has been extensively studied for its potential use as a drug delivery system, as well as for its ability to modify and enhance the properties of various biomolecules, such as proteins and peptides. Additionally, its hydrophilic nature and ability to improve solubility make it an attractive candidate for drug formulation. In this classification, we will explore the properties, applications, and potential uses of Carboxy-PEG-sulfonic acid in pharmaceutical research and development.