Methyl-PEG23-acid (methyl-PEG23-carboxylic acid) is a linear polyethylene glycol (PEG) derivative with the molecular formula C₅₀H₁₀₀O₂₆ and a molecular weight of approximately 1117.31. Its structure consists of a PEG chain terminated with a single methoxy group (containing 23 ethylene glycol units) and an end carboxylic acid group (-COOH), combining the biocompatibility of PEG with the reactive activity of carboxylic acid. The production process typically employs custom synthesis techniques, achieving uniform molecular weight through precise control of polymerization reaction conditions, with a purity of over 98%. This product is widely used in the biomedicine field, such as as a drug carrier modification molecule, targeted material modifier, and cell regulation reagent. Its carboxylic acid group can covalently bind to biomolecules, enhancing the water solubility and biological activity of materials.