Bis-PEG4-sulfonic acid is widely used as a linker or spacer in bioconjugation and chemical synthesis. Its PEG (polyethylene glycol) chains enhance solubility and stability, making it suitable for modifying biomolecules like proteins, peptides, and antibodies. This compound is particularly valuable in drug delivery systems, where it helps improve the pharmacokinetics and bioavailability of therapeutic agents. Additionally, it is utilized in the development of biosensors and diagnostic tools, where its sulfonic acid group facilitates binding to target molecules. Its biocompatibility and water solubility also make it a preferred choice in various biomedical and pharmaceutical research applications.