Bis(NHS)PEG9 is widely used in bioconjugation and crosslinking applications due to its reactive N-hydroxysuccinimide (NHS) ester groups. These groups enable efficient coupling with primary amines, making it a valuable tool for modifying proteins, peptides, and other biomolecules. It is particularly useful in creating stable amide bonds, which are essential for linking molecules in drug delivery systems, diagnostic assays, and surface functionalization. Its polyethylene glycol (PEG) spacer provides flexibility and solubility, reducing steric hindrance and improving biocompatibility. This chemical is also employed in the development of antibody-drug conjugates (ADCs) and other targeted therapies, where precise molecular attachment is critical. Additionally, it plays a role in materials science for modifying surfaces to enhance their interaction with biological systems.