Used in bioconjugation and surface modification, it serves as a linker molecule to attach biomolecules like proteins or peptides to surfaces or other molecules. Its peg4 spacer provides flexibility and solubility, while the phosphonic acid group allows strong binding to metal oxides, making it suitable for functionalizing nanoparticles or biosensors. The ethyl ester group can be hydrolyzed for further reactivity. It is particularly useful in drug delivery systems, diagnostic assays, and materials science for creating biocompatible interfaces.