Used extensively in bioconjugation and labeling applications, it serves as a linker molecule to attach biotin to various biomolecules, enabling their detection and purification through streptavidin-biotin interactions. It is particularly valuable in immunoassays, flow cytometry, and microscopy, where biotinylated probes are essential for visualizing and analyzing target molecules. The PEG4 spacer enhances solubility and reduces steric hindrance, improving binding efficiency. Additionally, it is employed in drug delivery systems to create biotinylated drug conjugates, leveraging the high affinity of biotin for targeted delivery to specific cells or tissues. Its versatility makes it a key tool in biochemical research and therapeutic development.