Bis-PEG6-Acid is widely used in bioconjugation and pharmaceutical development due to its hydrophilic, flexible spacer properties. It serves as a bifunctional linker in the synthesis of antibody-drug conjugates (ADCs), where it connects targeting moieties to cytotoxic agents, improving solubility and reducing aggregation. Its PEG-based structure enhances biocompatibility and prolongs circulation time in vivo. It is also employed in the formulation of PEGylated peptides and proteins to increase stability and reduce immunogenicity. Additionally, it finds use in surface modification of nanoparticles and medical devices to create non-fouling, hydrophilic interfaces that resist protein adsorption. The terminal carboxylic acid groups allow for straightforward activation and coupling to amines or hydroxyls under standard conjugation conditions.