Aminooxy-PEG2-amine hydrochloride (compound L3) is a crosslinking agent. The aminooxy group facilitates bioconjugation, reacting with aldehydes to form oxime bonds, and in the presence of a reducing agent, forming hydroxylamine bonds. The amine group can react with carboxylic acids, activated NHS esters, and carbonyls (ketones, aldehydes). Aminooxy compounds possess high reactivity and sensitivity; thus, they are unsuitable for long-term storage.