N-(Amino-PEG2)-N-bis(PEG3-azide) is a branched click chemistry reagent containing two azides (N3) and an amine moiety. The azide can react with alkyne, BCN, DBCO via Click Chemistry to yield a stable triazole linkage. An amine is reactive with activated NHS esters or carboxylic acid (CO2H) in the presence of HATU or EDC.