DBCO-PEG6-NHS ester is a PEG reagent with an NHS ester, designed for click chemistry applications. It reacts specifically and efficiently with primary amines, such as lysine side chains or amino silane-coated surfaces, under neutral to slightly basic conditions, forming covalent bonds. Additionally, DBCO-PEG6-NHS ester contains a DBCO group that facilitates strain-promoted alkyne-azide cycloaddition (SPAAC) reactions with azide groups.