t-Boc-aminooxy-PEG5-propargyl is a click crosslinker. Propargyl group is reactive with azide-bearing compounds or biomolecules via copper catalyzed azide-alkyne Click Chemistry to yield a stable triazole linkage. T-Boc-aminooxy can be converted to free aminooxy under mild acidic conditions and then can react with an aldehyde or ketone. The hydrophilic PEG spacer increases solubility in aqueous media.