t-Boc-aminooxy-PEG2-propargyl is a crosslinker containing a propargyl group and t-Boc-aminooxy group. The propargyl group can be reacted with azide-bearing compounds or biomolecules via copper catalyzed azide-alkyne Click Chemistry to yield a stable triazole linkage. The protected amine can be deprotected under mild acidic conditions. The hydrophilic PEG spacer increases solubility in aqueous media.