| Abstract
| - We describe herein the synthesis of functional gold nanorods suitable for carrying out “click” chemistry reactions.Gold nanorods modified with a copolymer containing sulfonate and maleic acid groups have been conjugated to abifunctional azide molecule (amine−PEG−azide). The maleic acid molecules in the copolymer participate incarbodiimide-mediated amide bond formation with amine groups of the azide linker, whereas the sulfonate groupsprevent nanorod aggregation in water. Spectroscopic and ζ-potential measurements have been used to confirm thesuccessful surface modification of the gold nanorods. These azide-functionalized nanorods can carry out chemicalreactions based on click chemistry. As a case study, we have demonstrated the “clicking” of azide−nanorods to anacetylene-functionalized enzyme, trypsin, by a copper-catalyzed 1,3-dipolar cycloaddition reaction. The enzyme isnot only stable after bioconjugation but is also biologically active, as demonstrated by its digestion of the protein casein.For comparison, the biological activity of trypsin conjugated to gold nanorods by two other commonly used methods(carbodiimide-mediated covalent attachment via amide bond formation and simple electrostatic adsorption) has beenstudied. The enzyme conjugated by click chemistry demonstrates improved biological activity compared with otherforms of bioconjugation. This general and simple approach is easy, specific with higher yields, environmentallybenign, and applicable to a wide range of analytes and biomolecules.
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