Study of the bioconjugation of ternary alloyed ZnCdTe nanocrystals to Concanavalin A

• Conjugation of ZnCdTe nanocrystals to Concanavalin A created cluster-like motif.
• Increasing amounts of protein decreased semiconductor photoluminescence.
• Quenching was only partial and protein remains active.
• Excitation profile of Concanavalin A changes with conjugation.

This work describes the first spectroscopic study of the covalent binding of Concanavalin A with ZnCdTe semiconductor nanocrystals, together with structural characterization of the bioconjugates. Glutathione-capped ZnCdTe nanocrystals were prepared in an aqueous medium and conjugated to Concanavalin A using glutaraldehyde as the coupling agent. Morphological characterization of the bioconjugates revealed the formation of nanoparticle clusters resulting from the binding of protein molecules and the formation of bridges between two or more ZnCdTe nanocrystals. This caused a progressive decrease in the photoluminescence intensity of the nanocrystals when the amount of protein was increased. Nonetheless, the emission intensity remained at a satisfactory level after bioconjugation. The presence of the protein also greatly reduced the thermal quenching of quantum dot photoluminescence at higher temperatures, indicating that changes in the protein conformation might favor passivation of the nanocrystal surface.

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