Studies on quantum dots synthesized in aqueous solution for biological labeling via electrostatic interaction

doi:10.1016/S0003-2697(03)00287-2

Analytical Biochemistry

Volume 319, Issue 2, 15 August 2003, Pages 239-243

https://doi.org/10.1016/S0003-2697(03)00287-2 Get rights and content

Abstract

3-Mercaptopropyl acid-stabilized CdTe nanoparticles synthesized in aqueous solution are effectively bound to a biomacromolecule, papain, via electrostatic interaction. The conjugation between the nanoparticles and the papain is demonstrated by UV-Vis absorption, photoluminescence spectroscopy, transmission electron microscopy, and fluorescence micrographs. The biological activity of papain is maintained after the conjugation. The effects of the quantity of papain and the size of nanoparticles on the fluorescence characteristics of the CdTe–papain bioconjugates were studied.

Section snippets

Materials

3-Mercaptopropyl acid (MPA) (99+%), tellurium powder (∼200 mesh, 99.8%), CdCl₂ (99+%), and NaBH₄ (99%) were purchased from Aldrich Chemical Com. Papain was used as obtained from Roche Diagnostics GmbH (Mannheim, Germany). The isoelectric point (pI) of papain is 8.75 [16]. All other reagents were of analytical reagent grade and used without further purification. Purified water (>18 MΩ cm) was used.

Preparation of water-soluble CdTe nanoparticles

MPA-modified CdTe nanoparticles were synthesized in aqueous solution using previously described

Results and discussion

The absorption spectrum of QDs–papain bioconjugates is flatter than that of the free QDs (Fig. 1); at the same time, the absorbance increases. The emission peak of the unconjugated QDs is at 542 nm; however, the emission peak of QDs–papain undergoes a red shift (557 nm), but the intrinsic spectral width is unchanged.

The changes of the absorption and fluorescence spectra result from the shortened distances between QDs owing to the electrostatic attraction between negatively charged CdTe quantum

Conclusions

CdTe nanoparticles synthesized in aqueous solution are effectively bound to a protein via electrostatic interaction. The method for labeling biomacromolecules with semiconductor nanoparticles presented in this paper is simple and feasible and can be applied to other inorganic nanomaterials with charged surfaces. These new types of nanoparticles–biomolecules conjugates could find their own potential application in cell surface labeling, intracellular tracking studies, and other imaging

Acknowledgements

This work was supported by the National Natural Science Foundation of China (No. 20075009). The authors thank Ms. Huijun Yu (College of Chemistry, Jilin University) for help with the enzymic activity measurement.

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¹: Also corresponding author.

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Studies on quantum dots synthesized in aqueous solution for biological labeling via electrostatic interaction

Abstract

Section snippets

Materials

Preparation of water-soluble CdTe nanoparticles

Results and discussion

Conclusions

Acknowledgements

Curr. Opin. Biotechnol.

Chem. Phys. Lett.

Thin Solid Films

Semiconductor nanocrystals as fluorescent biological labels

Science

Quantum dot bioconjugates for ultrasensitive nonisotopic detection

Science

Quantum-dot-tagged microbeads for multiplexed optical coding of biomolecules

Nat. Biotechnol.

Quantum dot-labeled trichosanthin

Analyst

Self-assembly of CdSe–ZnS quantum dot bioconjugates using an engineered recombinant protein

J. Am. Chem. Soc.

Avidin: a natural bridge for quantum dot-antibody conjugates

J. Am. Chem. Soc.

Synthesis and characterization of thiol-stabilized CdTe nanocrystals

Ber. Bunsenges. Phys. Chem.