Microchimica Acta

, 186:70 | Cite as

Electrostatically controlled fluorometric assay for differently charged biotargets based on the use of silver/copper bimetallic nanoclusters modified with polyethyleneimine and graphene oxide

  • Jinlan Yang
  • Naizhong Song
  • Qiong JiaEmail author
Original Paper


An electrostatically controlled fluorometric assay is described that is based on the use of silver/copper bimetallic nanoclusters. The nanoclusters were coated with polyethyleneimine (PEI-Ag/CuNCs). At pH 7.4, these particles are positively charged. Their blue fluorescence (with excitation/emission peaks at 341/464 nm) depends on local pH values and temperature. If graphene oxide (which is negatively charged at pH 7.4) is introduced, the fluorescence of the PEI-Ag/CuNCs is quenched. Based on various electrostatic interactions, three kinds of biomacromolecules were detected by fluorometry. These include (negatively charged) heparin, (positively charged) protamine, and (virtually uncharged) trypsin. Heparin is detected by using GO/PEI-Ag/CuNCs, protamine by using GO/heparin/PEI-Ag/CuNCs, and trypsin by using GO/protamine/heparin/PEI-Ag/CuNC. The detection limits and linear ranges are 4.8 nM and 10–450 nM for heparin, 0.09 μg·mL−1 and 0.25–5 μg·mL−1 for protamine, and 0.03 μg·mL−1 and 0.05–1 μg·mL−1 for trypsin. Zeta potentials of the various substances in the system were determined to elucidate the detection mechanism. Comceivably, the method provides a widely applicable approach for electrostatically controlled biomolecular assays.

Graphical abstract

Schematic presentation of electrostatically controlled fluorometric assay for the detection of heparin, protamine, and trypsin based on the silver/copper bimetallic nanoclusters modified with polyethyleneimine and graphene oxide.


Heparin Protamine Trypsin Electrostatic interactions Multiple targets sensing 



The project was supported by State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, China (2019-4).

Compliance with ethical standards

The author(s) declare that they have no competing interests.

Supplementary material

604_2018_3179_MOESM1_ESM.docx (1.4 mb)
ESM 1 (DOCX 1416 kb)


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Copyright information

© Springer-Verlag GmbH Austria, part of Springer Nature 2019

Authors and Affiliations

  1. 1.College of ChemistryJilin UniversityChangchunChina

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