Assessing the activity of antibodies conjugated to upconversion nanoparticles for immunolabeling

Yueying Cao, Jiehua Wu, Xianlin Zheng, Yanling Lu, James A. Piper, Yiqing Lu*, Nicolle H. Packer*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


Surface modification and functionalization is typically required to engineer upconversion nanoparticles (UCNPs) for biosensing and bioimaging applications. Nevertheless, despite various antibody conjugation methods having been applied to UCNPs, no consensus has been reached on the best choice, as the results from individual studies are largely unable to be compared due to inadequate assessment of the properties of the conjugated products. Here, we introduce a systematic approach to quantitatively evaluate the biological activity of antibody-conjugated UCNPs. We determine that the optimal antibody conjugation efficiency to our colominic acid polysaccharide-coated UCNPs via 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide/N-hydroxy succinimide (EDC/NHS) coupling is approximately 70%, corresponding to 16 antibodies per nanoparticle of 63 nm hydrodynamic diameter, with on average 12 of the 16 antibodies maintaining their affinity to the target antigens. The binding ability of the antibody-conjugated UCNPs to the antigen was well preserved, as verified by enzyme-linked immunosorbent assay (ELISA), flow cytometry, and cellular imaging. This is the first study to quantitate the active antibody binding capacity of polysaccharide coated UCNP nanoparticles, offering a practical guideline for benchmarking functionalised UCNPs in future studies.

Original languageEnglish
Article number339863
Pages (from-to)1-9
Number of pages9
JournalAnalytica Chimica Acta
Early online date23 Apr 2022
Publication statusPublished - 29 May 2022


  • Upconversion nanoparticles
  • Antibody
  • Antibody-conjugated nanoparticles
  • Immunofluorescent analysis
  • Bioimaging


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