Surface-Engineered Design of Efficient Luminescent Europium(III) Complex-Based Hydroxyapatite Nanocrystals for Rapid HeLa Cancer Cell Imaging

Takuya Kataoka, Shigeaki Abe, Motohiro Tagaya

Research output: Contribution to journalArticlepeer-review

29 Citations (Scopus)


We synthesized hydroxyapatite nanocrystals under the existence of tris(2,2,6,6-tetramethyl-3,5-heptanedionato)europium(III) (EuTH) complex to form inorganic/organic hybrid nanocrystal (EHA). Then, the folic acid derivative (folate N-hydroxysuccinimidyl ester (FA-NHS)) as the targeting ligand for the HeLa cancer cells was immobilized on the EHA by the mediation of both 3-aminopropyltriethoxysilane and methyltriethoxysilane molecules. Here, we investigated the photofunctions based on the interfacial interactions between the FA-NHS and EHA nanohybrids for preparing the novel bioimaging nanomaterials. As a result, the photofunctions could be changed by the FA-NHS molecular occupancy on the EHA. When the molecular occupancy ratio to the EHA surfaces is at around 3-5%, the intense luminescence from the f-f transition of the Eu 3+ ions as well as the charge transfer between the EuTH-FA-NHS was observed to exhibit higher quantum efficiency. Moreover, effective dispersibility in phosphate-buffered saline was confirmed with immobilizing the positively charged FA-NHS. The cytotoxicity against the HeLa cells was also evaluated to verify whether the nanohybrids can be the candidate for cell imaging. The affinity and noncytotoxicity between the FA-NHS-immobilized EHA nanohybrids and cells were monitored for 3 days. Red luminescence from the cells could be observed, and the labels with following the cellular shapes were achieved by an additional culture time of 1 h after injecting the FA-NHS-immobilized EHA nanohybrids to the spheres, indicating the rapid bioimaging process. Therefore, this is the first successful report to describe the synthesis of inorganic-organic nanohybrid systems for controlling the EuTH-FA-NHS interactions. The photofunction of the interfacial interactions was successfully designed to provide "efficient luminescent ability" as well as "rapid targeting to the cancer cells" in one particle.

Original languageEnglish
Pages (from-to)8915-8927
Number of pages13
JournalACS Applied Materials and Interfaces
Issue number9
Publication statusPublished - Mar 6 2019
Externally publishedYes


  • bioimaging particles
  • cancer cell imaging
  • europium(III) complex
  • hydroxyapatite nanocrystals
  • inorganic-organic nanohybrid systems
  • luminescent nanomaterials
  • photofunctional interfaces

ASJC Scopus subject areas

  • Materials Science(all)


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