Surface-engineered Design of Efficient Luminescent Europium(III) Complex-based Hydroxyapatite Nanocrystals for Rapid HeLa Cancer Cell Imaging.

Author(s) Kataoka, T.; Abe, S.; Tagaya, M.
Journal ACS Appl Mater Interfaces
Date Published 2019 Feb 07

We synthesized the 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 (APTES) and methyltriethoxysilane (MTES) molecules. Here, we investigated the photofunctions based on the interfacial interactions between the FA-NHS and EHA nanohybrids for preparing the novel bio-imaging 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 ions as well as the charge transfer between the EuTH‒FA-NHS was observed to exhibit the higher quantum efficiency. Moreover, the effective dispersibility in PBS 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 the cell-imaging. The affinity and non-cytotoxicity between the FA-NHS-immobilized EHA nanohybrids and cells were monitored for 3 days. The red luminescence from the cells could be observed, and the labels with following the cellular shapes were achieved by the additional culture time of 1 h after injecting the FA-NHS-immobilized EHA nanohybrids to the spheres, indicating the rapid bio-imaging process. Therefore, this is the first successful report to synthesize the inorganic-organic nanohybrid systems for controlling the EuTH-FA-NHS interactions. The photofunction of the interfacial interactions were successfully designed to provide "efficient luminescent ability" as well as "rapid targeting to the cancer cells" in one particle.

DOI 10.1021/acsami.8b22740
ISSN 1944-8252
Citation ACS Appl Mater Interfaces. 2019.

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