Investigation into the Photochemical Properties of Methylene Blue-Immobilized Hydroxyapatite Nanoparticles for Theranostic Application

Iori Yamada, Takuya Kataoka, Ryota Ikeda, Motohiro Tagaya

Research output: Contribution to journalArticlepeer-review


In the biomedical field, there has been a requirement for developing theranostic nanomaterials with higher biosafety, leading to both diagnosis and therapy. Methylene blue (MB+) is an organic dye with both photoluminescence (PL) and photosensitization abilities to generate singlet oxygen (1O2). However, MB+ easily loses its generation ability by hydrogen reduction in vivo or by forming aggregates. In this study, MB+ immobilized on biocompatible hydroxyapatite (HA) nanoparticles was applied for the bifunctions of efficient PL and photosensitization. The MB+-immobilized HA nanoparticles (MH) formed aggregates with sizes of 80-100 nm in phosphate buffer (PB). The generation amount and efficiency of 1O2 from the nanoparticles in PB seem to depend on the immobilized MB+ amount and the percentage of the monomer, respectively. Considering the larger immobilized amount and percentage of the MB+ monomer, it was found that there was MH with the lower generation amount and efficiency of 1O2 to exhibit the highest PL intensity. The photofunctional measurement of MB+ revealed the state of MB+ molecules on the HA surface, and it was suggested that the MB+ molecules immobilized on the MH surface would form more hydrogen bonds to change their excitation states. In the cellular experiments, the Hela cancer cells reacted with the nanoparticles and showed red-color PL, indicating cellular imaging. Furthermore, the adherent cell coverage decreased by 1O2 generation, indicating the importance of the immobilization amount of the MB+ monomer.

Original languageEnglish
JournalACS Applied Bio Materials
Publication statusAccepted/In press - 2022
Externally publishedYes


  • hydroxyapatite
  • inorganic−organic interfaces
  • methylene blue
  • photofunctional bioceramics
  • theranostics

ASJC Scopus subject areas

  • Biomaterials
  • Chemistry(all)
  • Biomedical Engineering
  • Biochemistry, medical


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