Development of wireless optically stimulable upconversion nanoparticle devices for non-invasive photodynamic therapy

Abstract Photodynamic therapy (PDT) is one of the treatment methods used for brain tumors. In PDT, red laser light is irradiated onto photosensitizers accumulated in tumor tissues. However, the red light used in PDT has low tissue penetration, requiring the opening of the head for surgery, which imposes a significant burden on the patient. Therefore, in this study, we proposed wireless optically stimulable implant devices using upconversion nanoparticles (UCNPs), including the UCNP fiber and the waveguiding (WG)-UCNP mesh sheet. The proposed devices enable wireless red light emission by external NIR irradiation, resulting in non-invasive PDT. Furthermore, the UCNP fiber and WG-UCNP mesh sheet have separate NIR light receiving and red light emitting areas, which reduces the attenuation of the entering NIR light in bone, tissue, and so on. In this study, the UCNP fiber and WG-UCNP mesh sheet were successfully fabricated, and the light strength characteristics were evaluated using emission tests.