Synthesis, Optical Characterization, and Biocompatibility Assessment of Rare-Earth Fluoride Nanoparticles for Optogenetics

At this initial stage, the materials were characterized using morphological, structural, and spectroscopic techniques, focusing on optimizing upconversion efficiency and evaluating cell viability and cytotoxicity for biophotonic applications. The nanoparticles were synthesized via a solvothermal route, yielding monophase hexagonal structures with rod-like morphology and sizes of 100–300 nm. A systematic study of dopant ion concentrations was conducted to maximize upconversion efficiency while preserving morphology suitable for biological use. In vitro assays were performed using human glioblastoma cell lines (T98-G and U87MG) and healthy cells, including NHF and human glial cells, across a broad concentration range to assess nanoparticle safety and determine the maximum non-toxic dose.