Folic Acid-Modified B-Type Y₂O₃:Eu³⁺ Quantum Dots: A Bright Approach to Fluorescence Imaging of Cancer Cells

Clinical applications of nanophosphors have gained extensive interest in research areas such as bioimaging and targeted drug delivery. The development of nontoxic semiconductor quantum dots (QDs), which can replace the conventional fluorescent probes, can bring significant developments in the bioimaging industry. This work reports the synthesis of monoclinic Y 2 O 3:Eu QDs, without and with surface functionalization using PEG/folic acid at low temperature and its application in live cancer cell imaging. The synthesized quantum dots show sharp absorption in the short UV region and an intense red emission at 614 nm. Concentration-dependent optical properties are studied in detail, and color purity is measured. Transmission electron microscopy substantiates the monoclinic structure, crystalline nature, and the lower particle dimensions essential for the biological applications. The surface-modified sample is characterized for its structural and luminescence properties. Biocompatibility was ensured by performing MTT Assay on L6 skeletal muscle cell lines (normal) and MCF 7 cell lines (cancer) for the samples without and with surface modification, respectively. Fluorescence detection experiments on SKMEL cells using an uncapped sample prove the suitability of the material as a fluorescent probe. The effect of surface functionalization on imaging results was established by carrying out fluorescence detection experiments on MCF 7 cells using PEG-folic acid-functionalized sample, which resulted in enhanced cell uptake, specific binding, and bright fluorescence emission. Thus, this work authenticates the suitability of the material to be used as a reliable nanophosphor and an efficient fluorescent probe for imaging cancer cells.