Post-synthetic citrate modification of Eu( iii ) doped hydroxyapatite nanoparticles for enhanced cellular uptake in bioimaging applications

) sites and improving colloidal stability. Interestingly, citrate modification does not affect the photoluminescent emission characteristics of the as-prepared NPs. Additionally, biocompatibility and cell-imaging properties are analyzed to evaluate the effect of citrate modification of NPs on cellular uptake capacity. Both bare and citrate-modified Eu:HAp NPs do not show any significant toxicity toward HEK-293 and MDA-MB-231 cell lines. Moreover, cells treated with citrate-modified Eu:HAp NPs exhibit stronger red luminescence in confocal images and enhanced cellular uptake in FACS analysis compared to those treated with bare Eu:HAp NPs. Therefore, due to their excellent biocompatibility and cellular uptake, the synthesized NPs are best suited for bioimaging applications. Furthermore, this approach can also be applied for surface modification with various targeting ligands for diverse applications.