Synthesis and photoluminescence properties of Ce3+/Tb3+ and Eu3+ ions doped GdB3O6/Ca10(PO4)6(OH)2 Core/Shell particles as well as its cytotoxicity against colon cancer cells

In this study, Ce³⁺/Tb³⁺ co-doped, Eu³⁺ doped GdB₃O₆ phosphor particles were synthesized by sol-gel method, coated with hydroxyapatite (HAP) and loaded with doxorubicin. Different chelating agents and surfactants (Cetyltrimethylammonium bromide (CTAB), citric acid, glycine, ethylenediaminetetraacetic acid (EDTA) and tartaric acid) were used in the synthesis in order to see their effect on the structure. While single phase Gadolinium triborate, GdB₃O₆ was obtained by using CTAB in precursor solution in the synthesis and Gadolinium orthoborate, GdBO₃ produced when EDTA was used in precursor solution. Other organic molecules added to precursor solution produced mixtures of both phases. The highest photoluminescence intensity was obtained in the Gd_0.95Ce_0.025Tb_0.025B₃O₆ and Gd_0.825Eu_0.175B₃O₆. In order to increase the drug loading efficiency, The Gd_0.825Eu_0.175B₃O₆ core was coated with Calcium hydroxyapatite, HAP. The core had an average size of 458.65 nm which increased to 616.85 nm after coating as seen with dynamic light scattering (DLS). Gd_0.825Eu_0.175B₃O₆@HAP particles were loaded with 7.82 % ± 0.80 wt doxorubicin and the release was studied at 37 °C in pH 7.4 phosphate-buffered saline (PBS) and pH 5.5 acetate buffer solutions. The total number of moles of drug released versus luminescence intensity was measured during the release studies and real-time imaging studies were carried out. Finally, cytotoxicity experiments were performed on HCT-116 colon cancer cells.