Europium and calcium-co-doped TiO2 nanocrystals: tuning the biocompatibility and luminescence traceability of Drosophila melanogaster

Abstract

The incorporation of europium (Eu) ions improves the biocompatibility of TiO₂ nanocrystals (NCs) and allows tracking by red luminescence. Calcium doping improves cellular compatibility while also facilitating better interaction with biological systems. Thus, in this work, were synthesized Eu and Ca co-doped TiO₂ NCs and physical–chemical and biological properties were investigated. The physical–chemical properties were performed in order to analised the effects of the doping on the crystalline phase of TiO₂ morphology, sized, zeta potential, hydrodynamic diameter, and photocatalytic properties. Biological assessments were conducted using in vitro assays with human osteosarcoma cells (SAOS-2) through cytotoxicity assays and in vivo assays with Drosophila melanogaster, where we evaluated the mortality rate during postembryonic development and the luminescence of nanomaterials in vivo. The physical–chemical properties confirmed with success the integration of Ca ions into the TiO₂:Eu crystal (TiO₂:Eu:xCa) NCs without additional phases. The co-doping of Ca led to a reduction of approximately 70% in photocatalytic activity. Moreover, co-doping with Ca was not cytotoxic to SAOS-2 cells. Our in vivo analysis showed no delays in postembryonic development and no larval or pupal lethality. The larval mortality rate and pupal formation rate were comparable to the control group when D. melanogaster was exposed to nanomaterials at concentrations of 1 mg mL⁻¹ or lower. Luminescence of the NCs was detected in confocal microscopy images, indicating the presence of NCs in the larval brain and intestines. This luminescence was observed in TiO₂:Eu:xCa NCs. These results showed that Ca doping improved the biocompatibility and enhanced the luminescence of these materials, making them traceable in biological tissues. Therefore, our research provides valuable insights into the tailored properties of TiO₂ for potential applications in various fields of biomedicine.