Cosubstitution of Lanthanides (Gd³⁺/Dy³⁺/Yb³⁺) in β-Ca₃(PO₄)₂ for Upconversion Luminescence, CT/MRI Multimodal Imaging

Abstract

Multifunctional Gd 3+ , Dy 3+ and Yb 3+ cosubstitutions in β-Ca 3 (PO 4 ) 2 were achieved through a facile synthetic technique. Gd 3+ and Dy 3+ prefer to occupy the 7-fold coordinated Ca 2+ (1), 6-or 8-fold coordinated Ca 2+ (2), and 8-fold coordinated Ca 2+ (3) sites of the β-Ca 3 (PO 4 ) 2 structure. The shortest Ca(5)O bond length of te Ca 2+ (5) site with 6-fold co-ordination favors Yb 3+ accommodation. The substitution limit of each dopant to attain β-Ca 3 (PO 4 ) 2 solid solution is determined as ∼1.25 mol %. The combined substitutions displayed upconversion emission in blue, yellow and red regions on excitation at 980 nm via the energy transfer mechanism from Yb 3+ to Dy 3+ . Yb 3+ and Dy 3+ combination induces a high X-ray absorption ability for computed tomography (CT). The materials also displayed paramagnetic behavior and exhibited high longitudinal (r 1 = 48.71 mM −1 s −1 ) and transverse relaxivity (r 2 = 61.79 mM −1 s −1 ) indicating their potential as T 1 and T 2 contrast agents in magnetic resonance imaging (MRI). The negligible toxicity of Gd 3+ /Dy 3+ /Yb 3+ cosubstitutions in β-Ca 3 (PO 4 ) 2 is also demonstrated. The overall results justify the potential of the developed material as possible contrast agent for T 1 and T 2 MRI/ CT/upconversion luminescence.

Unveiling the Effects of Rare-Earth Substitutions on the Structure, Mechanical, Optical, and Imaging Features of ZrO2 for Biomedical Applications

“…In recent years, RE-doped materials gained significance in orthopedic and imaging applications. Single and cosubstitutions of Gd 3+ , Dy 3+ , and Yb 3+ in β-Ca 3 (PO 4 ) 2 as a multifunctional bioprobe for magnetic resonance imaging (MRI), computed tomography (CT), and optical imaging application have been reported. − Nevertheless, the poor mechanical compatibility restricts the use of β-Ca 3 (PO 4 ) 2 in hard-tissue replacements. An additional work on Dy 3+ -doped ZrO 2 –SiO 2 binary oxide system presented good MRI contrast features .…”

Simultaneous accommodation of Dy3+ at the lattice site of β‐Ca3(PO4)2 and t‐ZrO2 mixtures: Structural stability, mechanical, optical, and magnetic features

“…Recent studies also witness the incorporation of rare earth (RE 3+ ) elements in both the bioactive and bio‐inert ceramics . The RE 3+ incorporation is mainly due to the attractive optical and magnetic features displayed by these elements in biomedicine .…”

“…It has been deduced that depending on the concentration of RE 3+ substitution in increasing order, a gradual phase transition in the order of tetragonal ( t ‐ZrO 2 ) to cubic ZrO 2 ( c ‐ZrO 2 ) and thereafter the formation of pyrochlore structure are witnessed . While the concentration of RE 3+ substitutions in β‐ Ca 3 (PO 4 ) 2 is limited in the range of 4‐5 mol% and the excess RE 3+ crystallizes to yield Dy 2 O 3 , GdPO 4 , and YbPO 4 as witnessed in case of Dy 3+ , Gd 3+ , and Yb 3+ . Moreover, the potential applications in magnetic resonance imaging, computed tomography, and fluorescence imaging features have been demonstrated by RE 3+ substitutions in both ZrO 2 and β‐ Ca 3 (PO 4 ) 2 .…”

“…20 Recent studies also witness the incorporation of rare earth (RE 3+ ) elements in both the bioactive and bio-inert ceramics. 21,22 The RE 3+ incorporation is mainly due to the attractive optical and magnetic features displayed by these elements in biomedicine. 23,24 RE 3+ substitution in ZrO 2 has been an extensive study that enumerates the positive impact in the resultant structure such as to accommodate a wide range of either individual or multiple RE 3+ substitutions devoid of significant structural distortion.…”

“…27 While the concentration of RE 3+ substitutions in β-Ca 3 (PO 4 ) 2 is limited in the range of 4-5 mol% and the excess RE 3+ crystallizes to yield Dy 2 O 3 , GdPO 4 , and YbPO 4 as witnessed in case of Dy 3+ , Gd 3+ , and Yb 3+ . 21 Moreover, the potential applications in magnetic resonance imaging, computed tomography, and fluorescence imaging features have been demonstrated by RE 3+ substitutions in both ZrO 2 and β-Ca 3 (PO 4 ) 2 . In this context, the present investigation is aimed at the development of structurally stable β-Ca 3 (PO 4 ) 2 /ZrO 2 composite through Dy 3+ substitution.…”