Encapsulation of ⁶⁷Cu therapeutic radiometal in luminescent lanthanide phosphate core and core-shell nanoparticles

Copper-67 (⁶⁷Cu) has physical characteristics useful for both therapy and imaging. However, its applicability has been hindered by the complexity of obtaining large quantities of a product with high specific activity. With the advancement of ⁶⁷Cu production methods, suitable radioisotope carriers are sought. Lanthanide phosphate nanoparticles have demonstrated their multifunctional characteristics for biomedical applications and, more recently, their potential in radiopharmaceuticals. Thus, we produced luminescent lanthanide phosphate nanoparticles with core and core-shell structures, incorporating ⁶⁷Cu during their synthesis. The nanoparticles exhibited hexagonal crystalline structure and spherical morphology with sizes below 6 nm. The luminescent colloidal suspensions evidenced the characteristic ⁵D₀-⁷F_J for Eu³⁺, providing the red color under UV light. A radiochemical yield of ⁶⁷Cu >95% was obtained with both core and core-shell LaPO₄:Eu. The core-shell nanoparticles reduced the release of ⁶⁷Cu by a factor of ∼2 over that from the core, which continuously decreased with time. Multifunctional LnPO₄ nanoparticles have the potential to be used as a carrier of single or multiple radioisotopes to enhance image-guided targeted nano-radiopharmaceutical therapy.