Dilute lattice doping of Cu-64 into 2D-nanoplates: its impact on radio-labeling efficiency and stability for target selective PET imaging

A quintinite nanoplate (Cu-64-QT-NP) isomorphically substituted with Cu-64, as the positron emission tomography (PET) imaging material, was prepared via two-step processes. A Cu-64 labeling efficiency of 99% was realized, for the first time, by immobilizing the Cu-64 radioisotope directly in the octahedral site of the 2-dimensional (2D) quintinite lattice. Furthermore, the Cu-64 labeling stability of Cu-64-QT-NPs was also achieved to be more than similar to 99% in various solutions such as saline, phosphate-buffered saline (PBS), and other biological media (mouse and human serums). In an in vivo xenograft mouse model, the passive targeting behavior of Cu-64-QT-NPs into tumor tissue based on the enhanced permeability and retention (EPR) effect was also demonstrated by parenteral administration, and successfully visualized using a PET scanner. For enhancing the tumor tissue selectivity, bovine serum albumin (BSA) was coated on Cu-64-QT-NPs to form Cu-64-QT-NPs/BSA, resulting in better colloidal stability and longer blood circulation time, which was eventually evidenced by the 2-fold higher tumor uptake rate when intravenousely injected in an animal model. It is, therefore, concluded that the present Cu-64-QT-NPs/BSA with tumor tissue selectivity could be an advanced nano-device for radio-imaging and diagnosis as well.