Ligand-functionalization of BPEI-coated YVO₄:Bi ³⁺,Eu³⁺ nanophosphors for tumor-cell-targeted imaging applications

In this study, surface-functionalized, branched polyethylenimine (BPEI)-modified YVO₄:Bi³⁺,Eu³⁺ nanocrystals (NCs) were successfully synthesized by a simple, rapid, solvent-free hydrothermal method. The BPEI-coated YVO₄:Bi³⁺,Eu ³⁺ NCs with high crystallinity show broad-band excitation in the λ=250 to 400 nm near-ultraviolet (NUV) region and exhibit a sharp-line emission band centered at λ=619 nm under excitation at λ=350 nm. The surface amino groups contributed by the capping agent, BPEI, not only improve the dispersibility and water/buffer stability of the BPEI-coated YVO₄:Bi³⁺,Eu³⁺ NCs, but also provide a capability for specifically targeted biomolecule conjugation. Folic acid (FA) and epidermal growth factor (EGF) were further attached to the BPEI-coated YVO₄:Bi³⁺,Eu³⁺ NCs and exhibited effective positioning of fluorescent NCs toward the targeted folate receptor overexpressed in HeLa cells or EGFR overexpressed in A431 cells with low cytotoxicity. These results demonstrate that the ligand-functionalized, BPEI-coated YVO ₄:Bi³⁺, Eu³⁺ NCs show great potential as a new-generation biological luminescent bioprobe for bioimaging applications. Moreover, the unique luminescence properties of BPEI-coated YVO ₄:Bi³⁺,Eu³⁺ NCs show potential to combine with a UVA photosensitizing drug to produce both detective and therapeutic effects for human skin cancer therapy. Packing a punch! Ligand-functionalized, branched polyethylenimine (BPEI)-coated YVO₄:Bi³⁺,Eu³⁺ nanocrystals (NCs; ≈20 nm) show a strong red luminescence under near-UV excitation (see picture). In vitro bioimaging results show that ligand-functionalized BPEI-coated YVO₄:Bi³⁺,Eu ³⁺ NCs can be specifically taken up by cancer cells through a receptor-mediated endocytosis mechanism.