Figure 4.

(A) Chemical structure of P-CyFF-Gd and proposed alkaline phosphatase (ALP)-mediated fluorogenic reaction and in situ self-assembly of P-CyFF-Gd into nanoparticles (NPs) that show increased NIR FL and r1 relaxivity. (B) Proposed mechanism of P-CyFF-Gd for NIR FL/MR bimodality imaging of ALP-positive tumor cells in vivo. Following systemic administration into mice, P-CyFF-Gd as a small molecule may easily across blood vessel and diffuse into tumor tissues. In tumor cells that express high levels of ALP, P-CyFF-Gd is dephosphorylated by membrane-bound ALP and converted into fluorescent CyFF-Gd, which subsequently selfassembles into fluorescent and magnetic NPs. (C) Chemical structure of the designed nonassembled control probe, P-Cy-Gd. Reproduced with permission from ⁵¹, copyright 2019, American Chemical Society.