A ratiometric fluorescent sensor for rapid detection of the pyroglutamate aminopeptidase-1 in mouse tumors

Abstract

Pyroglutamate aminopeptidase-1 (PGP-1) is an important enzyme that plays an indispensable role in the process of inflammation. Up to now, few reports have been reported on the detection of PGP-1 activity in vivo and in vitro, and there are no reports on ratiometric detection. Here, the first red-emitting ratiometric fluorescent sensor (DP-1) for the specific detection of PGP-1 both in vivo and in vitro was designed and synthesized by using DCD-NH₂ as the luminescent parent and pyroglutamate as a recognition group. After interacting with PGP-1, the amide bond is hydrolyzed by the enzyme and the color of the solution changes from yellow (λ_abs = 420 nm) to red (λ_abs = 520 nm), accompanied by obvious fluorescence emission wavelength change (from ∼564 nm to ∼616 nm). The probe has high specificity and sensitivity towards PGP-1 in about 10 min, and the DL is as low as 0.25 ng mL⁻¹. Interestingly, under the stimulation of Freund's incomplete adjuvant and lipopolysaccharide, the imaging of DP-1 in HepG2 and RAW264 cells shows that the expression of PGP-1 is associated with inflammation. What's more, for the first, the imaging of a mouse tumor model confirms that the enzyme is closely related to the occurrence of some inflammation and tumor diseases. These results indicate that DP-1 can be used as an effective tool for real-time monitoring of PGP-1 levels both in vivo and in vitro and the study of inflammatory tumor pathology.