Self-Assembling Ratiometric Fluorescent Micelle Nanoprobe for Tyrosinase Detection in Living Cells

Herein, a novel self-assembling ratiometric fluorescent micelle nanoprobe (NanoDPA-NMP-tyr) based on Förster Resonance Energy Transfer (FRET) was developed and was used to respond to tyrosinase (TYR) activity in B16 cells. The absorption band of the small organic molecular probe NMP-tyr (λabs = ∼450 nm) composed of fluorophore naphthalimide derivative and detecting group tyramine, and the emission band of 9,10-diphenylfluorene DPA (λem = ∼445 nm) overlap. NMP-tyr acts as energy acceptors, and DPA acts as donors to supplement energy. Both of these substances were encapsulated in the hydrophobic interior of the amphiphilic copolymer mPEG-DSPE. The FRET mechanism was formed when NanoDPA-NMP-tyr was excited at 377 nm. When TYR and oxygen were present at the same time, the maximum absorption peak of NMP-tyr blue-shifted from ∼450 nm to ∼350 nm (NMP-tyro), which blocked the energy transfer from DPA to NMP-tyr and effectively turned off FRET. The blue fluorescence of donor dye DPA was restored. NanoDPA-NMP-tyr is able to respond quickly to TYR in 7.5 min and exhibits excellent specificity and sensitivity toward TYR. Fluorescence imaging applied to B16 cells shows that NanoDPA-NMP-tyr is highly responsive to TYR in vivo.