Aminoluciferin 4-hydroxyphenyl amide enables bioluminescence detection of endogenous tyrosinase

Persistent and Efficient Multimodal Imaging for Tyrosinase Based on Two-Photon Excited Fluorescent and Room-Temperature Phosphorescent Probes

Tyrosinase is crucial to regulate the metabolism of phenol derivatives, playing an important role in the biosynthesis of melanin pigments, whereas an abnormal level of tyrosinase would lead to severe diseases. It is rather necessary to develop a sensitive and selective imaging tool to assess the level of tyrosinase in vivo. We thoroughly researched the luminous mechanism of the existing TPTYR probe and provided design strategies to improve its two-photon excited fluorescence properties. The designed probes benza2-TPTYR and product benza2-TPTYR-coumarin have large two-photon absorption cross sections at the NIR spectral region (41 GM/706 nm, 71 GM/852 nm), while benza2-TPTYR-coumarin possesses easily distinguishable spectrum in the visible region and a high fluorescence efficiency (Φ_F = 0.27). What is more, novel two-photon excited multimodal imaging based on the pure organic small molecule benza1-TPTYR-coumarin (61 GM/936 nm) is proposed first, simultaneously possessing strong instantaneous fluorescent (563.79 nm) and persistent room-temperature phosphorescent emissions (767.68 nm, 0.54 ms).

Colorimetric determination of tyrosinase based on in situ silver metallization catalyzed by gold nanoparticles

Gold nanoparticles (AuNPs) catalyze the mild reaction between the weak reducing agent kojic acid (KA) and silver ions (Ag⁺) to form Au@Ag bimetallic NPs by the combination of the intrinsic catalysis with plasmonic properties This is proposed as a novel optical assay to determine the tyrosinase (TYRase) concentration. The nanoparticles have been characterized by UV-vis spectroscopy, transmission electron microscope (TEM) images, and X-ray photoelectron spectroscopy (XPS). The sensing mechanism is based on the fact that KA binds to TYRase by chelating with dicopper active site of TYRase and the introduction of TYRase restrains the Au@Ag bimetallic NP formation by the precedent binding with KA. A clear color variation from yellow to pink and UV-vis spectral changes are observed at the optimal wavelength of 410 nm. The assay works in the range 0.13~0.73 U mL^-1 with a detection limit (LOD) of 0.019 U mL^-1. The impact from matrix interfering substances including glucose, uric acid, common oxidases, and amino acids is negligible. The applicability is demonstrated by quantitative determination of TYRase in human serum samples with 74 to 89% recovery and RSD less than 4.0%, which accords with the level for bio-sample analysis. Graphical abstract Schematic presentation of colorimetric assay for tyrosinase (TYRase) based on the inhibition effect on silver deposition onto catalytically active gold nanoparticles (AuNPs) and its application with a smartphone. Tyrosinase (TYRase); silver ions (Ag⁺); kojic acid (KA); gold nanoparticles (AuNPs); gold-silver core-shell nanoparticles (Au@Ag NPs).

Bioluminescence imaging of carbon monoxide in living cells based on a selective deiodination reaction

Modification of a heavy iodine atom for d-Luciferin was explored as a “turn-on” transduction scheme for CO detection. This new probe could image exogenous and endogenous CO in the luciferase-transfected cancer cells.