A label-free luminescent assay for tyrosinase activity monitoring and inhibitor screening with responsive lanthanide coordination polymer nanoparticles

Detecting phosphate using lysine-sensitized terbium coordination polymer nanoparticles as ratiometric luminescence probes

Probes for detecting phosphate ions (Pi) are required for environmental monitoring and to protect human health. Here, novel ratiometric luminescent lanthanide coordination polymer nanoparticles (CPNs) were successfully prepared and used to selectively and sensitively detect Pi. The nanoparticles were prepared from adenosine monophosphate (AMP) and Tb³⁺, and lysine (Lys) was used as a sensitizer (through the antenna effect) to switch on Tb³⁺ luminescence at 488 and 544 nm while Lys luminescence at 375 nm was quenched because of energy transfer from Lys to Tb³⁺. The complex involved is here labeled AMP-Tb/Lys. Pi destroyed the AMP-Tb/Lys CPNs and therefore decreased the AMP-Tb/Lys luminescence intensity at 544 nm and increased the luminescence intensity at 375 nm at an excitation wavelength of 290 nm, meaning ratiometric luminescence detection was possible. The ratio between the luminescence intensities at 544 and 375 nm (I₅₄₄/I₃₇₅) was strongly associated with the Pi concentration between 0.1 and 6.0 μM, and the detection limit was 0.08 μM. The dual-emission reverse-change ratio luminescence sensing method can exclude environmental effects, so the proposed assay was found to be very selective. The method was successfully used to detect Pi in real water samples, and acceptable recoveries were found, suggesting that the method could be used in practice to detect Pi in water samples.

Chemiluminescence “turn-on” detection of tyrosinase activity via in situ generation of dopamine based on a lucigenin and riboflavin system

A lucigenin and riboflavin chemiluminescence system was utilized for the first to achieve “turn-on” detection of tyrosinase activity via the in situ generation of dopamine.

A highly-sensitive "turn on" probe based on coumarin β-diketone for hydrazine detection in PBS and living cells

Herein, a new "turn on" fluorescent probe C-1 is developed to specifically detect hydrazine using coumarin nucleus as the fluorophore and β-diketone as the recognition group. The probe shows high selectivity towards hydrazine over other common ions and amine-containing species, as well as good water solubility and quantitative detectability of hydrazine in concentration range of 1-200 μM. The detection limit is as low as 1.89 ppb, which is lower than the threshold set by EPA (10 ppb). Probe-coated filter papers are confirmed to detect gaseous hydrazine successfully through obvious fluorescence color changes. In addition, the probe has been verified to detect hydrazine in actual water environment and living cells.

Selecting and Characterizing Tyrosinase Inhibitors from Atractylodis macrocephalae Rhizoma Based on Spectrum-Activity Relationship and Molecular Docking

Atractylodis macrocephalae Rhizoma (AMR) is a famous classical Chinese traditional medicine (CTM), which has been used as a tonic for many diseases for thousands of years. In ancient China, it was used as a supplementary food for beauty in the palace. In preliminary studies, the function of whitening skin and the significant inhibiting effect on tyrosinase (TYR) which is the reactive enzyme in the composition of melanin of AMR were discovered, and the relevant research was rarely reported. In this study, high-performance liquid chromatography (HPLC) along with partial least squares regression analysis (PLS) was applied to survey the coherence between the chemical constituents and the inhibiting activity of 11 batches of AMR on TYR activity. The results of PLS showed that the chromatographic peaks 11 (atractylenolide III) and 15 could be important effective ingredients of the inhibition TYR activity as ascertained by spectrum-activity relationships. Furthermore, TYR inhibitory activity of atractylenolide III was validated by in vitro test by β-arbutin served as a positive control drug. The results of the in vitro test and the molecular docking showed that atractylenolide III has high TYR inhibitory activity and could link to the residues in TYR catalytic pocket. Therefore, bioassay, molecular docking, and spectrum-activity relationships are appropriate for linking the quality of samples with pharmaceutical-related active ingredients. And our studying would lay a theoretical foundation for applying the water extracts of AMR in whitening cosmetics.

Detection of Tyrosinase in Real Food Samples and Living Cells by a Novel Near-Infrared Fluorescence Probe

A new near-infrared fluorescence probe was developed and applied to the fluorescence detection of tyrosinase in real food samples and living cells. The probe (E)-2-(2-(6-((3-hydroxybenzyloxy)carbonylamino)-2,3-dihydro-1H-xanthen-4-yl)vinyl)-3,3-dimethyl-1-propyl-3H-indolium (1) was designed and synthesized by coupling 3-hydroxybenzyl alcohol via carbamate bond with an amino hemicyanine skeleton, based on the high anti-interference ability of 3-hydroxybenzyl alcohol to reactive oxygen species and its binding affinity to tyrosinase. Compared with the existing tyrosinase probes, the proposed probe exhibits superior analytical performance, such as high selectivity, high sensitivity, superior spatiotemporal sampling ability, fluorescence signal switching at 706 nm, and low detection limit of 0.36 U mL^-1. More importantly, the probe has been successfully used to monitor tyrosinase in the browning of apple slices for the first time, and the results indicated that the strongest fluorescence intensity could be achieved at 2.5 h to realize precise visual recognition of tyrosinase. Notably, the probe determined tyrosinase in real food samples (apple, banana, cheese, and red wine) with a stable average recovery range of 95.7-108.3% and has been successfully used to monitor tyrosinase in the living B16 cells. The superior properties of the probe make it of great potential use in food nutritional value evaluation and clinical diagnosis of melanin-related diseases.

Development of luminol-fluorescamine-PVP chemiluminescence system and its application to sensitive tyrosinase determination

Fluorescamine is a popular fluorescent probe. We report for the first time that luminol chemiluminescence (CL) can be enhanced by fluorescamine in the presence of PVP. The CL intensity of luminol-fluorescamine-PVP is about 26 times stronger than that of luminol. Both the removal of oxygen and the addition of superoxide dismutase (SOD) decrease CL intensity, thiourea and NaN₃ have little effect on CL intensities, indicating that O₂^•- is critical for CL. Interestingly, o-quinone generated from phenol by tyrosinase obviously inhibited the CL intensity. Inspired by such quenching effect on the luminol-fluorescamine-PVP CL system, a sensitive CL sensing for the determination of tyrosinase activity was developed. The method can detect tyrosinase in the range of 0.07-1.5 μg mL^-1 (0.19-4.02 U mL^-1) with the detection limit of 0.035 μg mL^-1 (0.094 U mL^-1). Moreover, this method exhibits satisfied recoveries for the spiked human serum samples.

Substrate-Photocaged Enzymatic Fluorogenic Probe Enabling Sequential Activation for Light-Controllable Monitoring of Intracellular Tyrosinase Activity

Tyrosinase (TYR) is a crucial enzyme involved in melanogenesis, and its overexpression is closely associated with melanoma. To precisely monitor intracellular TYR activity, remote control of a molecule imaging tool is highly meaningful but remains to be explored. In this work, we present the first photocaged tyrosinase fluorogenic probe by caging the substrate of the enzymatic probe with a photolabile group. Because of the sequential light and enzyme-activation feature, this probe exhibits photocontrollable "turn on" response toward TYR with good selectivity and high sensitivity (detection limit: 0.08 U/mL). Fluorescence imaging results validate that the caged probe possesses the capability of visualizing intracellular endogenous tyrosinase activity in a photocontrol fashion, thus offering a promising molecule imaging tool for investigating TYR-related physiological function and pathological role. Moreover, our sequential activation strategy has great potential for developing more photocontrollable enzymatic fluorogenic probes with spatiotemporal resolution.

Fast tyrosinase detection in early stage melanoma with nanomolar sensitivity using a naphthalimide-based fluorescent read-out probe

We report an expeditious approach for selective tyrosinase detection in early stage melanoma with nanomolar sensitivity using a napthalimide-based fluorescent probe.