A FeS2NPs-Luminol-MnO2NSs system based on chemiluminescence resonance energy transfer platform for sensing glutathione

Molecular mechanism for the unusual enhancement of the second-step chemiluminescence production from the carcinogenic tetrabromohydroquinone and H2O2

We have found recently that two-step intrinsic hydroxyl radical (·OH)-dependent chemiluminescence (CL) could be produced by carcinogenic tetrahaloquinone and H2O2. However, the first-step CL was too fast to clearly detect the stepwise generation of ·OH and CL, and to distinguish the exact dividing point between the first-step and second-step CL. Here we found that, extremely clear two-step intrinsic CL could be produced by the relative slow reaction of tetrabromohydroquinone (TBHQ) with H2O2, which was directly dependent on the two-step ·OH generation. Interestingly, the second-step, but not the first-step CL production of TBHQ/H2O2 (CRET donor) was markedly enhanced by fluorescein (a typical xanthene dye, CRET acceptor) through a unique chemiluminescence resonance energy transfer (CRET) process. The novel CRET system of TBHQ/H2O2/fluorescein was successfully applied for the sensitive detection of TBHQ with the detection limit as low as 2.5 µmol/L. These findings will help to develop more sensitive and highly efficient CL or CRET systems and specific CL sensor to detect the carcinogenic haloquinones, which may have broad environmental applications.

O-Phthalaldehyde Derivatization for the Paper-Based Fluorometric Determination of Glutathione in Nutritional Supplements

Herein, a new, direct paper-based fluorimetric method is described for the quantitative determination of glutathione (GSH) molecules in nutritional supplements. Briefly, the proposed analytical method is based on the fluorescence emission resulting from the direct and selective chemical reaction of GSH molecules with the derivatization reagent that is o-phthalaldehyde (OPA) in acidic conditions at room temperature. The intensity of the emitted fluorescence on the surface of the analytical paper devices after irradiation with a lamp at 365 nm is proportional to the concentration of GSH and is measured using a smartphone as the detector. This methodology, which is suitable for measurements in laboratories with limited resources, does not require specialized instrumentation or trained personnel. The protocol governing the proposed method is simple and easily applicable. Essentially, the chemical analyst should adjust the value of pH on the surface of the paper by adding a minimal amount of buffer solution; then, after adding a few microliters of the derivatization reagent, wait for the surface of the paper to dry and, finally, add the analyte. Subsequently, the irradiation of the sensor and the measurement of the emitted fluorescence can be recorded with a mobile phone. In the present study, several parameters affecting the chemical reaction and the emitted fluorescence were optimized, the effect of interfering compounds that may be present in dietary supplements was examined, and the stability of these paper sensors under different storage conditions was evaluated. Additionally, the chemical stability of these paper devices in various maintenance conditions was studied, with satisfactory results. The detection limit calculated as 3.3 S/N was 20.5 μmol L-1, while the precision of the method was satisfactory, ranging from 3.1% (intra-day) to 7.3% (inter-day). Finally, the method was successfully applied to three different samples of dietary supplements.

Plasmon-Stimulated Colorimetry Biosensor Array for the Identification of Multiple Metabolites

Rationally designing highly catalytic and stable nanozymes for metabolite monitoring is of great importance because of their huge potential in early disease diagnosis. Herein, a novel nanozyme based on hierarchically structured CuS/ZnS with a highly efficient peroxidase (POD)-mimic capability was developed and synthesized for multiple metabolite determination and recognition via the plasmon-stimulated biosensor array strategy. The designed nanozyme can simultaneously harvest plasmon triggered hot electron-hole pairs and generate photothermal properties, leading to a sharply boosted POD-mimic capability under 808 nm laser irradiation. Interestingly, because of the interaction diversity of the metabolite with POD-like nanomaterials, the unique inhibitory effect of metabolites on the POD-mimic activity could be the signal response as the differentiation. Thus, utilizing TMB as a typical chromogenic substrate in the addition of H2O2, the designed colorimetric biosensor array can produce diverse fingerprints for the three vital metabolisms (cysteine (Cys), ascorbic acid (AA), and glutathione (GSH)), which can be precisely identified by principal component analysis (PCA). Notably, a distinct fingerprint of a single metabolite with different levels and metabolite mixtures is also achieved with a detection limit of 1 μM. Most importantly, cell lysis could be effectively discriminated by the biosensor assay, implying its great potential in clinical diagnosis.

A chemiluminescence method based on Ce-PA-Tb polymer for rapid determination of difloxacin in aquatic products

Ce-PA-Tb polymer with Ce and Tb as metal ion centers was prepared and applied in chemiluminescence (CL) reaction. The structure and property of Ce-PA-Tb were explored. Ce-PA-Tb combines both the oxidant ion (Ce(IV)) and luminescence ion (Tb(III)). Difloxacin can enhance the CL signal of Ce-PA-Tb-SO32- reaction in acidic medium. Under the optimized affecting factors, a CL method for the selective difloxacin determination was established. The CL intensity showed a good linear relationship from 10.0 to 300.0 μg/L (r = 0.9996) with the limit of detection was 1.1 μg/L. The method with the signal response at 0.5 s and completed the CL process within 10 s. The method was used to determine difloxacin in aquatic products, and the recovery rate was in the range of 88.1%-104.0%. The CL method designed Ce-PA-Tb based is demonstrated to be an excellent tool for difloxacin determination in aquatic products.

Cu/Au nanoclusters with peroxidase-like activity for chemiluminescence detection of α-amylase

Herein, a novel chemiluminescence method was developed for efficient and sensitive detection of α-amylase activity. α-Amylase is closely related to our life, and α-amylase concentration is a marker for the diagnosis of acute pancreatitis. In this paper, Cu/Au nanoclusters with peroxidase-like activity were prepared using starch as a stabilizer. Cu/Au nanoclusters can catalyze H₂O₂ to generate reactive oxygen species and increase the CL signal. The addition of α-amylase makes the starch decompose and causes the nanoclusters to aggregate. The aggregation of the nanoclusters caused them to increase in size and decrease in the peroxidase-like activity, resulting in a decrease in the CL signal. α-Amylase was detected by the CL method of signal changes caused by dispersion-aggregation in the range of 0.05-8 U mL^-1 with a low detection limit of 0.006 U mL^-1. The chemiluminescence scheme based on the luminol-H₂O₂-Cu/Au NC system is of great significance for the sensitive and selective determination of α-amylase in real samples, and the detection time is short. This work provides new ideas for the detection of α-amylase based on the chemiluminescence method and the signal lasts for a long time, which can realize timely detection.