Fluorometric detection of phytase enzyme activity and phosphate ion based on gelatin supported silver nanoclusters

Smart modulation by bifunctional probes PNAI@Co3O4/Au NPs of the light/electric response of Au-Ag NCs to realize the dual-channel precise detection of AOH

Mycotoxin contamination currently poses a significant concern and presents a major challenge to global food safety management. In this research, gold‑silver nanoclusters (Au-AgNCs) were utilized as platforms for electrogenerated chemiluminescence (ECL) and electrochemical (EC) responses, while polyaniline-coated cobalt tetraoxide and gold (PANI@Co3O4/AuNPs) served as bifunctional probes with intelligently modulated light/electric signals to develop a dual mode adaptor sensor for sensitive detection of alternariol (AOH). The sensor's benefits are evident in three areas:(1) Bandgap modulation allows Au-Ag to exhibit enhanced light/electric response;(2) PANI@Co3O4/AuNPs exhibit both ECL quenching effects and the capability to activate KHSO5, along with improved electrical conductivity, which collectively improves the sensor's detection performance;(3) The dual-channel signal outputs significantly reduce the risk of false detections. Testing results indicated that the ECL and EC sensors performed exceptionally well across AOH concentration ranges of 0.001-100 ng/mL and 0.01-1000 ng/mL, with detection limit of 0.803 pg/mL and 0.378 pg/mL, respectively.

Few-layered boron nitride nanosheet as a non-metallic phosphatase nanozyme and its application in human urine phosphorus detection

Human urine phosphorus (existing in the form of phosphate) is a biomarker for the diagnosis of several diseases such as kidney disease, hyperthyroidism, and rickets. Therefore, the selective detection of phosphate in urine samples is crucial in the field of clinical diagnosis. Herein, we reported the phosphatase-like catalytic activity of few-layered h-BNNS for the first time. As the phosphatase-like activity of few-layered h-BNNS could be effectively inhibited by phosphate, a selective fluorescent method for the detection of phosphate was proposed. The linear range for phosphate detection is 0.5-10 µM with a detection limit of 0.33 µM. The fluorescent method was then explored for the detection of human urine phosphorus in real samples. The results obtained by the proposed method were consistent with those of the traditional method, indicating that the present method has potential application for urine phosphorus detection in clinical disease diagnosis.

Two Novel Fluorescence Probes Based on Caffeic Acid Derivative for Phosphate Ions and Their Applications in Biological Samples

Phosphate is widely used in industry and agriculture fields. However, excess accumulation of PO43- causes several adverse effects on the human body and ecological environment. Consequently, it is important to develop a simple method for the detection of PO43- concentration in the ecological environment and in vivo. Herein, two caffeic acid derivative-based fluorescence probes (BAM-HM and BAM-HH) were developed for the detection of phosphate. The BAM-HM probe could detect phosphate via fluorescence enhancement at 500 nm, with the detection limit being 0.612 µM. Meanwhile, the BAM-HH probe showed a significant turn-on signal at 450 nm after the addition of phosphate, and the detection limit was calculated to be 0.318 µM. The sensing mechanism was determined by 1H NMR and MS. Furthermore, the two probes (BAM-HM and BAM-HH) were applied for PO43-detection in living cells and water samples.

4,5-Diamino-2-Thiouracil-Powered Dual-Mode Biosensor for Sensitive, Nonenzymatic Determination of Saliva Uric Acid Levels

Nonenzymatic and rapid monitoring of uric acid levels is of great value for early diagnosis, prevention, and management of oxidative stress-associated diseases. However, fast, convenient, and low-cost uric acid detection remains challenging, especially in resource-limited settings. In this study, a novel and rapid biosensing approach was developed for the simultaneous visualization and quantification of uric acid levels by using the unique surface plasmon resonance and photothermal property of 4,5-diamino-2-thiouracil (DT)-capped gold nanoparticles (AuNPs). With the presence of uric acid, DT-capped AuNPs rapidly aggregated, and a visible color/photothermal change was used for uric acid quantification within 15 min. The limit of detection was determined to be 11.3 and 6.6 μM for the dual-mode biosensor, leveraging the unique structure of DT to optimize reaction kinetics. Moreover, the sensor exhibited excellent anti-interference capabilities and demonstrated potential for detecting a wide range of uric acid concentrations in complex samples, thereby reducing the need for extensive sample dilution and complex material synthesis procedures. Furthermore, validation against gold standard testing indicates that this biosensor could serve as a highly sensitive assay for quantifying uric acid levels in point-of-care applications, particularly in resource-limited settings.

Development and validation of colorimetric-assisted chemometrics methods based on the localized gold nanoparticles surface plasmon resonance for fast simultaneous estimation of anti-hepatitis C virus drugs in their combined dosage form: A comparative study with HPLC method

The present work describes a developed analytical method based on a colorimetric assay using gold nanoparticles (AuNPs) along with chemometric techniques for the simultaneous estimation of sofosbuvir (SOF) and ledipasvir (LED) in their synthetic mixtures and tablet dosage form. The applied chemometric approaches were continuous wavelet transform (CWT) and least squares support vector machine (LS-SVM). Characterization of AuNPs and AuNPs in combination with the drug was performed by UV-vis spectrophotometer, transmission electron microscopy (TEM), dynamic light scattering (DLS), and Fourier transform infrared (FTIR) spectroscopy. In the CWT method, the zero amplitudes were determined at 427 nm with Daubechies wavelet family for SOF (zero crossing point of LED) and 440 nm with Symlet wavelet family for LED (zero crossing point of SOF) over the concentration range of 7.5-90.0 μg/L and 40.0-100.0 μg/L with coefficients of determination (R2) of 0.9974 and 0.9907 for SOF and LED, respectively. The limit of detection (LOD) and limit of quantification (LOQ) of this method were found to be 7.92, 9.96 μg/L and 12.02, 30.2 μg/L for SOF and LED, respectively. In the LS-SVM model, the mean percentage recovery of SOF and LED in synthetic mixtures was 98.29 % and 99.25 % with root mean square error of 2.392 and 1.034, which were obtained by the optimization of regularization parameter (γ) and width of the function (σ) based on the cross-validation method. The proposed methods were also applied for the determination concentration of SOF and LED in the combined dosage form, recoveries were higher than 95 %, and relative standard deviation (RSD) values were lower than 0.4 %. The achieved results were statistically compared with those obtained from the high-performance liquid chromatography (HPLC) technique for the concurrent estimation of components through one-way analysis of variance (ANOVA), and no significant difference was found between the suggested approaches and the reference one. According to these results, simplicity, high speed, lack of time-consuming process, and cost savings are considerable benefits of colorimetry along with chemometrics methods compared to other ways.

Fluorescent ratiometric supramolecular tandem assays for phosphatase and phytase enzymes

Ratiometric fluorescent assays have a built-in correction factor which enhances assay accuracy and reliability. We have developed fluorescent ratiometric supramolecular tandem assays for phosphatase and phytase enzymes using a mixture of three molecular components. One of the molecules is a tetra-cationic fluorescence quencher called CalixPyr which can bind and quench the polyanionic pyrene fluorophore, CMP, that emits at 430 nm. Polyphosphates can disrupt the CMP/CalixPyr complex and alter the fluorescence intensity (responsive signal). CalixPyr has no effect on the fluorescence emission of cationic pentamethine cyanine fluorophore, cCy5, which emits at 665 nm and acts as a non-responsive reference signal. The continuous ratiometric fluorescent assay for alkaline phosphatase monitored hydrolytic consumption of adenosine triphosphate (ATP). The continuous ratiometric fluorescent assay for phytase activity monitored hydrolytic consumption of phytate. With further development this latter assay may be useful for high throughput assessment of phytase activity in individual batches of fortified animal feed. It is likely that the three-molecule mixture (CMP, CalixPyr, cCy5) can become a general assay platform for other enzymes that catalyse addition/removal of phosphate groups from appropriate molecular substrates.

Ratiometric fluorescent detection of total phosphates in frozen shrimp samples using catalytic active Zr(IV) modified gold nanoclusters

Phosphate salts are important food additives in a variety of foods. In this study, the Zr(IV) modified gold nanoclusters (Au NCs) were prepared for ratiometric fluorescent sensing of phosphate additives in seafood samples. Compared with bare Au NCs, the synthesized Zr(IV)/Au NCs showed stronger orange fluorescence at 610 nm. On the other hand, the Zr(IV)/Au NCs retained the phosphatase-like activity of Zr(IV) ions and could catalyze the hydrolysis of fluorescent substrate 4-methylumbelliferyl phosphate to produce blue emission at 450 nm. The addition of phosphate salts could effectively inhibit the catalytic activity of Zr(IV)/Au NCs, resulting the fluorescence decrease at 450 nm. However, the fluorescence at 610 nm almost unchanged upon the addition of phosphates. Based on this finding, the ratiometric detection of phosphates using the fluorescence intensity ratio (I₄₅₀/I₆₁₀) was demonstrated. The method has been further applied for sensing total phosphates in frozen shrimp samples with satisfactory results.

Simultaneous electrochemical detection of multiple heavy metal ions in milk based on silica-modified magnetic nanoparticles

A sensitive and simple analytical method integrated with Fe₃O₄@SiO₂-based extraction with direct electrochemical detection was applied to individually and simultaneously analyze heavy metal ions, including Cd²⁺, Pb²⁺, Cu²⁺, and Hg²⁺. The Fe₃O₄@SiO₂-based electrochemical sensor was developed through the mixture of heavy metal ions with Fe₃O₄@SiO₂ after alkali treatment, which was modified onto the working electrode surface. The Fe₃O₄@SiO₂ with negative charges after alkali treatment could easily interact with heavy metal ions with positive charges by electrostatic force. Under the optimized conditions, the developed analytical method could be applied to individually and simultaneously detect heavy metal ions with good sensitivity. The detection limits were all in the nanomolar range, and the recoveries ranged from 96.0 to 104.3% for heavy metal ions in milk. Therefore, the proposed analytical method exhibited great potential for quantitatively analyzing multiple heavy metal ions in milk.