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Lysophosphatidylcholine (LPC) can be used as a biomarker for diseases such as cancer, diabetes, atherosclerosis, and sepsis. In this study, we demonstrated the ability of nanozymes to displace the natural derived enzyme in enzyme-based assays for the measurement of LPC. Synthesized polyvinylpyrrolidone-stabilized platinum–ruthenium nanozymes (PVP/PtRu NZs) had a uniform size of 2.48 ± 0.24 nm and superb peroxidase-mimicking activity. We demonstrated that the nanozymes had high activity over a wide pH and temperature range and high stability after long-term storage. The LPC concentration could be accurately analyzed through the absorbance and fluorescence signals generated by the peroxidation reaction using the synthesized nanozyme with substrates such as 3,3′,5,5′-tetramethylbenzidine (TMB) and 10-acetyl-3,7-dihydroxyphenoxazine (Ampliflu™ Red). LPC at a concentration of 0–400 µM was used for the analysis, and the coefficient of determination (R2) was 0.977, and the limit of detection (LOD) was 23.1 µM by colorimetric assay. In the fluorometric assay, the R2 was 0.999, and the LOD was 8.97 µM. The spiked recovery values for the determination of LPC concentration in human serum samples were 102–115%. Based on these results, we declared that PVP/PtRu NZs had an ability comparable to that of the native enzyme horseradish peroxidase (HRP) in the enzyme-based LPC detection method. [ABSTRACT FROM AUTHOR]

Artificial enzymes have attracted considerable attention because of their significant advantages over natural enzymes. Herein, the authors report a simple hydrothermal strategy for producing a bimetallic metal — N‐, S‐doped carbon (NS‐C@PtRu) hybrid derived from L‐cysteine‐mediated self‐assembly of PtRu. The peroxidase‐like activity and colloidal stability of the NS‐C@PtRu are tuned by varying the amount of L‐cysteine, the source material for the N‐, S‐doped carbon. The NS‐C@PtRu exhibits good dispersibility, synergistic interactions (metal–metal, metal–carbon), non‐metal (N, S) doping, more catalytic active sites, improved noble metallic catalyst performance, and high utilization efficiency. As an excellent peroxidase mimic, NS‐C@PtRu catalyzes the oxidation of 3,3′,5′,5′‐tetramethylbenzidine (TMB), and Amplex Red (AR) substrates, producing colorimetric and fluorometric signals that offer efficient detection of H2O2. Furthermore, colorimetric and fluorometric cholesterol detection is proposed by combining cholesterol oxidase‐catalyzed cholesterol oxidation with NS‐C@PtRu‐catalyzed TMB/AR oxidation. The fluorometric cholesterol sensor exhibited a lower limit of detection of 1.4 µmol L−1 and rapid response, whereas the colorimetric sensor exhibited a wide detection range of 0.1–6 mmol L−1 and colorimetric changes that can be seen with the naked eyes. Both sensing methods demonstrated excellent selectivity and recovery in determining cholesterol in spiked human serum samples. [ABSTRACT FROM AUTHOR]

The development of efficient and sensitive point-of-care testing is crucial for preparedness in the post-pandemic era. Although paper-based lateral flow assays have attracted attention and have various advantages for rapid, on-site diagnosis, they have low sensitivity. To overcome the limitations of the existing assays, in this study, we aimed to develop a new, one-step, nanozyme-amplified SlipChip for the sensitive detection of C-reactive protein (CRP). The SlipChip was constructed by combining wax-printed paper with different channel designs. The three-dimensional (3D) fluidic configuration of the SlipChip allowed for the sequential delivery of reagents, enabling mixing and signal amplification with a one-step sliding operation. As a signal-amplifying reagent, peroxidase-mimicking porous platinum nanozyme (pPtNZ) was synthesized using a simple wet chemical method. The pPtNZ conjugated on the test line catalyzes the oxidation of diaminobenzidine (DAB) in the presence of hydrogen peroxide, increasing the color intensity. The immunoassay results of the SlipChip were easily interpreted within 20 min, and the color intensity was visually enhanced by DAB precipitation over time, resulting in up to 6-fold signal amplification. The proposed pPtNZ-SlipChip exhibited high analytical performances for the one-step detection of serum and salivary CRP from 0.1 to 1000 ng/mL, with a limit of detection of 0.03 ng/mL. These results revealed the potential and applicability of the pPtNZ-SlipChip, with the advantages of simplicity, sensitivity, low cost, and portability for on-site detection and point-of-care testing. [ABSTRACT FROM AUTHOR]

We synthesized a poly acrylic acid‐coated nanoceria (PNC) and developed colorimetric and electrochemical methods for determining norepinephrine (NE) using 3,3′‐5,5′‐tetramethylbenzidine (TMB) as a redox marker. The PNC was the nanozyme, an oxidase mimic with effective catalytic activity. During the reaction, PNC oxidized the TMB (TMBox) in the absence of hydrogen peroxide. The product not only showed visible color change from transparent to blue, but also generated an electrochemical current. NE reduced the TMBox, and the color changed from blue back to colorless. As a result, we were able to determine the NE concentration using both colorimetric and electrochemical methods. The colorimetric determination showed a linearity from 0.2 to 19 μM, with an estimated detection limit of 126 nM. For point‐of‐care applications, NE concentration was also detected on paper‐based devices. NE was detected from 1.0 to 25 μM with the detection limit of 863 nM. For electrochemical detection, gold nanoparticles were deposited on indium tin oxide glass as the working electrode. NE ranged from 0.1 to 300 μM, with an estimated detection limit of 66 nM, which was lower than for the colorimetric methods. Spike recovery values for NE in human plasma samples ranged from 93.4 to 108 %. These results demonstrate that using PNC nanozymes for electrochemical detection is a promising assay to determine NE. [ABSTRACT FROM AUTHOR]

[Display omitted] • Polyvinylpyrrolidone (PVP) was used to enhance the dispersity and homogeneity of bimetallic nanozymes. • PVP-stabilized PtRu nanozymes (PVP/PtRu NZs) exhibited excellent peroxidase-mimic activity. • Cascade reaction of glucose oxidase and PVP/PtRu NZs was used for colorimetric and fluorometric glucose detection. • Glucose recovery test using human serum and artificial urine showed excellent recovery values. Nanozymes have significant advantages over natural enzymes. The intrinsic peroxidase-like activity of Pt-based nanomaterials can be enhanced by alloying with other transition metals, such as Ru, that have great catalytic activity. In this study, we used polyvinylpyrrolidone (PVP) to synthesize well-dispersed and homogeneous nanostructures. PVP-stabilized Pt-Ru nanozymes (PVP/PtRu NZs) were synthesized and characterized. The PVP/PtRu NZs had an average size of 3.54 ± 0.84 nm and exhibited an intense peroxidase-like activity. The PVP/PtRu NZs were used as peroxidase mimics for colorimetric and fluorometric glucose determination by the glucose oxidase and PVP/PtRu NZs cascade reaction. In the colorimetric assay, the linearly detectable range was 0.25–3.0 mM, with an R2 and limit of detection (LOD) of 0.988 and 138 μM, respectively. In the fluorometric assay, a linear relationship was found when the glucose concentration was between 5.0 and 300 μM (R2 = 0.997), with an LOD of 1.11 μM. Compared to the colorimetric assay, the fluorometric assay had greater sensitivity and a lower detection limit for the determination of glucose. Moreover, the PVP/PtRu NZs had high storage stability over a month and great recovery values in human serum and artificial urine, with a range of 94–106 %. From these results, PVP/PtRu NZs are expected to be used as promising peroxidase mimics in various fields such as biosensing, pharmaceutical processing, and the food industry. [ABSTRACT FROM AUTHOR]