Determination of lysophosphatidylcholine using peroxidase-mimic PVP/PtRu nanozyme.

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.

Mesoporous platinum nanoparticles as a peroxidase mimic for the highly sensitive determination of C-reactive protein.

The generation of a mesoporous structure in platinum nanoparticles can effectively enhance physical and chemical properties. In this study, mesoporous platinum nanoparticles (MPNs) were synthesized by a soft template-mediated one-pot chemical method. To develop a mesoporous structure, Pluronic F-127 was employed. The Pluronic F-127 surfactant forms self-assembled micelles, and the micelles act as the pore-directing agents in the synthesis of nanoparticles. Scanning electron microscopy results revealed that the MPN had a uniform size of 70 nm on average and a distinct mesoporous structure. The development of a concave mesoporous structure on the surface of the MPNs can increase the surface area and facilitate the efficient transport of reactants. The synthesized MPNs exhibited peroxidase-like activity. Furthermore, the MPNs showed excellent catalytic efficiency compared to HRP, due to the high surface area derived from the presence of the mesoporous structure. The peroxidase-like MPNs were applied to the enzyme-linked immunosorbent assay (ELISA) of C-reactive protein (CRP). The MPN-based ELISA exhibited sensitive CRP detection in the range from 0.24 to 7.8 ng/mL with a detection limit of 0.13 ng/mL. Moreover, the recoveries of the CRP concentrations in spiked human serum were 98.6% and 102%. These results demonstrate that as a peroxidase mimic, the MPNs can replace the natural enzymes in conventional ELISA for sensitive CRP detection.

PVP-stabilized PtRu nanozymes with peroxidase-like activity and its application for colorimetric and fluorometric glucose detection.

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 ±â€¯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.

Determination of glycated albumin using a Prussian blue nanozyme-based boronate affinity sandwich assay.

Nanozymes are effective substitutes for natural enzymes and offer multiple advantages. Here, synthesized Prussian blue nanoparticles (PBNPs) exhibited excellent peroxidase-like activity, catalyzing the oxidation of 3,5,3',5'-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide within 1 min. Oxidized TMB (TMBox) underwent a color change from transparent to blue and then yellow by a stop solution. Moreover, the TMBox could be reduced on an indium tin oxide electrode, generating an electrochemical current, indicating that TMB can be used as a colorimetric and electrochemical indicator. The PBNPs modified with 3-aminophenylboronic acid (APBA) captured glycated albumin (GA) with a boronate affinity sandwich assay. As boronic acid binds to glycoproteins using cis-diol bonding, it can be used to detect GA. The APBA-modified PBNPs (PBBA) were involved with a sandwich complex formation and employed as nanozymes for the quantitative analysis of GA using colorimetric and electrochemical methods. Both methods showed strong linearities for different concentrations of GA. The results show that PBBA is a suitable alternative for natural enzymes and can be applied to sensitive determination of GA.

Electrochemical Immunoassay for Determination of Glycated Albumin using Nanozymes.

We developed a new nanozyme-based electrochemical immunoassay method for the monitoring of glycated albumin (GA) known to reflect short-term glycaemic levels. For this study, we synthesized urchin-like Pt nanozymes (uPtNZs) and applied them to colorimetric and electrochemical assays for sensitive determination of GA in total human serum albumin (tHSA) using 3,3',5,5'-tetramethylbenzidine (TMB) and thionine as substrates, respectively. The uPtNZs showed peroxidase-mimic activity in the presence of hydrogen peroxide. Boronic acid (BA)-agarose bead was used to capture GA through specific cis-diol interactions. uPtNZs were modified with GA antibody (GA-Ab) to form sandwich complexes with GA/BA-agarose bead. The amount of Ab-uPtNZ/GA/BA-agarose bead complex increased with increasing percentage of GA in 50 mg/mL tHSA. The colorimetric assay exhibited linearity from 0.02 to 10% (10 µg/mL - 5 mg/mL) GA with an LOD of 0.02% (9.2 µg/mL). For electrochemical assay, GA was detected from 0.01 to 20% (5 µg/mL - 10 mg/mL) with an LOD of 0.008% (3.8 µg/mL). The recovery values of measured GA in human plasma samples were from 106 to 107%. These results indicate that electrochemical assay using uPtNZs is a promising method for determining GA.