Dual-Loading of Fe₃O₄ and Pd Nanoparticles on g-C₃N₄ Nanosheets Toward a Magnetic Nanoplatform with Enhanced Peroxidase-like Activity for Loading Various Enzymes for Visual Detection of Small Molecules

Abstract

Enzyme mimics now play a significant role in biochemistry. Especially, peroxidase mimics have been widely used for developing colorimetric sensors of blood glucose. The peroxidase mimics previously reported could not be recycled for reusing and may generate scattering to cause unwanted optical interference when it was used for fabricating colorimetric sensors. We herein prepared a broad-applicable and reusable magnetic enzyme-loading nanoplatform with enhanced peroxidase-like activity by simultaneously loading Fe3O4 nanoparticles (Fe3O4NPs) and palladium nanoparticles (PdNPs) on graphitic carbon nitride (g-C3N4) nanosheets (Fe3O4NPs/PdNPs/g-C3N4). The prepared Fe3O4NPs/PdNPs/g-C3N4 possesses stable and enhanced peroxidase-like activity and good enzyme-loading capacity and can be used to load various natural enzymes to form highly-efficient and stable double-active nanozyme for fabricating colorimetric sensors for the visual detection of small molecules. Especially, the magnetic feature facilitates the magnetic separation of Fe3O4NPs/PdNPs/g-C3N4 from sample solution, which is in favor of recycling and eliminating the optical interference caused by nanozyme in colorimetric sensors. The prepared Fe3O4NPs/PdNPs/g-C3N4 has been successfully used to load glucose oxidase (GOx) and cholesterol oxidase (Chox) to form magnetic peroxidase-GOx and peroxidase-Chox double-active nanozymes, which can be used to fabricate colorimetric methods for the detection of glucose and cholesterol, respectively, with a visual detection limit of 15 μM and a spectrometry detection limit of 1.0 μM. With the developed glucose and cholesterol detection methods, we have successfully detected glucose and cholesterol in serum with a recovery of 98–104% and a RSD (n = 5) < 5%. With high peroxidase-like activity, good stability, reusable features, and broad applicability of loading enzyme, the developed magnetic Fe3O4NPs/PdNPs/g-C3N4 provided a promising approach for fabricating cost-effective, sensitive, and simple colorimetric sensors for the visual detection of various small molecules.

Signal Amplification Strategy Design in Nanozyme‐Based Biosensors for Highly Sensitive Detection of Trace Biomarkers

“…In conclusion, the “hybridization” strategy not only improves the dispersion of hybrid nanozymes, and enhances stability, specific surface area, and electron transfer efficiency but also imparts multiple enzyme activities, resulting in a significant boost to catalytic activity. [ 130,145 ] Zhang et al [ 146 ] successfully prepared Fe 3 O 4 NPs/PdNPs/g‐C 3 N 4 by modifying graphite‐like carbon nitride (g‐C 3 N 4 ) NSs with Pd atom to enhance their POD‐like activity. These NSs were then loaded onto magnetic Fe 3 O 4 NPs, exhibiting enhanced POD‐like activity and facilitating the recovery and elimination of colorimetric optical interference in the sensor.…”

“…Reproduced with permission. [ 146 ] Copyright 2023, American Chemical Society. B) Schematic Illustration of Fe 3 O 4 @MOF@Pt‐Immunolabeled Lateral Flow Immunoassay.…”

Gold nanoparticle-loaded MoS2 nanosheets with peroxidase-like and pyranose oxidase-like activities for bio-enzyme-free visual detection of glucose, xylose and galactose

“…Natural enzymes play a key role in biochemistry because they can catalyse various biochemical reactions with high specificity and activity under mild conditions. 1 However, the intrinsic drawbacks of natural enzymes, such as thermal instability, a higher cost of preparation/purification and limited natural sources, restrict their practical application. 2 Compared with natural enzymes, artificial enzyme mimics, especially catalytically active nanomaterials (known as nanozymes), possess intrinsic advantages such as a lower cost of preparation, better thermal stability, tunable catalytic activity, and similar or higher catalytic activity and specificity.…”

Enhancement of the Peroxidase Activity of g-C3N4 with Different Morphologies for Simultaneous Detection of Multiple Antibiotics

“…Nanozymes, as potential substitutes for natural enzymes, are being widely developed due to their advantages of low cost, strong stability, excellent designability, etc. − Among them, g-C 3 N 4 has been successfully used as an excellent peroxide-like enzyme for the detection of glucose, H 2 O 2 , uric acid, and other small molecules and has been generally proven to have stronger activity than horseradish peroxidase. − More importantly, the different layer plane dimensions and interlayer stacking degree of g-C 3 N 4 directly affect its active site density and band gap changes, leading to differences in its peroxidase activity and fluorescence performance, making it a potential material for constructing sensor arrays. However, because these differences are not obvious, the differences in response signals to different antibiotics, especially similar forms of the same antibiotic, are not significant enough, resulting in low detection sensitivity of the array.…”