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Background: Hydrogen peroxide (H 2 O 2 ) is an important reactive oxygen species (ROS) molecule involved in cell metabolism regulation, transcriptional regulation, and cytoskeleton remodeling. Real-time monitoring of H 2 O 2 levels in live cells is of great significance for disease prevention and diagnosis., Results: We utilized carbon cloth (CC) as the substrate material and employed a single-atom catalysis strategy to prepare a flexible self-supported sensing platform for the real-time detection of H 2 O 2 secreted by live cells. By adjusting the coordination structure of single-atom sites through P and S doping, a cobalt single-atom nanoenzyme Co-NC/PS with excellent peroxidase-like activity was obtained. Furthermore, we explored the enzyme kinetics and possible catalytic mechanism of Co-NC/PS. Due to the excellent flexibility, high conductivity, strong adsorption performance of carbon cloth, and the introduction of non-metallic atom-doped active sites, the developed Co-NC/PS@CC exhibited ideal sensing performance. Experimental results showed that the linear response range for H 2 O 2 was 1-17328 μM, with a detection limit (LOD) of 0.1687 μM. Additionally, the sensor demonstrated good reproducibility, repeatability, anti-interference, and stability., Significance: The Co-NC/PS@CC prepared in this study has been successfully applied for detecting H 2 O 2 secreted by MCF-7 live cells, expanding the application of single-atom nanoenzymes in live cell biosensing, with significant implications for health monitoring and clinical diagnostics., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Efficient catalytic decomposition of H 2 O 2 is accompanied by electron transfer through Fe-N x active sites of hemin in the human body. Inspired by this reaction process, the Fe SAs/Co CNs were successfully synthesized by combined Co atomic sites with nitrogen-carbon doped Fe single-atom active sites (SAs). The synergy between transition metals not only reduces agglomeration during synthesis but also improves its own electrical conductivity due to the interaction between Fe and Co that promotes the formation of graphite surface. Crucially, the synergistic effect of the Co site significantly enhanced the peroxidase activity of the Fe SAs and the reaction rate of the Fenton-like reaction, resulting in an efficient detection of H 2 O 2 . Catalytic kinetic calculations and enzymatic kinetic calculations were used to verify the electron transfer rate and catalytic performance of their constructed electrochemical sensing interfaces. The results showed that Fe SAs/Co CNs@GCE showed better detection performance than Fe SAs CNs@GCE. It was applied successfully to detect H 2 O 2 released from cells in real-time as well. The linear detection range of Fe SAs/Co CNs@GCE for H 2 O 2 was 1-16664 μM, and the detection limit was as low as 0.25 μM. Furthermore, an electrochemical sensing chip was constructed using Fe SAs/Co CNs@SPE and the prepared microfluidic channel. The constructed portable FeSAs/Co CNs@SPE had a linear range of 1-400 μM and a detection limit of 0.36 μM and achieved the recovery detection of H 2 O 2 in serum. The electrochemical sensing interfaces constructed based on Fe SAs/Co CNs all have efficient catalytic performance and excellent real-time hydrogen peroxide detection performance, which have practical application potential for human oxidative stress level detection. And it provides a novel approach to the trace detection of bioactive small molecules., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

A properly designed sensing interface is crucial for the accurate and sensitive detection of biologically active molecules. Single-atom nanozymes from transition metal and nitrogen-doped carbon materials (M-N-C) have caught attention owing to their large surface area and strong bionic enzyme activity. Herein, a three-dimensional layered electrochemical electrode consisting of a Co-N-C nanoenzyme embedded in a reduced graphene oxide aerogel was prepared for the detection of hydrogen peroxide (H 2 O 2 ), dopamine (DA) and uric acid (UA). Due to its unique three-dimensional layered structure, rGA has excellent electrical conductivity and high material loading and is used to enhance the electrocatalytic performance of Co-N-C. The combination of single-atom nanozymes and electrochemical detection shows unique advantages in catalytic activity and selectivity. The limit of detection and detection range are 0.74 μM and 3-2991 μM respectively for H 2 O 2. Furthermore, it has been successfully implemented for the in-situ detection of H 2 O 2 in living cells. In addition, their simultaneous detection is also realized by the sensors for DA and UA. And it can accurately capture the signal of UA and DA in the urine. Meanwhile, the electrode displays satisfactory stability and repeatability. Therefore, this paper provides a new detection strategy for a variety of bioactive molecules, showing great potential in cell biology, pathophysiology and diagnostics., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Excessive accumulation of hydrogen peroxide (H2O2) in the physiological pool can cause oxidative stress of cells and eventually lead to the occurrence of diseases. Therefore, accurate and real-time detection of H2O2 is of great significance for disease detection and prevention. In this study, an Fe single-atom nanozyme (Fe-SNC) with an Fe-N4 active center was synthesized, which showed excellent peroxidase-like activity in an acidic environment and amazing electrocatalytic activity in H2O2 reduction reaction. Based on this, we proposed a colorimetric and electrochemical dual-signal detection strategy to real-time monitor H2O2 secreted by living cells. Compared with single-signal response mode, double-signal response mode has higher precision and sensitivity. The results show that the detection range of the colorimetric analysis method is 3–1000 μM and the detection limit is 1.3 μM. The detection range of the electrochemical analysis method is 1–8127 μM, and the detection limit is 0.61 μM. We believe that the dual-signal detection strategy based on Fe-SNC not only provides a way for the ultra-sensitive detection of hydrogen peroxide but also has a broad application prospect in clinical diagnosis. [ABSTRACT FROM AUTHOR]

Herein, a novel hemin functionalized hybrid aerogel (He@GMA) is synthesized and applied to an electrochemical chip for real-time analysis of hydrogen peroxide (H2O2). The He@GMA shows a typical three-dimensional morphology and excellent peroxidase-like catalytic performance. The He@GMA-enabled electrochemical chip presents satisfactory performance for H2O2 sensing with a low limit of detection (0.96 μM). Besides, the chip platform shows some advantages of less sample consumption and easier detection operation. [ABSTRACT FROM AUTHOR]

Reasonable sensor construction for precisely real-time detecting H2O2 produced from living cells has always been of great significance and challenges. Due to the excellent catalytic efficiency and unparalleled peroxidase-like activity, single-atomic catalysts with Fe-Nx active sites show great potential in H2O2 detection. These special atomic active sites make it easier for the Fenton reaction to occur, which provides basic support for H2O2 sensors. Their application in the in situ real-time detection of H2O2 has important market prospects. Herein, single-atomic Fe catalysts with distorted graphitic carbon are obtained through a simpler preparation method. A precursor hemin@zeolitic imidazolate framework-8 (hemin@ZIF-8) is calcined at a high temperature and carbonized to get the nitrogen-carbon codoped Fe single atoms (Fe SAs-N/C) and then successfully prepare a H2O2 electrochemical sensor by modifying it on a glassy carbon electrode (GCE). Its peroxidase activity is calculated by enzymatic kinetics, which shows a better peroxidase activity compared with horseradish peroxidase and other reported single-atom (SA) materials. Moreover, the electrocatalytic kinetics is explained by Laviron calculation, which more directly confirms that it has a faster electron transfer rate. Importantly, Fe SAs-N/C@GCE has a wider linear range than sensors combined with other SA materials and a low detection limit of 0.34 μM. It is an attractive design of H2O2 sensors and single-atomic catalysts with superior substrate affinity that are novel alternatives to natural enzymes. [ABSTRACT FROM AUTHOR]

Herein, a novel hemin functionalized hybrid aerogel (He@GMA) is synthesized and applied to an electrochemical chip for real-time analysis of hydrogen peroxide (H2O2). The He@GMA shows a typical three-dimensional morphology and excellent peroxidase-like catalytic performance. The He@GMA-enabled electrochemical chip presents satisfactory performance for H2O2 sensing with a low limit of detection (0.96 μM). Besides, the chip platform shows some advantages of less sample consumption and easier detection operation. [ABSTRACT FROM AUTHOR]