Search

Here we present a new method to fabricate enzyme-mimic metal-free catalysts for electrochemical detection of superoxide anion (O 2 •- ) by introducing phosphate groups into graphene-based foam. Through a template-free hydrothermal process, graphene oxide (GO) was treated with different amount of phytic acid (PA) to obtain 3D porous graphene-based foam (PAGF). Characterizations demonstrate that phosphate groups were successfully modified on the surface and inter layer structure of PAGF materials and the defects and disorder degree of PAGF could be controlled by adjusting the addition of PA precursors. Meanwhile, the synthesized PAGF was successfully immobilized on screen printed carbon electrodes (SPCEs) and employed in O 2 •- detection. With PA treated on graphene structure, the resulted PAGF/SPCEs exhibit distinct characteristic redox peaks, showing enzyme-mimic catalytic activity toward O 2 •- dismutation. Also, the amount of modified phosphate groups has caused a considerable variety on the performance of PAGF-based electrodes. Apart from high sensitivity, wide liner range, low detection limit, good selectivity and long-term stability, our sensors also present satisfying performance in the real-time monitoring of drug-induced O 2 •- released from Hela cells. The reliability of the biological measurement was further demonstrated via electron paramagnetic resonance (EPR) to characterize the released O 2 •- from stimulated cells by using 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPOL) to trap the transient O 2 •- . The above results indicate that our established sensors hold potential application in the real-time detection of O 2 •- in biological samples., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Quantification of superoxide anions (O 2 •- ) is significant in the monitoring of many serious diseases and the design of enzyme-mimic catalysts plays the main role in the development of non-enzymatic O 2 •- sensors. Herein, we proposed a facile self-assembly process to synthesize manganese phosphate modified carbon networks using three kinds of widely-used carbon materials (MWCNTs, NGS and GO) as pillar connectors. Characterizations demonstrate that manganese phosphate is widely dispersed inside and on the surface of carbon networks without visible morphology. Meanwhile, all three kinds of synthesized catalysts were successfully immobilized on the screen-printed carbon electrodes to evaluate the electrochemical performance of fabricated sensors. The results indicate that sensors based on Mn x (PO 4 ) y modified MWCNTs exhibit high sensitivity with an extremely low detection limit of 0.127μM (S/N = 3) and a wide liner range of 0-1.817mM (R 2 = 0.998). We further employed the recommended sensors in the real-time monitoring of HepG2 cells released O 2 •- under the stimulating of Zymosan (20mg/mL). Noticeably, the proposed sensors exhibit not only sensitive response but also stable current steps upon different addition of Zymosan. The calculated concentrations of cell-released O 2 •- vary from 6.772 to 24.652pM cell -1 for the Zymosan amount used in this work. The established novel sensors display low background current and signal noises, thus holding unique advantages in the trace analysis of O 2 •- in biological samples and in vivo environment., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Considering the critical roles of superoxide anion (O2(∙-)) in pathological conditions, it is of great urgency to establish a reliable and durable approach for real-time determination of O2(∙-). In this study, we propose a porous Pt-Pd decorated superoxide dismutase (SOD) sensor for qualitative and quantitative detection O2(∙-). The developed biosensor exhibits a fast, selective and linear amperometric response upon O2(∙-) in the concentration scope of 16 to 1,536 μM (R(2)=0.9941), with a detection limit of 0.13 μM (S/N=3) and a low Michaelis-Menten constant of 1.37 μM which indicating a high enzymatic activity and affinity to O2(∙-). Inspiringly, the proposed sensor possesses an ultrahigh sensitivity of 1270 μA mM(-1)cm(-2). In addition, SOD/porous Pt-Pd sensor exhibits excellent anti-interference property, reproducibility and long-term storage stability. Beyond our expectation, the trace level of O2(∙-) released from living cells has also been successfully captured. These satisfactory results are mainly ascribed to (1) the porous interface with larger surface area and more active sites to provide a biocompatible environment for SOD (2) the specific biocatalysis of SOD towards O2(∙-) and (3) porous Pt-Pd nanomaterials fastening the electron transfer. The superior electrochemical performance makes SOD/porous Pt-Pd sensor a promising candidate for monitoring the dynamic changes of O2(∙-)in vivo., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Abstract Quantification of superoxide anions (O 2 −) is of great significance for the pathological research of many diseases. In this work, a non-enzymatic electrochemical sensor for superoxide sensing was fabricated on the basis of metal-organic frameworks (MOFs)-derived porous carbon matrix loaded with Pt and Co nanoparticles (denoted as Pt-Co-PC). Zeolitic imidazolate framework-67 (ZIF-67) was utilized as the precursor through a one-step calcination under N 2 atmosphere to prepare cobalt nanoparticles-porous carbon composites (denoted as Co-PC). Pt-Co-PC was then obtained by using a facile galvanic replacement procedure with Co-PC and chloroplatinic acid solution. Furthermore, the home-made screen printed gold electrodes (SPGEs) were used to immobilize the as-synthesized materials, constructing Pt-Co-PC modified electrochemical sensors. The recommended Pt-Co-PC/SPGE sensors exhibit excellent electrochemical performance for the detection of O 2 − with an extremely low detection limit of 0.118 μM (S/N = 3) and a high sensitivity of 6.218 × 10−4 mA μM−1 cm−2. Meanwhile, the proposed sensors possess superior reproducibility and stability. More importantly, our sensors have successfully captured the electrochemical signals of O 2 − released from Hela cells, which means the fabricated sensors have potential application of monitoring O 2 − in pathological and biological fields. Highlights • A facile method to fabricate porous carbon matrix loaded with Pt and Co nanoparticles. • A novel non-enzymatic O 2 − sensor was established. • The recommended sensors can successfully capture the electrochemical signals of O 2 − released from Hela cells. [ABSTRACT FROM AUTHOR]

In this work, a highly sensitive enzyme- and metal-free electrochemical method for superoxide anion (O 2 − ) detection has been developed by employing screen-printed carbon electrodes (SPCE) modified by nitrogen doped hollow mesoporous carbon spheres (N-HMCS). For comparison, solid carbon spheres (SCS) and hollow mesoporous carbon spheres (HMCS) were also synthesized to fabricate the modified SPCE. Compared with SCS/SPCE and HMCS/SPCE, N-HMCS/SPCE displayed a higher electrochemical performance. When applied for electrochemical detection of O 2 − , N-HMCS/SPCE exhibited a high sensitivity of 1.49 μA cm −2 μM −1 , better than SCS/SPCE and HMCS/SPCE and many of enzyme- or metal-based superoxide anion sensors. N-HMCS is expected to become a new generation of sensing materials for electrochemical analysis of O 2 − . [ABSTRACT FROM AUTHOR]

Considering the double-sided roles of superoxide anion radical, monitoring of its track in living systems is attracting increasing academic and practical interest. Here we synthesized Prussian Blue (PB) cubes that were supported on nitrogen-doped graphene sheets (NGS) using a facile and scalable method, and explored their potential utilization in the electrochemical sensing of superoxide anion. As an efficient superoxide dismutase mimic, direct electron transfer of the prepared PB-NGS hybrid immobilized on a screen-printed gold electrode was harvested in physiological media. With the bifunctional activities, the synthetic mimic could catalyze the dismutation of superoxide anion via the redox cycle of active iron. By capturing the electro-reduction amperometric responses of superoxide anion radical to hydrogen peroxide in the cathodic polarization, highly sensitive determination (a sensitivity of as high as 0.32 μA cm −2 μM −1 ) of the target was achieved, with no interference from common coexisting species including ascorbic acid, dopamine, and uric acid observed. Compared to natural superoxide dismutases, the artificial enzyme mimic exhibited favorable activity stability, indicating its promising applications in the in vivo long-term monitoring of superoxide anion. [ABSTRACT FROM AUTHOR]