Elsevier

Sensors and Actuators B: Chemical

Volume 277, 20 December 2018, Pages 86-94
Sensors and Actuators B: Chemical

Porphyrin-based porous organic framework: An efficient and stable peroxidase-mimicking nanozyme for detection of H2O2 and evaluation of antioxidant

https://doi.org/10.1016/j.snb.2018.08.097Get rights and content

Highlights

  • A novel porphyrin-based porous organic polymer (PPOP) is designed and prepared.

  • Large surface area with adequately exposed catalytic active sites of the PPOP ensures its high peroxidase-like activity.

  • A versatile colorimetric biosensor for H2O2, glucose and three antioxidants detection with high sensitivity and stability is established with PPOP.

  • The distinguishing inhibitory behaviors of three antioxidants to PPOP imply different antioxidative mechanisms.

Abstract

As promising alternatives to natural enzymes, catalytically active nanomaterials (nanozymes) are of great interest due to their high activity, controlled synthesis, low-cost, and excellent stability against stringent conditions. Studies of the chemical interactions between antioxidants and nanozymes would provide valuable information about catalytic mechanisms, help to better understand some metabolic pathways and screen more effective artificial enzymes. In this work, a porphyrin-based porous organic polymer, named FePPOP-1 was synthesized via a Sonogashira–Hagihara coupling reaction between 1,3,5-triethynylbenzene and iron 5,10,15,20-tetrakis-(4′-bromophenyl)porphyrin (FeTBrPP). FePPOP-1 possesses large BET surface area as well as high thermal and chemical stability. The good peroxidase-like activity of FePPOP-1 was confirmed by catalyzing the oxidation reaction of 3,3′,5,5′-Tetramethylbenzidine (TMB) with H2O2. A FePPOP-1 based colorimetric biosensor was then established for H2O2, glucose and three antioxidants [ascorbic acid (AA), gallic acid (GA) and tannic acid (TA)] detection with high sensitivity and stability. Moreover, the inhibitory effects of these three natural antioxidants on peroxidase-like activity of FePPOP-1 and the relative strength of their anti-oxidative capacity were comparatively investigated. The distinguishing inhibitory behavior of AA, GA and TA implied their different anti-oxidative mechanisms.

Introduction

H2O2 is an important oxidizing product involved in many chemical, biological, pharmaceutical, clinical and environmental processes [1,2]. Therefore, accurate determination of H2O2 is very important. To date, many analytical methods have been developed to monitor H2O2, such as chemiluminescence [3], fluorescence [4], electrochemistry [5] and liquid chromatography [6]. These techniques show high selectivity, but also have some shortcomings, such as, expensive and not easily fielded in a small low-power package. Alternatively, colorimetric assay has been drawn attention due to its series of advantages such as timesaver, low-cost, pretty simplicity and sensitivity as well as practical application [7,8].

On the other hand, antioxidants are reducing agents that protect the body against oxidative damage via participating in redox reactions and scavenging the reactive oxygen species produced in biological systems. Thus, various antioxidants, such as ascorbic acid (AA), gallic acid (GA), and tannic acid (TA), have been used as additives in foods, drugs, and cosmetic applications [9]. Investigation revealed that the dosage and function of antioxidants are closely related with their anti-oxidative capabilities and anti-oxidative mechanisms. Therefore, it is desirable to develop simple and rapid methods for determination of antioxidants and evaluation of their anti-oxidative behaviors. Recent research has proved that the utilization of peroxidase-mimicking catalysts to determine anti-oxidative behavior is a simple and reliable method. However, relative reports in this area are very few [[10], [11], [12]].

Peroxidase, such as horseradish peroxidase (HRP), can be used as exquisite biocatalyst for H2O2 detection [13]. However, the practical application of these natural enzymes is often hampered by their intrinsic drawbacks, such as low operational stability and high catalytic sensitivity to environmental conditions [14]. Therefore, it is highly desirable to discover artificial peroxidase-mimicking enzymes with merits of high activity, controlled synthesis, low-cost, and excellent stability against stringent conditions to circumvent the drawbacks of natural enzyme. In 2007, Yan et al. first discovered that Fe3O4 nanoparticles have an intrinsic peroxidase-like activity [15]. Since then, various nanomaterial-based artificial enzymes (nanozymes) [[16], [17], [18], [19]] have been found to possess intrinsic activity similar to HRP and further been used to detect H2O2, glucose and tumor markers. Among them, most works are focused on metal oxide-based nanozymes, metal nanoparticle-based nanozymes, and carbon materials-based nanozmyes. Although significant progress has been made, it still remains highly demand and great challenging to explore new peroxidase-mimicking nanozymes with high efficiency.

Iron-porphyrin derivatives have attracted increasing attention due to their close biological relevance to cytochrome P450, which are responsible for catalyzing a wide variety of biological oxidations [20]. However, utilities of synthetic metalloporphyrins as catalysts in homogeneous oxidation reactions have been rather limited because of their rapid inactivity through either the oxidative degradation of porphyrin ring or formation of peroxo-bridged dimers [21]. To solve this problem, various approaches have been developed, such as loading porphyrins onto heteroid supports [22,23], protecting the porphyrin center by modifying the porphyrin macrocycle with bulky functional groups [24], and immobilizing porphyrins into metal-organic frameworks (MOFs) [25,26]. These strategies authentically enhance the catalytic activity of porphyrin catalysts but bring some new problems at the same time. For example, when porphyrins are coordinated by axial ligand as in case of porphyrin on supports, their catalytic activity is reduced.

Porphyrin-based porous organic polymers (PPOPs) constructed from metalloporphyrins building blocks and linked by covalent bonds are a new class of porous organic polymers and have received considerable interest in recent years [[27], [28], [29]]. The PPOPs possess intrinsic advantages of porous organic polymers (POPs), such as large specific surface area, tunable pore structures and high thermal/chemical/water stability. These advantages facilitate the electron transfer and mass transport due to the uniform open cavities, and effective avoid porphyrin deactivation via isolating each porphyrin ligand in a fixed position [30]. In particularly, the introduction of metalloporphyrins into POPs frameworks would endow the skeleton of PPOPs itself as catalysts and enhance the catalytic activity by adequate exposure of high-density catalytic active sites. Therefore, PPOPs would be promising candidates of nanozymes family. Although, PPOPs have been intensive researched in catalysis, there are a few reports about PPOPs-based nanozymes [[31], [32], [33], [34], [35]]. In addition, to the best of our knowledge, PPOPs have not been applied as biomimetic catalysts for colorimetric detection of antioxidants and evaluation of their anti-oxidative mechanisms.

In this paper, we present a novel platform for colorimetric determination of H2O2, glucose and some antioxidants (AA, GA and TA) by using a porphyrin-based porous organic polymer, FePPOP-1, produced by the reaction between iron 5,10,15,20-tetrakis-(4′-bromophenyl)porphyrin and 1,3,5-triethynylbenzene (Scheme 1). Due to the presence of the adequately exposed and high-density catalytic active sites, FePPOP-1 exhibited high peroxidase activity and low detection limit. In addition, we report the first application of FePPOP-1 for detecting three antioxidants (AA, GA and TA) effectively, evaluating their anti-oxidative capabilities and studying their anti-oxidative mechanisms.

Section snippets

Experimental section

The materials and characterization are described in the ESI. The synthetic process of the polymer can be divided into three sections in the ESI: (i) synthesis of 5,10,15,20-tetrakis(4′-bromophenyl)porphyrin (H2TBrPP), (ii) synthesis of iron 5,10,15,20-tetrakis-(4′-bromoph-enyl)porphyrin (FeTBrPP), and (iii) synthesis of FePPOP-1.

Synthesis and characterization of FePPOP-1

FePPOP-1 was synthesized through a Pd/CuI-catalyzed Sonogashira cross-coupling reaction between TRBE and FeTBrPP. Such a polycondensation reaction leads to an inherent porous with high yields. FePPOP-1 is brown powder with low density. It is chemically stable even upon exposure to dilute solutions of acid and base and insoluble in water and common organic solvents as a result of its cross-linked and robust network. The thermal stability of FePPOP-1 was examined by TGA. Under a nitrogen

Conclusion

In summary, we have demonstrated the highly sensitive and efficient intrinsic peroxidase-like activity of FePPOP-1 and explored its application for quantitative detection of H2O2, glucose and three antioxidants (AA, GA and TA). The large surface area of FePPOP-1 with adequately exposed high-density catalytic active sites strengthens the inherent peroxidase-like activity of FePPOP-1 and in turn results in its high detection sensitivity and stability. The ability of FePPOP-1 to decompose H2O2

Acknowledgements

We gratefully acknowledge the financial support from National Natural Science Foundation of China (Grant no. 21472117, 21605095), Natural Science Foundation of Shandong Province (Grant no. ZR2016BQ25) and Open Project of State Key Laboratory of Infrared Physics.

Chao Cui is a B.S. candidate in the department of School of Chemistry and Chemical Engineering, Shandong University. His main research interests are the synthesis of porphyrin-based porous organic polymers and their sensing application as enzyme mimics.

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    Chao Cui is a B.S. candidate in the department of School of Chemistry and Chemical Engineering, Shandong University. His main research interests are the synthesis of porphyrin-based porous organic polymers and their sensing application as enzyme mimics.

    Quanbo Wang received his PhD degree from Nanjing University, China. Now he is a lecturer in Laboratory of Immunology for Environment and Health, Shandong Analysis and Test Center and Qilu University of Technology, China. His main research interests are design and synthesis of nano-fluorescence probes for detection of biomolecules.

    Prof. Qingyun Liu received her PhD degree from Shandong University, China. Following postdoctoral research in Ocean University of China, she successively joined Prof. Yansheng Yin’s group. Now she is a professor at Shandong University of Science& Technology, China. Her research interests include inorganic-organic nanocomposites, colorimetric sensor and self-assembly of porphyrin and phthalocyanine.

    Tingting Liu is a PhD candidate in the department of School of Chemistry and Chemical Engineering, Shandong University. Her main research interests are the synthesis of porphyrin-based porous organic polymers and exploration their application as enzyme mimics and absorbents for environmental modification.

    Dekang Li is currently working toward the master degree under the supervision of Prof. Xiaomei Zhang in the department of School of Chemistry and Chemical Engineering, Shandong University. His main research interests are focus on nanomaterial-based sensors.

    Xiaomei Zhang received her PhD degree from Peking University. In 2003, she joined the faculty of Shandong University as a lecturer, and currently she is a professor at the School of Chemistry and Chemical Engineering. Her research interests include the design, synthesis and applications of multifunctional nanomaterials, such as porphyrin (phthalocyanine)-based porous organic polymers for biosensing and nanoporous metals for heterogeneous catalysis.

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