Catalysts

Research

9 pages, 1691 KiB

Open AccessArticle

Highly Sensitive and Selective Copper (II)-Catalyzed Dual-DNAzyme Colorimetric Biosensor Based on Exonuclease III-Mediated Cyclical Assembly

by Baiqiang Zhai, Kunlun Huang, Hongtao Wang, Dongmin Su and Yuancong Xu

Catalysts 2021, 11(11), 1352; https://doi.org/10.3390/catal11111352 - 11 Nov 2021

Cited by 4 | Viewed by 1866

Abstract

“Cu-DNAzyme” and “G4-DNAzyme” were used to develop a “turn-off” dual-DNAzyme colorimetric biosensor, which could be used to detect Cu²⁺ by employing exonuclease III-mediated cyclical assembly (EMCA). EMCA was based on the cleavage activity of Cu²⁺ to transfer the linkage sequences of [...] Read more.

“Cu-DNAzyme” and “G4-DNAzyme” were used to develop a “turn-off” dual-DNAzyme colorimetric biosensor, which could be used to detect Cu²⁺ by employing exonuclease III-mediated cyclical assembly (EMCA). EMCA was based on the cleavage activity of Cu²⁺ to transfer the linkage sequences of the substrate strand and enzyme strand into the transition sequence. The horseradish peroxidase (HRP)-mimicking activity of the G4-DNAzyme was lost after binding with the complementary transition sequence and was hydrolyzed by Exo III. These results demonstrate that the proposed colorimetric biosensor was an effective method for ultradetection of trace metals in a high original signal background. Due to the high sensitivity of the biosensor, the limit of detection (LOD) of Cu²⁺ is 0.16 nM. This design offers a general purpose platform that could be applied for the detection of any metal ion target through adjustment of metal-dependent DNA-cleaving DNAzymes, which is of great significance for the rapid determination of food safety. Full article

(This article belongs to the Special Issue State of the Art and Future Trends in Nanostructured Biocatalysis)

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19 pages, 3205 KiB

Open AccessArticle

Development of a Novel Bi-Enzymatic Nanobiocatalyst for the Efficient Bioconversion of Oleuropein to Hydroxytyrosol

by Archontoula Giannakopoulou, Alexandra V. Chatzikonstantinou, Nikolaos Chalmpes, Georgia Tsapara, Dimitrios Gournis, Angeliki C. Polydera and Haralambos Stamatis

Catalysts 2021, 11(6), 749; https://doi.org/10.3390/catal11060749 - 19 Jun 2021

Cited by 9 | Viewed by 3309

Abstract

Lipase A from Candida antarctica (CalA) and β-glucosidase from Thermotoga maritima (bgl) were covalently co-immobilized onto the surface of chitosan-coated magnetic nanoparticles (CS-MNPs). Several parameters regarding the co-immobilization procedure (glutaraldehyde concentration, incubation time, CS-MNPs to enzyme mass ratio and bgl to CalA [...] Read more.

Lipase A from Candida antarctica (CalA) and β-glucosidase from Thermotoga maritima (bgl) were covalently co-immobilized onto the surface of chitosan-coated magnetic nanoparticles (CS-MNPs). Several parameters regarding the co-immobilization procedure (glutaraldehyde concentration, incubation time, CS-MNPs to enzyme mass ratio and bgl to CalA mass ratio) were evaluated and optimized. The developed nanobiocatalyst was characterized by various spectroscopic techniques. Biochemical parameters such as kinetic constants and thermal stability were also evaluated. The nanobiocatalytic system revealed an increase in the K_m constant followed by a decrease in V_max value compared with the native enzymes, while a significant increase (>5-fold higher) of the thermal stability of the immobilized CalA, both in individual and in co-immobilized form, was observed after 24 h incubation at 60 °C. Finally, the nanobiocatalyst was efficiently applied for the bioconversion of oleuropein to hydroxytyrosol, one of the most powerful naturally derived antioxidants, and it could be recycled for up to 10 reaction cycles (240 h of constant operation) at 60 °C, retaining more than 50% of its initial activity. Full article

(This article belongs to the Special Issue State of the Art and Future Trends in Nanostructured Biocatalysis)

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11 pages, 652 KiB

Open AccessFeature PaperArticle

Progress Report on pH-Influenced Photocatalysis for Active Motion

by Sandra Heckel, Julia Hübner, Anne Leutzgen, Gregor Jung and Juliane Simmchen

Catalysts 2021, 11(5), 599; https://doi.org/10.3390/catal11050599 - 6 May 2021

Cited by 8 | Viewed by 3133

Abstract

Living systems use catalysis to achieve chemical transformations to comply with their needs in terms of energy and building blocks. The pH is a powerful means to regulate such processes, which also influences synthetic systems. In fact, the pH sensitivity of artificial photocatalysts, [...] Read more.

Living systems use catalysis to achieve chemical transformations to comply with their needs in terms of energy and building blocks. The pH is a powerful means to regulate such processes, which also influences synthetic systems. In fact, the pH sensitivity of artificial photocatalysts, such as bismuth vanadate, bears the strong potential of flexibly influencing both the motion pattern and the speed of catalytic microswimmers, but it has rarely been investigated to date. In this work, we first present a comprehensive view of the motion behavior of differently shaped bismuth vanadate microswimmers, discuss influences, such as shape, pH, and conductivity of the solutions, and find that the motion pattern of the swimmers switches between upright and horizontal at their point of zero charge. We then apply an immobilizable hydroxypyrene derivative to our substrates to locally influence the pH of the solution by excited-state proton transfer. We find that the motion pattern of our swimmers is strongly influenced by this functionalization and a third motion mode, called tumbling, is introduced. Taking other effects, such as an increased surface roughness of the modified substrates, into account, we critically discuss possible future developments. Full article

(This article belongs to the Special Issue State of the Art and Future Trends in Nanostructured Biocatalysis)

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15 pages, 2447 KiB

Open AccessArticle

Gold-Based Nanoparticles on Amino-Functionalized Mesoporous Silica Supports as Nanozymes for Glucose Oxidation

by M. Carmen Ortega-Liebana, Javier Bonet-Aleta, Jose L. Hueso and Jesus Santamaria

Catalysts 2020, 10(3), 333; https://doi.org/10.3390/catal10030333 - 16 Mar 2020

Cited by 34 | Viewed by 7318

Abstract

The transformation of glucose represents a topic of great interest at different levels. In the first place, glucose is currently conceived as a green feedstock for the sustainable production of chemicals. Secondly, the depletion of glucose at the cellular level is currently envisioned [...] Read more.

The transformation of glucose represents a topic of great interest at different levels. In the first place, glucose is currently conceived as a green feedstock for the sustainable production of chemicals. Secondly, the depletion of glucose at the cellular level is currently envisioned as a promising strategy to treat and alter the erratic metabolism of tumoral cells. The use of natural enzymes offers multiple advantages in terms of specificity towards the glucose substrate but may lack sufficient robustness and recyclability beyond the optimal operating conditions of these natural systems. In the present work, we have evaluated the potential use of an inorganic based nanohybrid containing gold nanoparticles supported onto ordered mesoporous supports. We have performed different assays that corroborate the enzyme-mimicking response of these inorganic surrogates towards the selective conversion of glucose into gluconic acid and hydrogen peroxide. Moreover, we conclude that these enzyme-like mimicking surrogates can operate at different pH ranges and under mild reaction conditions, can be recycled multiple times and maintain excellent catalytic response in comparison with other gold-based catalysts. Full article

(This article belongs to the Special Issue State of the Art and Future Trends in Nanostructured Biocatalysis)

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18 pages, 5644 KiB

Open AccessArticle

Flavin-Conjugated Iron Oxide Nanoparticles as Enzyme-Inspired Photocatalysts for Azo Dye Degradation

by Samer I. Nehme, Leander Crocker and Ljiljana Fruk

Catalysts 2020, 10(3), 324; https://doi.org/10.3390/catal10030324 - 13 Mar 2020

Cited by 11 | Viewed by 5273

Abstract

In this work, a new photocatalytic system consisting of iron oxide nanoparticles (IONPs), coated with a catechol-flavin conjugate (DAFL), is synthesized and explored for use in water remediation. In order to test the efficiency of the catalyst, the photodegradation of amaranth (AMT), an [...] Read more.

In this work, a new photocatalytic system consisting of iron oxide nanoparticles (IONPs), coated with a catechol-flavin conjugate (DAFL), is synthesized and explored for use in water remediation. In order to test the efficiency of the catalyst, the photodegradation of amaranth (AMT), an azo dye water pollutant, was performed under aerobic and anaerobic conditions, using either ethylenediaminetetraacetic acid (EDTA) or 2-(N-morpholino)ethanesulfonic acid (MES) as electron donors. Depending on the conditions, either dye photoreduction or photooxidation were observed, indicating that flavin-coated iron-oxide nanoparticles can be used as a versatile enzyme-inspired photocatalysts. Full article

(This article belongs to the Special Issue State of the Art and Future Trends in Nanostructured Biocatalysis)

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13 pages, 2749 KiB

Open AccessFeature PaperArticle

Oxidative Bio-Desulfurization by Nanostructured Peroxidase Mediator System

by Eliana Capecchi, Davide Piccinino, Bruno Mattia Bizzarri, Lorenzo Botta, Marcello Crucianelli and Raffaele Saladino

Catalysts 2020, 10(3), 313; https://doi.org/10.3390/catal10030313 - 9 Mar 2020

Cited by 17 | Viewed by 3224

Abstract

Bio-desulfurization is an efficient technology for removing recalcitrant sulfur derivatives from liquid fuel oil in environmentally friendly experimental conditions. In this context, the development of heterogeneous bio-nanocatalysts is of great relevance to improve the performance of the process. Here we report that lignin [...] Read more.

Bio-desulfurization is an efficient technology for removing recalcitrant sulfur derivatives from liquid fuel oil in environmentally friendly experimental conditions. In this context, the development of heterogeneous bio-nanocatalysts is of great relevance to improve the performance of the process. Here we report that lignin nanoparticles functionalized with concanavalin A are a renewable and efficient platform for the layer-by-layer immobilization of horseradish peroxidase. The novel bio-nanocatalysts were applied for the oxidation of dibenzothiophene as a well-recognized model of the recalcitrant sulfur derivative. The reactions were performed with hydrogen peroxide as a green primary oxidant in the biphasic system PBS/n-hexane at 45 °C and room pressure, the highest conversion of the substrate occurring in the presence of cationic polyelectrolyte layer and hydroxy-benzotriazole as a low molecular weight redox mediator. The catalytic activity was retained for more transformations highlighting the beneficial effect of the support in the reusability of the heterogeneous system. Full article

(This article belongs to the Special Issue State of the Art and Future Trends in Nanostructured Biocatalysis)

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20 pages, 2911 KiB

Open AccessArticle

Selectivity and Sustainability of Electroenzymatic Process for Glucose Conversion to Gluconic Acid

by Miroslava Varničić, Iva N. Zasheva, Edgar Haak, Kai Sundmacher and Tanja Vidaković-Koch

Catalysts 2020, 10(3), 269; https://doi.org/10.3390/catal10030269 - 1 Mar 2020

Cited by 9 | Viewed by 7515

Abstract

Electroenzymatic processes are interesting solutions for the development of new processes based on renewable feedstocks, renewable energies, and green catalysts. High-selectivity and sustainability of these processes are usually assumed. In this contribution, these two aspects were studied in more detail. In a membrane-less [...] Read more.

Electroenzymatic processes are interesting solutions for the development of new processes based on renewable feedstocks, renewable energies, and green catalysts. High-selectivity and sustainability of these processes are usually assumed. In this contribution, these two aspects were studied in more detail. In a membrane-less electroenzymatic reactor, 97% product selectivity at 80% glucose conversion to gluconic acid was determined. With the help of nuclear magnetic resonance spectroscopy, two main side products were identified. The yields of D-arabinose and formic acid can be controlled by the flow rate and the electroenzymatic reactor mode of operation (fuel cell or ion-pumping). The possible pathways for the side product formation have been discussed. The electroenzymatic cathode was found to be responsible for a decrease in selectivity. The choice of the enzymatic catalyst on the cathode side led to 100% selectivity of gluconic acid at somewhat reduced conversion. Furthermore, sustainability of the electroenzymatic process is estimated based on several sustainability indicators. Although some indicators (like Space Time Yield) are favorable for electroenzymatic process, the E-factor of electroenzymatic process has to improve significantly in order to compete with the fermentation process. This can be achieved by an increase of a cycle time and/or enzyme utilization which is currently low. Full article

(This article belongs to the Special Issue State of the Art and Future Trends in Nanostructured Biocatalysis)

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15 pages, 2344 KiB

Open AccessArticle

Sequestration and Oxidation of Cr(III) by Fungal Mn Oxides with Mn(II) Oxidizing Activity

by Ryohei Suzuki, Yukinori Tani, Hirotaka Naitou, Naoyuki Miyata and Kazuya Tanaka

Catalysts 2020, 10(1), 44; https://doi.org/10.3390/catal10010044 - 31 Dec 2019

Cited by 13 | Viewed by 3335

Abstract

Biogenic manganese oxides (BMOs) have gained increasing attention for environmental application because of their sequestration and oxidizing abilities for various elements. Oxidation and sequestration of Cr(III) by BMOs, however, still remain unknown. We prepared BMOs in liquid cultures of Acremonium strictum strain KR21-2, [...] Read more.

Biogenic manganese oxides (BMOs) have gained increasing attention for environmental application because of their sequestration and oxidizing abilities for various elements. Oxidation and sequestration of Cr(III) by BMOs, however, still remain unknown. We prepared BMOs in liquid cultures of Acremonium strictum strain KR21-2, and subsequently conducted single or repeated treatment experiments in Cr(NO₃)₃ at pH 6.0. Under aerobic conditions, newly formed BMOs exhibited a rapid production of Cr(VI) without a significant release of Mn(II), demonstrating that newly formed BMO mediates a catalytic oxidation of Cr(III) with a self-regeneration step of reduced Mn. In anaerobic solution, newly formed BMOs showed a cessation of Cr(III) oxidation in the early stage of the reaction, and subsequently had a much smaller Cr(VI) production with significant release of reduced Mn(II). Extraordinary sequestration of Cr(III) was observed during the repeated treatments under anaerobic conditions. Anaerobically sequestered Cr(III) was readily converted to Cr(VI) when the conditions became aerobic, which suggests that the surface passivation is responsible for the anaerobic cessation of Cr(III) oxidation. The results presented herein increase our understanding of the roles of BMO in Cr(III) oxidation and sequestration processes in potential application of BMOs towards the remediation of Cr(III)/Cr(VI) in contaminated sites. Full article

(This article belongs to the Special Issue State of the Art and Future Trends in Nanostructured Biocatalysis)

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22 pages, 4669 KiB

Open AccessArticle

Development of a Four-Enzyme Magnetic Nanobiocatalyst for Multi-Step Cascade Reactions

by Archontoula Giannakopoulou, Michaela Patila, Konstantinos Spyrou, Nikolaos Chalmpes, Dimitra Zarafeta, Georgios Skretas, Dimitrios Gournis and Haralambos Stamatis

Catalysts 2019, 9(12), 995; https://doi.org/10.3390/catal9120995 - 27 Nov 2019

Cited by 25 | Viewed by 4965

Abstract

We report the preparation, characterization and application of a novel magnetic four-enzyme nanobiocatalyst prepared by the simultaneous covalent co-immobilization of cellulase (CelDZ1), β-glucosidase (bgl), glucose oxidase (GOx) and horseradish peroxidase (HRP) onto the surface of amino-functionalized magnetic nanoparticles (MNPs). This nanobiocatalyst was characterized [...] Read more.

We report the preparation, characterization and application of a novel magnetic four-enzyme nanobiocatalyst prepared by the simultaneous covalent co-immobilization of cellulase (CelDZ1), β-glucosidase (bgl), glucose oxidase (GOx) and horseradish peroxidase (HRP) onto the surface of amino-functionalized magnetic nanoparticles (MNPs). This nanobiocatalyst was characterized by various spectroscopic techniques. The co-immobilization process yielded maximum recovered enzymatic activity (CelDZ1: 42%, bgl: 66%, GOx: 94% and HRP: 78%) at a 10% v/v cross-linker concentration, after 2 h incubation time and at 1:1 mass ratio of MNPs to total enzyme content. The immobilization process leads to an increase of K_m and a decrease of V_max values of co-immobilized enzymes. The thermal stability studies of the co-immobilized enzymes indicated up to 2-fold increase in half-life time constants and up to 1.5-fold increase in their deactivation energies compared to the native enzymes. The enhanced thermodynamic parameters of the four-enzyme co-immobilized MNPs also suggested increment in their thermal stability. Furthermore, the co-immobilized enzymes retained a significant part of their activity (up to 50%) after 5 reaction cycles at 50 °C and remained active even after 24 d of incubation at 5 °C. The nanobiocatalyst was successfully applied in a four-step cascade reaction involving the hydrolysis of cellulose. Full article

(This article belongs to the Special Issue State of the Art and Future Trends in Nanostructured Biocatalysis)

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11 pages, 2220 KiB

Open AccessArticle

Peptide–Gold Nanoparticle Conjugates as Artificial Carbonic Anhydrase Mimics

by Dorian J. Mikolajczak and Beate Koksch

Catalysts 2019, 9(11), 903; https://doi.org/10.3390/catal9110903 - 29 Oct 2019

Cited by 14 | Viewed by 4428

Abstract

We herein describe the design and synthesis of a catalytically active peptide–gold nanoparticle conjugate (Pep-Au-NP) that binds Zn(II) within its peptide monolayer and develops carbonic anhydrase activity. Specifically, a modified variant of the β-sheet forming IHIHIQI-peptide (IHQ), which forms an interstrand 3-His Zn(II)-binding [...] Read more.

We herein describe the design and synthesis of a catalytically active peptide–gold nanoparticle conjugate (Pep-Au-NP) that binds Zn(II) within its peptide monolayer and develops carbonic anhydrase activity. Specifically, a modified variant of the β-sheet forming IHIHIQI-peptide (IHQ), which forms an interstrand 3-His Zn(II)-binding site, was used as a ligand for spherical gold nanoparticles (Au-NPs). The resulting immobilized peptide maintains its ability to form β-sheets, as determined by circular dichroism (CD)-spectroscopy and, thus, maintains its ability to form Zn(II)-binding sites. The addition of Zn(II)-ions to the peptide–gold nanoparticle conjugates (Au@IHQ-NP) resulted in significant improvements in rates of ester hydrolysis of 4-nitrophenyl acetate (4-NPA) and the hydration of CO₂ compared to the unconjugated peptide variants. Recycling of the catalyst revealed that Au@IHQ-NP remains intact with at least 94% of its initial activity after five rounds of CO₂ hydration. The herein reported results reveal that Pep-Au-NPs are able to perform reactions catalyzed by natural metalloenzymes and open up new possibilities for the implementation of these conjugates. Full article

(This article belongs to the Special Issue State of the Art and Future Trends in Nanostructured Biocatalysis)

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10 pages, 1389 KiB

Open AccessArticle

Genetically Modified M13 Bacteriophage Nanonets for Enzyme Catalysis and Recovery

by Vincent Mauricio Kadiri, Mariana Alarcón-Correa, Jacqueline Ruppert, Jan-Philipp Günther, Joachim Bill, Dirk Rothenstein and Peer Fischer

Catalysts 2019, 9(9), 723; https://doi.org/10.3390/catal9090723 - 27 Aug 2019

Cited by 6 | Viewed by 5190

Abstract

Enzyme-based biocatalysis exhibits multiple advantages over inorganic catalysts, including the biocompatibility and the unchallenged specificity of enzymes towards their substrate. The recovery and repeated use of enzymes is essential for any realistic application in biotechnology, but is not easily achieved with current strategies. [...] Read more.

Enzyme-based biocatalysis exhibits multiple advantages over inorganic catalysts, including the biocompatibility and the unchallenged specificity of enzymes towards their substrate. The recovery and repeated use of enzymes is essential for any realistic application in biotechnology, but is not easily achieved with current strategies. For this purpose, enzymes are often immobilized on inorganic scaffolds, which could entail a reduction of the enzymes’ activity. Here, we show that immobilization to a nano-scaled biological scaffold, a nanonetwork of end-to-end cross-linked M13 bacteriophages, ensures high enzymatic activity and at the same time allows for the simple recovery of the enzymes. The bacteriophages have been genetically engineered to express AviTags at their ends, which permit biotinylation and their specific end-to-end self-assembly while allowing space on the major coat protein for enzyme coupling. We demonstrate that the phages form nanonetwork structures and that these so-called nanonets remain highly active even after re-using the nanonets multiple times in a flow-through reactor. Full article

(This article belongs to the Special Issue State of the Art and Future Trends in Nanostructured Biocatalysis)

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10 pages, 2762 KiB

Open AccessArticle

Biomimetic Mineralization of Cytochrome c Improves the Catalytic Efficiency and Confers a Functional Multi-Enzyme Composite

by Xiao-Qing Gong, Chuan-Wan Wei, Jia-Kun Xu, Xiao-Juan Wang, Shu-Qin Gao and Ying-Wu Lin

Catalysts 2019, 9(8), 648; https://doi.org/10.3390/catal9080648 - 29 Jul 2019

Cited by 6 | Viewed by 2999

Abstract

The encapsulated enzyme system by metal-organic frameworks (MOFs) exhibits great potential in biofuel cells, pharmaceuticals, and biocatalysis. However, the catalytic efficiency and the enzymatic activity are severely hampered due to enzyme leaching and deficiency of storage stability. In this study, we immobilized cytochrome [...] Read more.

The encapsulated enzyme system by metal-organic frameworks (MOFs) exhibits great potential in biofuel cells, pharmaceuticals, and biocatalysis. However, the catalytic efficiency and the enzymatic activity are severely hampered due to enzyme leaching and deficiency of storage stability. In this study, we immobilized cytochrome c (Cyt c) into dimethylimidazole-copper (Cu(Im)₂) by biomimetic mineralization, and constructed a bioinorganic hybrid material, termed Cyt c@Cu(Im)₂. Encapsulated Cyt c in Cu(Im)₂ with a nanosheet structure exhibited significantly improved catalytic efficiency, enzymatic activity and kinetic performance. The catalytic efficiency (k_cat/K_m) for Cyt c@Cu(Im)₂ was ~20-fold higher compared to that of free Cyt c. Moreover, the increased activity was not affected by long-term storage. Based on this system, we further constructed a multi-enzyme composite with glucose-oxidase (GOx), termed GOx-Cyt c@Cu(Im)₂, which exhibited greatly improved enzymatic activity, stability, and excellent selectivity for the detection of low concentrations of glucose. This strategy may provide new insights into the design of enzymes with high activity and stability, as well as the construction of multi-enzyme systems. Full article

(This article belongs to the Special Issue State of the Art and Future Trends in Nanostructured Biocatalysis)

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14 pages, 3205 KiB

Open AccessArticle

Minimally Invasive Glucose Monitoring Using a Highly Porous Gold Microneedles-Based Biosensor: Characterization and Application in Artificial Interstitial Fluid

by Paolo Bollella, Sanjiv Sharma, Anthony E. G. Cass, Federico Tasca and Riccarda Antiochia

Catalysts 2019, 9(7), 580; https://doi.org/10.3390/catal9070580 - 30 Jun 2019

Cited by 79 | Viewed by 9442

Abstract

In this paper, we present the first highly porous gold (h-PG) microneedles-based second-generation biosensor for minimally invasive monitoring of glucose in artificial interstitial fluid (ISF). A highly porous microneedles-based electrode was prepared by a simple electrochemical self-templating method that involves two steps, gold [...] Read more.

In this paper, we present the first highly porous gold (h-PG) microneedles-based second-generation biosensor for minimally invasive monitoring of glucose in artificial interstitial fluid (ISF). A highly porous microneedles-based electrode was prepared by a simple electrochemical self-templating method that involves two steps, gold electrodeposition and hydrogen bubbling at the electrode, which were realized by applying a potential of −2 V versus a saturated calomel electrode (SCE). The highly porous gold surface of the microneedles was modified by immobilization of 6-(ferrocenyl)hexanethiol (FcSH) as a redox mediator and subsequently by immobilization of a flavin adenine dinucleotide glucose dehydrogenase (FAD-GDH) enzyme using a drop-casting method. The microneedles-based FcSH/FAD-GDH biosensor allows for the detection of glucose in artificial interstitial fluid with an extended linear range (0.1–10 mM), high sensitivity (50.86 µA cm⁻² mM⁻¹), stability (20% signal loss after 30 days), selectivity (only ascorbic acid showed a response about 10% of glucose signal), and a short response time (3 s). These properties were favourably compared to other microneedles-based glucose biosensors reported in the literature. Finally, the microneedle-arrays-based second-generation biosensor for glucose detection was tested in artificial interstitial fluid opportunely spiked with different concentrations of glucose (simulating healthy physiological conditions while fasting and after lunch) and by placing the electrode into a simulated chitosan/agarose hydrogel skin model embedded in the artificial ISF (continuous glucose monitoring). The obtained current signals had a lag-time of about 2 min compared to the experiments in solution, but they fit perfectly into the linearity range of the biosensor (0.1–10 mM). These promising results show that the proposed h-PG microneedles-based sensor could be used as a wearable, disposable, user-friendly, and automated diagnostic tool for diabetes patients. Full article

(This article belongs to the Special Issue State of the Art and Future Trends in Nanostructured Biocatalysis)

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12 pages, 2015 KiB

Open AccessArticle

Revealing the Active Site of Gold Nanoparticles for the Peroxidase-Like Activity: The Determination of Surface Accessibility

by Ching-Ping Liu, Kuan-Chung Chen, Ching-Feng Su, Po-Yen Yu and Po-Wei Lee

Catalysts 2019, 9(6), 517; https://doi.org/10.3390/catal9060517 - 11 Jun 2019

Cited by 50 | Viewed by 6585

Abstract

Despite the fact that the enzyme-like activities of nanozymes (i.e., nanomaterial-based artificial enzymes) are highly associated with their surface properties, little is known about the catalytic active sites. Here, we used the sulfide ion (S²⁻)-induced inhibition of peroxidase-like activity to explore [...] Read more.

Despite the fact that the enzyme-like activities of nanozymes (i.e., nanomaterial-based artificial enzymes) are highly associated with their surface properties, little is known about the catalytic active sites. Here, we used the sulfide ion (S²⁻)-induced inhibition of peroxidase-like activity to explore active sites of gold nanoparticles (AuNPs). The inhibition mechanism was based on the interaction with Au(I) to form Au₂S, implying that the Au(I) might be the active site of AuNPs for the peroxidase-like activity. X-ray photoelectron spectroscopy (XPS) analysis showed that the content of Au(I) on the surface of AuNPs significantly decreased after the addition of S²⁻, which might be contributed to the more covalent Au–S bond in the formation of Au₂S. Importantly, the variations of Au(I) with and without the addition of S²⁻ for different surface-capped AuNPs were in good accordance with their corresponding peroxidase-like activities. These results confirmed that the accessible Au(I) on the surface was the main requisite for the peroxidase-like activity of AuNPs for the first time. In addition, the use of S²⁻ could assist to determine available active sites for different surface modified AuNPs. This work not only provides a new method to evaluate the surface accessibility of colloidal AuNPs but also gains insight on the design of efficient AuNP-based peroxidase mimics. Full article

(This article belongs to the Special Issue State of the Art and Future Trends in Nanostructured Biocatalysis)

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15 pages, 2642 KiB

Open AccessArticle

Suitability of Recombinant Lipase Immobilised on Functionalised Magnetic Nanoparticles for Fish Oil Hydrolysis

by Madan L Verma, Nalam M Rao, Takuya Tsuzuki, Colin J Barrow and Munish Puri

Catalysts 2019, 9(5), 420; https://doi.org/10.3390/catal9050420 - 3 May 2019

Cited by 46 | Viewed by 4807

Abstract

Recombinant Bacillus subtilis lipase was immobilised on magnetic nanoparticles by a facile covalent method and applied to fish oil hydrolysis. High loading of enzyme to the functionalised nanoparticle was achieved with a protein binding efficiency of 95%. Structural changes of the confined enzyme [...] Read more.

Recombinant Bacillus subtilis lipase was immobilised on magnetic nanoparticles by a facile covalent method and applied to fish oil hydrolysis. High loading of enzyme to the functionalised nanoparticle was achieved with a protein binding efficiency of 95%. Structural changes of the confined enzyme on the surface of the nanoparticles was investigated using transmission electron microscopy and spectroscopic techniques (attenuated total reflectance-Fourier transform infrared and circular dichroism). The biocatalytic potential of immobilised lipase was compared with that of free enzyme and biochemically characterised with respect to different parameters such as pH, temperature, substrate concentrations and substrate specificity. The thermal stability of functionalised nanoparticle bound enzyme was doubled that of free enzyme. Immobilised lipase retained more than 50% of its initial biocatalytic activity after recyclability for twenty cycles. The ability to the immobilised thermostable lipase to concentrate omega-3 fatty acids from fish oil was investigated. Using synthetic substrate, the immobilised enzyme showed 1.5 times higher selectivity for docosahexaenoic acid (DHA), and retained the same degree of selectivity for eicosapentaenoic acid (EPA), when compared to the free enzyme. Full article

(This article belongs to the Special Issue State of the Art and Future Trends in Nanostructured Biocatalysis)

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15 pages, 3866 KiB

Open AccessArticle

Synthesis and Characterization of Te Nanotubes Decorated with Pt Nanoparticles for a Fuel Cell Anode/Cathode Working at a Neutral pH

by Maria Rachele Guascito, Daniela Chirizzi, Emanuela Filippo, Francesco Milano and Antonio Tepore

Catalysts 2019, 9(4), 328; https://doi.org/10.3390/catal9040328 - 3 Apr 2019

Cited by 4 | Viewed by 3756

Abstract

In fuel-cell technology development, one of the most important objectives is to minimize the amount of Pt, the most employed material as an oxygen reduction and methanol oxidation electro-catalyst. In this paper, we report the synthesis and characterization of Te nanotubes (TeNTs) decorated [...] Read more.

In fuel-cell technology development, one of the most important objectives is to minimize the amount of Pt, the most employed material as an oxygen reduction and methanol oxidation electro-catalyst. In this paper, we report the synthesis and characterization of Te nanotubes (TeNTs) decorated with Pt nanoparticles, readily prepared from stirred aqueous solutions of PtCl₂ containing a suspension of TeNTs, and ethanol acting as a reducing agent, avoiding the use of any hydrophobic surfactants such as capping stabilizing substance. The obtained TeNTs decorated with Pt nanoparticles (TeNTs/PtNPs) have been fully characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area diffraction patterns (SAD), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV). We demonstrated that the new material can be successfully employed in fuel cells, either as an anodic (for methanol oxidation reaction) or a cathodic (for oxygen reduction reaction) electrode, with high efficiency in terms of related mass activities and on-set improvement. Remarkably, the cell operates in aqueous electrolyte buffered at pH 7.0, thus, avoiding acidic or alkaline conditions that might lead to, for example, Pt dissolution (at low pH), and paving the way for the development of biocompatible devices and on-chip fuel cells. Full article

(This article belongs to the Special Issue State of the Art and Future Trends in Nanostructured Biocatalysis)

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15 pages, 2696 KiB

Open AccessFeature PaperReview

Nanoscale Cerium Oxide: Synthesis, Biocatalytic Mechanism, and Applications

by Guangchun Song, Nan Cheng, Junjie Zhang, Huixian Huang, Yanfang Yuan, Xiaoyun He, Yunbo Luo and Kunlun Huang

Catalysts 2021, 11(9), 1123; https://doi.org/10.3390/catal11091123 - 18 Sep 2021

Cited by 38 | Viewed by 5586

Abstract

Nanoscale cerium oxide has excellent catalytic performance due to its unique surface properties and has very important applications in various fields. In this paper, the synthesis methods, catalytic mechanism and activity regulation of nanoscale cerium oxide in recent years are reviewed. Secondly, the [...] Read more.

Nanoscale cerium oxide has excellent catalytic performance due to its unique surface properties and has very important applications in various fields. In this paper, the synthesis methods, catalytic mechanism and activity regulation of nanoscale cerium oxide in recent years are reviewed. Secondly, the application of cerium oxide in the detection of organic and inorganic molecules is summarized, and its latest progress and applications in antibacterial, antioxidant and anticancer are discussed. Finally, the future development prospect of nanoscale cerium oxide is summarized and prospected. Full article

(This article belongs to the Special Issue State of the Art and Future Trends in Nanostructured Biocatalysis)

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24 pages, 4133 KiB

Open AccessFeature PaperReview

Recent Advances in Nucleic Acid Modulation for Functional Nanozyme

by Xin Wang, Yuancong Xu, Nan Cheng, Xinxian Wang, Kunlun Huang and Yunbo Luo

Catalysts 2021, 11(5), 638; https://doi.org/10.3390/catal11050638 - 17 May 2021

Cited by 13 | Viewed by 4232

Abstract

Nanozymes have the potential to replace natural enzymes, so they are widely used in energy conversion technologies such as biosensors and signal transduction (converting biological signals of a target into optical, electrical, or metabolic signals). The participation of nucleic acids leads nanozymes to [...] Read more.

Nanozymes have the potential to replace natural enzymes, so they are widely used in energy conversion technologies such as biosensors and signal transduction (converting biological signals of a target into optical, electrical, or metabolic signals). The participation of nucleic acids leads nanozymes to produce richer interface effects and gives energy conversion events more attractive characteristics, creating what are called “functional nanozymes”. Since different nanozymes have different internal structures and external morphological characteristics, functional modulation needs to be compatible with these properties, and attention needs to be paid to the influence of nucleic acids on nanozyme activity. In this review, “functional nanozymes” are divided into three categories, (nanozyme precursor ion)/ (nucleic acid) self-assembly, nanozyme-nucleic acid irreversible binding, and nanozyme-nucleic acid reversible binding, and the effects of nucleic acids on modulation principles are summarized. Then, the latest developments of nucleic acid-modulated nanozymes are reviewed in terms of their use in energy conversion technology, and their conversion mechanisms are critically discussed. Finally, we outline the advantages and limitations of “functional nanozymes” and discuss the future development prospects and challenges in this field. Full article

(This article belongs to the Special Issue State of the Art and Future Trends in Nanostructured Biocatalysis)

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30 pages, 2875 KiB

Open AccessReview

Green Catalysts: Applied and Synthetic Photosynthesis

by Alexandra H. Teodor, Benjamin D. Sherman, Zeah Yvette Ison, Eu-Jee Ooi, Jesse J. Bergkamp and Barry D. Bruce

Catalysts 2020, 10(9), 1016; https://doi.org/10.3390/catal10091016 - 3 Sep 2020

Cited by 12 | Viewed by 7091

Abstract

The biological process of photosynthesis was critical in catalyzing the oxygenation of Earth’s atmosphere 2.5 billion years ago, changing the course of development of life on Earth. Recently, the fields of applied and synthetic photosynthesis have utilized the light-driven protein–pigment supercomplexes central to [...] Read more.

The biological process of photosynthesis was critical in catalyzing the oxygenation of Earth’s atmosphere 2.5 billion years ago, changing the course of development of life on Earth. Recently, the fields of applied and synthetic photosynthesis have utilized the light-driven protein–pigment supercomplexes central to photosynthesis for the photocatalytic production of fuel and other various valuable products. The reaction center Photosystem I is of particular interest in applied photosynthesis due to its high stability post-purification, non-geopolitical limitation, and its ability to generate the greatest reducing power found in nature. These remarkable properties have been harnessed for the photocatalytic production of a number of valuable products in the applied photosynthesis research field. These primarily include photocurrents and molecular hydrogen as fuels. The use of artificial reaction centers to generate substrates and reducing equivalents to drive non-photoactive enzymes for valuable product generation has been a long-standing area of interest in the synthetic photosynthesis research field. In this review, we cover advances in these areas and further speculate synthetic and applied photosynthesis as photocatalysts for the generation of valuable products. Full article

(This article belongs to the Special Issue State of the Art and Future Trends in Nanostructured Biocatalysis)

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15 pages, 2519 KiB

Open AccessReview

Recent Advances in Enzyme-Nanostructure Biocatalysts with Enhanced Activity

by Jing An, Galong Li, Yifan Zhang, Tingbin Zhang, Xiaoli Liu, Fei Gao, Mingli Peng, Yuan He and Haiming Fan

Catalysts 2020, 10(3), 338; https://doi.org/10.3390/catal10030338 - 18 Mar 2020

Cited by 56 | Viewed by 6416

Abstract

Owing to their unique physicochemical properties and comparable size to biomacromolecules, functional nanostructures have served as powerful supports to construct enzyme-nanostructure biocatalysts (nanobiocatalysts). Of particular importance, recent years have witnessed the development of novel nanobiocatalysts with remarkably increased enzyme activities. This review provides [...] Read more.

Owing to their unique physicochemical properties and comparable size to biomacromolecules, functional nanostructures have served as powerful supports to construct enzyme-nanostructure biocatalysts (nanobiocatalysts). Of particular importance, recent years have witnessed the development of novel nanobiocatalysts with remarkably increased enzyme activities. This review provides a comprehensive description of recent advances in the field of nanobiocatalysts, with systematic elaboration of the underlying mechanisms of activity enhancement, including metal ion activation, electron transfer, morphology effects, mass transfer limitations, and conformation changes. The nanobiocatalysts highlighted here are expected to provide an insight into enzyme–nanostructure interaction, and provide a guideline for future design of high-efficiency nanobiocatalysts in both fundamental research and practical applications. Full article

(This article belongs to the Special Issue State of the Art and Future Trends in Nanostructured Biocatalysis)

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20 pages, 4316 KiB

Open AccessEditor’s ChoiceReview

Direct Electron Transfer-Type Bioelectrocatalysis of Redox Enzymes at Nanostructured Electrodes

by Taiki Adachi, Yuki Kitazumi, Osamu Shirai and Kenji Kano

Catalysts 2020, 10(2), 236; https://doi.org/10.3390/catal10020236 - 15 Feb 2020

Cited by 42 | Viewed by 5603

Abstract

Direct electron transfer (DET)-type bioelectrocatalysis, which couples the electrode reactions and catalytic functions of redox enzymes without any redox mediator, is one of the most intriguing subjects that has been studied over the past few decades in the field of bioelectrochemistry. In order [...] Read more.

Direct electron transfer (DET)-type bioelectrocatalysis, which couples the electrode reactions and catalytic functions of redox enzymes without any redox mediator, is one of the most intriguing subjects that has been studied over the past few decades in the field of bioelectrochemistry. In order to realize the DET-type bioelectrocatalysis and improve the performance, nanostructures of the electrode surface have to be carefully tuned for each enzyme. In addition, enzymes can also be tuned by the protein engineering approach for the DET-type reaction. This review summarizes the recent progresses in this field of the research while considering the importance of nanostructure of electrodes as well as redox enzymes. This review also describes the basic concepts and theoretical aspects of DET-type bioelectrocatalysis, the significance of nanostructures as scaffolds for DET-type reactions, protein engineering approaches for DET-type reactions, and concepts and facts of bidirectional DET-type reactions from a cross-disciplinary viewpoint. Full article

(This article belongs to the Special Issue State of the Art and Future Trends in Nanostructured Biocatalysis)

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35 pages, 4852 KiB

Open AccessReview

Quantum Dots and Gold Nanoparticles as Scaffolds for Enzymatic Enhancement: Recent Advances and the Influence of Nanoparticle Size

by Gregory A. Ellis, Scott N. Dean, Scott A. Walper and Igor L. Medintz

Catalysts 2020, 10(1), 83; https://doi.org/10.3390/catal10010083 - 7 Jan 2020

Cited by 22 | Viewed by 5373

Abstract

Nanoparticle scaffolds can impart multiple benefits onto immobilized enzymes including enhanced stability, activity, and recoverability. The magnitude of these benefits is modulated by features inherent to the scaffold–enzyme conjugate, amongst which the size of the nanoscaffold itself can be critically important. In this [...] Read more.

Nanoparticle scaffolds can impart multiple benefits onto immobilized enzymes including enhanced stability, activity, and recoverability. The magnitude of these benefits is modulated by features inherent to the scaffold–enzyme conjugate, amongst which the size of the nanoscaffold itself can be critically important. In this review, we highlight the benefits of enzyme immobilization on nanoparticles and the factors affecting these benefits using quantum dots and gold nanoparticles as representative materials due to their maturity. We then review recent literature on the use of these scaffolds for enzyme immobilization and as a means to dissect the underlying mechanisms. Detailed analysis of the literature suggests that there is a “sweet-spot” for scaffold size and the ratio of immobilized enzyme to scaffold, with smaller scaffolds and lower enzyme:scaffold ratios generally providing higher enzymatic activities. We anticipate that ongoing studies of enzyme immobilization onto nanoscale scaffolds will continue to sharpen our understanding of what gives rise to beneficial characteristics and allow for the next important step, namely, that of translation to large-scale processes that exploit these properties. Full article

(This article belongs to the Special Issue State of the Art and Future Trends in Nanostructured Biocatalysis)

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21 pages, 9943 KiB

Open AccessReview

Nanocatalysts Containing Direct Electron Transfer-Capable Oxidoreductases: Recent Advances and Applications

by Dalius Ratautas and Marius Dagys

Catalysts 2020, 10(1), 9; https://doi.org/10.3390/catal10010009 - 19 Dec 2019

Cited by 21 | Viewed by 5236

Abstract

Direct electron transfer (DET)-capable oxidoreductases are enzymes that have the ability to transfer/receive electrons directly to/from solid surfaces or nanomaterials, bypassing the need for an additional electron mediator. More than 100 enzymes are known to be capable of working in DET conditions; however, [...] Read more.

Direct electron transfer (DET)-capable oxidoreductases are enzymes that have the ability to transfer/receive electrons directly to/from solid surfaces or nanomaterials, bypassing the need for an additional electron mediator. More than 100 enzymes are known to be capable of working in DET conditions; however, to this day, DET-capable enzymes have been mainly used in designing biofuel cells and biosensors. The rapid advance in (semi) conductive nanomaterial development provided new possibilities to create enzyme-nanoparticle catalysts utilizing properties of DET-capable enzymes and demonstrating catalytic processes never observed before. Briefly, such nanocatalysts combine several cathodic and anodic catalysis performing oxidoreductases into a single nanoparticle surface. Hereby, to the best of our knowledge, we present the first review concerning such nanocatalytic systems involving DET-capable oxidoreductases. We outlook the contemporary applications of DET-capable enzymes, present a principle of operation of nanocatalysts based on DET-capable oxidoreductases, provide a review of state-of-the-art (nano) catalytic systems that have been demonstrated using DET-capable oxidoreductases, and highlight common strategies and challenges that are usually associated with those type catalytic systems. Finally, we end this paper with the concluding discussion, where we present future perspectives and possible research directions. Full article

(This article belongs to the Special Issue State of the Art and Future Trends in Nanostructured Biocatalysis)

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17 pages, 5158 KiB

Open AccessReview

Progress and Trend on the Regulation Methods for Nanozyme Activity and Its Application

by Li Hou, Gaoyan Jiang, Ying Sun, Xuanhan Zhang, Juanjuan Huang, Shendong Liu, Tianran Lin, Fanggui Ye and Shulin Zhao

Catalysts 2019, 9(12), 1057; https://doi.org/10.3390/catal9121057 - 12 Dec 2019

Cited by 35 | Viewed by 6807

Abstract

Natural enzymes, such as biocatalysts, are widely used in biosensors, medicine and health, the environmental field, and other fields. However, it is easy for natural enzymes to lose catalytic activity due to their intrinsic shortcomings including a high purification cost, insufficient stability, and [...] Read more.

Natural enzymes, such as biocatalysts, are widely used in biosensors, medicine and health, the environmental field, and other fields. However, it is easy for natural enzymes to lose catalytic activity due to their intrinsic shortcomings including a high purification cost, insufficient stability, and difficulties of recycling, which limit their practical applications. The unexpected discovery of the Fe₃O₄ nanozyme in 2007 has given rise to tremendous efforts for developing natural enzyme substitutes. Nanozymes, which are nanomaterials with enzyme-mimetic catalytic activity, can serve as ideal candidates for artificial mimic enzymes. Nanozymes possess superiorities due to their low cost, high stability, and easy preparation. Although great progress has been made in the development of nanozymes, the catalytic efficiency of existing nanozymes is relatively low compared with natural enzymes. It is still a challenging task to develop nanozymes with a precise regulation of catalytic activity. This review summarizes the classification and various strategies for modulating the activity as well as research progress in the different application fields of nanozymes. Typical examples of the recent research process of nanozymes will be presented and critically discussed. Full article

(This article belongs to the Special Issue State of the Art and Future Trends in Nanostructured Biocatalysis)

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31 pages, 6274 KiB

Open AccessReview

Cerium- and Iron-Oxide-Based Nanozymes in Tissue Engineering and Regenerative Medicine

by Michelle M. T. Jansman and Leticia Hosta-Rigau

Catalysts 2019, 9(8), 691; https://doi.org/10.3390/catal9080691 - 15 Aug 2019

Cited by 24 | Viewed by 6783

Abstract

Nanoparticulate materials displaying enzyme-like properties, so-called nanozymes, are explored as substitutes for natural enzymes in several industrial, energy-related, and biomedical applications. Outstanding high stability, enhanced catalytic activities, low cost, and availability at industrial scale are some of the fascinating features of nanozymes. Furthermore, [...] Read more.

Nanoparticulate materials displaying enzyme-like properties, so-called nanozymes, are explored as substitutes for natural enzymes in several industrial, energy-related, and biomedical applications. Outstanding high stability, enhanced catalytic activities, low cost, and availability at industrial scale are some of the fascinating features of nanozymes. Furthermore, nanozymes can also be equipped with the unique attributes of nanomaterials such as magnetic or optical properties. Due to the impressive development of nanozymes during the last decade, their potential in the context of tissue engineering and regenerative medicine also started to be explored. To highlight the progress, in this review, we discuss the two most representative nanozymes, namely, cerium- and iron-oxide nanomaterials, since they are the most widely studied. Special focus is placed on their applications ranging from cardioprotection to therapeutic angiogenesis, bone tissue engineering, and wound healing. Finally, current challenges and future directions are discussed. Full article

(This article belongs to the Special Issue State of the Art and Future Trends in Nanostructured Biocatalysis)

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1 pages, 399 KiB

Open AccessObituary

Remembering Prof. Dr. Peter Grunwald (1941–2020)

by Evangelos Topakas

Catalysts 2021, 11(4), 422; https://doi.org/10.3390/catal11040422 - 26 Mar 2021

Viewed by 1544

Abstract

On 28 December 2020, Prof. Dr. Peter Grunwald died after a short, serious illness. [...] Full article

(This article belongs to the Special Issue State of the Art and Future Trends in Nanostructured Biocatalysis)

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