Construction of magnetic nanoflower biocatalytic system with enhanced enzymatic performance by biomineralization and its application for bisphenol A removal

Magnetic nanoflowers: a hybrid platform for enzyme immobilization

The use of organic-inorganic hybrid nanoflowers as a support material for enzyme immobilization has gained significant attention in recent years due to their high stability, ease of preparation, and enhanced catalytic activity. However, a major challenge in utilizing these hybrid nanoflowers for enzyme immobilization is the difficulty in handling and separating them due to their low density and high dispersion. To address this issue, magnetic nanoflowers have emerged as a promising alternative enzyme immobilization platform due to their easy separation, structural stability, and ability to enhance catalytic efficiency. This review focuses on different methods for designing magnetic nanoflowers, as well as future research directions. Additionally, it provides examples of enzymes immobilized in the form of magnetic nanoflowers and their applications in environmental remediation, biosensors, and food industries. Finally, the review discusses possible ways to improve the material for enhanced catalytic activity, structural stability, and scalability.

"Microflower-Templated" Janus Sheets: Synthesis and Application in Stabilizing Foams

In this study, we proposed a method for fabricating Janus sheets using biological "microflowers" as a sacrificial template. The microflower-templated Janus sheets (MF-JNSs) were employed as a foam stabilizer in foam separation of the whey soybean protein (WSP). The MF-JNSs took inorganic hybrid microflowers (BSA@Cu3 (PO4)2-MF) as template, followed by the sequential attachment of protamine and silica to the surface of the BSA@Cu3(PO4)2-MF. Subsequently, the template was removed using ethylenediaminetetraacetic acid after the silicon dioxide was modified by 3-(methacryloyloxy) propyl trimethoxysilane. Upon template dissolution, the modified silica layer, lacking support from the core, fractured to form the MF-JNSs. This method omitted the step of treating the hollow ball by external force and obtained Janus sheets in one step, indicating that it was simple and feasible. The morphology, structure, and composition of the MF-JNSs were analyzed by SEM, TEM, AFM, XRD, and FT-IR. The MF-JNSs were found to delay the breakage time of the Pickering emulsion, demonstrating their emulsion stabilizing capability. Importantly, they significantly enhanced the foam half-life and foam height of soybean whey wastewater (SWW). Moreover, the recovery percentage and enrichment ratio of WSP, separated from SWW by foam separation, were improved to 81 ± 0.28 and 1.20 ± 0.05%, respectively.

Trametes versicolor Laccase-Based Magnetic Inorganic-Protein Hybrid Nanobiocatalyst for Efficient Decolorization of Dyes in the Presence of Inhibitors

In the present investigation, an ecofriendly magnetic inorganic-protein hybrid system-based enzyme immobilization was developed using partially purified laccase from Trametes versicolor (TvLac), Fe3O4 nanoparticles, and manganese (Mn), and was successfully applied for synthetic dye decolorization in the presence of enzyme inhibitors. After the partial purification of crude TvLac, the specific enzyme activity reached 212 U∙mg total protein-1. The synthesized Fe3O4/Mn3(PO4)2-laccase (Fe3O4/Mn-TvLac) and Mn3(PO4)2-laccase (Mn-TvLac) nanoflowers (NFs) exhibited encapsulation yields of 85.5% and 90.3%, respectively, with relative activities of 245% and 260%, respectively, compared with those of free TvLac. One-pot synthesized Fe3O4/Mn-TvLac exhibited significant improvements in catalytic properties and stability compared to those of the free enzyme. Fe3O4/Mn-TvLac retained a significantly higher residual activity of 96.8% over that of Mn-TvLac (47.1%) after 10 reuse cycles. The NFs showed potential for the efficient decolorization of synthetic dyes in the presence of enzyme inhibitors. For up to five reuse cycles, Fe3O4/Mn-TvLac retained a decolorization potential of 81.1% and 86.3% for Coomassie Brilliant Blue R-250 and xylene cyanol, respectively. The synthesized Fe3O4/Mn-TvLac showed a lower acute toxicity towards Vibrio fischeri than pure Fe3O4 nanoparticles did. This is the first report of the one-pot synthesis of biofriendly magnetic protein-inorganic hybrids using partially purified TvLac and Mn.

Enhancing the sustainable immobilization of laccase by amino-functionalized PMMA-reinforced graphene nanomaterial

Human health and the environment are negatively affected by endocrine-disrupting chemicals (EDCs), such as bisphenol A. Therefore, developing appropriate remediation methods is essential for efficiently removing phenolic compounds from aqueous solutions. Enzymatic biodegradation is a potential biotechnological approach for responsibly addressing water pollution. With its high catalytic efficiency and few by-products, laccase is an eco-friendly biocatalyst with significant promise for biodegradation. Herein, two novel supporting materials (NH2-PMMA and NH2-PMMA-Gr) were fabricated via the functionalization of poly(methylmethacrylate) (PMMA) polymer using ethylenediamine and reinforced with graphene followed by glutaraldehyde activation. NH2-PMMA and NH2-PMMA-Gr were utilized for laccase immobilization with an immobilization yield (IY%) of 78.3% and 82.5% and an activity yield (AY%) of 81.2% and 85.9%, respectively. Scanning electron microscope (SEM) and Fourier-transform infrared (FTIR) were used to study the characteristics of fabricated material supports. NH2-PMMA-Gr@laccase exhibited an optimal pH profile from 4.5 to 5.0, while NH2-PMMA@laccase exhibited optimum pH at 5.0 compared to a value of 4.0 for free form. A wider temperature ranges of 40-50 °C was noted for both immobilized laccases compared to a value of 40 °C for the free form. Additionally, it was reported that immobilized laccase outperformed free laccase in terms of substrate affinity and storage stability. NH2-PMMA@laccase and NH2-PMMA-Gr@laccase improved stability by up to 3.9 and 4.6-fold when stored for 30 days at 4 °C and preserved up to 80.5% and 86.7% of relative activity after ten cycles of reuse. Finally, the degradation of BPA was achieved using NH2-PMMA@laccase and NH2-PMMA-Gr@laccase. After five cycles, NH2-PMMA@laccase and NH2-PMMA-Gr@laccase showed that the residual degradation of BPA was 77% and 84.5% using 50 μm of BPA. This study introduces a novel, high-performance material for organic pollution remediation in wastewater that would inspire further progress.

Preparation and investigation of novel endopeptidase-exopeptidase co-immobilized nanoflowers with improved cascade hydrolysis

Enzymatic hydrolysis is a promising approach for protein and food processing. However, the efficiency of this approach is constrained by the self-hydrolysis, self-agglomeration of free enzymes and the limited applicability resulted from enzymes' selectivityt. Here, novel organic-inorganic hybrid nanoflowers (AY-10@AXH-HNFs) were prepared by coordinating Cu2+ with both endopeptidase of PROTIN SD-AY10 and exopeptidase of Prote AXH. The results indicate that the AY-10@AXH-HNFs exhibited 4.1 and 9.6 times higher catalytic activity than free Prote AXH and PROTIN SD-AY10, respectively, for the enzymatic hydrolysis of N-benzoyl-L-arginine ethyl ester (BAEE). The kinetic parameters of Km, Vmax and Kcat/Km by AY-10@AXH-HNFs were determined to be 0.6 mg/mL, 6.8 mL·min/mg and 6.1 mL/(min·mg), respectively, surpassing the values obtained from free endopeptidase and exopeptidase. Furthermore, the ability of AY-10@AXH-HNFs to retain 41 % of their initial catalytic activity after undergoing 5 cycles of repeated use confirmed their stability and reusability. This study introduces a novel approach of co-immobilizing endopeptidase and exopeptidase on nanoflowers, resulting in significantly enhanced stability and reusability of the protease in catalytic applications.

Nanozymes and nanoflower: Physiochemical properties, mechanism and biomedical applications

Natural enzymes possess several drawbacks which limits their application in industries, wastewater remediation and biomedical field. Therefore, in recent years researchers have developed enzyme mimicking nanomaterials and enzymatic hybrid nanoflower which are alternatives of enzyme. Nanozymes and organic inorganic hybrid nanoflower have been developed which mimics natural enzymes functionalities such as diverse enzyme mimicking activities, enhanced catalytic activities, low cost, ease of preparation, stability and biocompatibility. Nanozymes include metal and metal oxide nanoparticles mimicking oxidases, peroxidases, superoxide dismutase and catalases while enzymatic and non-enzymatic biomolecules were used for preparing hybrid nanoflower. In this review nanozymes and hybrid nanoflower have been compared in terms of physiochemical properties, common synthetic routes, mechanism of action, modification, green synthesis and application in the field of disease diagnosis, imaging, environmental remediation and disease treatment. We also address the current challenges facing nanozyme and hybrid nanoflower research and the possible way to fulfil their potential in future.

Hybridization of laccase with dendrimer-grafted silica-coated hercynite-copper phosphate magnetic hybrid nanoflowers and its application in bioremoval of gemifloxacin

Laccase was successfully hybridized with polyamidoamine (PAMAM) dendrimer-grafted silica-coated hercynite-copper phosphate magnetic hybrid nanoflowers (MHNFs) to increase the catalytic performance of the enzyme and apply in an effective bioremoval of gemifloxacin. For this purpose, the magnetic nanoparticles (MNPs) of hercynite were covered with a silica layer, and the core-shell SiO₂@hercynite was then modified with PAMAM dendrimer to increase the surface area of the carrier for the enzyme attachment. Subsequently, the whole complex was hybridized with laccase and copper phosphate to attain a large surface area (104.3 m² g^-1). The fabricated MHNFs acquired the entrapment yield and efficiency of 90 ± 3% and 66 ± 5%, respectively. The catalytic activity of the fabricated biocatalyst was remained up to 50% after 13 reusability cycles. Approximately 90% of gemifloxacin was removed by the constructed MHNFs after 3 h incubation by adsorption and degradation mechanisms. The biotransformation products were then identified, and degradation pathways were proposed as defluorination, decarboxylation, elimination of a cyclopropyl group, and cleavage of the pyrrolidine moiety. Furthermore, the toxicity of gemifloxacin was effectively diminished against some bacterial strains.

Biodegradation of environmental pollutants using catalase-based biocatalytic systems

The synergistic combination of biocatalysts and nanomaterials provides a new interface of a robust biocatalytic system that can effectively remediate environmental pollutants. Enzymes, such as catalase-based constructs, impart the desired candidature for catalytic transformation processes and are potential alternatives to replace conventional remediation strategies that have become laborious and somewhat inefficient. Furthermore, the controlled or uncontrolled discharge of various emerging pollutants (EPs) into water bodies is equally proportional to the fast-growing population and extensive urbanization. EPs affect the entire living being and continuously deteriorate the environmental system, directly or indirectly. The occurrence of EPs (even released after partial treatments, but still in bioactive forms) disturbs ecological integrity. Due to the ineffectiveness of in-practice traditional remediation processes, new and robust treatment measures as effective and sustainable remediation have become a meaningful goal. In this context, special attention has been shifted to engineering an enzyme (catalase)-based biodegradation system with immense prospects in environmental cleanup. The unique synergistic combination of nanomaterials (having multifunctional attributes) with enzymes of interest makes them a state-of-the-art interface that can further ameliorate bio-catalysis and biodegradation performance. This review covers current research and scientific advancement in developing and deploying catalase-based biocatalytic systems to mitigate several EPs from the environment matrices. The biocatalytic features of catalase, along with the mechanistic insight into H₂O₂ neutralization, several nano-based materials loaded with catalase, including nanoparticles (NPs), carbon nanotubes (CNTs), metal-organic frameworks (MOFs), polymeric-based composites, oxime-functionalized cryo-gel disks, electro-spun nanofibrous membranes, and other hybrid materials have also been discussed with suitable examples.

Graphene oxide functionalized with cobalt ferrites applied to the removal of bisphenol A: ionic study, reuse capacity and desorption kinetics

A new adsorbent material based on graphene oxide (GO) functionalized with magnetic cobalt ferrite nanoparticles (γCoFe₂O₄) was synthesized via ultrasonication to remove the endocrine-disrupting-chemical bisphenol A (BPA) from aqueous solutions. The synthesized material (GO-γCoFe₂O₄) was characterized by TEM, SEM, DRX and FTIR analysis. Magnetization measures proved that the adsorbent had superparamagnetic characteristics that facilitated its separation from the aqueous solution. The maximum adsorption capacity obtained was 30 mg g^-1 with adsorbent concentration of 1 g L^-1, temperature of 55°C and natural pH of the solution. The experimental data were better adjusted to the kinetic models of pseudo-second-order and Langmuir isotherm. The thermodynamic parameters showed that the BPA adsorption on GO-γCoFe₂O₄ was spontaneous, exothermic and thermodynamically favourable. Desorption kinetics was performed using 50% ethanol as solvent, resulting in an equilibrium time of 4 h with better adjustment to the pseudo-second order kinetic model. The adsorbent showed a high regeneration capacity maintaining adsorptive capacity above 75% after 6 cycles of reuse.

Facile strategy for the synthesis of silver nanoparticles on magnetic Fe3O4@C core-shell nanocomposites and their application in catalytic reduction

The integration of noble metal nanoparticles (NPs) on magnetic hollow structures is of particular importance for high catalytic activity, while the magnetic property is useful for the recovery of the composites. Herein, we prepared Ag NP decorated Fe₃O₄@C hollow magnetic microtubes by a facile and controllable approach. To this end, tannic acid-ferric ion (TA-Fe) first polymerized in situ on the MoO₃@FeOOH microrods and served as a reducing/stabilizing agent to integrate Ag NPs with high coverage. Moreover, no extra reductant was required owing to the reducibility of TA for the formation of FeOOH@TA-Fe/Ag microtubes. After thermal treatment under an N₂ atmosphere, hollow Fe₃O₄@C-Ag microtubes are obtained with a high surface area and excellent magnetism. Remarkable catalytic activity was achieved towards the reduction of 4-nitrophenol (4-NP) owing to the high coverage of Ag NPs on the tube-like structure, while the composite was easily collected with an external magnet. The integration of Ag NPs and the magnetic hollow structure provides a great platform for designing hybrid catalysts with high efficiency and recoverability.

Aptamer-functionalized and silver-coated polydopamine-copper hybrid nanoflower adsorbent embedded with magnetic nanoparticles for efficient mercury removal

Mercury (Hg) emissions are increasing annually owing to rapid global industrialization. Hg poisoning can severely affect the human body owing to its persistence and bioaccumulation. In this study, hybrid nanoflowers (NFs) were synthesized by promoting the formation of primary copper-phosphate crystals coordinated with polydopamine (PDA) and Fe₃O₄ magnetic nanoparticles (MNPs), followed by coating with silver nanoparticles on the surface of the NFs (Ag-MNP-PDA-Cu NFs). The results suggest that the hierarchical structure of the NFs enabled a large surface area with nanosized pores, which were exploited for Hg adsorption. The adsorbed Hg ions could be further eliminated from the solution based on the magnetic characteristics of the NFs. Additionally, hybrid NFs functionalized with Hg²⁺-binding aptamers (Apt-Ag-MNP-PDA-Cu NFs) were prepared based on the silver-sulfur interactions between the Ag-MNP-PDA-Cu NFs and thiol-modified aptamers. The performance of both adsorbents demonstrated that the immobilization of Hg²⁺-binding aptamers significantly improved the elimination of Hg from solution. The Hg²⁺ adsorption isotherm of the Apt-Ag-MNP-PDA-Cu NFs followed the Dubinin-Radushkevich model, with a maximum adsorption capacity of 1073.19 mg/g. The Apt-Ag-MNP-PDA-Cu NFs adsorbed greater amounts of Hg²⁺ than the non-functionalized NFs at the same concentrations, which confirmed that the functionalization of Hg²⁺-binding aptamers on the NFs improved the Hg²⁺ removal performance. The results suggest that Apt-Ag-MNP-PDA-Cu NFs could serve as an efficient Hg-removing adsorbent, possibly by providing binding sites for the formation of T-Hg²⁺-T complexes.

Structure-Property-Function Relationships of Iron Oxide Multicore Nanoflowers in Magnetic Hyperthermia and Photothermia

Magnetite and maghemite multicore nanoflowers (NFs) synthesized using the modified polyol-mediated routes are to date among the most effective nanoheaters in magnetic hyperthermia (MHT). Recently, magnetite NFs have also shown high photothermal (PT) performances in the most desired second near-infrared (NIR-II) biological window, making them attractive in the field of nanoparticle-activated thermal therapies. However, what makes magnetic NFs efficient heating agents in both modalities still remains an open question. In this work, we investigate the role of many parameters of the polyol synthesis on the final NFs' size, shape, chemical composition, number of cores, and crystallinity. These nanofeatures are later correlated to the magnetic, optical, and electronic properties of the NFs as well as their collective macroscopic thermal properties in MHT and PT to find relationships between their structure, properties, and function. We evidence the critical role of iron(III) and heating ramps on the elaboration of well-defined NFs with a high number of multicores. While MHT efficiency is found to be proportional to the average number of magnetic cores within the assemblies, the optical responses of the NFs and their collective photothermal properties depend directly on the mean volume of the NFs (as supported by optical cross sections numerical simulations) and strongly on the structural disorder in the NFs, rather than the stoichiometry. The concentration of defects in the nanostructures, evaluated by photoluminescence and Urbach energy (E_U), evidence a switch in the optical behavior for a limit value of E_U = 0.4 eV where a discontinuous transition from high to poor PT efficiency is also observed.

High Temperature Continuous Flow Syntheses of Iron Oxide Nanoflowers Using the Polyol Route in a Multi-Parametric Millifluidic Device

One of the most versatile routes for the elaboration of nanomaterials in materials science, including the synthesis of magnetic iron oxide nanoclusters, is the high-temperature polyol process. However, despite its versatility, this process still lacks reproducibility and scale-up, in addition to the low yield obtained in final materials. In this work, we demonstrate a home-made multiparametric continuous flow millifluidic system that can operate at high temperatures (up to 400 °C). After optimization, we validate its potential for the production of nanomaterials using the polyol route at 220 °C by elaborating ferrite iron oxide nanoclusters called nanoflowers (CoFe₂O₄, Fe₃O₄, MnFe₂O₄) with well-controlled nanostructure and composition, which are highly demanded due to their physical properties. Moreover, we demonstrate that by using such a continuous process, the chemical yield and reproducibility of the nanoflower synthesis are strongly improved as well as the possibility to produce these nanomaterials on a large scale with quantities up to 45 g per day.

Fabrication of immobilized bromelain using cobalt phosphate material prepared in deep eutectic solvent as carrier

The aim of the present work is to fabricate immobilized bromelain based on the specific interaction between the cobalt ions of carrier and the inherent cysteines contained in bromelain molecules. The cobalt phosphate material was prepared as solid support by using choline chloride (ChCl)/betaine-glycerol deep eutectic solvent (DES) as solvent and template for the first time. The Co-P material with lamellate-based structure obtained in the ChCl-glycerol DES at the Co/P ratio of 3:2 showed the best performance for the immobilization of bromelain. The specific interaction between Co²⁺ and bromelain promoted the aggregation of lamellar Co-P, forming flower-like Co-P@bromelain particles. Under the optimum immobilization conditions, the specific enzyme activity of the immobilized enzyme reached the maximum of 71244 U/g. Compared with Co₃(PO₄)₂ prepared in water system, the obtained Co-P@bromelain using the Co-P material synthesized in the ChCl-glycerol DES as carrier exhibited excellent structure stability. In addition, the immobilized Co-P@bromelain also showed higher catalytic efficiency than free bromelain.

Keratin-inorganic hybrid nanoflowers decorated with Fe3O4 nanoparticles as enzyme mimics for colorimetric detection of glucose

Fe3O4 magnetic nanoparticles (MNPs) are highly active enzyme-like catalysts. However, low stability is still a big challenge for Fe3O4-based enzyme mimics because the Fe3O4 MNPs can be easily dissolved when exposed to acidic conditions. Inspired by the numerous catalytic sites of a flower-like structure and the biological functions of amino acids in structural proteins, herein, by employing keratin as a protein component, stable Fe3O4-based MNP embedded keratin-Cu3(PO4)2 nanoflowers were constructed, from which hierarchical nanostructures with a three-dimensional petal-like morphology were selected for subsequent studies owing to their excellent enzymic catalytic activity. The keratin-nanoflower@Fe3O4 exhibited significantly enhanced catalytic activity compared with that of keratin-Cu3(PO4)2 nanoflowers and individual Fe3O4 MNPs. Remarkably, keratin-nanoflower@Fe3O4 exhibited superior long-term stability to Fe3O4 MNPs under more acidic conditions and favorable reusability. This method has been successfully exploited for the colorimetric determination of glucose in human serum with satisfactory sensitivity and specificity, offering a novel approach for glucose detection.

Immobilized enzymes in inorganic hybrid nanoflowers for biocatalytic and biosensing applications

Enzyme immobilization has been accepted as a powerful technique to solve the drawbacks of free enzymes such as limited activity, stability and recyclability under harsh conditions. Different from the conventional immobilization methods, enzyme immobilization in inorganic hybrid nanoflowers was executed in a biomimetic mineralization manner with the advantages of mild reaction conditions, and thus it was beneficial to obtain ideal biocatalysts with superior characteristics. The key factors influencing the formation of enzyme-based inorganic hybrid nanoflowers were elucidated to obtain a deeper insight into the mechanism for achieving unique morphology and improved properties of immobilized enzymes. To date, immobilized enzymes in inorganic hybrid nanoflowers have been successfully applied in biocatalysis for preparing medical intermediates, biodiesel and biomedical polymers, and solving the environmental or food industrial issues such as the degradation of toxic dyes, pollutants and allergenic proteins. Moreover, they could be used in the development of various biosensors, which provide a promising platform to detect toxic substances in the environment or biomarkers associated with various diseases. We hope that this review will promote the fundamental research and wide applications of immobilized enzymes in inorganic hybrid nanoflowers for expanding biocatalysis and biosensing.

Modulating the biofunctionality of enzyme-MOF nanobiocatalyst through structure-switching aptamer for continuous degradation of BPA

Encapsulating enzyme within MOF (enzyme-MOF) gives rise to new opportunity to improve the fragility of enzyme, but practical application of enzyme-MOF composite is far from being realized. The development of a novel enzyme-MOF composite system should simultaneously guarantee the enhanced activity and controllably complete recycling, and only in this way can we efficiently and economically utilize the enzyme-MOF composite. Herein, we addressed all these fundamental limitations of current enzyme-MOF composite by establishing aptamer-functionalized enzyme-MOF composite (HRP-ZIF-8@P1). HRP-ZIF-8@P1 relied on automatic structure switch of aptamer-target binding and aptamer-cDNA (complementary DNA) hybridization, achieving effectiveness in self-enriching substrate around HRP-ZIF-8@P1 to boost enzymatic activity first, subsequently hybridizing spontaneously with magnetically controllable cDNA sequence (Fe₃O₄@P3) to completely recover the HRP-ZIF-8@P1, where preferentially capturing substrate could further induce the release of the hybridized HRP-ZIF-8@P1 for automatically starting the cyclic enzyme catalysis. A 5.6-fold enhancement in the catalytic efficiency for BPA degradation was endowed, and 94.7% catalytic activity was retained for 8 consecutive degradations of BPA, both of which were even more significant than HRP-ZIF-8. Additionally, remarkable stability of HRP-ZIF-8@P1 was afforded by dual-layer protection of ZIF-8 and P1 in denaturing conditions. Taking the possibility of discovering an aptamer for any target into account, the aptamer-functionalized enzyme-MOF composites provide a generic and simple guide for simultaneously boosting enzymatic activity and controllably full recycling the enzyme-MOF systems, accelerating their commercial utilizations.

A novel enhanced enrichment glucose oxidase@ZIF-8 biomimetic strategy with 3-mercaptophenylboronic acid for highly efficient catalysis of glucose

Herein, a glucose oxidase@ZIF-8 composite (3-MPBA/GOx@ZIF-8) with enhanced enrichment was enabled the rapid encapsulation of glucose oxidase (GOx) into microporous zeolitic imidazolate framework-8 (ZIF-8) for the first time. The 3-MPBA/GOx@ZIF-8 not only has improved affinity and catalytic efficiency to the substrate but also can shorten the formation time. The optimum loading amount of GOx on ZIF-8 was determined to be 470 mg/g. The as-prepared 3-MPBA/GOx@ZIF-8 composite maintained the native conformation of the enzyme and showed excellent bioactivity, even in chemical agents or at high temperature. Furthermore, the 3-MPBA/GOx@ZIF-8 showed satisfactory reusability, preserving almost 80.8 % activity after 7 cycles. The Michaelis constant K_m and specificity constant k_cat/K_m of the 3-MPBA/GOx@ZIF-8 were 0.03 ± 0.02 mM and 63.87 ± 1.96 s^-1 mM^-1, respectively, which were superior to corresponding values of free GOx. Therefore, the 3-MPBA/GOx@ZIF-8 displayed high catalytic efficiency, high loading efficiency and enhanced stability. Moreover, a new type of visual colorimetric sensor for screening of the diabetes was realized through the 3-MPBA/GOx@ZIF-8, which provided a new strategy for the analysis field of glucose.

Exploring current tendencies in techniques and materials for immobilization of laccases - A review

Nanotechnology has transformed the science behind many biotechnological sectors, and applied bio-catalysis is not the exception. In 2017, the enzyme industry was valued at more than 7 billion USD and projected to 10.5 billion by 2024. The laccase enzyme is an oxidoreductase capable of oxidizing phenolic and non-phenolic compounds that have been considered an essential tool in the fields currently known as white biotechnology and green chemistry. Laccase is one of the most robust biocatalysts due to its wide applications in different environmental processes such as detecting and treating chemical pollutants and dyes and pharmaceutical removal. However, these biocatalytic processes are usually limited by the lack of stability of the enzyme, the half-life time, and the application feasibility at an industrial scale. Physical or chemical approaches have performed different laccase's immobilization methods to improve its catalytic properties and reuse. Emerging technologies have been proven to reduce the manufacturing process cost and increase application feasibility while looking for ecological and economical materials that can be used as support. Therefore, this review discusses the trends of enzyme immobilization recently studied, analyzing biomaterials and agro-industrial waste used for that intention, their advantages, and disadvantages. Finally, the work also highlights the performance obtained with these materials and current challenges and potential alternatives.

Synergistic mediation of metallic bismuth and oxygen vacancy in Bi/Bi2WO6-x to promote 1O2 production for the photodegradation of bisphenol A and its analogues in water matrix

Bi/Bi₂WO_6-x heterostructures has been successfully prepared by a facile one-step hydrothermal method. By maneuvering reaction time and Bi/W molar ratio of the precursors, we have been able to selectively introduce oxygen vacancy and metallic Bi into Bi₂WO₆ nanostructures. The obtained Bi/Bi₂WO_6-x heterostructures with more oxygen vacancy and moderate metallic Bi exhibit significantly improved photocatalytic activity for the photodegradation of bisphenol A (BPA) and its analogues due to its great ability for the generation of singlet oxygen (¹O₂), which has proven to work as the main reactive oxygen species during photocatalysis. It is also found the ¹O₂ concentration is highly depended on and modulated by the content of oxygen vacancy and metallic bismuth. Besides, we also demonstrate that the obtained Bi/Bi₂WO_6-x products display efficient photocatalytic performance toward BPA derivatives degradation and enhanced stability to resist the interferences in the water matrix.

A two-step method for the synthesis of magnetic immobilized cellulase with outstanding thermal stability and reusability

The cellulase electrostatically adsorbed on the surface of Fe₃O₄@C magnetic nanoparticles was embedded with silica to form the immobilized cellulase. The stability and reusability were greatly improved, while the synthesis process was simple.

Separation and purification of horseradish peroxidase from horseradish roots using a novel integrated method

The aim of the present work was to develop a novel method integrating two-step aqueous two-phase extraction and temperature-controlled affinity precipitation for the separation and purification of horseradish peroxidase (HRP) from horseradish roots.

Mussel-Inspired Magnetic Nanoflowers as an Effective Nanozyme and Antimicrobial Agent for Biosensing and Catalytic Reduction of Organic Dyes

Mussel-inspired chemistry has been embodied as a method for acquiring multifunctional nanostructures. In this research, a novel mussel-inspired magnetic nanoflower was prepared through a mussel-inspired approach. Herein, magnetic PDA-Cu nanoflowers (NFs) were assembled via incorporating magnetic Fe3O4@SiO2-NH2 core/shell nanoparticles (NPs) into mussel-inspired polydopamine (PDA) and copper phosphate as the organic and inorganic portions, respectively. Accordingly, the flower-like morphology of MNPs PDA-Cu NFs was characterized by scanning electron microscopy (SEM) images. X-ray diffraction (XRD) analysis confirmed the crystalline structure of magnetic nanoparticles (MNPs) and copper phosphate. Vibrating sample magnetometer (VSM) data revealed the superparamagnetic behavior of MNPs (40.5 emu/g) and MNPs PDA-Cu NFs (35.4 emu/g). Catalytic reduction of MNPs PDA-Cu NFs was evaluated through degradation of methylene blue (MB). The reduction of MB pursued the Langmuir-Hinshelwood mechanism and first-order kinetics, in which the apparent reduction rate K app of MB was higher than 1.44 min-1 and the dye degradation ability was 100%. MNPs PDA-Cu NFs also showed outstanding recyclability and reduction efficiency, for at least six cycles. Furthermore, the prepared MNPs PDA-Cu NFs demonstrated a peroxidase-like catalytic activity for catalyzing 3,3',5,5'-tetramethylbenzidine (TMB) to a blue oxidized TMB (oxTMB) solution in the presence of H2O2. Antimicrobial assays for MNPs PDA-Cu and PDA-Cu NFs were conducted on both Gram-negative and Gram-positive bacteria. Moreover, we demonstrated how the existence of magnetic nanoparticles in PDA-Cu NFs influences the inhibition of an increasing zone. Based on the results, mussel-inspired magnetic nanoflowers appear to have great potential applications, including those relevant to biological, catalysis, and environmental research.

Construction of luffa sponge-based magnetic carbon nanocarriers for laccase immobilization and its application in the removal of bisphenol A

The raw material of resin, Bisphenol A (BPA), is an endocrine-disrupting compound that can be continuously released into the environment and directly harms health. In this study, luffa sponge was used as the raw material to prepare magnetic carbon chemicals for laccase immobilization and BPA degradation. The MLC-1 was synthesized by one-step carbonization-magnetization method, which showed good magnetic properties and a strong load capacity for laccase. Compared with free laccase, Laccase@MLC-1 showed stronger thermal stability, better acid-tolerate performance and reusability. Moreover, Laccase@MLC-1 showed higher BPA degradation efficiency than free laccase. 100 mg/L of BPA can be completely removed by Laccase@MLC-1 in 4 h, while only 62.70% of BPA was removed by the same amount of free laccase. By improving reuse strategies, a complete BPA degradation ratio was obtained in each reoperation process. All results proved that Laccase@MLC-1 might be a suitable biocatalyst candidate for BPA removal.

Organic-inorganic nanoflowers: from design strategy to biomedical applications

Organic-inorganic hybrid nanoflowers (NF) with sizes or features on a nanoscale are a class of flower-shaped nanomaterials self-assembled from metal ions and organic components. Here, to be more specific, the organic components mainly refer to biomolecules ranging from proteins, peptides, and amino acids to DNA/RNA. Beyond their pleasing aesthetics, their unique properties and integrated functions have attracted widespread interest and made them promising candidates in the application of biomedical areas. Great efforts have been made to design and synthesize versatile functional hybrid nanoflowers. In this review, we begin with the clarification of versatile recently reported hybrid nanoflowers according to the types of metal ions and biomolecules employed. To highlight the design of organic-inorganic hybrid nanoflowers, their synthetic methods and mechanisms, structural and biological characteristics are discussed. After that, the state-of-the-art applications of hybrid nanoflowers in biomedical fields including biosensing, biocatalysis, and cancer therapy are demonstrated. In the end, we discuss the prospects of organic-inorganic hybrid nanoflowers and highlight the challenges and opportunities for future research.