Organic-inorganic hybrid nanoflowers: types, characteristics, and future prospects

Enzyme-Loaded Flower-Shaped Nanomaterials: A Versatile Platform with Biosensing, Biocatalytic, and Environmental Promise

As a result of their unique structural and multifunctional characteristics, organic-inorganic hybrid nanoflowers (hNFs), a newly developed class of flower-like, well-structured and well-oriented materials has gained significant attention. The structural attributes along with the surface-engineered functional entities of hNFs, e.g., their size, shape, surface orientation, structural integrity, stability under reactive environments, enzyme stabilizing capability, and organic-inorganic ratio, all significantly contribute to and determine their applications. Although hNFs are still in their infancy and in the early stage of robust development, the recent hike in biotechnology at large and nanotechnology in particular is making hNFs a versatile platform for constructing enzyme-loaded/immobilized structures for different applications. For instance, detection- and sensing-based applications, environmental- and sustainability-based applications, and biocatalytic and biotransformation applications are of supreme interest. Considering the above points, herein we reviewed current advances in multifunctional hNFs, with particular emphasis on (1) critical factors, (2) different metal/non-metal-based synthesizing processes (i.e., (i) copper-based hNFs, (ii) calcium-based hNFs, (iii) manganese-based hNFs, (iv) zinc-based hNFs, (v) cobalt-based hNFs, (vi) iron-based hNFs, (vii) multi-metal-based hNFs, and (viii) non-metal-based hNFs), and (3) their applications. Moreover, the interfacial mechanism involved in hNF development is also discussed considering the following three critical points: (1) the combination of metal ions and organic matter, (2) petal formation, and (3) the generation of hNFs. In summary, the literature given herein could be used to engineer hNFs for multipurpose applications in the biosensing, biocatalysis, and other environmental sectors.

Succinic anhydride-based chemical modification making laccase@Cu3(PO4)2 hybrid nanoflowers robust in removing bisphenol A in wastewater

To prepare a robust biocatalyst and enhance the removal of bisphenol A in wastewater, succinic anhydride was reacted with laccase to obtain succinic anhydride-modified laccase (SA-laccase) and then co-crystallized with Cu₃(PO₄)₂ to form SA-laccase@Cu₃(PO₄)₂ hybrid nanoflowers (hNFs). The activity of SA-laccase@Cu₃(PO₄)₂ reached 5.27 U/mg, 1.86-, 2.88- and 2.15-fold those of bare laccase@Cu₃(PO₄)₂, laccase@Ca₃(PO₄)₂ and laccase@epoxy resin, respectively. Compared with free laccase, the obtained hNFs present enhanced activity and tolerance to pH and high temperature in the removal of BPA. Under the optimum conditions of pH 6.0 and 35 °C, BPA removal reached 93.2% using SA-laccase@Cu₃(PO₄)₂ hNFs, which was 1.21-fold of that using free laccase. In addition, the obtained SA-laccase@Cu₃(PO₄)₂ hNFs retained nearly 90% of their initial catalytic activity for BPA removal after 8 consecutive batch cycles. This efficient method for preparing immobilized laccase can also be further developed and improved to acquire green biocatalysts for removing persistent organic pollutants in wastewater.

Preparation of efficient, stable, and reusable copper-phosphotriesterase hybrid nanoflowers for biodegradation of organophosphorus pesticides

Phosphotriesterase (PTE) is considered to be a good biodegradation agent for organophosphorus pesticides. However, the instability of the free PTE limits its application. In this study, the free PTE was hybridized with copper ions (Cu²⁺) to enhance its catalytic stability and activity. The acquired particles were freeze-dried after precipitation with PO₄^3- at 4 °C for 72 h. Scanning electron microscopy showed that the Cu-PTE complexes formed flower-like nanoparticles after hybridization. The characteristic peaks of both the enzyme and metal material were revealed by Fourier transform-infrared spectroscopy. X-ray diffraction analysis indicated that PTE was encapsulated in the Cu₃(PO₄)₂·3H₂O based hybrid nanoflowers. Compared with free PTE, the catalytic activity of Cu-PTE hybrid nanoflowers was significantly increased about 2.2 fold. The catalytic efficiency (k_cat/V_max) of Cu-PTE hybrid nanoflowers was 1.76 fold than that of free PTE. The stability of the immobilized PTE under thermal and pH conditions was improved and the tolerance of it to organic solvents was also enhanced. Moreover, the Cu-PTE hybrid nanoflowers still exhibited 72.3 % relative activity after ten consecutive reactions. In general, this is the first time to use copper based hybrid nanoflowers to immobilize PTE, and the immobilized enzyme shows excellent performance on OPs degradation. The Cu-PTE hybrid nanoflowers may have great potential in the biodegradation of organophosphorus compounds in future.

Protein morphology drives the structure and catalytic activity of bio-inorganic hybrids

Bio-hybrid materials have received a lot of attention in view of their bio-mimicking nature. One such biomimetic material with catalytic activity are the protein derived floral nanohybrid. Copper phosphate coordinated flakes can be curated to distinct floral morphology using proteins. Structurally two different proteins with similar size and with no known enzymatic activity are used to evaluate the role of protein structure and morphology, on the structure-activity relationship of the developed hybrid nanoflowers. Globular protein BSA and bacterial microcompartment domain protein PduBB' are selected. PduBB' because of self-assembling nature forms extended sheets, whereas BSA lacks specific assembly. The developed hybrid NFs differ in their morphology and also in their mimicry as a biological catalyst. The present investigation highlights the importance of the quaternary structure of proteins in tailoring the structure and function of the h-NFs. The results in this manuscript will motivate and guide designing, engineering and selection of glue material for fabricating biomacromolecule derived biohybrid material to mimic natural enzymes of potential industrial application.

Tuning the Morphology of Protein-Inorganic Calcium-Phosphate Supraparticles via Directed Assembly

Understanding the phenomena that govern complex interfacial and directed assemblies is essential for both control and scale-up of particle syntheses. The present work describes an effort to understand, control, and tune the formation of protein-inorganic calcium-phosphate supraparticles that are produced at an oscillating air-water interface created by end-over-end rotation of the synthesis solution. Supraparticles were synthesized under an array of different conditions that varied reagent concentration, the presence of additives, tube size, and rotational speed. Paired with a fluid mechanics model of the end-over-end rotation and dimensional analysis, the sensitivity of the synthesis to physicochemical and mechanical parameters was determined. Surface tension and bubble formation were found to be important criteria for changing the size distribution of supraparticles. Thresholds for the values of the Froude, Iribarren, and rotational Reynolds numbers were identified for narrowing particle size distribution. These results both guide the specific protein-inorganic supraparticle synthesis described here and inform future manipulation and scale-up of other complex interfacial colloidal assemblies.

Identification, characterization, and immobilization of a novel YbfF esterase from Halomonas elongata

The YbfF esterase family, which has a bifurcated binding pocket for diverse ligands, could serve as excellent biocatalysts in industrial and biotechnological applications. Here, the identification, characterization, and immobilization of a novel YbfF esterase (YbfF_{Halomonas elongata}) from Halomonas elongata DSM 2581 is reported. Biochemical characterization of YbfF was carried out using activity staining, chromatographic analysis, kinetic analysis, activity assay, acetic acid release, and pH-indicator-based hydrolysis. YbfF_H.elongata displayed broad substrate specificity, including that for p-nitrophenyl esters, glucose pentaacetate, tert-butyl acetate, and β-lactam-containing compounds, with high efficiency. Based on a homology model of YbfF_H.elongata, Trp²³⁷ in the substrate-binding pocket, a critical residue for catalytic activity and substrate specificity was identified and characterized. Furthermore, crosslinked enzyme aggregates and nanoflower formation were explored to enhance the chemical stability and recyclability of YbfF_H.elongata. The present study is the first report of a YbfF esterase from extremophiles, and explains its protein stability, catalytic activity, substrate specificities and diversities, kinetics, functional residues, amyloid formation, and immobilization.

Flower-Like Superstructures: Structural Features, Applications and Future Perspectives

Mimicking natural objects such as flowers, is an objective of scientists not only because of their attractive appearance, but also to understand the natural phenomena that underpin real world applications such as drug delivery, enzymatic reactions, electronics, and catalysis, to name few. This article reviews the types, preparation methods, and structural features of flower-like structures along with their key applications in various fields. We discuss the various types of flower-like structures composed of inorganic, organic-inorganic hybrid, inorganic-protein, inorganic-enzyme and organic compositions. We also discuss recent development in flower-like structures prepared by self-assembly approaches. Finally, we conclude our review with the future prospects of flower-like micro-structures in key fields, being biomedicine, sensing and catalysis.

Vortex Fluidic-Mediated Fabrication of Fast Gelated Silica Hydrogels with Embedded Laccase Nanoflowers for Real-Time Biosensing under Flow

The fabrication of hybrid protein-Cu3(PO4)2 nanoflowers (NFs) via an intermediate toroidal structure is dramatically accelerated under shear using a vortex fluidic device (VFD), which possesses a rapidly rotating angled tube. As-prepared laccase NFs (LNFs) exhibit ≈1.8-fold increase in catalytic activity compared to free laccase under diffusion control, which is further enhanced by ≈ 2.9-fold for the catalysis under shear in the VFD. A new LNF immobilization platform, LNF@silica incorporated in a VFD tube, was subsequently developed by mixing the LNFs for 15 min with silica hydrogel resulting in gelation along the VFD tube surface. The resulting LNFs@silica coating is highly stable and reusable, which allows a dramatic 16-fold enhancement in catalytic rates relative to LNF@silica inside glass vials. Ultraviolet-visible spectroscopy-based real-time monitoring within the LNFs@silica-coated tube reveals good stability of the coating in continuous flow processing. The results demonstrate the utility of the VFD microfluidic platform, further highlighting its ability to control chemical and enzymatic processes.

Improving the Catalytic Performance of Pectate Lyase Through Pectate Lyase/Cu3(PO4)2 Hybrid Nanoflowers as an Immobilized Enzyme

Pectate lyases (Pels) can be used in the textile industrial process for cotton scouring and ramie degumming, and its hydrolyzed products oligo galacturonic acid, are high-value added agricultural and health products. In our previous studies, an alkaline pectate lyase PEL168 mutant, PEL3, was obtained with improved specific activity and thermostability. Here, a facile and rapid method for preparing an immobilized PEL3-inorganic hybrid nanoflower was developed, as it could improve its biocatalytic performance. With 0.02 mg/mL (112.2 U/mL) PEL3 in PBS buffer, five different divalent ions, including Mn2+, Ca2+, Co2+, Zn2+, and Cu2+, were used as inorganic component. The results showed that PEL3/Cu3(PO4)2 hybrid nanoflowers presented the highest relative activity with 2.5-fold increase, compared to the free PEL3. X-ray diffraction analysis confirmed that the composition of PEL3/Cu3(PO4)2 hybrid nanoflowers were pectate lyase PEL3 and Cu3(PO4)2⋅5H2O. The optimum temperature and pH of PEL3/Cu3(PO4)2 hybrid nanoflowers were ascertained to be 55°C and pH 9.0, respectively, exhibiting subtle difference from the free PEL3. However, the PEL3/Cu3(PO4)2 hybrid nanoflowers maintained 33% residual activity after 24 h incubation at 55°C, while the free PEL3 completely lost its activity after 18 h incubation at 55°C. Furthermore, over 50% residual activity of the PEL3/Cu3(PO4)2 hybrid nanoflowers was remained, even after four times of repetitive utilization, demonstrating its promising stability for practical application.

Recent Advances in Enzyme-Nanostructure Biocatalysts with Enhanced Activity

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.

Supported growth of inorganic-organic nanoflowers on 3D hierarchically porous nanofibrous membrane for enhanced enzymatic water treatment

Organic-inorganic nanoflower is a new type of functional material that can effectively immobilize a wide range of enzymes to form flower-like structures for various enzymatic applications with enhanced catalytic performance and stability. In order to avoid the processing inconvenience and flower structure damage caused by the particular form of these hybrid nanoflowers during material fabrication and catalytic application, different substrates have been used to carry out supported growth of hybrid nanoflowers. However, all previously used substrates have only 2-dimensional feature and only incorporate hybrid nanoflowers on surface with limited nanoflower loading. In this study, three-dimensional (3D) hierarchically porous nanofibrous PVA-co-PE membranes (HPNM) are prepared by a simple template method for effectively immobilizing laccase-Cu₂(PO₄)₃•3H₂O hybrid nanoflowers. Compared with dense nanofibre membrane with only small sized pores (<1 micron), the coexistence of both small and large sized (30-80 microns) pores of HPNM could significantly increase the nanoflower density and allow the penetrated growth of hybrid nanoflowers into the inner structure of the membrane. The hybrid nanoflower containing hierarchically porous nanofibrous membranes (HNF-HPNM) show excellent catalytic performance in degrading different types of textile dyes (reactive blue 2, acid blue 25, acid yellow 76 and indigo carmine), with a degradation efficiency of ˜99.5% for indigo carmine. In addition, the HNF-HPNM could be reused at least 14 times for indigo carmine degradation, with a negligible degradation efficiency drop from 99.48% to 98.52%. These results indicate that hierarchically porous nanofibrous membrane can be a promising type of materials for supported hybrid nanoflower growth for practical applications such as waste water treatment, dye degradation and biosensing.

Inky flower-like supermicelles assembled from π-conjugated block copolymers

Conjugated block copolymers PPV₇-b-P2VP_n are utilized as building blocks to construct inky flower-like hierarchical supermicelles. The assembly process is tracked and the control of morphology is successfully realized.

Facile synthesis of Au@Mn3O4 magneto-plasmonic nanoflowers for T1-weighted magnetic resonance imaging and photothermal therapy of cancer

The integration of advanced diagnostic contrast agents with versatile therapeutic nanoparticles presents an effective method for cancer treatment.

Selectivity and bio-compatibility of self-assembled chiral flower-like and helical nanostructures

The molecular building block NDI–LCA was synthesized via substitution of NDA at the di-imide position with two lithiocholic acid moieties, resulted into chiral flower line and helical nanostructures.

Ciprofloxacin Functionalized Biogenic Gold Nanoflowers as Nanoantibiotics Against Pathogenic Bacterial Strains

PURPOSE

Antibiotics are currently being rendered non-functional by the rising incidence of multi-drug resistance amongst pathogenic bacteria. Research has now been focused on developing solutions to this problem by creating new antibiotics and enhancing the functionality of the existing ones.

PATIENTS AND METHODS

In the present study, ciprofloxacin was conjugated to biogenic gold nanoflowers (GNFs) from Bacillus subtilis RSB64 by a robust adsorption method under optimized conditions. The resultant drug-nanoflower conjugate was characterized by UV-visible spectroscopy and Fourier transform infrared spectroscopy (FTIR). Addition of ciprofloxacin to gold nanoflowers changed the extinction spectrum towards longer wavelength. The ciprofloxacin-conjugated gold nanoflowers were tested for the drug release statistically. The prepared nanoflower-drug conjugate was subjected to an in vitro microbiological assay against different Gram-positive and Gram-negative bacterial strains to verify the effect of GNF-ciprofloxacin conjugate on the cell growth inhibitory activity of ciprofloxacin.

RESULTS

The GNF-ciprofloxacin conjugates demonstrated enhanced bactericidal activity against Gram-negative bacteria as compared to Gram-positive. The enhancement of the antibacterial activity of the nanoflower-drug conjugate could be attributed to the interaction of the conjugate with phosphate/amine group of the outer membrane of Gram-negative bacterial cell wall making them susceptible to the antibacterial effect of the conjugate.

CONCLUSION

This study demonstrates the positive attributes of GNF-ciprofloxacin conjugates as a promising antibacterial therapeutic agent against pathogens.

Molecular Characterization of a Novel Family VIII Esterase with β-Lactamase Activity (PsEstA) from Paenibacillus sp

Molecular information about family VIII esterases, which have similarities with class C β-lactamases and penicillin-binding proteins, remains largely unknown. In this study, a novel family VIII esterase with β-lactamase activity (PsEstA) from Paenibacillus sp. was characterized using several biochemical and biophysical methods. PsEstA was effective on a broad range of substrates including tertiary butyl acetate, glyceryl tributyrate, glucose pentaacetate, olive oil, and p-nitrophenyl esters. Additionally, PsEstA hydrolyzed nitrocefin, cefotaxime, and 7-aminocephalosporanic acid. Interestingly, two forms of immobilized PsEstA (CLEAs-PsEstA and mCLEAs-PsEstA) showed high recycling property and enhanced stability, but hybrid nanoflowers (hNFs) of PsEstA require improvement. This study provides a molecular understanding of substrate specificities, catalytic regulation, and immobilization of PsEstA, which can be efficiently used in biotechnological applications.

Cu-nanoflower decorated gold nanoparticles-graphene oxide nanofiber as electrochemical biosensor for glucose detection

A novel electrospinning approach is proposed for the fabrication of copper (Cu)-nanoflower decorated gold nanoparticles (AuNPs)-graphene oxide (GO) nanofiber (NF) as an electrochemical biosensor for the glucose detection. In this study, GO was mixed with poly(vinyl alcohol) (PVA) and used as a fiber precursor, which greatly improves the electrochemical properties. The above solution was uniformly coated onto the surfaces of gold chip to form GO NFs via electrospinning. AuNPs were coated onto the surface of GO NFs and then incorporated organic-inorganic hybrid nanoflower [Cu nanoflower-glucose oxidase (GOx) and horseradish peroxidase (HRP)]. The electrochemical experiments revealed that Cu-nanoflower@AuNPs-GO NFs exhibited outstanding electrochemical catalytic nature, and selectivity for the conversion of glucose to gluconic acid in the presence of GOx-HRP-Cu nanoflower. The Cu-nanoflower@AuNPs-GO NFs coated Au chip exhibited good linear range 0.001-0.1 mM, with a detection limit of 0.018 μM. The Cu-nanoflower@AuNPs-GO NFs modified Au chip exhibited higher catalytic properties, which are attributed to the coating of unique organic-inorganic nanostructured materials on the surfaces of Au chip. These results indicate that the nano-bio hybrid materials can be applied as a promising electrochemical biosensor to monitor glucose levels in biofluids.

Facile synthesis of alcalase-inorganic hybrid nanoflowers used for soy protein isolate hydrolysis to improve its functional properties

In this work, a facile approach was developed to synthesized alcalase-inorganic hybrid nanocomposite (alcalase@CaHPO4) by immobilizing alcalase with calcium hydrogen phosphate (CaHPO4). The nanocomposite possessed flower-like morphological features with excellent hydrolysis activity on soybean protein isolates (SPI) with 1.57 fold higher compared to free alcalase. The experiment was evident of alcalase@CaHPO4 hybrid nanoflowers with 90% sustainability after the seven cycles of reusability and 80-100% relative activity at 50-70 °C and with 65% at pH 4 in acidic condition. Soybean protein hydrolysates (SPHs) produced by immobilized alcalase possessed 70% radical-scavenging capacity at 0.8 mg/mL concentration and 20% calcium-binding capacity at pH 6. The solubility of SPHs produced by alcalase@CaHPO4 hybrid nanoflowers was also improved by 15% compared to free alcalase. The high radical scavenging capability, good calcium binding capacity and improved solubility of SPHs prepared through alcalase@CaHPO4 hybrid nanoflowers would be highly promising in food industries.

Engineering enzyme-coupled hybrid nanoflowers: The quest for optimum performance to meet biocatalytic challenges and opportunities

The current industrial revolution signifies the high-value of biocatalysis engineering. Over the past decade, multiple micro- and nanostructured materials have been attempted for immobilization of enzymes to improve their catalytic properties. Conventional immobilization strategies result in improved stability, while insolubilized enzymes generally lost their activity compared to free counterparts. Recently, a new generation organic-inorganic hybrid nanoflowers with unique properties have received great attention as a novel and incentive immobilization approach owing to their simple fabrication, high biocatalytic efficiency, and enzyme stabilizing capability. The hybrid nanoflowers biocatalytic system implicates metal ions and biomolecules (enzymes). In contrast to free or conventionally immobilized enzymes, single enzyme or multi enzyme-incorporated flowers-like hybrid nanoconstructs demonstrated elevated catalytic activities and stabilities over a very broader range of experimental conditions, i.e., pHs, temperatures and salt concentration. This review discusses the recent developments in the fabrication strategies to diversifying nanoflowers, types, characteristics, and applications of organic-inorganic hybrid nanoflowers as a host platform to engineer different kinds of enzymes with requisite functionalities for biocatalysis applications in different sectors of the modern world. Based on experimental and theoretical literature data, the review is wrapped up with concluding remarks and an outlook in terms of upcoming challenges and prospects for their scale-up applications.

Fullerene-Directed Synthesis of Flowerlike Cu3(PO4)2 Crystals for Efficient Photocatalytic Degradation of Dyes

Biomineralization is a typical methodology developed by nature to produce calcium-based materials. A method mimicking this process has nowadays become popular for the preparation of artificial organic-inorganic hybrids. Here, Cu₃(PO₄)₂ crystals with a flowerlike morphology have been prepared using water-soluble derivatives of fullerene C₆₀ as templates. In a typical system, flowerlike crystals of Cu₃(PO₄)₂ (denoted FLCs-Cu) were obtained by simply dropping an aqueous solution of CuSO₄ into phosphate-buffered saline (PBS) containing a highly water-soluble multiadduct of C₆₀ (fullerenol). The best condition for the preparation of FLCs-Cu appeared at 0.20 mg·mL^-1 fullerenol and 0.10 mol·L^-1 PBS. During the formation of FLCs-Cu, fullerenol acts as a template and its content in FLCs-Cu is trace (less than 5% by atom) as confirmed by scanning electron microscopy mapping and thermogravimetric analysis. This feature makes fullerenol reusable, and the FLCs-Cu can be prepared repeatedly using the same fullerenol aqueous solution at least 10 times without a noticeable change in the morphology. The N₂ adsorption/desorption isotherm showed that the doping of fullerenol increased the specific surface area of the Cu₃(PO₄)₂ crystal. When fullerenol was replaced by C₆₀ monoadducts that are cofunctionalized with a pyrrolidine cation and oligo(poly(ethylene oxide)) chains, FLCs-Cu can form as well, indicating that the strategy of using water-soluble C₆₀ derivative as a template to get FLCs-Cu is universal. As a typical example of practical applications, the photocatalytic activity of the FLCs-Cu was investigated toward the degradation of dyes including rhodamine B and rhodamine 6G. In both cases, efficient photodegradation has been confirmed.

Magnetic Nanoparticles-Embedded Enzyme-Inorganic Hybrid Nanoflowers with Enhanced Peroxidase-Like Activity and Substrate Channeling for Glucose Biosensing

It is reported that glucose oxidase (GOx)-copper hybrid nanoflowers embedded with Fe₃ O₄ magnetic nanoparticles (MNPs) exhibit superior peroxidase-mimicking activity as well as substrate channeling for glucose detection. This is due to the synergistic integration of GOx, crystalline copper phosphates and MNPs being in close proximity within the nanoflowers. The preparation of MNP-embedded GOx-copper hybrid nanoflowers (MNPs-GOx NFs) begins with the facile conjugation of amine-functionalized MNPs with GOx molecules via electrostatic attraction, followed by the addition of copper sulfate that leads to full blooming of the hybrid nanoflowers. In the presence of glucose, the catalytic action of GOx entrapped in the nanoflowers generates H₂ O₂ , which is subsequently used by peroxidase-mimicking MNPs and copper phosphate crystals, located close to GOx molecules, to convert Amplex UltraRed substrate into a highly fluorescent product. Using this strategy, the target glucose is successfully determined with excellent selectivity, stability, and magnetic reusability. This biosensor based on hybrid nanoflowers also exhibits a high degree of precision and reproducibility when applied to real human blood samples. Such novel MNP-embedded enzyme-inorganic hybrid nanoflowers have a great potential to be expanded to any oxidases, which will be highly beneficial for the detection of various other clinically important target molecules.

Fabrication of pioneering 3D sakura-shaped metal-organic coordination polymers Cu@L-Glu phenomenal for signal amplification in highly sensitive detection of zearalenone

Low molecular weight pollutants from foods have aroused global attention due to their toxicity after long-time exposure. There is an increased demand for appropriate methods to detect these pollutants in foods. In this study, a brand-new type of nano metal-organic coordination polymers (MOCPs) nanocarriers (3D sakura-shaped copper (II) ions@L-glutamic acid (L-Glu)) has been first synthesized. We herein demonstrate a facile chelated method that allows the combination of copper (II) ions and L-Glu. A series of controlled experiments have revealed that the reaction time and the ratio of reactants played the crucial roles in affecting the morphology of the final product. 3D sakura-shaped Cu@L-Glu combined with palladium-platinum nanoparticle (Pd-PtNPs) to obtain Cu@L-Glu/Pd-PtNPs acting as the signal tag, which applied in electrochemical aptasensor for ultrasensitive detection of zearalenone (ZEN). A glassy carbon electrode was first modified with spherical Au-PANI-Au nanohybrids to enhance the conductivity and immobilize more amino modified ZEN aptamer. Cu@L-Glu/Pd-PtNPs were labeled with Complementary DNA (partial matching with ZEN aptamer) to form bioconjugates for signal amplification. After the hybridization reaction of ZEN aptamer and the bioconjugates, a significant electrochemical signal from the catalysis of H₂O₂ by Cu@L-Glu/Pd-PtNPs can be observed. ZEN competed with bioconjugates for binding to ZEN aptamer, resulting in decreased the electrochemical signal. Chronoamperometry was applied to record the final electrochemical signals. Under optimal conditions, the electrochemical aptasensor exhibited desirable sensitive detection of ZEN with a wide linearity ranging from 1 fg/mL to 100 ng/mL and a relatively low detection limit of 0.45 fg/mL (S/N = 3). Furthermore, the proposed electrochemical aptasensor shows excellent selectivity to the ZEN in the presence of possible interfering substances, and has potential application for ZEN detection in food samples.

Purification and Characterization of A New Cold-Adapted and Thermo-Tolerant Chitosanase from Marine Bacterium Pseudoalteromonas sp. SY39

Chitosanases play an important role in chitosan degradation, forming enzymatic degradation products with several biological activities. Although many chitosanases have been discovered and studied, the enzymes with special characteristics are still rather rare. In this study, a new chitosanase, CsnM, with an apparent molecular weight of 28 kDa was purified from the marine bacterium Pseudoalteromonas sp. SY39. CsnM is a cold-adapted enzyme, which shows highest activity at 40 °C and exhibits 30.6% and 49.4% of its maximal activity at 10 and 15 °C, respectively. CsnM is also a thermo-tolerant enzyme that recovers 95.2%, 89.1% and 88.1% of its initial activity after boiling for 5, 10 and 20 min, respectively. Additionally, CsnM is an endo-type chitosanase that yields chitodisaccharide as the main product (69.9% of the total product). It’s cold-adaptation, thermo-tolerance and high chitodisaccharide yield make CsnM a superior candidate for biotechnological application to produce chitooligosaccharides.

Green biotransformations catalysed by enzyme-inorganic hybrid nanoflowers in environmentally friendly ionic solvents

Environmentally friendly ionic solvents such as (a) ionic liquids (ILs) formulated with hydroxyl ammonium cations and various carboxylic acid anions and (b) choline chloride or ethyl ammonium chloride-based deep eutectic solvents (DES) were tested as media for hydrolytic and synthetic reactions catalysed by lipase-inorganic hybrid nanoflowers. The nature of ionic solvents used has a significant effect on the hydrolytic and synthetic activity of the immobilized lipase, as well as on its stability and reusability. In choline chloride-based DES, the activity and especially the operational stability of the biocatalyst are significantly increased compared to those observed in buffer, indicating the potential application of these solvents as green media for various biocatalytic processes of industrial interest.

Morphology Evolution and Control of Mo-polydopamine Coordination Complex from 2D Single Nanopetal to Hierarchical Microflowers

Controllable synthesis of functional materials is of widespread interest for particle engineering. Such a method has not been widely promoted due to the lack of recognition of the fundamental principle, especially for organic-inorganic hybrid materials. Here, as an entrance, the controllable synthesis of Mo-polydopamine coordination flowers is realized through a facile foaming method, and a 2D nanopetal as the building monomer of the flower is synthesized. Depending on the morphology evolution of Mo-dopamine complex under different conditions, and the surface iterative topology growth of the Mo-polydopamine petal, the reasons of why the Mo-polydopamine complex self-assembles into a flower structure can be attributed to the synergistic effect of multicore symbiosis and structural self-protective growth behaviors. Benefiting from the strong structure stability of the Mo-polydopamine nanopetal, a hybrid structure of MoO₂ quantum dot in situ anchoring in the N-doped 2D carbon framework is prepared by direct pyrolysis, which shows a highly reversible performance in application for lithium-ion secondary batteries (LIBs). This work enhances the possibility for the controllable synthesis of organic-inorganic hybrid materials by adjusting the multicore intergrowth and inhibiting the interfacial assembly.

Synthesis of cross-linked protein-metal hybrid nanoflowers and its application in repeated batch decolorization of synthetic dyes

Herein, we report the preparation of a cross-linked protein-metal hybrid nanoflower (NF) system for laccase immobilization. The immobilized laccase showed effective encapsulation yield and activity recovery of 78.1% and 204%, respectively. The catalytic efficiency (k_catV_max^-1) of cross-linked NF (CL-NF) was 2.2-fold more than that of free laccase. The CL-NF also exhibited significantly higher stability towards pH and temperature changes. It exhibited excellent storage stability and tolerance towards solvents and inhibitors as compared with the free enzyme. After 10 cycles of reuses, the NF and CL-NF laccase showed 41.2% and 92.3% residual activity, respectively. The CL-NF showed high oxidation potential, 265% that of the free enzyme, towards phenolic compounds. The CL-NF laccase retained the residual decolorization efficiency of up to 84.6% for synthetic dyes under repeated batch conditions of 10 cycles. These results suggested that the preparation of CL-NF is an effective approach to enhance the enzymatic properties and has great potential in many industrial applications.

Nanoflowers: the future trend of nanotechnology for multi-applications

Nanoflowers are a newly developed class of nanoparticles showing structure similar to flower and gaining much attention due to their simple method of preparation, high stability and enhance efficiency. This article focuses on advantages, disadvantages, method of synthesis, types and applications of nanoflowers with futuristic approaches. The applications of nanoflower include its use as a biosensor for quick and precise detection of conditions like diabetes, Parkinsonism, Alzheimer, food infection, etc. Nanoflowers have been revealed for site-specific action and controlled delivery of drugs. The extended applications of nanoflowers cover purification of enzyme, removal of dye and heavy metal from water, gas-sensing using nickel oxide. Recent investigation shows 3 D structure of nanoflowers for enhancing surface sensitivity using Raman spectroscopy. This nanoflower system will act as a smart material in the near future due to high surface-to-volume ratio and enhance adsorption efficiency on its petals.

A trypsin–calcium carbonate hybrid nanosphere based enzyme reactor with good stability and reusability

Trypsin not only acts as a novel robust biotemplate to mediate the growth of CaCO₃ crystals, but also enhances their biological properties as an excellent enzyme.

Self-assembled 2,4-dichlorophenol hydroxylase-inorganic hybrid nanoflowers with enhanced activity and stability

2,4-Dichlorophenol hydroxylase (2,4-DCP hydroxylase) is a key enzyme in the degradation of 2,4-dichlorophenoxyacetic acid in the hydroxylation step in many bacteria. Our previous study demonstrated that a cold-adapted 2,4-DCP hydroxylase (tfdB-JLU) exhibits broad substrate specificity for chlorophenols, biphenyl derivatives and their homologues. However, the stability of this enzyme is not satisfactory in practical use. There have been no reports of immobilizing a cold-adapted enzyme to improve its activity and stability so far. This study for the first time reports a facile approach for the synthesis of hybrid nanoflowers (hNFs) formed from cold-adapted 2,4-dichlorophenol hydroxylase (tfdB-JLU) and Cu₃(PO₄)₂·3H₂O. The influence of experimental factors, such as the pH of the solution mixture and the enzyme and Cu²⁺ concentrations, on the activity of the prepared tfdB-JLU-hNFs is investigated. The morphologies of the tfdB-JLU-hNFs are further analyzed by SEM and TEM. Compared to the free enzyme, the tfdB-JLU-hNFs exhibit up to 162.46 ± 1.53% enhanced 2,4-dichlorophenol degradation activity when encapsulated at different enzyme concentrations. The tfdB-JLU-hNFs exhibit excellent durability with 58.34% residual activity after six successive cycles, and up to 90.58% residual activity after 20 days of storage. These results demonstrate that this multistage and hierarchical flower-like structure can effectively increase enzyme activity and stability with respect to those of the free enzyme. The satisfactory removal rate of 2,4-dichlorophenol catalyzed by tfdB-JLU-hNFs suggests that this immobilized enzyme exhibits great potential for application in bioremediation.

Highly stable and active hydroxylase-inorganic hybrid nanoflowers with great potential for application in bioremediation were obtained.

Synthesis of α-glycosidase hybrid nano-flowers and their application for enriching and screening α-glycosidase inhibitors

To rapidly and accurately screen compounds present in traditional Chinese herbal medicines for α-glycosidase inhibitors, we synthesized a novel nano-affinity material to enable the targeted screening of α-glycosidase inhibitors.

Novel organic/inorganic hybrid flower-like structure of selenium nanoparticles stabilized by pullulan derivatives

We proudly present the first organic/inorganic hybrid pullulan/SeNPs hybrid microflower material obtained using a simple and bio-inspired strategy. The chemical structures of pullulan, folic acid decorated cationic pullulan (FA-CP) were designed for stabilizing selenium nanoparticles (SeNPs). SeNPs stabilized by FA-CP hybrid microflowers were observed after the addition of a cysteine hydrochloride solution into the solution mixture of Na₂SeO₃ and FA-CP. We suggested that the concentrations of cysteine and FA-CP were the key factors for the formation of flower-like structure. In addition, the formation mechanism of the microflowers was tentatively identified as anisotropic hierarchical growth. The microflowers exhibited effective drug adsorption with the loading capacity of 142.2 mg g^-1 for doxorubicin which was three times higher than that for the doxorubicin-loaded spherical SeNPs and showed more potent activity against cancer cells while showing less toxicity against normal cells. These data demonstrated that the microflower-like FA-CP/SeNPs structure could be a candidate anticancer drug template in drug delivery systems.

A simple and eco-friendly one-pot synthesis of nuclease-resistant DNA–inorganic hybrid nanoflowers

A simple and eco-friendly method has been developed for the one-pot synthesis of DNA–copper nanoflowers that exhibit high loading efficiencies, low cytotoxicities, and strong resistance against nucleases.