Copper Phosphinate Complexes as Molecular Precursors for Ethanol Dehydrogenation Catalysts

Nowadays, the production of acetaldehyde heavily relies on the petroleum industry. Developing new catalysts for the ethanol dehydrogenation process that could sustainably substitute current acetaldehyde production methods is highly desired. Among the ethanol dehydrogenation catalysts, copper-based materials have been intensively studied. Unfortunately, the Cu-based catalysts suffer from sintering and coking, which lead to rapid deactivation with time-on-stream. Phosphorus doping has been demonstrated to diminish coking in methanol dehydrogenation, fluid catalytic cracking, and ethanol-to-olefin reactions. This work reports a pioneering application of the well-characterized copper phosphinate complexes as molecular precursors for copper-based ethanol dehydrogenation catalysts enriched with phosphate groups (Cu-phosphate/SiO2). Three new catalysts (CuP-1, CuP-2, and CuP-3), prepared by the deposition of complexes {Cu(SAAP)}n (1), [Cu6(BSAAP)6] (2), and [Cu3(NAAP)3] (3) on the surface of commercial SiO2, calcination at 500 °C, and reduction in the stream of the forming gas 5% H2/N2 at 400 °C, exhibited unusual properties. First, the catalysts showed a rapid increase in catalytic activity. After reaching the maximum conversion, the catalyst started to deactivate. The unusual behavior could be explained by the presence of the phosphate phase, which made Cu2+ reduction more difficult. The phosphorus content gradually decreased during time-on-stream, copper was reduced, and the activity increased. The deactivation of the catalyst could be related to the copper diffusion processes. The most active CuP-1 catalyst reaches a maximum of 73% ethanol conversion and over 98% acetaldehyde selectivity at 325 °C and WHSV = 2.37 h-1.

Rational design of polymeric nanozymes with robust catalytic performance via copper-ligand coordination

Incorporating copper (Cu) ions into polymeric particles can be a straightforward strategy for mimicking copper enzymes, but it is challenging to simultaneously control the structure of the nanozyme and of the active sites. In this report, we present a novel bis-ligand (L₂) containing bipyridine groups connected by a tetra-ethylene oxide (4EO) spacer. In phosphate buffer the Cu-L₂ mixture forms coordination complexes that (at proper composition) can bind polyacrylic acid (PAA) to produce catalytically active polymeric nanoparticles with well-defined structure and size, which we refer to as 'nanozymes'. Manipulating the L₂/Cu mixing ratio and using phosphate as a co-binding motif, cooperative copper centres are realized that exhibit promoted oxidation activity. The structure and activity of the so-designed nanozymes remain stable upon increasing temperature and over multiple cycles of application. Increasing ionic strength causes enhanced activity, a response also seen for natural tyrosinase. By means of our rational design we obtain nanozymes with optimized structure and active sites that in several respects outperform natural enzymes. This approach therefore demonstrates a novel strategy for developing functional nanozymes, which may well stimulate the application of this class of catalysts.

Therapeutic Potency of NO Loaded into Anticancer Copper Metal-Organic Framework through Nonclassical Hydrogen Bonding

Metal-organic frameworks (MOFs) are potential exogenous scaffolds for therapeutic nitric oxide (NO) delivery because they can store drug or bioactive gas molecules within pores or on active metal sites. Herein, we employed a Cu-MOF coordinated with glutarate (glu) and 1,2-bis(4-pyridyl)ethane (bpa) to obtain NO-loaded Cu-MOF (NO⊂Cu-MOF). NO loading transformed the space group of Cu-MOF from monoclinic C2/c to triclinic P-1 through nonclassical hydrogen bonding with glu and bpa. Cu-MOF showed good stability in deionized water and phosphate-buffered saline. NO⊂Cu-MOF released up to 1.10 μmol mg-1 NO over 14.6 h at 37 °C, which is suitable for therapeutic applications. NO⊂Cu-MOF showed moderate biocompatibility with L-929 cells and significant anticancer activity against HeLa cells, suggesting an apoptosis-mediated cell death mechanism. These insights into NO bonding modes with Cu-MOF that enable controlled NO release can inspire the design of functional MOFs as hybrid NO donors for drug delivery.

Preparation of Fetal Bovine Serum-Copper Phosphate Hybrid Particles under Cell Culture Conditions for Cancer Cell Treatment

Fetal bovine serum (FBS) particles, which mainly consist of bovine serum albumin, have the potential for biological and medical applications as drug carriers. The coacervation of albumin is a common technique for preparing albumin-based particles. The replacement of salt with novel metal salts such as Cu is an affordable way to embed the metal ion in the albumin-based particles. Further, increased Cu distribution is prevalent in many cancers. Here, we prepared adhesive cell-like FBS-copper phosphate hybrid particles [FBS-Cu₃(PO₄)₂], which exhibited toxicity toward cancer cells, with a narrow size distribution under cell culture conditions for preventing tumor progression. FBS-Cu₃(PO₄)₂ showed peroxidase-like activity. In addition, FBS-Cu₃(PO₄)₂ was successfully loaded with rhodamine B and conjugated with fluorescein isothiocyanate as models of drugs by coincubation. Thus, we designed a simple preparation method for optimizing FBS-Cu₃(PO₄)₂ synthesis under cell culture conditions. FBS-Cu₃(PO₄)₂ has significant potential as an efficient reactive oxygen species generator and drug-delivery agent against cancer cells. Furthermore, the RhoB-loaded FBS-Cu₃(PO₄)₂ successfully interacted with 4T1 mouse mammary tumor cells and were confirmed to exhibit toxicity.

Instantaneous synthesis and full characterization of organic-inorganic laccase-cobalt phosphate hybrid nanoflowers

A novel approach termed the "concentrated method" was developed for the instant fabrication of laccase@Co₃(PO₄)₂•hybrid nanoflowers (HNFs). The constructed HNFs were obtained by optimizing the concentration of cobalt chloride and phosphate buffer to reach the highest activity recovery. The incorporation of 30 mM CoCl₂ and 160 mM phosphate buffer (pH 7.4) resulted in a fast anisotropic growth of the nanomaterials. The purposed method did not involve harsh conditions and prolonged incubation of precursors, as the most reported approaches for the synthesis of HNFs. The catalytic efficiency of the immobilized and free laccase was 460 and 400 M⁻¹S⁻¹, respectively. Also, the enzymatic activity of the prepared biocatalyst was 113% of the free enzyme (0.5 U mL⁻¹). The stability of the synthesized HNFs was enhanced by 400% at pH 6.5–9.5 and the elevated temperatures. The activity of laccase@Co₃(PO₄)₂•HNFs declined to 50% of the initial value after 10 reusability cycles, indicating successful immobilization of the enzyme. Structural studies revealed a 32% increase in the α-helix content after hybridization with cobalt phosphate, which improved the activity and stability of the immobilized laccase. Furthermore, the fabricated HNFs exhibited a considerable ability to remove moxifloxacin as an emerging pollutant. The antibiotic (10 mg L⁻¹) was removed by 24% and 75% after 24 h through adsorption and biodegradation, respectively. This study introduces a new method for synthesizing HNFs, which could be used for the fabrication of efficient biocatalysts, biosensors, and adsorbents for industrial, biomedical, and environmental applications.

Therapeutic Application of Metal–Organic Frameworks Composed of Copper, Cobalt, and Zinc: Their Anticancer Activity and Mechanism

Effective penetration into cells, or binding to cell membranes is an essential property of an effective nanoparticle drug delivery system (DDS). Nanoparticles are generally internalized through active transport mechanisms such as apoptosis, and cargo can be released directly into the cytoplasm. A metal–organic framework (MOF) is a network structure consisting of metal clusters connected by organic linkers with high porosity; MOFs provide a desirable combination of structural features that can be adjusted with large cargo payloads, along with Cu, Co, and Zn-MOFs, which have the chemical stability required for water-soluble use. Bioactive MOFs containing copper, cobalt, and zinc were prepared by modifying previous methods as therapeutic drugs. Their structures were characterized via PXRD, single-crystal crystallographic analysis, and FT-IR. The degradability of MOFs was measured in media such as deionized water or DPBS by PXRD, SEM, and ICP-MS. Furthermore, we investigated the anticancer activity of MOFs against the cell lines SKOV3, U87MG, and LN229, as well as their biocompatibility with normal fibroblast cells. The results show that a nanoporous 3D Cu-MOF could potentially be a promising candidate for chemoprevention and chemotherapy.

Hydrogen-Bonding 2D Coordination Polymer for Enzyme-Free Electrochemical Glucose Sensing

Regular detection of blood glucose levels is a critical indicator for effective diabetes management. Owing to the intrinsic highly sensitive nature of enzymes, the performance of enzymatic glucose sensors is...

Bioinspired self-cleaning surface with microflower-like structures constructed by electrochemically corrosion mediated self-assembly

Developing facile and low-cost methods for the fabrication of bioinspired self-cleaning surfaces is of significant importance but still very challenging. In this work, we present a simple facile and low-cost...

Immobilization of transaminase from Bacillus licheniformis on copper phosphate nanoflowers and its potential application in the kinetic resolution of RS-α-methyl benzyl amine

This study reports the isolation and partial purification of transaminase from the wild species of Bacillus licheniformis. Semi-purified transaminase was immobilized on copper nanoflowers (NFs) synthesized through sonochemical method and explored it as a nanobiocatalyst. The conditions for the synthesis of transaminase NFs [TA@Cu3(PO4)2NF] were optimized. Synthesized NFs revealed the protein loading and activity yield-60 ± 5% and 70 ± 5%, respectively. The surface morphology of the synthesized hybrid NFs was examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), which revealed the average size to be around 1 ± 0.5 μm. Fourier-transform infrared (FTIR) was used to confirm the presence of the enzyme inside the immobilized matrix. In addition, circular dichroism and florescence spectroscopy were also used to confirm the integrity of the secondary and tertiary structures of the protein in the immobilized material. The transaminase hybrid NFs exhibited enhanced kinetic properties and stability over the free enzyme and revealed high reusability. Furthermore, the potential application of the immobilized transaminase hybrid NFs was demonstrated in the resolution of racemic α-methyl benzylamine.

Understanding intricacies of bioinspired organic-inorganic hybrid nanoflowers: A quest to achieve enhanced biomolecules immobilization for biocatalytic, biosensing and bioremediation applications

The immobilization of biomolecules has been a subject of interest for scientists for a long time. The organic-inorganic hybrid nanoflowers are a new class of nanostructures that act as a host platform for the immobilization of such biomolecules. It provides better practical applicability to these functional biomolecules while also providing superior activity and reusability when catalysis is involved. These nanostructures have a versatile and straightforward synthesis process and also exhibit enzyme mimicking activity in many cases. However, this facile synthesis involves many intricacies that require in-depth analysis to fully attain its potential as an immobilization technique. A complete account of all the factors involving the synthesis process optimisation is essential to be studied to make it commercially viable. This paper explores all the different aspects of hybrid nanoflowers which sets them apart from the conventional immobilization techniques while also giving an overview of its wide range of applications in industries.

Facile synthesis of recyclable laccase-mineral hybrid complexes with enhanced activity and stability for biodegradation of Evans Blue dye

Two morphologies of laccase-mineral hybrid complexes, i.e., laccase-mineral hybrid nanoflowers (La-HNF) and nanopetals (La-HNP), were synthesized via biomineralization using Cu₃ (PO₄)₂·3H₂O as the mineral for Evans Blue (EB) dye biodegradation. XRD patterns and FT-IR spectra results revealed the successful immobilization of laccase via in-situ formed Cu₃(PO₄)₂·3H₂O crystals. Compared with free laccase, laccase-mineral hybrid complexes showed higher enzymatic activity due to the activation effect induced by copper ions of Cu₃(PO₄)₂·3H₂O, further, the improved kinetic parameters of laccase-mineral hybrid complexes could be ascribed to nanoscale-dispersed laccase molecules within hybrid complexes. For EB dye biodegradation, the reason why the biodegradation efficiency (94.9%) of La-HNF was higher than that (86.8%) of La-HNP could be synergistic effect of immobilized laccase within 3D hierarchical structure of La-HNF. In addition, the optimized biodegradation conditions (pH 4.6 and 40 °C) of La-HNF were obtained, moreover, 93.2% and 48.1% of EB dye were biodegraded by La-HNF after stored for 30 days and reused for 10 cycles, respectively, demonstrating La-HNF have good practicability.

A Cu(II)-MOF Based on a Propargyl Carbamate-Functionalized Isophthalate Ligand as Nitrite Electrochemical Sensor

This paper investigates the electrochemical properties of a new Cu(II)-based metal-organic framework (MOF). Noted as Cu-YBDC, it is built upon a linker containing the propargyl carbamate functionality and immobilized on a glassy carbon electrode by drop-casting (GC/Cu-YBDC). Afterward, GC/Cu-YBDC was treated with HAuCl4 and the direct electro-deposition of Au nanoparticles was carried at 0.05 V for 600 s (GC/Au/Cu-YBDC). The performance of both electrodes towards nitrite oxidation was tested and it was found that GC/Au/Cu-YBDC exhibited a better electrocatalytic behavior toward the oxidation of nitrite than GC/Cu-YBDC with enhanced catalytic currents and a reduced nitrite overpotential from 1.20 to 0.90 V. Additionally GC/Au/Cu-YBDC showed a low limit of detection (5.0 μM), an ultrafast response time (<2 s), and a wide linear range of up to 8 mM in neutral pH.

Development and demonstration of functionalized inorganic-organic hybrid copper phosphate nanoflowers for mimicking the oxidative reactions of metalloenzymes by working as a nanozyme

Copper phosphate nanoflowers (CuPNFs) have been synthesized in the presence of different aromatic phenanthroline derivatives (Ln), leading to inorganic-organic hybrid materials (Ln-CuPNFs). Studies revealed that the morphology of nanoflowers varies as a function of the aromatic moiety present in the derivative, Ln (where 'n' corresponds to phenyl, naphthyl, anthracenyl, and pyrenyl) used for coating the nanomaterial. Other noticeable changes were the increase in the size of the flower by ∼2-3 fold in the presence of these derivatives. In the absence of such aromatic phenanthroline derivatives, i.e., the use of 1,10-phenanthroline-5-amine did not induce the formation of nanoflowers, suggesting that the organic derivatization used in the present study stabilizes the nanoflower structure. Nanoflowers were characterized using X-ray diffraction, Brunauer-Emmett-Teller (BET) isotherm, X-ray photoelectron spectroscopy, Raman and Infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy, thus covering a range of diffraction, spectroscopy, and microscopy techniques. Nanoflowers, Ln-CuPNFs, have been demonstrated for the oxidative reactions mimicking copper metalloenzymes in the presence and absence of hydrogen peroxide using different substrates. Thus, hybrid Ln-CuPNFs mediate the complete oxidation of o-phenylenediamine, dopamine, ascorbate oxidase, and terephthalic acid without causing much change in the morphology of the hybrid nanoflower material and with the retention of the activity supporting the hybrid as an acceptable enzyme mimicking material. Oxidation is mediated through hydroxyl radical formation and the order of the oxidative activity is pyrenyl > anthracenyl > naphthyl > phenyl for the inorganic-organic hybrid nanoflowers. The copper complex of pyrenyl-appended phenanthroline derivative also showed similar biomimetic activity.

A new application of inorganic sorbent for biomolecules: IMAC practice of Fe3+-nano flowers for DNA separation

Selection of purification method and type of adsorbent has high significance for separation of a biomolecule like deoxyribonucleic acid (DNA). Nanoflowers are a newly improved class of adsorbent. Due to showing very structural similarity to plant flowers, they are named as nanoflowers. Herein, after synthesize of copper phosphate three hydrate nanoflowers [(Cu₃(PO₄)₂.3H₂O), CP-NFs], Fe³⁺ ions were attached to their surfaces. Obtained Fe³⁺-CP-NFs, before investigation of some adsorption parameters for DNA, they were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Some attained data from the results of adsorption experiments as follows: While maximum DNA adsorption on Fe³⁺-CP-NFs was found as an excellent value of 845.8 mg/g, nanoflowers without Fe³⁺ ions adsorbed DNA as only 25.3 mg/g. Optimum media conditions for DNA adsorption were observed at pH 7 and 25 °C with an initial concentration of 1.5 mg/mL DNA. Langmuir and Freundlich adsorption equations were applied to determine which adsorption model was appropriate, and it was seen that Langmuir model was fit with a R² of 0.9885.

Removal of doxorubicin by magnetic copper phosphate nanoflowers for individual urine source separation

Doxorubicin (DOX) originated from users' urine has been an emerging environmental pollutant due to its significant genotoxicity to mankind. Thus, urine source separation is a potential strategy to isolate DOX at a higher concentration and reduce the burden of downstream wastewater treatment. To develop highly efficient, easy separation and retrievable materials for individual patient to conveniently remove DOX from own urine, magnetic Cu₃(PO₄)₂ nanoflowers were prepared through anchoring amino-functionalized magnetic nanoparticles on the Cu₃(PO₄)₂ nanoflowers. Characterizations revealed the magnetic nanoflowers were spherical in shape with a mean size of 15 μm, and porous and hierarchical in structure. Magnetic nanoparticles located the surface of petals. Multibatch experiments were performed to assess the removal performance of DOX from aqueous solution. The magnetic nanoflowers exhibited excellent removal efficiency of DOX under weakly alkaline condition at ambient temperature. Linear and non-linear analyses were carried out to compare the best fitting kinetics and isotherms. Sorption kinetic data best fitted the pseudo-second order model. The Freundlich isotherm explained equilibrium sorption data with R² = 0.993 higher than that for the Langmuir isotherm. When the pH of synthetic urine was adjusted to weakly alkaline (pH 8.0-9.0), over 95% of DOX (20 mg L^-1) was removed by a little of magnetic nanoflowers (50 mg L^-1) within 5 min. Meanwhile, the magnetic nanoflowers could be easily separated and recovered from the synthetic urine by a magnet. So, for individual urine source separation strategy, the magnetic nanoflower seems to be an efficient, convenient and inexpensive approach to remove DOX from human urine.

Bacteria accumulate copper ions and inhibit oxide formation on copper surface during antibacterial efficiency test

Copper surface after antibacterial test against E. coli was examined in the aspect of corrosion. Results from scanning electron microscope (SEM), grazing incidence X-ray diffractometer (GIXRD) and Raman spectroscopy together confirmed less oxidation on copper surface with the presence of E. coli. The inhibition of the cuprous oxide (Cu₂O) layer instead ensured the continuous exposure of copper surface, letting localised corrosion attacks observable and causing a stronger release of copper ions. These phenomena are attributed to the fact that E. coli act as ions reservoirs since high amount of copper accumulation were found by energy dispersive X-ray spectroscopy (EDS).

Enzyme immobilisation on poly-l-lysine-containing calcium phosphate particles for highly sensitive glucose detection

High catalytic activities of enzymes are necessary for enzyme immobilising technology for the development of glucose sensors. The aim of this study is to synthesise two types of poly(l-lysine)-containing calcium phosphate particles (pLys-HAp) and to achieve the immobilisation of glucose oxidase (GOX) on them. The oxidation activity of GOX immobilised on these particles was more than 80% compared to that of native GOX (considered to be 100%). Additionally, the relative activity of GOX immobilised on poly-ε-lysine-containing HAp (ε-pLys-HAp) remained approximately 70% after ten cycles. Moreover, glucose detection was able to be performed in the linear range of 4–400 μM using GOX immobilised on pLys-HAp composites. In the direct electrochemistry measurement using the cyclic voltammetry (CV) method, a glassy carbon electrode (GCE) modified by ε-pLys-HAp was a good enzyme electrode and can be used for glucose detection with high sensitivity. From these results, poly(l-lysine)-containing HAp composites can be expected to be enzyme immobilisation agents with high stability and biosensors with high sensitivity.

The as-synthesised poly-l-lysine-containing HAp with high enzyme stability could be a candidate for a glucose sensor with high sensitivity.

Cobalt Phosphate Nanostructures for Non-Enzymatic Glucose Sensing at Physiological pH

Nanostructured materials have potential as platforms for analytical assays and catalytic reactions. Herein, we report the synthesis of electrocatalytically active cobalt phosphate nanostructures (CPNs) using a simple, low-cost, and scalable preparation method. The electrocatalytic properties of CPNs toward the electrooxidation of glucose (Glu) were studied by cyclic voltammetry and chronoamperometry in relevant biological electrolytes, such as phosphate-buffered saline (PBS), at physiological pH (7.4). Using CPNs, Glu detection could be achieved over a wide range of biologically relevant concentrations, from 1 to 30 mM Glu in PBS, with a sensitivity of 7.90 nA/mM cm² and a limit of detection of 0.3 mM, thus fulfilling the necessary requirements for human blood Glu detection. In addition, CPNs showed a high structural and functional stability over time at physiological pH. The CPN-coated electrodes could also be used for Glu detection in the presence of interfering agents (e.g., ascorbic acid and dopamine) and in human serum. Density functional theory calculations were performed to evaluate the interaction of Glu with different faceted cobalt phosphate surfaces; the results revealed that specific surface presentations of under-coordinated cobalt led to the strongest interaction with Glu, suggesting that enhanced detection of Glu by CPNs can be achieved by lowering the surface coordination of cobalt. Our results highlight the potential use of phosphate-based nanostructures as catalysts for electrochemical sensing of biochemical analytes.