Immobilized laccase on magnetic nanoparticles for enhanced lignin model compounds degradation

As a natural aromatic polymer, lignin has great potential but limited industrial application due to its complex chemical structure. Among strategies for lignin conversion, biodegradation has attracted promising interest recently in term of efficiency, selectivity and mild condition. In order to overcome the issues of poor stability and non-reusability of enzyme in the biodegradation of lignin, this work explored a protocol of immobilized laccase on magnetic nanoparticles(MNPs) with rough surfaces for enhanced lignin model compounds degradation.Scanning electron microscope with energy dispersive spectrometer(SEM-EDS), flourier transformation infrared spectroscopy(FTIR) and thermal gravimetric analysis(TGA) were utilized to characterize the immobilization of laccase. The results showed a maximum activity recovery of 64.7% towards laccase when it was incubated with MNPs and glutaraldehyde(GA) with concentrations of 6 mg·ml~(-1) and 7.5 mg·ml~(-1) for 5 h, respectively. The immobilized laccase showed improved thermal stability and pH tolerance compared with free laccase, and remained more than 80% of its initial activity after 20 days of storage at 4 ℃. In addition, about 40% residual activity of the laccase remained after 8 times cycles. Gas chromatography–mass spectrometry(GC–MS) was utilized to characterize the products of lignin model compound degradation and activation, and the efficiency of immobilized laccase was calculated to be 1–5 times that of free laccase. It was proposed that the synergistic effect between MNPs and laccase displays an important role in the enhancement of stability and activity in lignin model compound biodegradation.     

Immobilization of glucose oxidase and platinum on mesoporous silica nanoparticles for the fabrication of glucose biosensor

In this study, amino group modified mesoporous silica nanoparticles (MSN) were prepared and used to immobilize both platinum nanoparticles (PtNP) and glucose oxidase (GOx). The prepared MSN–PtNP demonstrated high stability and reactivity for catalyzing H₂O₂ electro-reduction, mainly due to the large amount of PtNP immobilized, the high surface area of these catalysts and the unique nanostructures formed through the synthetic route. Working at −0.2 V, the linear range in response to H₂O₂ by the prepared MSN–PtNP can be 5 × 10⁻⁷ to 6 × 10⁻² mol L⁻¹. After immobilizing GOx onto MSN–PtNP, the resulting MSN–PtNP–GOx was capable of interference-free determination of glucose with the linear range as wide as 1 × 10⁻⁶ to 2.6 × 10⁻² mol L⁻¹. Furthermore, the fabricated glucose biosensor can offer significant advantages compared with its conventional counterparts, typically like the high sensitivity, good reproducibility and stability, and rapid response ability as well. The fabricated glucose biosensor demonstrated its potential in clinical applications, so as to enable the determination of glucose in real serum samples.     

Immobilization of lipase on surface modified magnetic nanoparticles using alkyl benzenesulfonate

The surface of nano-sized magnetite (NSM) particles synthesized by coprecipitation method was modified by alkyl benzenesulfonate (ABS) as a coating material. ABS on the NSM was expected to form a spacer between the surface of the NSM particles and the enzyme adsorbed and to play a role of strong enzyme adsorption onto a hydrophobic surface. Transmission electron microscopy showed that the NSM particles had an average size of 10 nm. Magnetic measurement revealed that the nanoparticles were superparamagnetic and the saturation magnetization was about 68 emu/g. Porcine pancreas lipase (PPL) was immobilized onto the ABS-NSM, which was to catalyze hydrolysis of olive oil and showed enhanced durability in the reuse after being recovered by magnetic separations.     

Research progress on magnetic nanoparticles for magnetic induction hyperthermia of malignant tumor

As a new malignant tumor therapy method with low side effect, high safety and efficiency, magnetic induction hyperthermia (MIH) has attracted great attention in recent years. As magnetic induction heating media, magnetic nanoparticles (MNPs) are critical for the development of MIH. For clinical safety, the MNPs need a high heating efficiency to reduce the applied dose, minimizing the risk of side effect. Increasing the saturation magnetization and initial susceptibility, adjusting the magnetocrystalline anisotropy constant and particle size to the optimal values are the effective methods of improving heating efficiency. On the other hand, a suitable Curie temperature is desired to realize the self-regulation of the therapy temperature, avoiding the use of clumsy and expensive temperature monitoring and control devices. Substituting the magnetic ions in tetrahedral (A) site of the spinel ferrite with nonmagnetic ions or magnetic ions with smaller magnetic moments can effectively reduce the superexchange interaction between the A and B (octahedral) sites, decreasing Curie temperature. Yet, the reduction of the Curie temperature by ion doping usually reduces the saturation magnetization, decreasing heating efficiency. Increasing the fraction of heat generated by relaxation loss and increasing the saturation magnetization may be used to improve the heating efficiency.     

Structural properties of magnetic nanoparticles determine their heating behavior - an estimation of the in vivo heating potential

Magnetically induced heating of magnetic nanoparticles (MNP) in an alternating magnetic field (AMF) is a promising minimally invasive tool for localized tumor treatment by sensitizing or killing tumor cells with the help of thermal stress. Therefore, the selection of MNP exhibiting a sufficient heating capacity (specific absorption rate, SAR) to achieve satisfactory temperatures in vivo is necessary. Up to now, the SAR of MNP is mainly determined using ferrofluidic suspensions and may distinctly differ from the SAR in vivo due to immobilization of MNP in tissues and cells. The aim of our investigations was to study the correlation between the SAR and the degree of MNP immobilization in dependence of their physicochemical features.In this study, the included MNP exhibited varying physicochemical properties and were either made up of single cores or multicores. Whereas the single core MNP exhibited a core size of approximately 15 nm, the multicore MNP consisted of multiple smaller single cores (5 to 15 nm) with 65 to 175 nm diameter in total. Furthermore, different MNP coatings, including dimercaptosuccinic acid (DMSA), polyacrylic acid (PAA), polyethylenglycol (PEG), and starch, wereinvestigated. SAR values were determined after the suspension of MNP in water. MNP immobilization in tissues was simulated with 1% agarose gels and 10% polyvinyl alcohol (PVA) hydrogels.The highest SAR values were observed in ferrofluidic suspensions, whereas a strong reduction of the SAR after the immobilization of MNP with PVA was found. Generally, PVA embedment led to a higher immobilization of MNP compared to immobilization in agarose gels. The investigated single core MNP exhibited higher SAR values than the multicore MNP of the same core size within the used magnetic field parameters. Multicore MNP manufactured via different synthesis routes (fluidMAG-D, fluidMAG/12-D) showed different SAR although they exhibited comparable core and hydrodynamic sizes. Additionally, no correlation between ζ-potential and SAR values after immobilization was observed.Our data show that immobilization of MNP, independent of their physicochemical properties, can distinctly affect their SAR. Similar processes are supposed to take place in vivo, particularly when MNP are immobilized in cells and tissues. This aspect should be adequately considered when determining the SAR of MNP for magnetic hyperthermia.     

Complementary Roles of Two DNA Protection Proteins from Deinococcus geothermalis

The roles of two interrelated DNA protection protein in starved cells (Dps)—putative Dps Dgeo_0257 and Dgeo_0281—as orthologous proteins to DrDps1 for DNA binding, protection, and metal ion sensing were characterised in a Deinococcus geothermalis strain. Dgeo_0257 exhibited high DNA-binding affinity and formed a multimeric structure but lacked the conserved amino acid sequence for ferroxidase activity. In contrast, the Dgeo_0281 (DgDps1) protein was abundant in the early exponential phase, had a lower DNA-binding activity than Dgeo_0257, and was mainly observed in its monomeric or dimeric forms. Electrophoretic mobility shift assays demonstrated that both purified proteins bound nonspecifically to DNA, and their binding ability was affected by certain metal ions. For example, in the presence of ferrous and ferric ions, neither Dgeo_0257 nor Dgeo_0281 could readily bind to DNA. In contrast, both proteins exhibited more stable DNA binding in the presence of zinc and manganese ions. Mutants in which the dps gene was disrupted exhibited higher sensitivity to oxidative stress than the wild-type strain. Furthermore, the expression levels of each gene showed an opposite correlation under H₂O₂ treatment conditions. Collectively, these findings indicate that the putative Dps Dgeo_0257 and DgDps1 from D. geothermalis are involved in DNA binding and protection in complementary interplay ways compared to known Dps.     

Facile and high-efficient immobilization of histidine-tagged multimeric protein G on magnetic nanoparticles

This work reports the high-efficient and one-step immobilization of multimeric protein G on magnetic nanoparticles. The histidine-tagged (His-tag) recombinant multimeric protein G was overexpressed in Escherichia coli BL21 by the repeated linking of protein G monomers with a flexible linker. High-efficient immobilization on magnetic nanoparticles was demonstrated by two different preparation methods through the amino-silane and chloro-silane functionalization on silica-coated magnetic nanoparticles. Three kinds of multimeric protein G such as His-tag monomer, dimer, and trimer were tested for immobilization efficiency. For these tests, bicinchoninic acid (BCA) assay was employed to determine the amount of immobilized His-tag multimeric protein G. The result showed that the immobilization efficiency of the His-tag multimeric protein G of the monomer, dimer, and trimer was increased with the use of chloro-silane-functionalized magnetic nanoparticles in the range of 98% to 99%, rather than the use of amino-silane-functionalized magnetic nanoparticles in the range of 55% to 77%, respectively.     

Effects of hydrothermal process parameters on the physical,magnetic and thermal properties of Zn0.3Fe2.7O4 nanoparticles for magnetic hyperthermia applications

Effects of hydrothermal temperature and time on physical, magnetic and thermal properties of Zn-substituted magnetite nanoparticles (Zn_0.3Fe_2.7O₄) were assessed. The magnetic nanoparticles were synthesized via citric acid-assisted hydrothermal reduction route at temperatures of 150, 175 and 200 °C for duration of 10, 15 and 20 h. The nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), vibrating sample magnetometer (VSM) and specific loss power (SLP) measurements. The results showed that temperature and time of the hydrothermal process both had significant effects on nanoparticles composition and properties. It was observed that at 150 °C, heat generation was insufficient to produce activation energy required for nucleation of Zn_0.3Fe_2.7O₄ spinel nanoparticles, even after a long time. At 175 °C, although temperature was low, but the suitable condition for nucleation of nanoparticles was made and spinel nanoparticles with the size of about 13 nm were formed after 15 h. Nonetheless, since crystallinity and SLP of the nanoparticles was low, they showed weak performance for magnetic hyperthermia. At 200 °C, the required activation energy was provided for nanoparticles nucleation; however, the spinel was oxidized to hematite, resulting in a decrease in thermal and magnetic properties. In overall, the nanoparticles synthesized at 200 °C for 15 h possessed the best characteristics of reasonable purity, saturation magnetization of about 35.9 emu/g and SLP of 18.7 W/g.     

Synthesis,structural, magnetic and NO2 gas sensing property of CuO nanoparticles

Cupric oxide (CuO) nanoparticles are synthesized by the oxidation of Cu/Cu₂O, which is obtained by the chemical reduction of Cu²⁺ ions with ascorbic acid. XRD pattern confirmed the formation of CuO, and FE-SEM image shows the clusters consisting of 25–30 nm sized particles. The band gap energy (3.7 eV) from optical absorption spectra is blue shifted to that of bulk values. The Néel temperature, T_N ≈ 230 K for paramagnetic to antiferromagnetic transition was clearly seen. The magnetic hysteresis loops at 5 K showed weak ferromagnetic behavior. Based on the dc electrical conductivity (300–500 K), the apparent activation energy was 0.36 eV. The NO₂ gas sensing property of CuO was reasonably good in the temperature range of 200–300 °C, and the sensitivity increased with an increase in gas concentration but the effect of temperature is marginal.     

Preparation of water-soluble magnetic nanoparticles with controllable silica coating

This work provides a general method for preparing monodisperse,water-soluble and paramagnetic magnetic nanoparticles which are easy to be modified.Firstly,magnetic silica with core-shell structure was prepared according to a previous work.Then,the magnetic silica was treated with alkali solution to afford magnetic nanoparticles.With the increase of calcination temperature for the preparation of magnetic silica,the crystallinity and the magnetic responsibility of magnetic silica strengthened,meanwhile,the corresponding magnetic nanoparticles kept monodisperse without any aggregation.The magnetic nanoparticles are comprised of cobalt ferrite and a silica coating.The silica coating on the cobalt ferrite facilitates the magnetic nanoparticles well-dissolved and monodisperse in water,and easily modified.     

Structural,magnetic and electric properties of ZrO2 tapes decorated with magnetic nanoparticles

We produced ZrO₂ ceramic tape decorated with magnetic nanoparticles through tape casting technique. The green and sintered magnetic tapes were characterized by XRD, SEM, EDS, magnetic measurements, and I–V curves. We investigated the changes in the structural, magnetic and electrical properties, after the sintering process, and discussed the connections between them. The magnetic properties, performed in a wide range of external magnetic field and temperature, show magnetite phase for the magnetic nanoparticles governing the magnetic and electric properties of the green tape. On the other hand, for the sintered tape, the increase in the hematite phase led to remarkable changes in the magnetic and electrical properties. The electrical characterization reflects the observed changes in the structural properties after the sintering process. Additionally, the main advantages of the ceramic tapes decorated with magnetic nanoparticles reside in the possibility of producing functional thin ceramic materials that are easily moldable for electronic devices applications.     

Spinel nanoparticles characterization by inverting scanning magnetic microscope maps

Research in nanotechnology, especially in nanoparticles, has been growing in several fields of study, from nanoelectronics to biotechnology. This wide range of applications requires different techniques for characterizing these nanoparticles in terms of properties such as structure, morphology, magnetic profile and chemical composition. The Scanning Magnetic Microscopy can be used for the magnetic characterization of these materials obtaining the magnetic maps and, with the use of the inversion technique, making it possible to recover the magnetic moment and then obtain the magnetization curve of these measurements. In this work, iron-aluminum spinel nanoparticles were produced by combustion reaction and characterized structurally by Transmission Electron Microscopy, and the magnetic properties by Scanning Magnetic Microscopy. For the inversion process, we model a set of magnetic maps using a cylindrical shape to obtain the magnetic moments, and then construct a magnetization curve. The inversion method is thereby validated by comparing the results with an in-line method already used in previous works.     

Preparation and magnetic behavior of carbon-encapsulated cobalt and nickel nanoparticles from starch

Carbon-encapsulated cobalt and nickel nanoparticles with core/shell structure have been successfully synthesized with maize-derived starch as carbon source and metal nitrate as metal precursors in flowing hydrogen. The as-prepared M@Cs materials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction technique (XRD) and vibrating sample magnetometer (VSM). The effects of the metal precursors on the structure and the size of the M@Cs materials were investigated, and the magnetic properties of the M@Cs materials were measured. The results show that the structure and the size of the M@Cs materials are different in terms of the different metal precursors. The Co@Cs materials are made of the fcc-Co core and the graphitic carbon shell, of which the core diameter is in a range of 20–35 nm, while the Ni@Cs materials are composed of fcc-Ni core and the amorphous carbon shell, of which the core diameter ranges from 30 to 50 nm. The hysteresis loops of the as-made M@Cs materials show that some of the nanoparticles are in a superparamagnetic state at room temperature. A mechanism is proposed to explain the growth process of the M@Cs materials. It is believed that the starch with the helical structure is responsible for the formation of the M@Cs materials featuring the core/shell structure.     

硫矿硫化叶菌麦芽寡糖基海藻糖合成酶基因的克隆与表达

引言 海藻糖(α-D-葡糖基-[1,1]-α-D葡糖苷)是一种广泛存在于低等植物、藻类、细菌、真菌、酵母、昆虫等的非还原性二糖.在自然界中,海藻糖既是一种贮藏性糖类,又是应激代谢的重要产物,具有保护生物细胞和生物活性物质在脱水、干旱、高温、冷冻、高渗透压及有毒试剂等不良环境条件下活性免遭破坏的功能.     

Chemical synthesis of FePt nanoparticles with high alternate current magnetic susceptibility for biomedical applications

The present paper describes ordered alloy FePt nanoparticles with high magnetic susceptibility to alternate current (ac) fields at around room temperature for biomedical applications such as magnetic sensing devices for diagnostics and magnetic hyperthermia for cancer therapy. Since ac magnetic susceptibility takes the maximum value at a temperature near the blocking temperature of magnetic nanoparticles, the blocking temperature of the FePt nanoparticles is required to be adjusted at around room temperature to improve biomedical performances. Ordered alloy FePt has much higher magnetic anisotropy than iron oxides, and it can be the best candidate in the case of their particle size less than 10 nm. The ordered alloy FePt nanoparticles are synthesized by reduction of Fe and Pt organo-metallic compounds with tetraethylene glycol using poly(N-vinyl-2-pyrrolidone) (PVP) as a protective agent. PVP is a water-soluble polymer, and is proper to obtain dispersion into water. Influences of reaction temperature on crystallite size (particle size) and blocking temperature and the relationship between the blocking temperature and the value of ac magnetic susceptibility at around room temperature are investigated. Furthermore, PVP concentration at the synthesis to obtain well dispersed nanoparticle-suspension is examined.     

The cytotoxicity evaluation of magnetic iron oxide nanoparticles on human aortic endothelial cells

One major obstacle for successful application of nanoparticles in medicine is its potential nanotoxicity on the environment and human health. In this study, we evaluated the cytotoxicity effect of dimercaptosuccinic acid-coated iron oxide (DMSA-Fe₂O₃) using cultured human aortic endothelial cells (HAECs). Our results showed that DMSA-Fe₂O₃ in the culture medium could be absorbed into HAECs, and dispersed in the cytoplasm. The cytotoxicity effect of DMSA-Fe₂O₃ on HAECs was dose-dependent, and the concentrations no more than 0.02 mg/ml had little toxic effect which were revealed by tetrazolium dye assay. Meanwhile, the cell injury biomarker, lactate dehydrogenase, was not significantly higher than that from control cells (without DMSA-Fe₂O₃). However, the endocrine function for endothelin-1 and prostacyclin I-2, as well as the urea transporter function, was altered even without obvious evidence of cell injury in this context. We also showed by real-time PCR analysis that DMSA-Fe₂O₃ exposure resulted in differential effects on the expressions of pro- and anti-apoptosis genes of HAECs. Meanwhile, it was noted that DMSA-Fe₂O₃ exposure could activate the expression of genes related to oxidative stress and adhesion molecules, which suggested that inflammatory response might be evoked. Moreover, we demonstrated by in vitro endothelial tube formation that even a small amount of DMSA-Fe₂O₃ (0.01 and 0.02 mg/ml) could inhibit angiogenesis by the HAECs. Altogether, these results indicate that DMSA-Fe₂O₃ have some cytotoxicity that may cause side effects on normal endothelial cells.     

Therapeutic effect of magnetic nanoparticles on calcium silicate bioceramic in alternating field for biomedical application

The cancerous bone may be treated using magnetite nanoparticles (MNPs) coupled with hyperthermia treatment technology. During the last three decades, calcium-silicate (CS) based bioceramics have been investigated as a proper choice due to their bioactivity, biocompatibility, magnetization property, and ability to form suitable apatite for hard tissue engineering approaches. For this purpose, three-dimensional bio-nanocomposite scaffolds utilizing bioactive wollastonite (WS) and bioglass (BG) as composed based materials with 0 wt% (S1), 5 wt% (S2), 10 wt% (S3), and 15 wt% (S4) of Zr–Fe₃O₄ are considered in this study. These materials with two various space-agents such as sodium chloride (NaCl) and sodium bicarbonate (NaHCO₃) particles containing ball mill with high energy and pressing under 150 MPa, and sintered at 850 °C are analyzed. Additionally, X-ray diffraction (XRD), scanning electron microscopy (SEM), vibrating-sample magnetometer (VSM), and mechanical tests include of toughness and compressive strength are investigated. The powder's and scaffold's crystals size are measured between 30 and 50 nm, and the pores and porosity size are measured from 70 to 180 μm and 25%–40%. The VSM curves illustrate that the zirconium-ferrite has a soft magnetic property, which is easily magnetized by applying a small amount of magnetic field, and it rapidly loses its magnetic moment by cutting off the field. The low coercive force, as well as high magnetic saturation with low residue, are represented for the S2 and S3. The obtained outcomes indicate that the best amounts of mechanical properties amongst the specimens are related to the specimen with 15 wt%, 7.9 ± 1 MPa of compressive strength, and 203.3 ± 10 MPa of elastic modulus. Likewise, the biological assessment shows that the sample containing 10 wt% MNPs provides a better apatite creation on porous scaffolds after 28 days. The gained outcomes represent that those specimens containing 10 and 15 wt% MNPs provide proper biological and mechanical replies.