Electrochemical peptide nucleic acid functionalized α-Fe2O3/Fe3O4 nanosheets for detection of CYP2C19*2 gene.

The CYP2C19*2 gene carriers and non-carriers are closely related to the dosage of clopidogrel. To correctly guide the use of clopidogrel and promote individualized therapy, an ultra-sensitive electrochemical biosensor was developed for the detection of CYP2C19*2 gene. The heterogeneous α-Fe2O3/Fe3O4 nanosheets were prepared via the hydrothermal-calcination process, and the preparation parameters were optimized. The average diameter and thickness of the nanosheets were approximately 150 nm and 53 nm, respectively; and the saturation magnetization was 80.2 emu/g. The α-Fe2O3/Fe3O4@Au nanosheets were prepared by sodium borohydride reduction method, and self-assembled to the electrode surface with magnetic field. Ultra-sensitive detection of CYP2C19*2 gene was realized through the recognition ability of strong single base mismatching of peptide nucleic acid and signal amplification effect of magnetic α-Fe2O3/Fe3O4@Au nanosheets. Under optimal detection conditions, the current had a good linear correlation with the negative logarithm of CYP2C19*2 gene concentration in the range 1 pM-1 nM, and the detection limit was 0.64 pM (S/N = 3). Meanwhile, the electrochemical signals of target DNA and incomplete complementary DNA were detected. The constructed biosensor exhibited good selectivity, reproducibility, and stability, providing a promising strategy for the detection of other gene mutations by electrochemical biosensors.

Nucleic acid aptasensor with magnetically induced self-assembly for the detection of EpCAM glycoprotein.

A "turn-on" aptasensor for label-free and cell-free EpCAM detection was constructed by employing magnetic α-Fe2O3/Fe3O4@Au nanocomposites as a matrix for signal amplification and double-stranded complex (SH-DNA/Apt probes) immobilization through Au-S binding. α-Fe2O3/Fe3O4@Au could be efficiently assembled into uniform and stable self-assembly films via magnetic-induced self-assembly technique on a magnetic glassy carbon electrode (MGCE). The effectiveness of the platform for EpCAM detection was confirmed through differential pulse voltammetry (DPV). Under optimized conditions, the platform exhibited excellent specificity for EpCAM, and a strong linear correlation was observed between the current and the logarithm of EpCAM protein concentration in the range 1 pg/mL-1000 pg/mL (R2 = 0.9964), with a limit of detection (LOD) of 0.27 pg/mL. Furthermore, the developed platform demonstrated good stability during a 14-day storage test, with fluctuations remaining below 93.33% of the initial current value. Promising results were obtained when detecting EpCAM in spiked serum samples, suggesting its potential as a point-of-care (POC) testing.

Magnetically induced self-assembly DNAzyme electrochemical biosensor based on gold-modifiedα-Fe2O3/Fe3O4heterogeneous nanoparticles for sensitive detection of Ni2.

A magnetically induced self-assembly DNAzyme electrochemical biosensor based on gold-modifiedα-Fe2O3/Fe3O4heterogeneous nanoparticles was successfully fabricated to detect Nickel(II) (Ni2+). The phase composition and magnetic properties ofα-Fe2O3/Fe3O4heterogeneous nanoparticles controllably prepared by the citric acid (CA) sol-gel method were investigated in detail. Theα-Fe2O3/Fe3O4heterogeneous nanoparticles were modified by using trisodium citrate as reducing agent, and the magnetically induced self-assemblyα-Fe2O3/Fe3O4-Au nanocomposites were obtained. The designed Ni2+-dependent DNAzyme consisted of the catalytic chain modified with the thiol group (S1-SH) and the substrate chain modified with methylene blue (S2-MB). The MGCE/α-Fe2O3/Fe3O4-Au/S1/BSA/S2 electrochemical sensing platform was constructed and differential pulse voltammetry was applied for electrochemical detection. Under the optimum experimental parameters, the detection range of the biosensor was 100 pM-10µM (R2 = 0.9978) with the limit of detection of 55 pM. The biosensor had high selectivity, acceptable stability, and reproducibility (RSD = 4.03%).

1,25(OH)2D3 Activates Autophagy to Protect against Oxidative Damage of INS-1 Pancreatic Beta Cells.

Diabetes mellitus is a serious disease endangering human health worldwide. Vitamin D (Vit D) is a well-characterized regulator of calcium-phosphorus metabolism that also exerts other biological effects extending far beyond mineral homeostasis. Some epidemiological studies have suggested that Vit D has a role in defense against diabetes, although the mechanism remains unclear. Autophagy, an intracellular catabolic process, is necessary to maintain the normal structure and function of host cells. In our previous study, we found that Vit D could induce autophagy of pancreatic beta cells and prevent insulitis, although the underlying mechanisms remain to be fully elucidated. In this study, the protective effect of 1,25(OH)2D3, the physiologically active metabolite of Vit D, against streptozotocin-induced cytotoxicity in rat insulinoma cell line (INS-1) cells was explored. Cell viability and insulin secretion of INS-1 cells in response to different treatments were measured with a cell counting kit and enzyme-linked immune absorbent assay (ELISA), respectively. In addition, malondialdehyde (MDA) content and total antioxidant capacity (T-AOC) were measured by ELISA. RT-PCR and Western blot analyses were used to detect autophagy levels, reactive oxygen species (ROS) was assessed by fluorescence microscope, ultrastructure analysis was performed using transmission electron microscopy. The results demonstrated that 1,25(OH)2D3 could increase cell viability and insulin secretion of INS-1 cells, and protected cells from oxidative damage induced by streptozotocin (STZ) through autophagy activation. These findings shed light on mechanisms underlying the ameliorative effects of Vit D on diabetes mellitus.

Effects of Solution Concentration on Magnetic NiFe2O4 Nanomaterials Prepared via the Rapid Combustion Process.

A rapid combustion process for the preparation of magnetic NiFe2O4 nanomaterials was introduced. The experimental results showed that the solution concentration of ferric nitrate was a key factor to control the structure and the properties of magnetic NiFe2O4 nanomaterials: the magnetic NiFe2O4 nanorods with the diameter of about 15 nm, the length of approximately 100 nm and the saturation magnetization of 18.4-25.3 emu/g could be formed when the solution concentration of ferric nitrate was equal or greater than 1.68 mol/L; the magnetic NiFe2O4 nanoparticles with the average particle sizes of 20-32 nm and the saturation magnetization of 10.0-31.8 emu/g could be formed when the solution concentration of ferric nitrate was lower than 1.12 mol/L.

Removal of Congo Red by Magnetic MnFe2O4 Nanosheets Prepared via a Facile Combustion Process.

Magnetic MnFe2O4 nanosheets were prepared via the facile combustion process, the morphology, chemical composition, microstructure and magnetic properties of them were investigated by SEM, EDX, XRD, TEM, SAED and VSM. The as-prepared magnetic MnFe2O4 nanosheets calcined at 400 °C for 2 h with absolute alcohol of 30 mL were characterized with average diameter of about 55 nm, the thickness of around 20 nm, the specific magnetization of 44.0 Am²/kg and the specific surface area of 49.6 m²/g. The removal behavior of Congo red (CR) from aqueous solutions onto MnFe2O4 nanosheets was investigated by UV spectroscopy at room temperature; the adsorption kinetics data related to the adsorption of CR from aqueous solutions were in good agreement with the pseudo-second-order kinetic model in the initial concentrations of 80-400 mg/L. By comparison of the Langmuir, Freundlich and Temkin models for adsorption isotherms of CR, the Temkin model (correlation coefficient R² = 0.998) could be used to evaluate the adsorption isotherm of CR onto the magnetic MnFe2O4 nanosheets at room temperature, which suggested that the adsorption of CR onto the magnetic MnFe2O4 nanosheets was a hybrid of monolayer and multilayer absorbing mechanism.

A Facile Solution Combustion and Gel Calcination Process for the Preparation of Magnetic MnFe2O4 Nanoparticles.

A facile solution combustion and gel calcination process for the preparation of magnetic MnFe²O4 nanoparticles was introduced. The experimental results showed that the volume of absolute alcohol and the calcination temperature were two key factors to grain size, crystallinity and magnetic properties of MnFe²O4 nanoparticles. With the volume of absolute alcohol increasing from 15 to 100 mL, the average grain size of MnFe²O4 nanoparticles calcined at 400 °C for 2 h increased from 13.4 nm to 36.0 nm, and the saturation magnetization (Ms) value of MnFe²O4 nanoparticles increased from 1.2 emu/g to 105.5 emu/g; while, with the calcination temperature increasing from 400 °C to 800 °C, the average grain size increased from 13.4 nm to 32.9 nm, and the saturation magnetization value increased from 1.2 emu/g to 15.3 emu/g. The specific surface area of MnFe²O4 nanoparticles calcined at 400 °C for 2 h with absolute alcohol of 30 mL was measured, which was large of 49.6 m²/g.

Response Surface Optimization on Adsorption of Methyl Blue onto Magnetic (1 - x)NiFe2O4/xSiO2 Nanocomposites.

Methyl blue (MB) was adsorbed from aqueous solution by magnetic (1 - x)NiFe2O4/xSiO2 (x = 0-0.2) nanocomposites prepared via the facile solution combustion process. The effects of pH of MB solutions, silica content in nanocomposites and the calcination temperature for nanocomposites on the adsorption capacity of MB onto nanocomposites were investigated. Response surface methodology (RSM) based on three-level three-factorial Box-behnken design (BBD) was employed to optimize the adsorption technology of MB onto magnetic (1 - x)NiFe2O4/xSiO2 (x = 0-0.2) nanocomposites, the optimum adsorption conditions (pH value of 7.3, the silica content in nanocomposites of 10.3 wt.%, and the calcination temperature of 423 °C) were determined by the results of statistical analysis, and the linear term of the pH value, the silica content and the calcination temperature, the quadratic term of the silica content and the calcination temperature, and the interaction of pH value and the silica content in nanocomposites were significant factors to affect the adsorption. The adsorption capacity could reach 37.40 mg/g with the initial MB concentration of 100 mg/g under the optimum adsorption conditions.

Optimization of Citrate-Gel Preparation Process for Magnetic Ni-Zn Ferrite Nanoparticles.

Magnetic Ni-Zn ferrite nanoparticles were prepared via the citrate-gel process, their microstructure and the properties were characterized by XRD, VSM, SEM, and TEM techniques. For smaller grain size and larger specific saturation magnetization, the preparation technology for magnetic Ni-Zn ferrite nanoparticles was optimized, and the optimization conditions followed as: the molar ratio of Ni, Zn and Fe was 1:1:4, citric acid was applied according to the mole ratio of 1:1 for citric acid and metal, the solvent of 100 mL was the mixed liquor of alcohol and water with volume ratio of 1:1, pH value was 1, reaction time was 24 h, the calcination temperature was 400 °C, and the heating rate was 3 °C/min. The average crystallite size of the as-prepared Ni0.5Zn0.5Fe2O4 nanoparticles calcined under the optimization conditions was around 14 nm, and the specific saturation magnetization was about 46 emu/g.

A Facile Preparation Process of Magnetic Aldehyde-Functionalized Ni(0.5)Zn(0.5)Fe2O4@SiO2 Nanocomposites for Immobilization of Penicillin G Acylase (PGA).

A facile sol combustion and gel calcination process has been reported for the preparation of core­ shell magnetic Zn0.5Fe2O4@SiOnanocomposites. The morphology, chemical composition, structure and magnetic property of as-prepared nanocomposites were investigated by XRD, VSM, BET, SEM, and TEM, and the magnetic Ni0.5Zn0.5Fe2O4@SiO2 nanocomposites were characterized with average size of about 25 nm, saturation magnetization of 90.8 Am²/kg and the specific surface area of 67.1 m2/g. The surface of Ni0.5Zn0.5Fe2O4@SiO2 nanocomposites was functionalized with glutaraldehyde to form the aldehyde-functionalized magnetic Ni0.5Zn0.5Fe2O4@SiO2 nanocomposites, and penicillin G acylase (PGA) was successfully immobilized onto them. And the immobilized PGA exhibited high effective activity, good stability of enzyme catalyst and good reusability, and could retain 63.5% of initial activity after 12 consecutive operations. The kinetic parameters were determined, and the value of K m for the immobilized PGA (161.7 mmol/L) is higher than that of the free PGA (3.5 mmol/L), while v max (1.626 mmol/min) is also larger than that of the free PGA (0.838 mmol/min), which revealed that the immobilization of PGA onto Ni0.5Zn0.5Fe2O4@SiO2 nanocomposites was an efficient and simple way for preparation of stable PGA.

Formation Mechanism of alpha-Fe2O3 Nanotubes via Electrospinning and Their Adsorption Characteristics of BSA and DNA.

The alpha-Fe2O3 nanotubes with diameters of 400-700 nm have been prepared via the sol-gel assisted electrospinning and subsequent one-step heat treatment with ferric nitrate, ethanol and poly(vinyl pyrrolidone) as starting regents. The resultant alpha-Fe2O3 nanotubes were characterized by XRD, SEM, TEM, and VSM techniques. The hollow structure is mainly influenced by the water content in the gel precursor and the heating rate, and the hollow formation mechanism of alpha-Fe2O9 nanotubes is discussed. Adsorption of BSA onto the as-prepared alpha-Fe2O3 nanotubes exhibits a good capacity of 56.5 mg/g with the initial BSA concentration of 1.0 mg/mL, which demonstrates their feasibility in delivery of biomacromolecules. Subsequently, the adsorption characteristics of DNA onto the alpha-Fe2O3 nanotubes were investigated, and the adsorbance of DNA can achieve a maximum value of 4.19 microg/g when the initial DNA concentration is 50 microg/mL. The adsorption process of DNA onto alpha-Fe2O3 nanotubes can be described well by the pseudo-first-order kinetic model at room temperature according to the correlation coefficient R2 = 0.9978.

Immobilization and Characterization of Penicillin G Acylase (PGA) Immobilized on Magnetic Ni0.5Zn0.5Fe2O4 Nanoparticles.

Magnetic Ni0.5Zn0.5Fe2O4 nanoparticles were prepared via the solution combustion process and their microstructure and magnetic properties were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The as-prepared magnetic Ni0.5Zn0.5Fe2O4 nanoparticles are characterized with average grain size of about 20 nm and magnetization of 90.3 Am²/kg. The surface of magnetic Ni0.5Zn0.5Fe2O4 nanoparticles was modified by use of sodium silicate and N-(3-Dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride, and the penicillin G acylase (PGA) was successfully immobilized on the surface-modified magnetic Ni0.5Zn0.5Fe2O4 nanoparticles. The results show that the activity for the immobilized PGA is affected less by pH and temperature than that for the free PGA, and the immobilized PGA exhibits a high effective activity, good stability of enzyme catalyst. This immobilized PGA on magnetic Ni0.5Zn0.5Fe2O4 nanoparticles can be separated from the solution by the external magnetic field for cyclic utilization, and they could retain about 70% of initial enzyme activity after 11 consecutive operations. The kinetic parameters (Km and Vmax) were determined, and the value of Km for the immobilized PGA (204.53 mmol/L) is higher than that of the free enzyme (3.50 mmol/L), while Vmax (1.93 mmol/min) is also larger than that of the free enzyme (0.838 mmol/min).

Application of Molecular Imprinted Magnetic Fe3O4@SiO2 Nanoparticles for Selective Immobilization of Cellulase.

Magnetic Fe3O4@SiO2 nanoparticles were prepared with molecular imprinting method using cellulase as the template. And the surface of the nanoparticles was chemically modified with arginine. The prepared nanoparticles were used as support for specific immobilization of cellulase. SDS-PAGE results indicated that the adsorption of cellulase onto the modified imprinted nanoparticles was selective. The immobilization yield and efficiency were obtained more than 70% after the optimization. Characterization of the immobilized cellulase revealed that the immobilization didn't change the optimal pH and temperature. The half-life of the immobilized cellulase was 2-fold higher than that of the free enzyme at 50 degrees C. After 7 cycles reusing, the immobilized enzyme still retained 77% of the original activity. These results suggest that the prepared imprinted nanoparticles have the potential industrial applications for the purification or immobilization of enzymes.

Cationic Poly-L-Lysine-Fe2O3/SiO2 nanoparticles loaded with small interference RNA: Application to silencing gene expression in primary rat neurons.

The cationic PLL-Fe2o3/SiO2-siRNA nanoparticles with an average crystallite size of about 20 nm were prepared and delivered into primary rat neurons for knockdown of gene expression. Primary rat fetal neurons were scratched to simulate the injury of central nervous system and then were transfected with PLL-Fe2O3/SiO2-siRNA nanoparticles. Optical microscopy, fluorescence microscopy, Western blotting, immunofluorescence, and MTT assays were employed to test the cytotoxicity, the efficiency of encapsulation and targeted gene silencing. The results indicated that the PLL-Fe2O3/SiO2-siRNA nanoparticles have a remarkable efficiency of encapsulation and targeted gene silencing with negligible cytotoxicity. It could be concluded that the PLL-Fe2O3/SiO2 nanoparticles are a promising delivery carrier of siRNA.

Mesoporous iron oxide nanofibers and their loading capacity of curcumin.

Mesoporous iron oxide nanofibers were obtained by calcination of electrospun precursors at various temperatures. Their microstructure is influenced by the calcination temperature. As the calcination temperature is at 350 degrees C, the resultant iron oxide nanofibers largely consist of magnetic Fe3O4 and gamma-Fe2O3, with a specific surface area of about 120 m2/g and magnetization of about 66.5 Am2/kg. When the precursor calcined at 450 degrees C, the pure mesoporous alpha-Fe2O3 nanofibers with a specific surface area of about 92 m2/g are obtained and they show a high loading for curcumin. All the adjusted R-squares for the pseudo-second-order model overtop 0.99 in the initial curcumin ethanol solution concentrations of 30, 40 and 60 microg/mL, which suggests the pseudo-second-order kinetics model fit the adsorption kinetics of curcumin onto the mesoporous alpha-Fe2O3 nanofibers, and the adsorption can reach equilibrium in 60 min. While, Langmuir model (R2 = 0.9980) fits well the curcumin adsorption isotherm onto alpha-Fe2O3 mesoporous nanofibers, and the adsorption capacity is up to 12.48 mg/g at the curcumin concentration of 60 microg/mL.

Preparation of La1-xKxFeO3 microtubes and their adsorption kinetics of methyl blue.

The nanocrystalline La1-xKxFeO3 (x < or = 0.2) microtubes with a high specific surface area were prepared by the citrate-gel and thermal transformation process. These microtubes were characterized by X-ray diffraction (XRD), Brunauere-Emmette-Teller method (BET), and field emission scanning electron microscopy (FE-SEM). With the increase in K content (x) from 0 to 0.2, the average grain size decreases from 32.4 to 24.4 nm, and the specific surface area increases from 8.9 to 36.4 m2/g. The adsorption of methyl blue was analyzed by UV visible spectrophotometer. The adsorption capacity increases with the increase of the substituted-K content and the surface area of the La1-xKxFeO3 microtubes. The adsorption results shows that all the La1-xKxFeO3 microtubes exhibit a high adsorption activity for methyl blue, with the value of x ranging from 0 to 0.2, the adsorbance increases from 139.7 to 173.7 mg/g at the initial methyl blue concentration of 0.5 mg/mL in aqueous solution, and the kinetics data related to the adsorption of methyl blue onto the La1-xKxFeO3 microtubes are in good agreement with the pseudo-second-order kinetic model in the initial methyl blue concentration of 0.1-0.5 mg/mL.

Preparation of alpha-Fe2O3 nanotubes by calcination of electrospun precursors.

The alpha-Fe2O3 nanotubes with diameters of 400-700 nm were prepared by calcination of electrospun precursors. The morphology of alpha-Fe2O3 nanotubes is mainly influenced by the water content in solution and heating rate during the calcination process. When the water content is about 17 wt.%, heating rate is 5 degrees C/min and calcination temperature at 500 degrees C for 2 h, the optimized alpha-Fe2O3 nanotubes are obtained. These alpha-Fe2O3 nanotubes have a magnetization (M(s)) of 0.36 emu x (9-1) and coercivity (H(o)) of 1942 Oe and can be used in the nanospace technology.

Removal of heavy metals and dyes by supported nano zero-valent iron on barium ferrite microfibers.

The binary nano zero-valent iron/barium ferrite (NZVI/BFO) microfibers with uniform diameters and high porosity were prepared by the organic gel-thermal selective reduction process. The composite microfibers are fabricated from nano zero-valent iron and nano BaFe12O19 grains. The effects of pH, adsorbent dosage, and contact time on the adsorption of heavy metals and dyes have been investigated. The adsorption isotherms of heavy metals and dyes on the microfibers are well described by the Langmuir model, in which the estimated adsorption capacities are 14.5, 29.9, 68.3 and 110.4 mg/g for Pb(II), As(V), Congo red and methylene blue, respectively. After five cycles, these microfibers still exhibit a high removal efficiency for As(V), Pb(II), Congo red and methylene blue. The enhanced adsorption characteristics can be attributed to the porous structure, strong surface activity and electronic hopping. Therefore, the magnetic NZVI/BFO microfibers can be used as an efficient, fast and high capacity adsorbent for heavy metals and dyes removal.

Magnetic self-assembled label-free electrochemical biosensor based on Fe3O4/α-Fe2O3 heterogeneous nanosheets for the detection of Tau proteins.

A type of electrochemical biosensors based on magnetic Fe3O4/α-Fe2O3 heterogeneous nanosheets was constructed to detect Tau proteins for early diagnosis and intervention therapy of Alzheimer's disease (AD). Firstly, Fe3O4/α-Fe2O3 heterogeneous nanosheets were fabricated as the substrate to realize magnetic self-assembly and magnetic separation to improve current response, and Fe3O4/α-Fe2O3@Au-Apt/ssDNA/MCH biosensors were successfully constructed through the reduction process of chloroauric acid, the immobilizations of aptamer (Apt) and ssDNA, and the intercept process of 6-Mercapto-1-hexanol (MCH); the construction process of the electrochemical biosensor was monitored using Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), and the factors affecting the current response of this sensor (concentration of Fe3O4/α-Fe2O3@Au and Apt/ssDNA, incubation temperature and time of Tau) were explored and optimized using differential pulse voltammetry (DPV). Analyzing the performance of this sensor under optimal conditions, the linear range was finally obtained to be 0.1 pg/mL-10 ng/mL, the limit of detection (LOD) was 0.08 pg/mL, and the limit of quantification (LOQ) was 0.28 pg/mL. The selectivity, reproducibility and stability of the biosensors were further investigated, and in a really sample analysis using human serum, the recoveries were obtained in the range of 93.93 %-107.39 %, with RSD ranging from 1.05 % to 1.94 %.

Adsorption kinetics and isotherms of arsenic(V) from aqueous solution onto Ni0.5Zn0.5Fe2O4 nanoparticles.

Magnetic Ni0.5Zn0.5Fe2O4 nanoparticles were synthesized by the facile citrate-gel process. Their morphology, chemical composition, microstructure, and magnetic properties were investigated by XRD, TEM, EDX, BET, and VSM. The as-prepared magnetic Ni0.5Zn0.5Fe2O4 nanoparticles consisting of grains about 20 nm were characterized with specific surface area of 49.0 m2/g and magnetization of 46.1 A m2/kg. The arsenic(V) adsorption onto these magnetic Ni0.5Zn0.5Fe2O4 nanoparticles at room temperature was determined by the ICP-AES measurement of arsenic(V) in aqueous solution. The results show that the pseudo-second-order kinetic model is fitted well to describe the arsenic(V) adsorption process with a determination coefficient (R2 = 0.9862). By comparing with the two- and three-parameter models for adsorption isotherms of arsenic(V) onto the magnetic Ni0.5Zn0.5Fe2O4 nanoparticles at room temperature, the Temkin and Redlich-Peterson model can be used to evaluate the arsenic(V) adsorption isotherm at room temperature. The arsenic(V) equilibrium adsorption quantity is up to 7.2 mg/g for these magnetic Ni0.5Zn0.5Fe2O4 nanoparticles when the initial arsenic(V) concentration is 3 mg/L in aqueous solution.