Magnetic Microcarriers with Accurate Localization and Proliferation of Mesenchymal Stem Cell for Cartilage Defects Repairing.

Magnetic biomaterials are widely used in the field of tissue engineering because of their functions such as drug delivery and targeted therapy. In this study, a magnetically responsive composite microcarrier was prepared through in situ polymerization of dopamine with Fe3O4 (MS) to form a complex. The magnetic composite microcarriers are paramagnetic and have certain magnetic responsiveness, suitable pore size porosity for cell growth, and good blood compatibility and biocompatibility. The bone marrow mesenchyml stem cells (BMSCs) were cultured on magnetic composite microcarriers, and a static magnetic field (SMF) was applied. The results showed that BMSCs adhered to the microcarriers proliferated under the action of horizontal and vertical forces. Magnetic composite microcarriers loaded with BMSCs were implanted into the SD rat model of cartilage defect, and a magnet was added to the operative side. After 12 weeks, cartilage regeneration was observed. The results of gross observation and histological immunostaining 1 month, 2 months, and 3 mounths after operation showed that the magnetic composite microcarriers of loaded cells promoted the early maturation of cartilage and collagen secretion, and the effect of cartilage repair was significantly better than that of the control group. Gait analysis showed that implanting magnetic composite microcarriers loaded with stem cells can reduce postoperative pain and promote limb recovery in SD rats. In conclusion, this study suggests that magnetic composite microcarriers are promising tissue-engineered scaffolds for cartilage regeneration and repair.

Colorimetric immunoassay for human chorionic gonadotropin by using peroxidase-mimicking MnO2 nanorods immobilized in microplate wells.

A colorimetric immunoassay is described for the pregnancy marker human chorionic gonadotropin (HCG). The assay is based on the use of MnO2 nanorods acting as a peroxidase mimic. The nanorods were prepared by a hydrothermal method using EDTA as a template. They exhibit excellent peroxidase-like activity and stability. The nanorods were immobilized in a chitosan matrix in the wells of a BSA-modified microplate which then were further modified with streptavidin and biotinylated capture antibodies. The specific recognition between HCG and the antibodies in wells inhibit the peroxidase-like activity of the nanorods. Hence, the substrate 3,3',5,5'-tetramethylbenzidine is less efficiently catalytically oxidized by H2O2 to form a blue colored product. This results in a decrease in the absorbance at 652 nm. Response is linear in the 0.5 to 400 mIU·mL-1 HCG concentration range, and the detection limit is 0.36 mIU·mL-1 under optimized conditions. The method is highly specific, acceptably reproducible and stable. It was applied to the determination of HCG concentration in serum samples, and results were in good agreement with data obtained by the reference method." Graphical abstract Schematic presentation of colorimetric immunoassay for human chorionic gonadotropin (HCG) by using MnO2 nanorods with peroxidase-like activity immobilized in microplate wells. The specific recognition between HCG and the antibodies in wells inhibits the peroxidase-like activity of the nanorods. TMB: 3,3',5,5'-tetramethylbenzidine.

Desulfurization with Thialkalivibrio versutus immobilized on magnetic nanoparticles modified with 3-aminopropyltriethoxysilane.

OBJECTIVE: Thialkalivibrio versutus D301 cells were immobilized on Fe3O4 nanoparticles (NPs) synthesized by an improved chemical coprecipitation method and modified with 3-aminopropyltriethoxysilane (APTES), then the immobilized cells were used in sulfur oxidation. RESULTS: The prepared Fe3O4-APTES NPs had a narrow size distribution (10 ± 2 nm) and were superparamagnetic, with a saturation magnetization of 60.69 emu/g. Immobilized cells had a saturation magnetization of 34.95 emu/g and retained superparamagnetism. The optimum conditions for cell immobilization were obtained at pH 9.5 and 1 M Na+. The immobilization capacity of Fe3O4-APTES NPs was 7.15 g DCW/g-NPs that was 2.3-fold higher than that of Fe3O4 NPs. The desulfurization efficiency of the immobilized cells was close to 100%, having the same sulfur oxidation capacity as free cells. Further, the immobilized cells could be reused at least eight times, retaining more than 85% of their desulfurization efficiency. CONCLUSION: Immobilization of cells with the modified magnetic NPs efficiently increased cell controllability, have no effect on their desulfurization activity and could be effectively used in large-scale industrial applications.

Desulfurization of immobilized sulfur-oxidizing bacteria, Thialkalivibrio versutus, by magnetic nanaoparticles under haloalkaliphilic conditions.

OBJECTIVES: As a haloalkaliphilic, sulfur-oxidizing bacteria, Thialkalivibrio versutus D301 can remove sulfide, thiosulfate and polysulfide in wastewater, we investigated how it might be reused when mixed with high concentrations of elemental sulfur. RESULTS: A process is described to immobilize T. versutus cells by using superparamagnetic Fe3O4 nanoparticles (NPs) under haloalkaliphilic conditions (i.e. pH 9.5, 0.5 M Na(+)). The saturation magnetization value (δs) of immobilized cells was 55.1 emu/g. The Fe3O4 NPs-coated cells had the similar sulfur oxidization activity to that of free cells, and they could be reused six batch cycles. Analysis of hydraulic diameters showed that bacterial cells were immobilized by Fe3O4 NPs due to the nano-size effects. CONCLUSIONS: Magnetic immobilization is a convenient technique for cell immobilization under haloalkaliphilic conditions and is a promising technology for large scale application.

Nanotubular surface modification of metallic implants via electrochemical anodization technique.

Due to increased awareness and interest in the biomedical implant field as a result of an aging population, research in the field of implantable devices has grown rapidly in the last few decades. Among the biomedical implants, metallic implant materials have been widely used to replace disordered bony tissues in orthopedic and orthodontic surgeries. The clinical success of implants is closely related to their early osseointegration (ie, the direct structural and functional connection between living bone and the surface of a load-bearing artificial implant), which relies heavily on the surface condition of the implant. Electrochemical techniques for modifying biomedical implants are relatively simple, cost-effective, and appropriate for implants with complex shapes. Recently, metal oxide nanotubular arrays via electrochemical anodization have become an attractive technique to build up on metallic implants to enhance the biocompatibility and bioactivity. This article will thoroughly review the relevance of electrochemical anodization techniques for the modification of metallic implant surfaces in nanoscale, and cover the electrochemical anodization techniques used in the development of the types of nanotubular/nanoporous modification achievable via electrochemical approaches, which hold tremendous potential for bio-implant applications. In vitro and in vivo studies using metallic oxide nanotubes are also presented, revealing the potential of nanotubes in biomedical applications. Finally, an outlook of future growth of research in metallic oxide nanotubular arrays is provided. This article will therefore provide researchers with an in-depth understanding of electrochemical anodization modification and provide guidance regarding the design and tuning of new materials to achieve a desired performance and reliable biocompatibility.

Peroxidase-like activity of amino-functionalized magnetic nanoparticles and their applications in immunoassay.

Amino-functionalized Fe3O4 magnetic nanoparticles with high peroxidase-like activity (MNPs-NH2) are reported in this work. The peroxidase-like activity is approximately the same as naked Fe3O4 magnetic nanoparticles (MNPs). MNPs-NH2 displayed much better thermal stability and pH tolerance than horseradish peroxidase (HRP). The optimal pH and temperature are approximately pH 4 and 40 °C, respectively. We showed that the MNPs-NH2 were successfully applied in a double-antibody sandwich "enzyme"-linked immunosorbent assay to replace of HRP, in which MNPs-NH2 were not only separation carriers, but also detection indicator.

Magnetic nanoparticles (MNPs) covalently coated by PEO-PPO-PEO block copolymer for drug delivery.

A stable drug carrier has been prepared by covalently coating magnetic nanoparticles (MNPs) with PEO-PPO-PEO block copolymer Pluronic P85. The particles were characterized by TEM, XRD, DLS, VSM, FTIR, and TGA. A typical product has a 15 nm magnetite core and a 100 nm hydrodynamic diameter with a narrow size distribution and is superparamagnetic with large saturation magnetization (57.102 emu/g) at room temperature. The covalently-coated Pluronic-MNPs (MagPluronics) were proven to be stable in different conditions, such as aqueous solution, 0.2 M PBS solution, and pH 13.5 solution, which would be significant for biological applications. Furthermore, MagPluronics also possess temperature-responsive property acquired from the Pluronic copolymer layer on their surface, which can cause conformational change of Pluronics and improve load and delivery efficiency of the particles. The temperature-controlled loading and releasing of hydrophobic model drug curcumin were tested with these particles. A loading efficiency of 81.3% and a sustained release of more than 4 days were achieved in simulated human body condition. It indicates that the covalently-coated MagPluronics are stable carriers with good drug-loading capacity and controlled-release property.

High-capacity adsorption of hexavalent chromium from aqueous solution using magnetic microspheres by surface dendrimer graft modification.

The magnetic poly-(methyl acrylate-divinyl benzene) (MA-DVB) microspheres with micron size were synthesized by modified suspension polymerization method. Through stepwise reaction with methyl acrylate (MA) and ethylenediamine (EDA), the magnetic poly-(MA-DVB) microspheres with surface dendrimer containing amino groups were obtained. The above mentioned magnetic microspheres were applied for the adsorption of hexavalent chromium from aqueous solution. The effects of solution pH value, adsorption temperature, and adsorption and desorption of Cr(VI) were studied. The results showed that the optimum pH value for Cr(VI) adsorption was found at pH=3, and the adsorption capacity increased with the increase in adsorption temperature. The adsorption equilibrium of Cr(VI) was obtained in about 12 min and more than 98% of adsorbed Cr(VI) were desorbed from the magnetic microspheres in about 30 min using Na(2)SO(4) solution. By fitting the experimental data to Langmuir equation, the maximum capacity for Cr(VI) of magnetic poly-(MA-DVB) microspheres was estimated at 231.8 mg/g.

Removal of low concentration Cr(VI) from aqueous solution by magnetic-fluids fixed bed using the high gradient magnetic separation.

The focus of this paper was a novel model of Cr(VI) extraction process. The original so-called "magnetic-fluids fixed bed" (MFFB), which bridged the solvent extraction and the fixed-bed extraction by the theory of the high gradient magnetic separation (HGMS), has been explained. The MFFB integrated the advantages of the two above mentioned classical extraction methods and overcame their drawbacks. The feasibility of this method was studied by extraction experiments of Cr(VI) from aqueous solution. The influences of the design of ferromagnetic steel wires in magnetic separation column, the pH value of feed solution, TBP concentration in magnetic fluids, and flow rate of aqueous solution in column were investigated. Under the optimum conditions, the proposed method obtained high extraction efficiency with continuous process.

Adsorption and magnetic removal of neutral red dye from aqueous solution using Fe3O4 hollow nanospheres.

Fe(3)O(4) hollow nanospheres were prepared via a simple one-pot template-free hydrothermal method and were fully characterized. These magnetic spheres have been investigated for application as an adsorbant for the removal of dye contaminants from water. Because of the high specific surface area, nano-scale particle size, and hollow porous material, Fe(3)O(4) hollow spheres showed favorable adsorption behavior for Neutral red. Factors affecting adsorption, such as, initial dye concentration, pH and contact time were evaluated. Langmuir and the Freundlich adsorption isotherms were selected to explicate the interaction of the dye and magnetic adsorbant. The characteristic parameters for each isotherm have been determined. The overall trend followed an increase of the sorption capacity with increasing dye concentration with a maximum of 90% dye removal. The monolayer adsorption capacity of magnetic hollow spheres (0.05 g) for NR in the concentration range studied, as calculated from the Langmuir isotherm model at 25 degrees C and pH 6, was found to be 105 mg g(-1). Adsorption kinetic followed pseudo-second-order reaction kinetics. Thermodynamic study showed that the adsorption processes are spontaneous and endothermic. The combination of the superior adsorption and the magnetic properties of Fe(3)O(4) nanospheres can be useful as a powerful separation tool to deal with environmental pollution.

[Preparation and properties of SiO2 tubes immobilized antibody for HCAg detection].

In order to optimize the fabrication of SiO2 tubes immobilized with antibody for hepatitis C virus antigen (HCAg) detection, we formed the activated amino on the surface of SiO2 tubes by using the activation of aminosilane. Then we immobilized the hepatitis C virus (HCV) monoclonal antibody on the surface of SiO2 tubes by using glutaraldehyde as a chemical cross-linker, followed by detecting HCAg. Sequence tests showed that when the SiO2 tubes were treated in 10% (V/V) aminosilane solution and 3% (V/V) glutaraldehyde solution for 3 hours and 2 hours, respectively, the HCV monoclonal antibody had high immobilization efficiency and low nonspecificity, and the HCAg was detected to 1 ng/mL. This experiment can provide principle and experimental data for establishment of HCAg magnetic immunoassay system.

Surface functionalization and characterization of magnetic polystyrene microbeads.

A new approach to the surface functionalization of magnetic polystyrene microbeads with chloroacetyl chloride in the presence of aluminum chloride was reported. Composite microbeads consisting of polymer-coated iron oxide nanoparticles were prepared by spraying suspension polymerization. Functional chloride groups were introduced onto the surface of magnetic polystyrene microbeads by surface chemical reaction without destroying the magnetite nanoparticles within the microbeads. First, a complex was synthesized by a reaction between aluminum chloride and chloroacetyl chloride. Then, the complex was added dropwise to the solution of magnetic polystyrene microbeads, and a surface acylation reaction between complex and polystyrene microbeads was carried out. Subsequently, the amino groups were coupled to the magnetic microbeads via an ammonolysis reaction between ethylenediamine and chloride groups on the acylated magnetic polystyrene microbeads. The chemical composition, surface functional groups, and magnetism of the magnetic polystyrene microbeads before and after surface functionalization were characterized by Fourier transform infrared spectroscopy and vibrating sample magnetometry. The results showed that the surface functionalization reaction had little impact on the magnetism of the microbeads. The content of surface amino groups on the magnetic polystyrene microbeads was found to be 0.2 mmol/g. An affinity dye, Cibacron Blue F3G-A (CB), was then immobilized to prepare a magnetic affinity adsorbent. It was confirmed from X-ray photoelectron spectroscopy spectra that the CB molecules were covalently coupled on the magnetic microbeads.

Superparamagnetic poly(methyl methacrylate) beads for nattokinase purification from fermentation broth.

An effective method for purification of nattokinase from fermentation broth using magnetic poly(methyl methacrylate) (PMMA) beads immobilized with p-aminobenzamidine was proposed in this study. Firstly, magnetic PMMA beads with a narrow size distribution were prepared by spraying suspension polymerization. Then, they were highly functionalized via transesterification reaction with polyethylene glycol. The surface hydroxyl-modified magnetic beads obtained were further modified with chloroethylamine to transfer the surface amino-modified magnetic functional beads. The morphology and surface functionality of the magnetic beads were examined by scanning electron microscopy and Fourier transform infrared. An affinity ligand, p-aminobenzamidine was covalently immobilized to the amino-modified magnetic beads by the glutaraldehyde method for nattokinase purification directly from the fermentation broth. The purification factor and the recovery of the enzyme activity were found to be 8.7 and 85%, respectively. The purification of nattokinase from fermentation broth by magnetic beads only took 40 min, which shows a very fast purification of nattokinase compared to traditional purification methods.

Immobilization of lipase onto micron-size magnetic beads.

A novel and economical magnetic poly(methacrylate-divinylbenzene) microsphere (less than 8 microm in diameter) was synthesized by the modified suspension polymerization of methacrylate and cross-linker divinylbenzene in the presence of magnetic fluid. Then, surface aminolysis was employed to obtain a high content of surface amino groups (0.40-0.55 mmolg(-1) supports). The morphology and properties of these magnetic supports were characterized with scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and a vibrating sample magnetometer. These magnetic supports exhibited superparamagnetism with a high specific saturation magnetization (sigma(s)) of 14.6 emicrog(-1). Candida cylindracea lipase was covalently immobilized on the amino-functionalized magnetic supports with the activity recovery up to 72.4% and enzyme loading of 34.0 mgg(-1) support, remarkably higher than the previous studies. The factors involved in the activity recovery and enzymatic properties of the immobilized lipase prepared were studied in comparison with free lipase, for which olive oil was chosen as the substrate. The results show that the immobilized lipase has good stability and reusability after recovery by magnetic separation within 20s.

Surface modification and characterization of magnetic polymer nanospheres prepared by miniemulsion polymerization.

A novel and effective protocol for the surface modification and quantitative characterization of magnetic polymeric nanospheres prepared by miniemulsion polymerization is reported. Composite nanospheres consisting of polymer-coated iron oxide nanoparticles were prepared by the miniemulsion polymerization of methyl methacrylate and divinylbenzene in the presence of magnetic fluid. Surface modification reaction of the magnetic polymer with poly(ethylene glycol) (PEG) was employed to obtain a hydrophilic hydroxyl-group-functionalized magnetic nanospheres. An affinity dye, Cibacron blue F3G-A (CB), was then coupled covalently to prepare a magnetic nonporous affinity adsorbent. The morphology and magnetic property of the polymer nanospheres obtained were examined by transmission electron microscopy and a vibrating sample magnetometer. The contents of surface groups modified were quantitatively measured by using diffusive reflectance Fourier transform infrared spectroscopy on the basis of a linear relationship between the intensity ratio of IC-O-C/IC=O and the content of PEG. X-ray photoelectron spectroscopy (XPS) was used to examine the surface of magnetic nanospheres. It was confirmed by the comparison of XPS spectra of both dye-coated and uncoated magnetic nanospheres to which the CB ligand was coupled, and the surface of the PEG-modified nanospheres had an exact 3:7 atomic ratio of sulfur to nitrogen.