Glycolic acid-g-chitosan-Pt-Fe3O4 nanoparticles nanohybrid scaffold for tissue engineering and drug delivery

This work presents the potential use of novel nanohybrid based on chitosan-g-glycolic acid and Pt-Fe(3)O(4) composite nanoparticles in drug delivery and tissue engineering applications. The Pt-Fe(3)O(4) hybrid nanoparticles are prepared by thermal decomposition of H(2)PtCl(6)·6H(2)O at high temperature. The prepared nanoparticles were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and physical property measurement system (PPMS). Next step of this paper reveals the potential use of novel hybrids of chitosan-g-glycolic acid and Pt-Fe(3)O(4) hybrid nanoparticles in controlled drug delivery applications. The drug loaded nanohybrid scaffold is prepared by freeze drying of grafted polymer solution. Drug loading and grafting of chitosan was characterized by Fourier transform infrared spectroscopy (FTIR). The cell proliferation also shows that the prepared nanohybrids are biocompatible. The nanohybrid was found to be stable regardless of pH of the medium. Therefore, Pt-Fe(3)O(4) hybrid nanoparticles are viable additive for sustained drug delivery and it could be applied in the field of biomedical.     

Synthesis and study of cross-linked chitosan-N-poly(ethylene glycol) nanoparticles

The present investigation describes the synthesis and characterization of novel biodegradable nanoparticles based on chitosan. Poly(ethylene glycol) dicarboxylic acid was used for intramolecular cross-linking of the chitosan linear chains. The condensation reaction of carboxylic groups and pendant amino groups of chitosan was performed by using water-soluble carbodiimide. The prepared nanosystems were stable in aqueous media. The structure of the products was determined by nuclear magnetic resonance (NMR) spectroscopy, and the particle size was identified by dynamic light scattering (DLS) and transmission electron microscopy (TEM) measurements. It was found that biodegradable cross-linked chitosan nanoparticles experienced considerable swelling because of the length and flexibility of the cross-linking agent. The aqueous solutions or dispersions of nanoparticles were stable and clear or mildly opalescent systems depending on the ratio of cross-linking and molecular weight of chitosan, findings consistent with values of transmittance above 75%. Particle size measured by TEM varied in the range of 4-24 nm. In the swollen state, the average size of the individual particles measured by DLS was in the range of 50-120 nm depending on the molecular weight of chitosan and the ratio of cross-linking.     

Separation of lysozyme using superparamagnetic carboxymethyl chitosan nanoparticles

Functionalized Fe(3)O(4) nanoparticles conjugated with polyethylene glycol (PEG) and carboxymethyl chitosan (CM-CTS) were developed and used as a novel magnetic absorbing carrier for the separation and purification of lysozyme from the aqueous solution and chicken egg white, respectively. The morphology of magnetic CM-CTS nanoparticles was observed by transmission electron microscope (TEM). It was found that the diameter of superparamagnetic carboxymethyl chitosan nanoparticles (Fe(3)O(4) (PEG+CM-CTS)) was about 15 nm, and could easily aggregate by a magnet when suspending in the aqueous solution. The adsorption capacity of lysozyme onto the superparamagnetic Fe(3)O(4) (PEG+CM-CTS) nanoparticles was determined by changing the medium pH, temperature, ionic strength and the concentration of lysozyme. The maximum adsorption loading reached 256.4 mg/g. Due to the small diameter, the adsorption equilibrium of lysozyme onto the nanoparticles reached very quickly within 20 min. The adsorption equilibrium of lysozyme onto the superparamagnetic nanoparticles fitted well with the Langmuir model. The nanoparticles were stable when subjected to six repeated adsorption-elution cycles. Separation and purification were monitored by determining the lysozyme activity using Micrococcus lysodeikticus as substrate. The lysozyme was purified from chicken egg white in a single step had higher purity, as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Considering that the superparamagnetic nanoparticles possess the advantages of high efficiency, cost-effectiveness and excellent binding of a larger amount of lysozyme and easier separation from the reaction system, thus this type of superparamagnetic nanoparticles would bring advantages to the conventional separation techniques of lysozyme from chicken egg white.     

Biodesulfurization of dibenzothiophene by microbial cells coated with magnetite nanoparticles

Microbial cells of Pseudomonas delafieldii were coated with magnetic Fe3O4 nanoparticles and then immobilized by external application of a magnetic field. Magnetic Fe3O4 nanoparticles were synthesized by a coprecipitation method followed by modification with ammonium oleate. The surface-modified Fe3O4 nanoparticles were monodispersed in an aqueous solution and did not precipitate in over 18 months. Using transmission electron microscopy (TEM), the average size of the magnetic particles was found to be in the range from 10 to 15 nm. TEM cross section analysis of the cells showed further that the Fe3O4 nanoparticles were for the most part strongly absorbed by the surfaces of the cells and coated the cells. The coated cells had distinct superparamagnetic properties. The magnetization (delta(s)) was 8.39 emu.g(-1). The coated cells not only had the same desulfurizing activity as free cells but could also be reused more than five times. Compared to cells immobilized on Celite, the cells coated with Fe3O4 nanoparticles had greater desulfurizing activity and operational stability.     

Preparation and characterization of Saccharomyces cerevisiae alcohol dehydrogenase immobilized on magnetic nanoparticles

The covalently immobilized of Saccharomyces cerevisiae alcohol dehydrogenase (SCAD) to magnetic Fe(3)O(4) nanoparticles via glutaraldehyde coupling reaction was studied. The magnetic Fe(3)O(4) nanoparticles were prepared by hydrothermal method using H(2)O(2) as an oxidizer. Functionalization of surface-modified magnetic particles was performed by the covalent binding of chitosan onto the surface. The amino functional group on the magnetic Fe(3)O(4)-chitosan particles surface and the amino group of the dehydrogenase were coupled with glutaraldehyde. The immobilization process did not affect the size and structure of magnetic nanoparticles. For the reduction of phenylglyoxylic acid by immobilized SCAD, the kinetic analysis data indicated that the immobilized SCAD retained 48.77% activity of its original activity. The activation energy within 20-40 degrees C, the maximum specific activity and the Michaelis constants for phenylglyoxylic acid were 7.79 KJ mol(-1), 279.33 nmol min(-1) and 37.77 mmol l(-1), respectively. Furthermore, the immobilized SCAD enhanced thermal stability and good durability in the repeated use after recovered by magnetic separations.     

A novel multifunctional nanocomposite C225-conjugated Fe3O4/Ag enhances the sensitivity of nasopharyngeal carcinoma cells to radiotherapy

Radiotherapy is the major treatment for nasopharyngeal carcinoma, a malignant tumor of epithelial origin. In this process, a tracer with high sensitivity is pivotal for diagnostic imaging in radiotherapy. Here, we designed a novel multifunctional magnetic silver nanocomposite, Fe(3)O(4)/Ag conjugated to an epidermal growth factor receptor-specific antibody (C225), which can be potentially used for synchronous cancer therapy and diagnosis via magnetic resonance imaging. Characteristics of Fe(3)O(4)/Ag/C225 were determined by transmission electron microscopy, energy dispersive X-ray spectroscopy, ultraviolet spectra, and dynamic light scattering. The results demonstrated that Fe(3)O(4)/Ag/C225 nanoparticles were spherical and dispersed well in water. The activity of C225 was preserved ～80% in the Fe(3)O(4)/Ag/C225 nanoparticles. Futhermore, we tested the cytotoxicity and radiosensitivity of the nanocomposite for human nasopharyngeal carcinoma cell lines (CNEs) in vitro. MTT analysis revealed that Fe(3)O(4)/Ag/C225 could inhibit the proliferation of CNEs in a dose- and time-dependent manner. The clonogenic assay indicated that Fe(3)O(4)/Ag/C225 combined with X-ray treatment could increase the sensitivity of CNEs to irradiation. In a summary, the novel multifunctional nanocomposite Fe(3)O(4)/Ag/C225 might be a potential radiosensitizer for treating malign tumors in the clinic.     

Preparation and properties of hybrid monodispersed magnetic α-Fe2O3 based chitosan nanocomposite film for industrial and biomedical applications

In this study, hydrothermally prepared magnetic α-Fe2O3 nanoparticles were dispersed in chitosan (CH) solution to fabricate nanocomposite film. X-ray diffraction (XRD) patterns indicated that the α-Fe2O3 nanoparticles were pure α-Fe2O3 with rhombohedral structures, and the fabrication of CH did not result in a phase change. The scanning electron microscopy (SEM) and transmission electron microscope (TEM) results showed that the hexagonal and spherical monodispersed α-Fe2O3 nanoparticles were encapsulated into the spherical dumb shaped CH-α-Fe2O3 nanocomposite film with a mean diameter of ～87 and ～110 nm respectively. The α-Fe2O3 nanoparticles and CH-α-Fe2O3 nanocomposite film were also characterized by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and vibrating sample magnetometer (VSM). Magnetic measurements revealed that the saturated magnetization (Ms) and remanent magnetization (Mr) of the pure α-Fe2O3 nanoparticles reached 0.573 emu/g and 0.100 emu/g respectively and the nanoparticles showed the characteristics of weak ferromagnetic before and after coating with CH.     

Bioconjugation of papain on superparamagnetic nanoparticles decorated with carboxymethylated chitosan

Functionalized Fe3O4 nanoparticles decorated with carboxymethylated chitosan were developed and used as a novel magnetic support for the covalent conjugation of papain, one of the most important industrial proteases. The analyses of transmission electron micrographs (TEM) and X-ray diffraction (XRD) showed that the size and structure of functionalized Fe3O4 nanoparticles had no significant changes after conjugation with papain. Magnetic measurement revealed that the resultant papain-conjugated nanoparticles were superparamagnetic with a saturation magnetization of 59.3 emu/g. Analyses of Fourier transform infrared (FTIR) spectroscopy and measurement of zeta potentials confirmed the conjugation of papain with the functionalized Fe3O4 nanoparticles. Compared with the native papain, the conjugated papain was found to exhibit enhanced enzyme activity, better tolerance to the variations of medium pH and temperature, and improved storage stability as well as good reusability. Considering that the magnetic separation technique possesses the advantages of rapidity, high efficiency, cost-effectiveness, and lack of negative effect on biological activity, such a bioconjugate system may hold potential applications in food, pharmaceutical, leather, cosmetic, and textile industries.     

Recyclable antibacterial magnetic nanoparticles grafted with quaternized poly(2-(dimethylamino)ethyl methacrylate) brushes

Highly efficient recyclable antibacterial magnetite nanoparticles consisting of a magnetic Fe(3)O(4) core with an antibacterial poly(quaternary ammonium) (PQA) coating were prepared in an efficient four-step process. The synthetic pathway included: (1) preparation of Fe(3)O(4) nanoparticles via coprecipitation of Fe(2+)/Fe(3+) in the presence of an alkaline solution; (2) attachment of an ATRP initiating functionality to the surface of the nanoparticles; (3) surface-initiated atom transfer radical polymerization (ATRP) of 2-(dimethylamino)ethyl methacrylate (DMAEMA); and (4) transformation of PDMAEMA brushes to PQA via quaternization with ethyl bromide. The success of the surface functionalization was confirmed by FT-IR, thermal gravimetric analysis (TGA), elemental analysis, and transmission electron microscopy (TEM). The PQA-modified magnetite nanoparticles were dispersed in water and exhibited a response to an external magnetic field, making the nanoparticles easy to remove from water after antibacterial tests. The PQA-modified magnetite nanoparticles retained 100% biocidal efficiency against E. coli (10(5) to 10(6)E. coli/mg nanoparticles) during eight exposure/collect/recycle procedures without washing with any solvents or water.     

Direct binding and characterization of lipase onto magnetic nanoparticles

Lipase was covalently bound onto Fe(3)O(4) magnetic nanoparticles (12.7 nm) via carbodiimide activation. The Fe(3)O(4) magnetic nanoparticles were prepared by coprecipitating Fe(2+) and Fe(3+) ions in an ammonia solution and treating under hydrothermal conditions. The analyses of transmission electron microscopy (TEM) and X-ray diffraction (XRD) showed that the size and structure of magnetic nanoparticles had no significant changes after enzyme binding. Magnetic measurement revealed the resultant lipase-bound magnetic nanoparticles were superparamagnetic with a saturation magnetization of 61 emu/g (only slightly lower than that of the naked ones (64 emu/g)), a remanent magnetization of 1.0 emu/g, and a coercivity of 7.5 Oe. The analysis of Fourier transform infrared (FTIR) spectroscopy confirmed the binding of lipase onto magnetic nanoparticles. The binding efficiency of lipase was 100% when the weight ratio of lipase bound to Fe(3)O(4) nanoparticles was below 0.033. Compared to the free enzyme, the bound lipase exhibited a 1.41-fold enhanced activity, a 31-fold improved stability, and better tolerance to the variation of solution pH. For the hydrolysis of pNPP by bound lipase at pH 8, the activation energy within 20-35 degrees C was 6.4 kJ/mol, and the maximum specific activity and Michaelis constant at 25 degrees C were 1.07 micromol/min mg and 0.4 mM, respectively. It revealed that the available active sites of lipase and their affinity to substrate increased after being bound onto magnetic nanoparticles.     

Adsorption of bovin serum albumin (BSA) onto the magnetic chitosan nanoparticles prepared by a microemulsion system

The adsorption characteristics of BSA onto the magnetic chitosan nanoparticles have been investigated in this paper. The magnetic chitosan nanoparticles were prepared by adding the basic precipitant of NaOH solution into a W/O microemulsion system. The morphology of magnetic chitosan nanoparticles was observed by transmission electron microscope (TEM). It was found that the diameter of magnetic chitosan nanoparticles was from 10nm to 20 nm, and the nanoparticles suspending in the aqueous solution could easily aggregate by a magnet, which suggested that the nanoparticles had good magnetic characteristics. The BSA adsorption experiment indicated that when pH of BSA solution was equal to 4, the maximum adsorption loading reached 110 mg/g. Through measuring the zeta potential of BSA solution and the magnetic nanoparticles, it was found that under this situation the surface of BSA took the negative charge, but the magnetic nanoparticles took the positive charge. Due to the small diameter, the adsorption equilibrium of BSA onto the nanoparticles reached very quickly within 10 min. The adsorption equilibrium of BSA onto the magnetic chitosan nanoparticles fitted well with the Freundlich model. The experimental results showed that the magnetic chitosan nanoparticles have potential to be used for the quick pretreatment in the protein analysis process.     

Compatible ternary blends of chitosan/poly(vinyl alcohol)/poly(lactic acid) produced by oil-in-water emulsion processing

Ternary compatible blends of chitosan, poly(vinyl alcohol), and poly(lactic acid) were prepared by an oil-in-water (O/W) emulsion process. Solutions of chitosan in aqueous acetic acid, poly(vinyl alcohol) (PVA) in water, and poly(lactic acid) (PLA) in chloroform were blended with a high-shear mixer. PVA was used as an emulsifier to stabilize the emulsion and to reduce the interfacial tension between the solid polymers in the blends produced. It proved to work very well because the emulsions were stable for periods of days or weeks and compatible blends were obtained when PVA was added. This effect was attributed to a synergistic effect of PVA and chitosan because the binary blends PVA/PLA and chitosan/PLA were completely incompatible. The blends were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermal mechanical analysis (TMA), stress-strain tests, and Fourier transform infrared spectroscopy (FTIR). The results indicated that despite the fact that the system contained distinct phases some degree of molecular miscibility occurred when the three components were present in the blend.     

The Tunable and Well-Controlled Surface Plasmon Resonances of Au Hollow Nanostructures by a Chemical Route

Au plasmonic hollow spherical nanostructures were synthesized by electrochemical reduction (GRR, the Galvanic Replacement Reaction) using Ag nanoparticles as templates. From UV-visible absorption spectroscopy, it was found that the surface plasmon resonance (SPR) of gold hollow spherical nanostructures first showed red shift and then blue shift. However, further addition of gold precursor (HAuCl₄) resulted into a red shift of SPR peak. The morphological changes from Ag nanoparticles to Au hollow nanostructures were assessed by transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX)analysis. The Mie Scattering theory based simulations of SPR of Au hollow nanostructures were performed which are in good agreement with the experimental observations. Based on the experimental observations and theoretical calculations, a complete growth mechanism for Au hollow nanostructures is proposed.     

Immobilization of Burkholderia sp. lipase on a ferric silica nanocomposite for biodiesel production

In this work, lipase produced from an isolated strain Burkholderia sp. C20 was immobilized on magnetic nanoparticles to catalyze biodiesel synthesis. Core-shell nanoparticles were synthesized by coating Fe(3)O(4) core with silica shell. The nanoparticles treated with dimethyl octadecyl [3-(trimethoxysilyl) propyl] ammonium chloride were used as immobilization supporters. The Burkholderia lipase was then bound to the synthesized nanoparticles for immobilization. The protein binding efficiency on alkyl-functionalized Fe(3)O(4)-SiO(2) was estimated as 97%, while the efficiency was only 76% on non-modified Fe(3)O(4)-SiO(2). Maximum adsorption capacity of lipase on alkyl-functionalized Fe(3)O(4)-SiO(2) was estimated as 29.45 mg g(-1) based on Langmuir isotherm. The hydrolytic kinetics (using olive oil as substrate) of the lipase immobilized on alkyl-grafted Fe(3)O(4)-SiO(2) followed Michaelis-Menten model with a maximum reaction rate and a Michaelis constant of 6251 Ug(-1) and 3.65 mM, respectively. Physical and chemical properties of the nanoparticles and the immobilized lipase were characterized by Brunauer-Emmett-Teller (BET) analysis, scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FT-IR). Moreover, the immobilized lipase was used to catalyze the transesterification of olive oil with methanol to produce fatty acid methyl esters (FAMEs), attaining a FAMEs conversion of over 90% within 30 h in batch operation when 11 wt% immobilized lipase was employed. The immobilized lipase could be used for ten cycles without significant loss in its transesterification activity.     

Increased conformational rigidity of humic substances by oxidative biomimetic catalysis

A synthetic water-soluble meso-tetra(2,6-dichloro-3-sulfonatophenyl)porphyrinate of iron(III) chloride, Fe(TDCPPS)Cl, was employed as a biomimetic catalyst in the oxidative coupling of terrestrial humic materials. High-performance size-exclusion chromatography (HPSEC), solid-state nuclear magnetic resonance (CPMAS-(13)C NMR), electron paramagnetic resonance (EPR), and diffuse reflectance infrared spectroscopy (DRIFT) were used to follow conformational and structural changes brought about in different humic materials by the oxidative coupling. Increase in apparent weight-average molecular weight (Mw(a)) occurred invariably for all humic substances with the oxidative polymerization catalyzed by Fe(TDCPPS)Cl. HPSEC further showed that the polymerization reaction turned the loosely bound humic supramolecular structures into more stable conformations which could no longer be disrupted by the disaggregating effect of acetic acid. DRIFT spectroscopy suggested the formation of new alkyl and aromatic ethers following the oxidative coupling with the biomimetic catalyst. CPMAS-(13)C NMR and EPR spectra suggested a reduced molecular mobility of humic components and enhanced stabilization of free radicals in larger oxidized fragments. All findings concur in indicating that the biomimetic catalysis by Fe(TDCPPS)Cl increased the molecular mass and chemical rigidity of humic materials by formation of intermolecular covalent bonds via a free-radical mechanism. The development of a technology based on oxidative polymerization by biomimetic catalysis may be of importance in controlling the properties and reactivity of humic matter for industrial and environmental applications.     

Novel magnetic microspheres of P (GMA-b-HEMA): preparation, lipase immobilization and enzymatic activity in two phases

Magnetic oleic-acid-coated Fe?O? nanoparticles were first introduced into 1, 1-diphenylethylene (DPE)-controlled radical polymerization system to prepare superparamagnetic microspheres for enzyme immobilization by two steps of polymerization. In the presence of DPE, glycidyl methacrylate, 2-hydroxyethyl methacrylate and methacryloxyethyl trimethyl ammonium chloride with charge were selected as copolymering monomers based on their reactive functional group and excellent biocompatibility which were suitable for immobilization of Candida rugosa lipase (CRL). The resulting magnetic microspheres were characterized by means of scanning electron microscope, Fourier transform infrared spectrum, thermogravimetric analysis and vibrating sample magnetometry. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis SDS-PAGE analysis was also conducted to demonstrate whether CRL is covalently immobilized or only physically adsorbed. The results indicated that the polymerization was successfully carried out, and lipase was immobilized on the magnetic microspheres through ionic adsorption and covalent binding under mild conditions. The immobilized lipase exhibited high activity recovery (69.7%), better resistance to pH and temperature inactivation in aqueous phase, as well as superior reusability in nonaqueous phase. The data showed that the resulting carrier could hold an amphiphilic property.     

Synthesis of wheat straw-g-poly(acrylic acid) superabsorbent composites and release of urea from it

Wheat straw (WS) was used as raw material for synthesizing a novel wheat straw-g-poly(acrylic acid) (WS/PAA) superabsorbent composite by graft polymerization with wheat straw powder and acrylic acid in aqueous solution. The effect of wheat straw on water absorbency was discussed and the highest water absorbency was obtained when the amount of wheat straw in the feed was 20%. The superabsorbent composite was characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The results of FTIR spectra showed OH of WS participated in graft polymerization with acrylic acid. The influences of pH, cations and anions on equilibrium water absorbency of WS/PAA were investigated. The superabsorbent composite was swollen in aqueous solution of urea to load urea, and the results showed urea concentration had no obvious effect on the swelling behaviors of WS/PAA. Furthermore, the release of urea from loaded WS/PAA was analyzed in water and in soil. Urea diffusion coefficient D was calculated.     

D-mannose-modified iron oxide nanoparticles for stem cell labeling

New surface-modified iron oxide nanoparticles were developed by precipitation of Fe(II) and Fe(III) salts with ammonium hydroxide according to two methods. In the first method, precipitation was done in the presence of D-mannose solution (in situ coating); the second method involved oxidation of precipitated magnetite with sodium hypochlorite followed by addition of D-mannose solution (postsynthesis coating). Selected nanoparticles were characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), elemental analysis, dynamic light scattering, infrared (IR), X-ray powder analysis, and ultrasonic spectrometry. While the first preparation method produced very fine nanoparticles ca. 2 nm in diameter, the second one yielded ca. 6 nm particles. Addition of D-mannose after synthesis did not affect the iron oxide particle size. UV-vis spectroscopy suggested that D-mannose suppresses the nonspecific sorption of serum proteins from DMEM culture medium on magnetic nanoparticles. Rat bone marrow stromal cells (rMSCs) were labeled with uncoated and d-mannose-modified iron oxide nanoparticles and with Endorem (Guerbet, France; control). Optical and transmission electron microscopy confirmed the presence of D-mannose-modified iron oxide nanoparticles inside the cells. D-mannose-modified nanoparticles crossed the cell membranes and were internalized well by the cells. Relaxivity measurements of labeled cells in gelatin revealed very high relaxivities only for postsynthesis D-mannose-coated iron oxide nanoparticles.     

Hollow chitosan/poly(acrylic acid) nanospheres as drug carriers

The preparation, in-vitro release, in-vitro cytotoxicity, and in-vivo drug delivery of doxorubicin (DOX)-loaded chitosan (CS)-poly(acrylic acid) (PAA) hollow nanospheres were investigated. The loading was done by dissolving a certain amount of DOX in non-cross-linked CS-PAA nanospheres aqueous solution followed by cross-linking chitosan with glutaraldehyde. The drug-loading content was up to 4.3% and the size of drug-loaded hollow nanospheres, determined by dynamic light scattering, was 118 nm. The nanospheres showed a continuous release of the entrapped DOX up to 10 days in vitro and showed comparable in-vitro cytotoxicity against HepG2 cells compared to the free DOX. In-vivo DOX delivery of DOX-loaded CS-PAA nanospheres showed that DOX concentration in blood can be maintained for a longer period than free DOX solution, and the DOX concentration in mice liver can be maintained constantly at relatively high level. The interesting feature of DOX-loaded CS-PAA hollow nanopspheres is that the loaded DOX can be delivered into the mice brain. The confocal laser scanning microscopy analysis reveals that fluorescein isothiocyanate (FITC)-labeled CS-PAA can deposit in different organs including liver, spleen, and brain.     

Microbial production and characterization of superparamagnetic magnetite nanoparticles by Shewanella sp. HN-41

A facultative dissimilatory metal-reducing bacterium, Shewanella sp. strain HN-41, was used to produce magnetite nanoparticles from a precursor, poorly crystalline ironoxyhydroxide akaganeite (beta-FeOOH), by reducing Fe(III). The diameter of the biogenic magnetite nanoparticles ranged from 26 nm to 38 nm, characterized by dynamic light scattering spectrophotometry. The magnetite nanoparticles consisted of mostly uniformly shaped spheres, which were identified by electron microscopy. The magnetometry revealed the superparamagnetic property of the magnetic nanoparticles. The atomic structure of the biogenic magnetite, which was determined by extended X-ray absorption fine structure spectroscopic analysis, showed similar atomic structural parameters, such as atomic distances and coordinations, to typical magnetite mineral.