Influence of polymeric coating on capillary electrophoresis of iron oxide nanoparticles

In this work, electrophoresis was successfully used to separate three different polymer-coated magnetic iron oxide nanoparticles with similar sizes (nominally 50 nm) using high-pH borate buffer system. The coating polymers were dextran, polyethylene glycol, or carboxymethyl dextran. The results showed that the migration time of carboxymethyl dextran coated nanoparticles is the longest due to relatively more negative surface charges. Investigation of the effects of buffer concentration, pH, electric field strength and the capillary temperature, on electrophoretic properties of samples was also carried out. The results showed that pH, electric field strength and the capillary temperature had indirect relations with both of the migration time and the separation resolution of three different polymer-coated nanoparticles while the buffer concentration had a direct relation.     

Preparation of dextran immunological magnetic nanoparticles and their application to combined targeting carrier

Superparamagnetic dextran nanoparticles were prepared by coprecipitation. Effects of concentration of dextran, amount of ironic salts, stirring speed, concentration of ammonium hydroxide and mole ratio of Fe3+/Fe2+ on the effective diameter of dextran magnetic nanopartides (DMNP) were studied. Dextran immunological magnetic nanoparticles (DIMNP) were formed by the reaction of the monoclonal anti-human mammary cancer antibody with DMNP oxidized by sodium periodate, and the properties of magnetic susceptibility, shape and retention of antibody activity were investigated. The in vitro cancer antigen binding ability of DIMNP was demonstrated by radioimmunoassay, and the in vivo magnetic localization and antibody targeting ability of radiolabeled DIMNP were studied.     

葡聚糖分子量和接枝度对阿霉素/白蛋白-葡聚糖纳米粒子体外抗肿瘤效果的影响

以Maillard反应制备的牛血清白蛋白-葡聚糖共价接枝物作为载体, 通过调节混合溶液的pH值和温度制备负载阿霉素的白蛋白-葡聚糖纳米粒子. 利用分子量为5×10³, 10×10³和62×10³的葡聚糖制备了多种共价接枝物, 研究了共价接枝物分子量对载药纳米粒子的粒径和稳定性及载药量的影响. 用短链葡聚糖(分子量5×10³和10×10³)制备的纳米粒子粒径为60 nm左右, 用长链葡聚糖(分子量62×10³)制备的纳米粒子粒径约为200 nm; 阿霉素的包埋效率为81%~98%, 包埋量为7.4%~16.9%. 细胞实验结果表明, 共价接枝物具有很好的生物相容性; 与自由阿霉素相比, 纳米粒子可以促进阿霉素进入人口腔上皮癌细胞; 受缓释性质的影响, 纳米粒子在低浓度时的细胞毒性要小于自由阿霉素. 与长链葡聚糖纳米粒子相比, 接枝度高的短链葡聚糖纳米粒子由于具有较小的粒径、 密集的葡聚糖分子刷表面、 一定的自由阿霉素浓度和较快的阿霉素释放速率, 因而更容易进入细胞并具有更好的体外抗肿瘤活性.     

One-pot synthesis,characterization, and drug loading of polysaccharide-based nanoparticles with carboxy functional groups

Herein, various polysaccharide-based nanoparticles were synthesized from dextran, hydroxypropyl cellulose, and hydroxyethyl cellulose, respectively, by a self-assembly assisted approach. This approach enables us to prepare stable polysaccharide-based nanoparticles with carboxy functional groups directly from monomers without using any surfactant and organic solvent. The existence of abundant carboxyls in these polysaccharide-based nanoparticles provides them obvious pH sensitivity as verified by ¹H nuclear magnetic resonance as well as the potential in loading cationic drug.     

Purification and stabilization of colloidal ZnO nanoparticles in methanol

Purification and stabilization of colloidal ZnO nanoparticles synthesized from zinc acetate dihydrate and potassium hydroxide in methanol have been performed. Isopropanol and hexane were utilized to achieve the precipitation-redispersion washing procedure in methanol. The results from atomic absorption spectroscopy show that the concentration of K⁺ cation can be dramatically reduced by washing. X-ray diffraction and transmission electron microscopy results show that zinc layered double hydroxide formed in the ZnO precipitate can be effectively removed through concentrating the unpurified ZnO colloids by solvent evaporation. The purified ZnO nanoparticles can be fully redispersed in methanol, but become unstable with time due to the low concentration of acetate in the colloids. Fortunately, the unstable ZnO methanol colloids are found to become stable after addition of a small amount of hexane. The present study is of particular significance for the preparation of purified colloidal ZnO nanoparticles for device fabrication, functional ZnO coatings and polymer nanocomposite applications.     

Facile route to enzyme immobilization: core-shell nanoenzyme particles consisting of well-defined poly(methyl methacrylate) cores and cellulase shells

A one-step method for preparing cellulase-immobilized nanoparticles that consist of well-defined poly(methyl methacrylate) (PMMA) cores and cellulase shells has been developed. The core-shell nanoparticles are synthesized from a direct graft copolymerization of methyl methacrylate (MMA) from cellulase in an aqueous medium. Particle formation strongly depends on the surface nature of the cellulase (e.g., pH of reaction media) and MMA to cellulase weight ratio. Under optimized conditions, high MMA conversions (>90%) were achieved, and the PMMA-cellulase nanoparticles produced were very stable with narrow size distributions ( Dv/Dn < 1.20). Particle sizes in the range between 80 and 124 nm (volume average diameter) could be tailored by a variation of cellulase concentration. Transmission electron microscopy micrographs revealed that the nanoparticle had a well-defined PMMA core which was evenly coated with cellulase shell. Study of cellulase activity of the PMMA-cellulase nanoparticles indicated that even though activity of immobilized cellulase on the nanoparticles was 41% less than that of the native cellulase after the polymerization, the immobilized cellulase showed improved properties such as broader working pH range and better thermal stability. Other important advantages of this approach include that the PMMA-cellulase nanoparticles could be produced in high concentrations (up to 18% w/w solids content) and the nanoparticles have thick and evenly distributed enzyme shells. Thus, this method may provide a new commercially viable route to the immobilization of thermally stable enzyme to form nanoenzyme particles.     

Design of polymeric nanoparticles for the encapsulation of monoacylglycerol

Dextran-covered nanoparticles were produced by two different processes: emulsion/solvent evaporation and nanoprecipitation for the encapsulation of monomyristin. The inner core was formed by poly(lactic acid) or by a hydrophobically modified dextran (carrying n-decyl chains). According to the core materials and/or to the process, the average size of nanoparticles as well as the extent of aggregate formation was modulated. It was shown that the presence of monomyristin induced significant modifications on the characteristics of the resulting suspension (size and aggregate formation). Varying the matrix polymer as well as the amount of monomyristin in the feed allowed obtaining nanoparticles with convenient size. The use of hydrophobically modified dextran as the matrix material appeared promising.     

Size control of self-assembled nanoparticles by an emulsion/solvent evaporation method

A novel and simple method for size control of self-assembled nanoparticles is suggested in this paper. Polymeric nanoparticles were prepared from amphiphilic chitosan derivatives fluorescein isothiocyanate (FITC)-conjugated glycol chitosans (FGCs). The attachment of hydrophobic FITC onto hydrophilic glycol chitosan induced the amphiphilic conjugate to form self-assembled nanoparticles in aqueous media, depending on degree of substitution. The size of self-assembled nanoparticles was controlled by a novel emulsion/solvent evaporation method. Adding a small amount of an immiscible solvent with water (chloroform) to FGC nanoparticle suspensions in aqueous media followed by ultrasonification and solvent evaporation led to partial dissociation and subsequent reformation of nanoparticles. The evaporation of chloroform facilitated the hydrophobic association, which resulted in more dense and hardened hydrophobic cores. The size of nanoparticles was closely related with the FGC concentration in the emulsion. The mean diameters of self-assembled nanoparticles were 150–500 nm at the FGC concentrations of 0.3–2.5 mg/ml. Higher FGC concentration resulted in larger particles. The polydispersity factors (μ ₂/Γ ²) of the reformed nanoparticles were fairly low (0.001–0.094), indicating narrow size distribution. The FGC nanoparticles were stable in phosphate-buffered saline at 37°C up to 20 days. Lactose was a good excipient for maintaining the structural integrity of nanoparticles during freeze-drying. Without lactose, the freeze-dried nanoparticles were not homogeneously redispersed in aqueous media. However, the freeze-dried nanoparticles with lactose were spontaneously redispersed in aqueous milieu with their own sizes.     

Silica Meets Tannic Acid: Designing Green Nanoplatforms for Environment Preservation

Hybrid tannic acid-silica-based porous nanoparticles, TA-SiO₂ NPs, have been synthesized under mild conditions in the presence of green and renewable tannic acid biopolymer, a glycoside polymer of gallic acid present in a large part of plants. Tannic acid (TA) was exploited as both a structuring directing agent and green chelating site for heavy metal ions recovery from aqueous solutions. Particles morphologies and porosity were easily tuned by varying the TA initial amount. The sample produced with the largest TA amount showed a specific surface area an order of magnitude larger than silica nanoparticles. The adsorption performance was investigated by using TA-SiO₂ NPs as adsorbents for copper (II) ions from an aqueous solution. The effects of the initial Cu²⁺ ions concentration and the pH values on the adsorption capability were also investigated. The resulting TA-SiO₂ NPs exhibited a different adsorption behaviour towards Cu²⁺, which was demonstrated through different tests. The largest adsorption (i.e., ~50 wt% of the initial Cu²⁺ amount) was obtained with the more porous nanoplatforms bearing a higher final TA content. The TA-nanoplatforms, stable in pH value around neutral conditions, can be easily produced and their use would well comply with a green strategy to reduce wastewater pollution.     

Hydrogels Produced by Photocrosslinking of Dextran Chain: Characterization and Properties

The present study describes the synthesis and characterization of dextran hydrogels produced by photocrosslinking of dextran chains. The hydroxyl groups of native dextran were converted to acrylate groups to make hydrogel precursors with different substitution degrees. The hydrogels were photopolymerizated in the presence of a suitable photoinitiator system (thionine/triethylamine) and characterized by ¹³C,¹H NMR, and infrared spectroscopy. The information about microenvironment formed in hydrogel solutions was obtained by fluorescence spectroscopy using pyrene and nabumetone probes. This technique was used also to study the crosslinking process. The results about the solubility and swelling index data of hydrogels showed that their use as models of drug delivery is technically feasible.     

A Simple Method Involving Aqueous Two-Phase Separation-Systems for Activity Determination of Enzymes Hydrolyzing Macromolecular Substrates

Abstract

A new general procedure for quantitation of enzymes degrading macromolecular substrates is described. With the use of chromogenic substrates combined with separation of substrate and product by aqueous two-phase systems, rapid separation and accurate measurements can be achieved.

Furthermore, in competitive substrate assays using constant amounts of enzyme and chromogenic substrate in combination with a varying amount of native substrate, unknown concentrations of native substrate can easily be determined.

The principle is illustrated here by a system consisting of the enzyme, dextranase; the chromogenic substrate, blue dextran; and the native substrate, dextran.     

Novel Green Route of Synthesis of ZnO Nanoparticles by Using Natural Biodegradable Polymer and Its Application as a Catalyst for Oxidation of Aldehydes

ZnO nanoparticles have been synthesized by using biodegradable natural biopolymer viz. Gum Tragacanth. This single step approach is very cost effective and reproducible. The reaction time and concentration of precursor zinc acetate play a major role in the nature and growth of ZnO nanoparticles. ZnO nanoparticles were characterized by X-ray diffraction, SEM, FTIR, EDAX, UV-visible spectroscopy and TEM. ZnO nanoparticles with 20-30 nm in diameter and hexagonal morphology were found; dispersed uniformly. Raman spectrum shows the mode E₂ high at 437 cm^?1 that is related to the vibration of wurtzite Zn-O bond in crystal structure of ZnO. The space between adjacent lattice fringes is ～ sharp 2.42 Å. UV-visible absorption spectrum shows the sharp absorption band at 308 nm assigned to the intrinsic transition from valance band to conduction band. The ZnO nanoparticles display superior catalytic activity of conversion of aldehyde to acid as compared to bulk-ZnO material, because of high surface area of ZnO nanoparticles. A trace amount of ZnO nanoparticles catalyst required for organic conversion. The ZnO nanoparticles as catalyst are highly stable, recyclable and efficient in its activity.     

Concentration-Dependent Influence of Silver Nanoparticles on Amyloid Fibrillation Kinetics of Hen Egg-White Lysozyme

Understanding the influence of nanoparticles on the formation of protein amyloid fibrillation is crucial to extend their application in related biological diagnosis and nanomedicines. In this work, Raman spectroscopy was used to probe the amyloid fibrillation of hen egg-white lysozyme in the presence of silver nanoparticles (AgNPs) at different concentrations, combined with atomic force microscopy and thioflavin T (ThT) fluorescence assays. Four representative Raman indicators were utilized to monitor transformation of the protein tertiary and secondary structures at the molecular level: the Trp doublet bands at 1340 and 1360 cm^-1, the disulfide stretching vibrational peak at 507 cm^-1, the N-C$\alpha$-C stretching vibration at 933 cm^-1, and the amide Ⅰ band. All experimental results confirmed the concentration-dependent influence of AgNPs on the hen egg-white lysozyme amyloid fibrillation kinetics. In the presence of AgNPs at low concentration (17 μg/mL), electrostatic interaction of the nanoparticles stabilizes disulfide bonds, and protects the Trp residues from exposure to hydrophilic environment, thus leading to formation of amorphous aggregates rather than fibrils. However, with the action of AgNPs at high concentration (1700 μg/mL), the native disulfide bonds of hen egg-white lysozyme are broken to form Ag-S bonds owing to the competition of electrostatic interaction from a great deal of nanoparticles. As for providing functional surfaces for protein to interact with, AgNPs play a bridge role in direct transformation from $\alpha$-helices to organized $\beta$-sheets. The present investigation sheds light on the controversial effects of AgNPs on the kinetics of hen egg-white lysozyme amyloid fibrillation.     

Separation of pharmacologically active nitrogen-containing compounds on silica gels modified with 6,10-ionene,dextran sulfate,and gold nanoparticles

New stationary phases for HPLC are obtained via layer-by-layer deposition of polyelectrolytes and studied: (1) silica gel modified layer-by-layer with 6,10-ionene and dextran sulfate (Sorbent 1); (2) silica gel twice subjected to the above modification (Sorbent 2); and (3) silica gel modified with 6,10-ionene, gold nanoparticles, and dextran sulfate (Sorbent 3). The effect the content of the organic solvent in the mobile phase and the concentration and pH of the buffer solution have on the chromatographic behavior of several pharmacologically active nitrogen-containing compounds is studied. The sorbents are stable during the process and allow the effective separation of beta-blockers, calcium channel blockers, alpha-agonists, and antihistamines. A mixture of caffeine, nadolol, tetrahydrozoline, pindolol, orphenadrine, doxylamine, carbinoxamine, and chlorphenamine is separated in 6.5 min on the silica gel modified with 6,10-ionene, gold nanoparticles, and dextran sulfate.

     

A hydrogen peroxide biosensor based on direct electron transfer from hemoglobin to an electrode modified with Nafion and activated nanocarbon

A biosensor for hydrogen peroxide (HP) was developed by immobilizing hemoglobin on a glassy carbon electrode modified with activated carbon nanoparticles/Nafion. The characteristics of the sensor were studied by UV?Cvis spectroscopy and electrochemical methods. The immobilized Hb retained its native secondary structure, undergoes direct electron transfer (with a heterogeneous rate constant of 3.37?±?0.5?s^?1), and displays excellent bioelectrocatalytic activity to the reduction of HP. Under the optimal conditions, its amperometric response varies linearly with the concentration of HP in the range from 0.9???M to 17???M. The detection limit is 0.4???M (at S/N?=?3). Due to the commercial availability and low cost of activated carbon nanoparticles, it can be considered as a useful supporting material for construction of other third-generation biosensors.

Improvement of Nanoprecipitation Technique for Preparation of Gelatin Nanoparticles and Potential Macromolecular Drug Loading

An optimum nanoprecipitation technique for gelatin nanoparticles is established, based on aqueous gelatin solution and ethanolic solution containing stabilizer. Crosslinking with glutaraldehyde results in stable gelatine nanoparticles. Several factors such as the surfactant concentration, type of surfactant, type of nonsolvent and gelatin concentration are evaluated. Gelatin nanoparticles with 200–300 nm can be produced using 20–30 mg mL^?1 of gelatin and a minimum of 7% w/v stabilizer (Poloxamer 407 or 188). Furthermore, methanol and ethanol are good nonsolvents, whereas other nonsolvents such as acetone, isopropyl alcohol, and acetonitrile, result in phase separation and visible precipitates. The entrapment efficiency of fluorescein‐isothiocyanate (FITC)‐dextran as model drug was determined to 50% with no substantial effect on particle size. 80% of the drug is only released after enzymatic digestion.

     

A laser light-scattering study of the structure of agarose gels

Diffusion coefficients of dextran fractions within agarose gels surrounded by dextran solution have been measured by laser light scattering using the autocorrelation method. Plots were made of the diffusion coefficient relative to that in dilute solution, D/D₀, against the logarithm of hydrodynamic diameter logd for each concentration of agarose, and superimposed by displacing horizontally to produce a unified plot. In this way it was shown that D/D₀ is a function of C^bd, where C is agarose concentration, with b = 1/3 and 1/2 for the cases in which the dextrans were mixed in before gelation and allowed to diffuse in afterwards, respectively, the plots being the same for a reference concentration of 0.7%. A value of b = 1/2 is that which would be expected if the molecular weight per unit length of the gel fibers were independent of concentration, and a value of 25 kg mol^?1 nm^?1 is calculated. Mobile concentrations of dextran within the gels relative to those in the surrounding solutions were found by determining the scattered intensity associated with the diffusing dextran molecules from the zero-time value of the autocorrelation function. All results and calculations are discussed in terms of current theories, and compared with earlier work on calcium alginate gels for which a molecular weight per unit length of gel fiber of 0.59 kg mol^?1 nm^?1 was calculated. The nature of the spectral broadening of the light scattered from agarose gels in the absence of dextran is described.     

The Inherent Electrochemistry of Nickel/Nickel‐Oxide Nanoparticles

The direct detection of nanoparticles is at the forefront of research owing to their environmental and toxicological applications. Herein, we studied the inherent electrochemistry of Ni and NiO nanoparticles and proposed a simple and direct electrochemical method for the determination of the concentrations of both nickel (Ni) and nickel oxide (NiO) nanoparticles in alkaline solution. A highly sensitive voltammetry technique was used to measure the oxidative signal of Ni(OH)₂ that formed spontaneously on the surface of Ni and NiO nanoparticles in alkaline media. Detection limits of 220 μg mL^?1 for Ni and 13 μg mL^?1 for NiO nanoparticles were obtained. Ni and NiO nanoparticles are used as electrode modifiers or as electrochemical signal labels in various biosensing applications. Therefore, methods to rapidly quantify the amount of Ni and NiO nanoparticles are of widespread potential use.     

A Molecular Study of Aspirin and Tenofovir Using Gold/Dextran Nanocomposites and Surface-Enhanced Raman Spectroscopy

In this study, we show how surface enhanced Raman spectroscopy (SERS) can be used to monitor the molecular behaviour of aspirin and tenofovir as a means of screening medication for quality control purposes. Gold-coated slides combined with gold/dextran nanoaggregates were used to provide signal enhancement of the drugs using SERS. Aspirin (10% w/v) and tenofovir (20% v/v) were analysed in the presence of the nanomaterials to determine trends in molecular response to changes in gold/dextran concentrations. Qualitative analysis of the functional groups showed specific trends where the peak area increased with polarizability, electron density and decreased atomic radii. Steric hinderance effects also affected the trends in peak area due to the amount of gold/dextran nanoparticles in solution. Statistical analysis provided accurate and precise linear relationships (R² = 0.99) for the ester and adenine functional groups of aspirin and tenofovir, respectively. From the above findings, the combined use of gold nano-scaffolds and gold/dextran nanomaterials amplified the Raman signal from the drugs to allow for systematic evaluation of their molecular properties. Although more experiments to correlate the findings are still needed, this SERS approach shows great potential as a screening method in the quality control of medications.     

SURFACE MULTI-FUNCTIONALIZATION OF POLY(LACTIC ACID) NANOPARTICLES AND C6 GLIOMA CELL TARGETING in vivo

Polysaccharide coated PLA nanoparticles bearing aldehyde groups were prepared by dialysis of DMSO solution of cholesterol hydrophobic-modified dextran polyaldehyde and PLA against water.The average diameter of the nanoparticles was about 160 nm,and the size distribution was nearly homogenous.The nanoparticles were functionalized simultaneously with CD71 and EGFR antibody through the Schiff's base reaction,and then radiolabeled with ~(99m)Tc.After perfused the radiolabeled nanoparticles into tumor-bearing...