Surface modification of Mitoxantrone-loaded PLGA nanospheres with chitosan

The purpose of this research was to develop polylactic-co-glycolic acid (PLGA) nanospheres surface modified with chitosan (CS). Mitoxantrone- (MTO-) loaded PLGA nanospheres were prepared by a solvent evaporation technique. The PLGA nanospheres surface was modified with CS by two strategies (adsorption and covalent binding). PLGA nanospheres of 248.4 ± 21.0 nm in diameter characterized by the laser light scattering technique, scanning electron microscopy (SEM) are spherical and its drug encapsulation efficiency is 84.1 ± 3.4%. Zeta potential of unmodified nanospheres was measured to be negative −21.21 ± 2.13 mV. The positive zeta potential of modified nanospheres reveals the presence of CS on the surface of the modified nanospheres. Modified nanospheres were characterized for surface chemistry by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR). FT-IR spectra exhibited peaks at 3420 cm⁻¹ and 1570 cm⁻¹, XPS spectra shows the N 1s (atomic orbital 1s of nitrogen) region of the surface of the nanospheres, corresponding to the primary amide of CS. In vitro drug release demonstrated that CS-modified nanospheres have many advantages such as prolonged drug release property and decreased the burst release over the unmodified nanospheres, and the modified nanospheres by covalent binding method could achieve the release kinetics of a relatively constant release. These data demonstrate high potential of CS-modified PLGA nanospheres for the anticancer drug carrier.     

Deposition of PdPtAu Nanoparticles on Hollow Nanospheres of Fe3O4 as a New Catalyst for Methanol Electrooxidation: Application in Direct Methanol Fuel Cell

In this study, immobilized hollow nanospheres of Fe₃O₄ with Palladium, Platinum and Gold nanoparticles (Fe₃O₄HNS‐PdPtAuNPs) was synthesized by hydrothermal and chemical reduction methods and characterized by various techniques such as field emission scanning electron microscopy, energy dispersive analysis of X‐rays and elemental mapping images. The electrocatalytic activity of the modified glassy carbon electrode (GCE) with Fe₃O₄HNS‐PdPtAuNPs (GCE/Fe₃O₄HNS‐PdPtAuNPs) toward methanol electrooxidation was investigated by cyclic voltammetry and chronoamperometry in 1 M NaOH solution. According to the results, Fe₃O₄HNS‐PdPtAuNPs catalyst demonstrated the highest efficiency for methanol electrooxidation in comparison with Fe₃O₄HNS‐PdNPs, Fe₃O₄HNS‐PtNPs, Fe₃O₄HNS‐PdAuNPs, Fe₃O₄HNS‐PtAuNPs and Fe₃O₄HNS‐PdPtNPs. The value of electron transfer coefficient (α ) and the ratio of current densities (I_f /I_b ) for methanol oxidation on the Fe₃O₄HNS‐PdPtAuNPs/GC catalyst were calculated 0.61 and 5.13, respectively. The reaction order was discovered to be 0.98 for CH₃OH. A direct methanol fuel cell was developed with the suggested catalyst under several conditions.     

Fabrication, in vitro degradation and the release behaviours of poly(DL-lactide-co-glycolide) nanospheres containing ascorbic acid

Ascorbic acid (vitamin C) is essential for preserving optimal health and is used by the body for many purposes. The problem is that ascorbic acid easily decomposes into biologically inactive compounds making its use very limited in the field of pharmaceuticals, dermatological and cosmetics. By encapsulating the ascorbic acid into a polymer matrix it is assumed that its chemical instability can be overcome as well as higher, more efficient and equally distributed concentration throughout extended period of time can be achieved. This paper is describing the process of obtaining poly(dl-lactide-co-glycolide) (DLPLG) nanospheres (110-170 nm) using chemical method with solvent/non-solvent systems where obtained solutions have been centrifuged. The encapsulation of the ascorbic acid in the polymer matrix is performed by homogenisation of water and organic phases. Nanoparticles of the copolymer DLPLG with the different contents of the ascorbic acid have different morphological characteristics, i.e. variable degree of uniformity, agglomeration, sizes and spherical shaping. The degradation of the nanospheres of DLPLG, DLPLG/ascorbic acid nanoparticles and release rate of the ascorbic acid were studied for 8 weeks in a physiological solution (0.9% sodium chloride in water). The samples have been characterised by infrared spectroscopy (IR), scanning electron microscopy (SEM), stereological analysis and ultraviolet (UV) spectroscopy.     

Novel lipid-based colloidal dispersions as potential drug administration systems – expectations and reality

 Colloidal drug carriers offer a number of potential advantages as delivery systems for, for example, poorly soluble compounds. The first generation of colloidal carriers, in particular liposomes and sub-micron-sized lipid emulsions, are, however, associated with several drawbacks which so far have prevented the extensive use of these carriers in drug delivery. As an alternative colloidal delivery system melt-emulsified nanoparticles based on solid lipids have been proposed. Careful physicochemical characterization has demonstrated that these lipid-based nanosuspensions (solid lipid nanoparticles) are not just “emulsions with solidified droplets”. During the development process of these systems interesting phenomena have been observed, such as gel formation on solidification and upon storage, unexpected dynamics of polymorphic transitions, extensive annealing of nanocrystals over significant periods of time, stepwise melting of particle fractions in the lower-nanometer-size range, drug expulsion from the carrier particles on crystallization and upon storage, and extensive supercooling. These phenomena can be related to the crystalline nature of the carrier matrix in combination with its colloidal state. Observation of the supercooling effect has led to the development of a second new type of carrier system: nanospheres of supercooled melts. This novel type of colloidal lipidic carrier represents an intermediate state between emulsions and suspensions. Moreover, these dispersions are particularly suited to the study of the basic differences between colloidal triglyceride emulsions and suspensions. For many decades drug carriers have represented the only group of colloidal drug administration systems. Nowadays a fundamentally different group of dispersions is also under investigation: drug nanodispersions. They overcome a number of carrier-related drawbacks, such as limitations in drug load as well as side effects due to the matrix material of the carrier particles. Utilizing this concept virtually insoluble drugs can be formulated as colloidal particles, of solid or supercooled nature. For example, coenzyme Q₁₀ (Q₁₀) has been successfully processed into a dispersion of a supercooled melt. Droplet sizes in the lower nanometer range and shelf lives of more than 3 years can easily be achieved for Q₁₀ dispersions. The drug load of the emulsion particles reaches nearly 100%. Received: 15 July 1999/Accepted: 11 November 1999     

Induction heating studies of magnetite nanospheres synthesized at room temperature for magnetic hyperthermia

An investigation of the synthesis of Fe₃O₄ nanopowders by the co-precipitation method is reported from aqueous and ethanol mediums. X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer are utilized to study the effect of variation of synthesis conditions on the crystal structure, crystallite size, microstructure and magnetic properties of the formed powders. The XRD analysis showed that the crystalline Fe₃O₄ phase was formed at Fe³⁺/Fe²⁺ molar ratio 2.0 prepared at room temperature for 1 h at pH 10. The crystallite size was in the range between 8 and 11 nm. TEM micrographs showed that the particles appeared as nanospheres. Superparamagnetic nanoparticles with low coercivity and remanence magnetization were achieved. Heating properties of the nanosphere samples in an alternating magnetic field at 160 KHz were evaluated. An excellent heating efficiency for the sample prepared in ethanol medium is a result of more relaxation losses occurring due to its small particle size.     

Magnetic multilayers on nanosphere arrays with various curvature radius

[Co/Pt]_n multilayers with different Co thickness have been deposited on a silicon (Si) substrate to obtain better perpendicular anisotropy. The 0.5 nm thickness of the Co layer was chosen as the optimized thickness of the multilayer. Magnetic nanostructures with cap configuration were fabricated based on the template of polystyrene (PS) colloid sphere arrays with various curvature radius. Compared to the flat multilayer, the cap multilayer showed an oblique average anisotropy axis. When the curvature radius of the colloidal sphere increased, the shape of the multilayers changed from ellipsoidal to spherical, which led to a different dependence of magnetic properties on the field angles. The varying shape anisotropy, the dipole-dipole interaction between small magnetic caps, and the special nucleation mechanism on the spheres larger than 400 nm caused the M_r/M_s ratio and the coercivity to first increase and then decrease with varying curvature radius of the PS spheres.     

Synthesis and characterizations of AgSCN nanospheres using AgCl as the precursor

Nanospheres of AgSCN with an average radius of 30–80 nm have been prepared by a simple reaction between AgCl suspension and KSCN in the presence of gelatin. Gelatin played a decisive role as an inhibitor of the direct attack of SCN⁻ ions to AgCl surfaces and coagulation of the growing AgSCN in producing the spherical AgSCN nanoparticles. The products were characterized by X-ray powder diffraction, transmission electron microscopy and X-ray photoelectron spectra techniques. The electrical conductivity of thin films of as-prepared AgSCN nanoparticles and polyethylene oxide (PEO) at room temperature was measured. The maximum value of electrical conductivity of as-prepared AgSCN–PEO was 1.53 × 10⁻⁵ S cm⁻¹.     

Biosynthesis of different morphologies of CaCO3 nanomaterial assisted by thermophilic strains HEN-Qn1

Thermophilic bacterial strains HEN-Qn1 were incubated at 60 °C in a solution containing calcium chloride. With slow release of CO₂ metabolic end products from the bacteria, CaCO₃ nanomaterials were found after 12 h through a transmission electron microscope (TEM). CaCO₃ nanorods were obtained extracellularly, whereas a unique morphology of nanosphere was observed intracelluarly. A single crystal was further characterized by electron pattern (ED) and X-ray powder diffraction (XRD). Moreover, a putative mechanism has been proposed based on theoretical analyses and experimental evidences. These results indicated that thermophilic bacteria had a well-controlled effect during the crystal growth of inorganic materials, which provided us a promising application of bacteria in biosynthesis of nanomaterials.     

The synthesis of ZnS hollow nanospheres with nanoporous shell

ZnS hollow nanospheres with nanoporous shell were successfully synthesized through the evolvement of ZnO nanospheres which were synthesized by hydrothermal method with poly (sodium-p-styrene sulfonate) (PSS) as surfactant at low temperature. The as-synthesized samples were characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), UV/vis spectrum and N₂ adsorption. The results showed that the shell of as-synthesized ZnS hollow structure was composed of many fine crystallites and had a nanoporous structure with pore diameter about 4 nm demonstrated by N₂ adsorption/desorption isotherm. The sample possessed efficiency of photocatalytic degradation on X-containing (X=Cl, Br, I) organic pollutants.     

β-Cyclodextrin assisted one-pot synthesis of mesoporous magnetic Fe3O4@C and their excellent performance for the removal of Cr Ⅵ from aqueous solutions

Mesoporous magnetic Fe3O4@C nanoparticles have been synthesized by a one-pot approach and used as adsorbents for removal of Cr (Ⅳ) from aqueous solution. Magnetic iron oxide nanostructured materials encapsulated by carbon were characterized by scanning electron microscope (SEM), nitrogen adsorption and desorption, X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The adsorption performance of the nanomaterial adsorbents is tested with the removal of Cr (Ⅳ) from aqueous solution. The results reveal that the mesoporous magnetic Fe3O4@C nanospheres exhibit excellent adsorption efficiency and be easily isolated by an external magnetic field. In comparison with magnetic Fe3O4 nanospheres, the mesoporous magnetic Fe3O4@C exhibited 1.8 times higher removal rate of Cr Ⅵ. Themesoporous structure and an abundance of hydroxy groups on the carbon surfacemay be responsible for high absorbent capability.