Two-Level Finite Element Iterative Algorithm Based on Stabilized Method for the Stationary Incompressible Magnetohydrodynamics.

In this paper, based on the stabilization technique, the Oseen iterative method and the two-level finite element algorithm are combined to numerically solve the stationary incompressible magnetohydrodynamic (MHD) equations. For the low regularity of the magnetic field, when dealing with the magnetic field sub-problem, the Lagrange multiplier technique is used. The stabilized method is applied to approximate the flow field sub-problem to circumvent the inf-sup condition restrictions. One- and two-level stabilized finite element algorithms are presented, and their stability and convergence analysis is given. The two-level method uses the Oseen iteration to solve the nonlinear MHD equations on a coarse grid of size H, and then employs the linearized correction on a fine grid with grid size h. The error analysis shows that when the grid sizes satisfy h=O(H2), the two-level stabilization method has the same convergence order as the one-level one. However, the former saves more computational cost than the latter one. Finally, through some numerical experiments, it has been verified that our proposed method is effective. The two-level stabilized method takes less than half the time of the one-level one when using the second class Nédélec element to approximate magnetic field, and even takes almost a third of the computing time of the one-level one when adopting the first class Nédélec element.

Highly stable amorphous calcium phosphate porous nanospheres: microwave-assisted rapid synthesis using ATP as phosphorus source and stabilizer, and their application in anticancer drug delivery.

Highly stable amorphous calcium phosphate (ACP) porous nanospheres with a relatively uniform size and an average pore diameter of about 10 nm have been synthesized by using a microwave-assisted hydrothermal method with adenosine 5'-triphosphate disodium salt (ATP) as the phosphorus source and stabilizer. The as-prepared ACP porous nanospheres have a high stability in the phosphate buffer saline (PBS) solution for more than 150 h without phase transformation to hydroxyapatite, and the morphology and size were essentially not changed. The important role of ATP and effects of experimental conditions on the formation of ACP porous nanospheres were also investigated. The ACP porous nanospheres were characterized by X-ray powder diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). This method is facile, rapid, surfactant-free and environmentally friendly. The as-prepared ACP porous nanospheres are efficient for anticancer drug (docetaxel) loading and release. The ACP porous nanosphere drug-delivery system with docetaxel shows a high ability to damage tumor cells, thus, is promising for the application in anticancer treatment.

Calcium phosphate drug nanocarriers with ultrahigh and adjustable drug-loading capacity: One-step synthesis, in situ drug loading and prolonged drug release.

Calcium phosphates (CPs) are regarded as the most biocompatible inorganic biomaterials; however, they are limited in the drug-delivery applications, especially for hydrophobic drugs. Achieving high drug-loading capacity and a controllable drug-release property are two main challenges. In this study we report a strategy for the preparation of novel drug delivery systems based on a concerted process in which the formation of the CP nanocarriers and the drug storage are accomplished in one step in mixed solvents of water and ethanol. The key advantage of this strategy is that the formation of CP nanocarriers and in situ loading of the drug occur simultaneously in the same reaction system, which makes it possible to achieve ultrahigh drug-loading capacity and prolonged drug release due to ultrahigh specific surface area and numerous binding sites of the CP nanocarriers. A series of hydrophobic drug-delivery systems with adjustable drug-loading capacities and drug-release rates have been successfully synthesized. In addition, the drug-release kinetics of the as-prepared drug-delivery systems have been found in which the cumulative amount of drug release has a linear relationship with the natural logarithm of release time. FROM THE CLINICAL EDITOR: Calcium phosphates (CPs) are highly biocompatible inorganic biomaterials with thus far limited drug-delivery applications. This study reports the preparation of a novel drug delivery system where the formation of CP nanocarriers and in situ loading of the drug occur simultaneously in the same reaction, enabling ultra-high drug-loading.

Size-control and optical properties of organic nanocrystals.

We prepared the organic nanocrystals by the reprecipitation method using a carbosiloxane dendrimer. The dispersing process can be controlled by the carbosiloxane dendrimer which presented good site-isolation effect in host-guest chemistry. The size and shape of the controlled nanocrystals were analyzed by UV/vis spectroscopy and SEM. The absorbance of UV/vis spectra varied during the evolving process. The shape was more regular and the size can be well controlled under 100 nm. The results indicated the optical properties of organic nanocrystals strongly depends on their sizes.

Europium-doped amorphous calcium phosphate porous nanospheres: preparation and application as luminescent drug carriers.

Calcium phosphate is the most important inorganic constituent of biological tissues, and synthetic calcium phosphate has been widely used as biomaterials. In this study, a facile method has been developed for the fabrication of amorphous calcium phosphate (ACP)/polylactide-block-monomethoxy(polyethyleneglycol) hybrid nanoparticles and ACP porous nanospheres. Europium-doping is performed to enable photoluminescence (PL) function of ACP porous nanospheres. A high specific surface area of the europium-doped ACP (Eu3+:ACP) porous nanospheres is achieved (126.7 m2/g). PL properties of Eu3+:ACP porous nanospheres are investigated, and the most intense peak at 612 nm is observed at 5 mol% Eu3+ doping. In vitro cytotoxicity experiments indicate that the as-prepared Eu3+:ACP porous nanospheres are biocompatible. In vitro drug release experiments indicate that the ibuprofen-loaded Eu3+:ACP porous nanospheres show a slow and sustained drug release in simulated body fluid. We have found that the cumulative amount of released drug has a linear relationship with the natural logarithm of release time (ln(t)). The Eu3+:ACP porous nanospheres are bioactive, and can transform to hydroxyapatite during drug release. The PL properties of drug-loaded nanocarriers before and after drug release are also investigated.

Hydroxyapatite nanorods/poly(vinyl pyrolidone) composite nanofibers, arrays and three-dimensional fabrics: electrospun preparation and transformation to hydroxyapatite nanostructures.

Electrospinning has been recognized as an efficient technique for fabricating polymer nanofibrous biomaterials. However, the study of electrospun inorganic biomaterials with well-designed three-dimensional (3-D) structures is still limited and little reported. In this study hydroxyapatite (HAp) nanorods with an average diameter of approximately 7 nm and length of approximately 27 nm were synthesized through a simple precipitation method and used for the fabrication of inorganic/organic [poly(vinyl pyrolidone) (PVP)] composite nanofibers by electrospinning in ethanol solution. 3-D fabrics and aligned nanofiber arrays of the HAp nanorods/PVP composite were obtained as precursors. Thereafter, 3-D single phase HAp fabrics, tubular structures and aligned nanofiber arrays were obtained after thermal treatment of the corresponding composite precursors. Cytotoxicity experiments indicated that the HAp fabric scaffold had good biocompatibility. In vitro experiments showed that mesenchymal stem cells could attach to the HAp fabric scaffold after culture for 24h.

Preparation and sustained-release property of triblock copolymer/calcium phosphate nanocomposite as nanocarrier for hydrophobic drug.

The P123/ACP nanocomposite with sizes less than 100 nm consisting of triblock copolymer P123 and amorphous calcium phosphate (ACP) has been prepared by using an aqueous solution containing CaCl2, (NH4)3PO4, and P123 at room temperature. The P123/ACP nanocomposite is used as the nanocarrier for hydrophobic drug ibuprofen, based on the combined advantages of both amphiphilic block copolymer and calcium phosphate delivery system. The P123/ACP nanocomposite has a much higher ibuprofen loading capacity (148 mg/g) than the single-phase calcium phosphate nanostructures. The drug release percentage of the P123/ACP nanocomposite in simulated body fluid reaches about 100% in a period of 156 h, which is much slower than that of single-phase calcium phosphate nanostructures. It is expected that the P123/ACP nanocomposite is promising for the application in the controlled delivery of hydrophobic drugs.

Porous nanocomposites of PEG-PLA/calcium phosphate: room-temperature synthesis and its application in drug delivery.

We report room-temperature preparation of poly(ethylene glycol)-block-polylactide (PEG-PLA)/calcium phosphate (CP) nanocomposites with a porous morphology. The reaction time and concentration of the inorganic ingredients play an important role in the morphology and chemical composition of the nanocomposite. Thermogravimetry analysis shows that there is approximately 8.5 wt.% of PEG-PLA block copolymer in the nanocomposite. A typical anti-inflammatory drug, ibuprofen, is used to evaluate the drug loading ability and the release behavior of the porous PEG-PLA/CP nanocomposite. The experiments reveal that the nanocomposite has a higher drug loading capacity and favorable drug release property. The drug release kinetics of the porous PEG-PLA/CP nanocomposite is discussed as a three-stage process. The as-prepared porous PEG-PLA/CP nanocomposite is promising for application in drug delivery.