Shao-Wen Cao

Monodisperse α-Fe2O3 Mesoporous Microspheres: One-Step NaCl-Assisted Microwave-Solvothermal Preparation, Size Control and Photocatalytic Property

A simple one-step NaCl-assisted microwave-solvothermal method has been developed for the preparation of monodisperse α-Fe2O3 mesoporous microspheres. In this approach, Fe(NO3)3 · 9H2O is used as the iron source, and polyvinylpyrrolidone (PVP) acts as a surfactant in the presence of NaCl in mixed solvents of H2O and ethanol. Under the present experimental conditions, monodisperse α-Fe2O3 mesoporous microspheres can form via oriented attachment of α-Fe2O3 nanocrystals. One of the advantages of this method is that the size of α-Fe2O3 mesoporous microspheres can be adjusted in the range from ca. 170 to ca. 260 nm by changing the experimental parameters. High photocatalytic activities in the degradation of salicylic acid are observed for α-Fe2O3 mesoporous microspheres with different specific surface areas.

Nanostructured porous hollow ellipsoidal capsules of hydroxyapatite and calcium silicate: preparation and application in drug delivery

We have successfully prepared for the first time hydroxyapatite (HAp) and calcium silicate (CaSiO3) nanostructured porous hollow ellipsoidal capsules which are constructed by nanoplate networks using the inorganic CaCO3 template. CaCO3 ellipsoids are synthesized via the reaction between Ca(CH3COO)2 and NaHCO3 in water and ethylene glycol mixed solvent at room temperature and they are used as the Ca2+ source and cores. Then a PO43− or SiO32− source is added to react with CaCO3 to form a HAp or CaSiO3 shell on the surface of CaCO3 ellipsoids. Dilute acetic acid is used to remove remaining CaCO3 cores. The size and shape of the HAp and CaSiO3 hollow capsules are determined by those of the cores. The thickness of the capsule shell can be controlled by adjusting the concentration of PO43− or SiO32− source. A number of PO43− sources such as dilute H3PO4, Na3PO4 and Na2HPO4 can be used to form HAp hollow capsules with similar morphologies. The drug loading and release behavior of HAp hollow capsules is also investigated. A typical anti-inflammatory drug, ibuprofen, is used for drug loading. The result indicates that HAp hollow capsules have a high specific surface area and high storage capacity, and favorable drug release behavior.

Hierachically nanostructured mesoporous spheres of calcium silicate hydrate: surfactant-free sonochemical synthesis and drug-delivery system with ultrahigh drug-loading capacity.

Adv. Mater. 2010, 22, 749–753 2010 WILEY-VCH Verlag Gm Since MCM-41 was proposed as a drug-delivery system by Vallet-Regı́ et al. in 2001, silica-based mesoporous materials have been widely investigated as drug carriers and controlled drug-release systems due to their high specific surface area, large pore volume, low-toxic nature, and good biocompatibility. Surfactants are generally employed as templates to obtain the mesoporous structures and the pore-wall surfaces are modified or functionalized with organic groups to facilitate the drug adsorption and/or the control of drug release. However, the residual surfactants and/or the introduced organic groups may result in cytotoxicity for clinical applications and the drug loading capacities (DLCs) are commonly at low levels. Besides, for bone-implantable delivery systems, the bioactivity of silica is not so satisfying and the clinic-applicable poly(methyl methacrylate) (PMMA)-bead systems have the drawbacks that they should be removed by a second surgical operation to avoid infections because of their poor bioactivity and biodegradability. To overcome these disadvantages, one strategy is to synthesize hierachically nanostructured mesoporous spheres (HNMS) of calcium silicate hydrate (CSH) without using any surfactants. The Ca2þ cations on the pore-wall surface can serve as the ‘‘inherent surface modifier’’ to effectively adsorb those drug molecules with acid groups, such as ibuprofen, aspirin, and amoxicillin. Furthermore, the incorporation of CaO in SiO2 structures can lead to superior bioactivity. Also, the CaO SiO2 composition has been proved to be of clinical safety. In the past decade, calcium silicate (CS) materials have drawn growing attention on their potential applications in the bone tissue engineering field. Some studies have been carried out on their transformation to bonelike apatite/hydroxyapatite but only few have involved their applications in drug delivery systems. Jain et al. and Li et al. reported CS/polymer composite spheres for drug release. However, the spheres reported were too large and the DLCs remained at low levels. It has been reported that large specific surface area and large pore volume are vital factors for achieving high DLC and that 3D and well-defined microstructure with an interconnected pore network is important for an ideal delivery system. Therefore, hierachically nanostructured mesoporous CS materials with well-defined morphologies are highly desirable for applications in drug delivery. Nevertheless, this kind of CS nanomaterials is usually difficult to prepare using most of the known methods (coprecipitation, sol–gel, hydrothermal, etc.), which is an inherent drawback for their wide applications in the biomedical field. The sonochemical method is an excellent alternative to conventional chemical methods for this intention, since ultrasound has great promise for promoting and accelerating a range of homogeneous chemical reactions. It is based on the acoustic cavitation deriving from the continuous formation, growth and implosive collapse of bubbles in a liquid. The large quantities of cavitation bubbles resulting from the high-intensity ultrasonic irradiation may contribute to the mesoporous nanostructures of the resulting products. Up to now, several types of mesoporous materials, such as titania, zirconia, silica and ferric oxide, have been synthesized via sonochemical methods, but most of them were prepared in the presence of surfactants and the synthesis of mesoporous CS materials by the surfactant-free sonochemical method has not been reported yet. Herein, we report, for the first time, the low-cost, surfactantfree sonochemical synthesis of HNMS of CSH (HNMS-CSH) with well-defined 3D network structures constructed by nanosheets as building blocks. As illustrated in Scheme 1, tetraethyl orthosilicate (TEOS) is employed as the silicon source, which rapidly hydrolyzes and reacts with Ca2þ cations in basic aqueous solution under high-intensity ultrasonic irradiation. The excess of Ca2þ cations enriches the surface of resultant HNMS-CSH with Ca2þ ions. Using ibuprofen (IBU) as a model drug, the ultrahigh DLC and the linear relationship between the cumulative amount of released drug and the natural logarithm of release time have been found in the HNMS-CSH system for the first time. In particular, when the IBU-loaded HNMS-CSH (IBU–HNMS-CSH) releases the absorbed IBU in simulated body fluid (SBF), the CSH component will gradually transform to hydroxyapatite as a result of its good bioactivity (Scheme 1). A surfactant-free sonochemical route has been developed for the synthesis of HNMS-CSH under ambient conditions. As shown in Figure 1, the structural features of as-synthesized HNMS are characterized by bird-nestlike 3D hierachical networks constructed by stacking of nanosheets as building blocks with mesopores and macropores. The HNMS has relatively uniform sizes of ca. 1mm and the building blocks of nanosheets

ZnFe2O4 nanoparticles: microwave-hydrothermal ionic liquid synthesis and photocatalytic property over phenol.

We report the microwave-hydrothermal ionic liquid (MHIL) synthesis and photocatalytic property over phenol of ZnFe(2)O(4) nanoparticles. Zn(CH(3)COO)(2).2H(2)O and Fe(NO(3))(3).9H(2)O were used as the zinc and iron sources, respectively, in the presence of CO(NH(2))(2) and the ionic liquid 1-n-butyl-3-methyl imidazolium tetrafluoroborate ([BMIM][BF(4)]). Deionized water was used as a solvent. The ionic liquid [BMIM][BF(4)] and microwave heating temperature have significant influences on the crystal phase of the product. Different dosages of [BMIM][BF(4)] or microwave heating temperature could lead to the formation of different products such as ZnFe(2)O(4) and beta-FeOOH. The MHIL method has the advantages such as simplicity, rapidness and energy saving. The ZnFe(2)O(4) nanoparticles prepared by the MHIL method exhibit high photocatalytic activity for the degradation of phenol, which was up to 73% within 360 min. The TOC measurement confirmed the good photocatalytic efficiency of ZnFe(2)O(4) nanoparticles.

Fe3O4 polyhedral nanoparticles with a high magnetization synthesized in mixed solvent ethylene glycol–water system

We report a solvothermal approach for the synthesis of high-magnetization Fe3O4 polyhedral nanoparticles in the ethylene glycol (EG)–H2O system. In this approach, ferric chloride (FeCl3·6H2O) is used as the iron source, and EG acts as both the solvent and reductant in the presence of sodium hydroxide (NaOH) and dodecylamine (DDA). The presence of deionized water plays an important role in the control over the size of Fe3O4 particles. The Fe3O4 particles prepared are well dispersed with single-crystal-like features, showing superparamagnetism with a high saturation magnetization close to that of bulk Fe3O4 (92 emu g−1). The stability of the Fe3O4nanoparticles in deionized water is also investigated.

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

UNLABELLED 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.

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.

Rapid microwave-assisted synthesis and characterization of cellulose-hydroxyapatite nanocomposites in N,N-dimethylacetamide solvent

Preparation of nanocomposites was carried out using microcrystalline cellulose, CaCl(2), and NaH(2)PO(4) in N,N-dimethylacetamide (DMAc) solvent by a microwave-assisted method at 150 degrees C. XRD results showed that the nanocomposites consisted of cellulose and hydroxyapatite (HA). The cellulose existed as a matrix in the nanocomposites. SEM and TEM analysis showed that HA nanorods were homogeneously dispersed in the cellulose matrix. The effects of the microwave heating time on the products were investigated. This method has advantages of being simple, rapid, low-cost, and environmentally friendly.

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.