Aihua Yao

Preparation and characterization of temperature-responsive magnetic composite particles for multi-modal cancer therapy.

The temperature-responsive magnetic composite particles were synthesized by emulsion-free polymerization of N-isopropylacrylamide (NIPAAm) and acrylamide (Am) in the presence of oleic acid-modified Fe3O4 nanoparticles. The magnetic properties and heat generation ability of the composite particles were characterized. Furthermore, temperature and alternating magnetic field (AMF) triggered drug release behaviors of vitamin B12-loaded composite particles were also examined. It was found that composite particles enabled drug release to be controlled through temperature changes in the neighborhood of lower critical solution temperature. Continuous application of AMF resulted in an accelerated release of the loaded drug. On the other hand, intermittent AMF application to the composite particles resulted in an “on–off”, stepwise release pattern. Longer release duration and larger overall release could be achieved by intermittent application of AMF as compared to continuous magnetic field. Such composite particles may be used for magnetic drug targeting followed by simultaneous hyperthermia and drug release.

BMP2-loaded hollow hydroxyapatite microspheres exhibit enhanced osteoinduction and osteogenicity in large bone defects

The regeneration of large bone defects is an osteoinductive, osteoconductive, and osteogenic process that often requires a bone graft for support. Limitations associated with naturally autogenic or allogenic bone grafts have demonstrated the need for synthetic substitutes. The present study investigates the feasibility of using novel hollow hydroxyapatite microspheres as an osteoconductive matrix and a carrier for controlled local delivery of bone morphogenetic protein 2 (BMP2), a potent osteogenic inducer of bone regeneration. Hollow hydroxyapatite microspheres (100±25 μm) with a core (60±18 μm) and a mesoporous shell (180±42 m2/g surface area) were prepared by a glass conversion technique and loaded with recombinant human BMP2 (1 μg/mg). There was a gentle burst release of BMP2 from microspheres into the surrounding phosphate-buffered saline in vitro within the initial 48 hours, and continued at a low rate for over 40 days. In comparison with hollow hydroxyapatite microspheres without BMP2 or soluble BMP2 without a carrier, BMP2-loaded hollow hydroxyapatite microspheres had a significantly enhanced capacity to reconstitute radial bone defects in rabbit, as shown by increased serum alkaline phosphatase; quick and complete new bone formation within 12 weeks; and great biomechanical flexural strength. These results indicate that BMP2-loaded hollow hydroxyapatite microspheres could be a potential new option for bone graft substitutes in bone regeneration.

Precise adsorption behavior and mechanism of Ni(II) ions on nano-hydroxyapatite.

The goal of this study was to synthesize use of hydroxyapatite as a high-efficiency adsorbent for Ni(II) ions, and to study its adsorption behavior. Three tests--Fourier-transform infrared spectroscopy, transmission electron microscopy, and Brunauer-Emmett-Teller were carried out to determine the chemical functionality of the hydroxyapatite powders, to observe its crystal morphology, and to measure the specific surface area. Results indicate that proves the n-HA synthesized by chemical precipitation is an effective adsorbent for the removal of Ni(II) ions from water solution. The synthesized, needle-like nano-hydroxyapatite (n-HA) have a uniform average size of 31.9 X 21.3nm, a large specific surface area (135 m2/g), and typically is a weak crystal with a broad pore distribution. The adsorption isotherm shows the Langmuir model is applicable only when the initial Ni2+ concentration is lower than 0.1 mol/L. Multilayer adsorption was attributed to uneven pore distribution that occurred at higher Ni2+ concentration. The adsorption of Ni2+ onto n-HA was attributed to electrostatic attraction, ion exchange, and dissolution-precipitation reaction. As the result, Ni2+ substitutes Ca2+ and binds with the oxygen atom on the surface, which resulted from the change in crystal-phase composition and in the binding energy of surface elements of n-HA before and after adsorption.

Study on Hollow Hydroxyapaptite Microspheres Prepared by a Borate Glass Conversion Process: Study on Hollow Hydroxyapaptite Microspheres Prepared by a Borate Glass Conversion Process

Hollow hydroxappatite(HAP) microspheres consisting of a hollow core and a porous shell were prepared by a Li-Ca-B glass conversion process.The phase composition,morphology and pore structure on the shell wall were investigated using XRD,SEM and BET.The results showed that the as-prepared microspheres possessed good internal hollow structure.The shell wall of the microsphere was made up of HAP crystals fully.After heat-treated at 600℃ for 2h,the compressive strength of the microsphere was determined to be(2.1±0.6)MPa,and the porosity and pore size of the shell wall were 85% and 60nm,respectively.Furthermore,the formation mechanism of the hollow HAP microsphere was also suggested.In phosphate solution,Ca-P-OH hydrate was in-situ formed on the surface of the glass and precipitated in the position initially occupied by Ca2+,while the pores were formed in the position initially occupied by Li+ and B3+.These hollow HAP microspheres may be useful for drug delivery.