Shi Pu Li

Molecular Modification of Hydroxyapatite to Introduce Interfacial Bonding with Poly (Lactic Acid) in Biodegradable Composites

Six silane-modified hydroxyapatite (HA) / poly(lactic acid) (PLA) composites at 20% volume HA are prepared through absorption in liquid phase, volatilization, milling, and hot-press molding. Bending testing results indicate that their bending strengths are higher than that of control HA composite (unmodified HA composite) and the maximum strength enhances 27.8%. Calcium precipitation and calcium release experiments are designed to examine the bioactivity of the modified HA. The results show that the presence of the modification coating does not really impair the bioactivity and mineralization tendency of HA particles. Relationship of swelling property of the composites as function of time is investigated. Swelling equilibriums of silane-modified HA / PLA composites are reached after 48 h or 72 h, but the equilibrium of the unmodified HA / PLA composite is reached within 24 h. The swelling experiment also suggests that the desired swelling property of the composites could be achieved by changing modification molecules of HA according to necessity. Finally, SEM micrographs show that there is an improved interfacial binding between the modified HA and PLA matrix.

Inhibitory Effect of Hydroxyapatite Nanoparticles on K562 Cells

HAP Nanoparticles Was Synthesized by Homogeneous Precipitation. the Size Distribution, Crystallization Degree and Morphology of the Precipitation Were Characterized by Laser Granularity Instrument, X-Ray Diffraction (XRD), and Transmission Electron Microscope (TEM) Respectively. the Prepared HAP Nanoparticles Were Used for the Treatment of Human Chronic Myeloid Leukemia K562 Cells. the Inhibition Effect of the Nanoparticles on the Proliferation of K562 Cells Was Measured by MTT Assay and Growth Curve Test. the Results Showed that the HAP Nanoparticles Inhibit the Proliferation of K562 Cells Dramatically in Vitro. the Likely Inhibition Mechanism of HAP Nanoparticles on the K562 Cells Is that the Nanoparticles Entered into the Dells, Induced a Series of Cell Changes, through Cell Death of Apoptosis, Oncosis and Autoschizis, Thus Led to the Death of K562 Cells.

Preparation and Characterization of Calcium Phosphate Crystals by Precursor Thermolysis Method

In this paper, a simple precursor thermolysis method is applied to prepare calcium phosphate crystals and macroporous ceramic. The phase composition of sample was determined by XRD and the morphology of sample was observed by TEM and SEM. The macroporous ceramic was observed by 3D digital microscope. Results show that 25-100 nm HAP nanocrystals were obtained at 500°C and HAP rod-like crystals with an equivalent diameter of about 0.50-1.6μm and a length of about 5-10μm were obtained at 700°C. In addition, about 100 nm β-TCP nanoparticles were also obtained at 900°C. The colloidal precursors can also be used to fabricate macroporous calcium phosphate ceramic. The size of pores is about 100-200μm. Pores are well opened and interconnected in three dimensions.

Preparation and Characterization of Strontium-Containing HAP Sol and Studies on Its Effects on Cancer and Normal Cells

Saturated calcium hydroxide solution and monocalcium phosphate were used as initial materials for hydroxyapatite preparation. The strontium hydroxide was used as strontium nitrition. The initial materials were prepared for nano strontium-containing hydroxyapatite sol. Nano strontium-containing hydroxyapatite particles were characterized. They are sized in scope of 20 nm to 60 nm. The particles were analyzed by XRD and TEM, which verified the particles were strontium-containing apatite. The sol was applied to interact with Bel-7402 cells and L-02 cells. Experimental results revealed that nano strontium-containing hydroxyapatite has different bioeffects on cell line Bel-7402 and L-02.

Electron Transfer Effect between Pd and Fe(Bi) in Pd-(Fe or Bi)2O3-Polymer Hybrid Catalytic Materials

X-ray photoelectron spectroscopy (XPS) and FTIR spectroscopy have been employed to investigate the surface electron property and interaction between components of multi – components hybrid systems Pd – (Fe or Bi) 2O3 – polymers. One – way electron transfers from Fe (III) to Pd (0) in PdFe 2O3 – polymer and from Pd (0) to Bi (III) in Pd – Bi 2O3 – polymer are found, respectively. According to the electron transfer effects, the c atalytic activities of Pd-(Fe or Bi) 2O3 – polymer hybrid materials are successfully explained, an elec tron transfer from Fe (III) to Pd (0) species resulting in an increased activity of the Pd – Fe 2O3 – polymer, whereas, that from Pd (0) to Bi(III) species leads to a decreased activity of the Pd – Bi 2O3polymer. However, FTIR results indicate that there is no strong interaction between palladium (or etallic oxides) and the polymeric supporter, the Pd and Fe 2O3 or Bi2O3 are supported on the polymer only by physical adsorption. Finally, based on the above electron transfer concept, the possibili ties of theoretical design and preparation strategy of multi-components hybrid catalytic mate rials by selecting the additive components and regulating their atomic fractions are also discussed.

A Novel Method for the Covalent Modification of Hydroxyapatite

A novel method of the covalent modification of hydroxyapatite(HAP) ba sed on various silane derivatives has been developed in which a carefully dried orga nic solvent system is used in order to avoid production of reactive silanol. XPS results and IR differ ential spectra indicate that HAP and the silane derivatives are connected via P-O-Si chemica l bonds. This new covalent bonding provides a possibility for HAP to produce more effective adhes ion to polymer matrix, which is essential for HAP/polymer composite bone substitute mater ials with higher interfacial property. Introduction Hydroxyapatite (HAP) materials have been the subject of intens e study in recent years because of their diverse uses in chemical, biological, material and medical fields[1-5]. One of the recent developments is to utilize HAP as a reinforcement for organic pol ymer to synthesize a composite biomaterial[6,7].The reasons for selecting HAP as a filler in composites is to improve the stiffness of materials and bone bonding properties which are essential for a chieving early bone ingrowth and fixation of implants by bone tissue[8].In addition, the incorporation of HAP filler into a polymer matrix may combine the osteoconductivity of HAP with easy polymer processing. And the wide range of mechanical and biological properties of polymers also of fers the possibility of making composites with various desired properties. However, most of HAP polymer composites lost their strength rapi dly when exposed to the aqueous physiological environment, failures occur mainly at the inter face of HAP and polymer because of a lack of effective adhesion between the two phases [9,10]. A range of approaches have been suggested to improve the interfacial properties including the u se of various coupling agents[11-15], among which silane modification has attracted more att ention. In the literatures, however, silanes are only treated as coating or coverage on the HAP filler’s surface, none of these techniques is capable of generating a direct chemical bonding betw een HAP and the coupling agent molecule of silane, which extremely decreases the modification effect. In this paper, we report a novel method for direct covalent bonding bet ween HAP and silane derivatives, and the subsequent relevant characterization is also de monstrated. Property of the composites is also investigated in another paper. Methods A typical covalent modification experiment is as follows: 5g of dr ied HAP particle or fiber, then 150 mL of toluene were put into a 250mL 3-necked flask. The stirred react ion mixture was maintained at an appropriate temperature (reflux) and under N 2 p otection for 30min, followed by dropwise addition of 1mL of the silane derivative selected (Tabl e1). After reaction, the modified HAP was separated by centrifugation and washed with CHCl 3 and absolute EtOH. Finally, the sample was dried at 60 C for the following uses. Key Engineering Materials Online: 2003-09-15 ISSN: 1662-9795, Vol. 249, pp 433-436 doi:10.4028/www.scientific.net/KEM.249.433

Embolic Materials of BaFe12O19/Polyurethane Microspheres

Spherical nano-BaFe12O19 was prepared by Colloid template, layer-by-layer electrostatic self-assembly and heat treatment method. BaFe12O19/polyurethane (BF/PU) composite microspheres were prepared by Suspension in-situ polymerization. The Physical and chemical properties of the microspheres were analyzed by SEM, FTIR and TG-DSC, etc. The biocompatibility of microspheres was evaluated. Embolization experiments were performed in rete mirabile (RMB) of pigs. The results showed that BF/PU microspheres had a core-shell structure and good heat stability. The content of BaFe12O19 was 11.11wt% in microspheres. The density ofmicrospheres was 1.055g·cm-3, which was near to that of blood. The composite microspheres had agood biocompatibility and successfully embolized arteriovenous malformation (AVM) with different flow. BF/PU microspheres could be a new type of embolization material for cerebral AVM and has great potential as a therapeutic embolic agent.

Synthesis and Characterization of Comb-Type Grafted Hydrogels

The grafted hydrogels of N-isopropylacrylamide (IPAAm) with 2-hydroxyethylacrylate (HEA) was prepared in an aqueous solution using ammonium persulfate (APS) and N,N,N’,N’-tetramethylethylene diamine (TEMED) as an accelerator. Lower critical solution temperature (LCST) and swelling ratios were measured as a function of temperature. The properties of the hydrogels contained pyrenyl probe in water were investigated by fluorescence spectroscopy.

Tetracycline Double Labelling Tracing Investigation for In Vivo Osteogenetic Course of PDLLA/HA Composite

The PDLLA(DL-Poly lactic acids)/HA(Hydroxyapatite) composite and pure PDLLA control were implanted in bone for test. Using fluorescent pictures of tetracycline double label and advanced image analysis system, the trend of bone-formation rate for the implanting region of PDLLA/HA composite was obtained via morphometry measurement of the slices labeled with tetracycline. The investigation and calculation results show that, the formation rate of new bone is stable and high (reaches 2.044μm/day) in the early stage of implantation for the PDLLA/HA composite, demonstrating the advantageous capability of bone formation for the composite. The formation rate of new bone seems to decrease continuously with time, and then the bone formation and bone decomposition tend towards equilibration. Namely, the dynamic balance of bony tissue’s metabolism is maintained.

Effect of Macrophage on Degradation of β-TCP Ceramics

Mice macrophages which were mixed with β-tricalcium phosphate (β-TCP) ceramics powder were cultured, both calcium and phosphorus concentrations in the culture medium were evidently higher than that of β-TCP ceramics powder without cells. The microscope and SEM observation showed that macrophages wrapped β-TCP particles, and then phagocytized them into cytoplasm. The pH values inside and outside macrophage in β-TCP-bearing were tested. The histochemistry observation showed that there were many carbonic anhydrase positive grains in the cytochylema of macroghage after β-TCP ceramics powder being implanted. TEM investigation indicated that many β-TCP particles were phagocytized into the cytochylema of macroghage, and then vacuole was found after particles had degraded. The results showed that macrophages could take part in the degradation of calcium phosphate ceramics in two different ways.