Papers by Keyword: Nano-Hydroxyapatite

Abstract: Nano-hydroxyapatite was synthesized by coprecipitation method and tested its antibacterial properties. Nano-hydroxyapatite was synthesized using CaO precursors from snakehead (Channa striata) fish bones and (NH₄)₂HPO₄. The synthesis was carried out with temperature variations of 30, 60, 80, and 100 °C. Antibacterial activity was determined using two types of bacteria, namely gram-positive and gram-negative. The XRD spectra show that the highest peak is hydroxyapatite synthesized at a temperature of 100 °C. Hydroxyapatite produced from various synthesis temperatures has the size of nanoparticles in the range 37.32-49.27 nm. The nano-hydroxyapatite functional groups are characterized using FTIR, the analysis indicate the presence of OH, CO₃^2‒ and PO₄^3‒. The molar ratio Ca/P is obtained of 1.71 approaching theoretical hydroxyapatite of 1.67. The resulted nano-hydroxyapatite has significant antibacterial properties to Escherichia coli and Staphylococcus aureus.

Abstract: In order to evaluate the cytocompatibility and hemolytic properties of n-HA/PEEK biocomposites the nanohydroxyapatite/polyetheretherketone (n-HA/PEEK) biocomposites were successfully prepared. The mechanical properties of the biocomposites were proximal to human bone, at the same time, they had the optimal value with the HA volume content of 5%. The PEEK and n-HA/PEEK biocomposites with different HA content extraction medium was prepared with fresh medium. Simple DMEM culture solution was taken as negative control group. The pure PEEK and 5vol.%, 15vol.%, 30vol.% n-HA/PEEK biocomposites were the testing group. The relative proliferation rate of L929 cells was determined on the 1^st, 2^nd, 3^rd and 6^th days with CCK-8 assay. The cytotoxicity of n-HA/PEEK biocomposites were evaluated according to ISO 10993-5: 2009. The L929 cells morphology and growth on the 1^st, 2^nd, 3^rd and 6^th days were determined under inverted microscope. The hemolysis test in vitro of n-HA/PEEK biocomposites were evaluated through measuring erythrocyte lysis and ferro-hemoglobin freeing degree with indirect contact method basing on ISO 10993-4:2009. The experimental results showed that the growth and morphology of cells in pure PEEK and n-HA/PEEK biocomposites extraction medium had no difference from negative control group. Cytotoxicity test showed that PEEK and n-HA/PEEK biocomposites did not have obvious toxicity on L929 cells, and the cytotoxicity of these extracts was in grade 0-1. Hemolysis test suggested that PEEK and n-HA/PEEK biocomposites did not have obvious hemolysis reaction, and the hemolysis rate of PEEK and n-HA/PEEK biocomposites were 2.37%, 1.71%, 1.05% and 1.32% respectively, which are less than the national standard (5%). It may be concluded that the n-HA/PEEK biocomposites did not have obvious cytotoxicity and hemolysis reaction, which demonstrated that n-HA/PEEK biocomposites had good cytocompatibility.

Abstract: Hydroxyapatite (Ca10(PO4)6(OH)2-HAp), is an excellent inorganic biomaterial and finds various applications. As it is similar to inorganic matrix of human bone and dental enamel, pure and doped HAps are widely studied. In the present study, pure nano-HAp and Strontium doped nano-HAp (Sr-HAp) with different concentrations were synthesized by surfactant mediated approach. The doping of strontium was confirmed by EDAX. The powder XRD study was carried out and it suggested nano-crystalline nature of the sample and the extra peaks observed other than HAp were due to the presence of brushite phase for higher concentration of Sr. TEM study revealed the needle type morphology for all the samples with size ranging from 23 nm to 78 nm. The dielectric study was carried out at room temperature within the frequency range from 102 Hz to 107 Hz and the variations of dielectric constant with frequency of applied field as well as with the concentration of strontium were studied. The results are discussed.

Abstract: Poly (3-hydroxybutyrate) (PHB)/poly (L-lactide) (PLLA)/nanohydroxyapatite (n-HA) composite Ultrafine Fibers with diameter of 610 ~ 830 nm were prepared by electro-spinning. The surface morphology was studied by scanning electron microscopy (SEM). The effect of the process of prepareing spinning solutions, the constituent of spinning solutions, the concentration of PHB/PLLA/ n-HA blends spinning solutions and the collection distance on the surface morphology of fibers were discussed. The results indicated that n-HA mixing with solvent prior to other materimals for electrospingning could prepare the homogeneity of the spinning mixture. In all of the spinning conditions investigated ,When using chloroform (CF) /N, N-dimethyl formamide (DMF ) mixture as spinning solvent , PHB/PLLA/HA composite ultrafine fibers were not fabricated by electro-spinning, but chloroform can do. The average diameter of as-spun fibers increased with increasing concentration of PHB/PLLA/HA blends spinning solutions and collection distance.

Abstract: In this study, we prepared porous nano-hydroxyapatite/ polyamide 66 (n-HA/ PA66) porous scaffolds by injection molding method. The morphology, macrostructure and mechanical strength of the scaffolds were characterized. Osteoblasts (OBs) derived from cranial bone of SD rats were cultured and seeded on n-HA/ PA66 scaffolds. The OB/scaffold constructs were cultured for up to 18 days and the adhesion, proliferation and osteogenic activity of OBs were observed by scanning electron microscope and detected by alkaline phosphatase activity. The results showed that the porous n-HA/PA66 porous scaffolds are biocompatible and have no negative effects on the OBs in vitro. The scaffolds fulfill the basic requirements of bone tissue engineering scaffold, and have the potential application in orthopedic, reconstructive and maxillofacial surgery areas.

Abstract: While nano-hydroxyapatite (nano-HAP) has been well known for series of amazing properties in chemical or physical, the controversy on the risks of its applications has also been existed. The worries of nano-HAP applications in preclinic and clinic indicate the blank researches of nano-HAP pharmacodynamics. It is important and necessary to trace and clarify the localizations of HAP nanoparticles in vivo. In the present paper, 18F is used as radiotracer for Positron Emission Tomography (PET) imaging of HAP nanoparticles. Through the transverse plane slices and three-dimensional reconstruction pictures, it is very clear to observe the localization of nano-HAP in vivo at real time. Most nano-HAP particles were noted in organs lump, liver, spleen, stomach and existed for period of time. Therefore, PET can be a new powerful technique for tracing nano-biomaterial and their pharmacodynamics researches.

Abstract: nanohydroxyapatite (nHA) and collagen were utilized to fabricate the bio-inspired organic-inorganic composite coating (OICC) via the Drop-on-Demand (DoD) micro-dispensing technique, which could flexibly construct multi-layer structures with varied materials composition within a layer and /or among layers reliably. This technique has been further investigated on its capability of OICC fabrication with regards to various materials (hydroxyapatite and collagen) as well as its dispensing parameters. A four-layered structure was formed, with the sequence of nHA-collagen-nHA-collagen from bottom to top. The dispensing parameters were also investigated with regards to the characteristics of the OICC fabrication. The coating was then subjected to various characterizations including scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS) and adhesion test. SEM and XRD results revealed that the DoD micro-dispensing technique did not change the morphology and phase of these two coating materials. And the results of EDS further demonstrated the corresponding elemental distributions within the four-layered coating structure which demonstrated the feasibility of the DoD micro-dispensing technique for the fabrication of thin-layered OICC.

Abstract: The dynamic mechanical properties of nano-hydroxyapatite (n-HA) reinforced polyamide 66 (PA66) biocomposites were studied with reference to the effect of n-HA content, frequency and physiological saline. The intrinsic properties of the components, morphology of the system and the nature of interface between the phases determine the dynamic mechanical properties of the composite. The storage modulus (E') values of n-HA/PA66 composites were much higher than those of pure PA66, indicating that the incorporation of n-HA in PA66 matrix induced reinforcing effects obviously. And the E' values of composites increased with increasing of n-HA content. The loss modulus (E") of the composite with 30wt% n-HA was higher that those of pure PA66 and the composite with 40wt% n-HA below 55°C, however, above 55°C, the E" values enhanced with increase of n-HA content. Both frequency and physiological saline had obvious effects on the dynamic mechanical properties for n-HA/PA66 composite. E' and E" values enhanced with increase of frequency, but tanδ values decreased with increasing of frequency. After soaked in physiological saline, the E' and E" values of the composite decreased.

Abstract: Calcium hydroxide cement used in dentistry has advantages of proper alkaline pH, releasing calcium ions and promoting tissue regeneration. However, it also has some drawbacks such as high solubility and low strength. In this study, the properties of nano-hydroxyapatite (nHA) added calcium hydroxide cement was investigated for overcoming these drawbacks. Stoichiometric nHA powder was synthesized using orthophosphoric acid and calcium hydroxide. 5, 10 and 15 percent (in w/w) of synthesized nHA powder was added to commercial calcium hydroxide cement and the obtained nanocomposite was characterized by setting time, compressive strength, pH, Ca dissolution, antibacterial tests and SEM. Nanometric size and purity of synthesized apatite was confirmed by XRD and TEM. Setting time increased by increasing the content of nHA. SEM micrographs showed less microporosity for sample with 5% nHA. Adding 5% nHA to calcium hydroxide cement increased compressive strength to 60%, while further additions had an adverse effect. Adding nHA slightly decreased pH and increased Ca dissolution. The antibacterial test revealed that inhibition zone was about 2-2.5 mm for calcium hydroxide cement and sample with 5% nHA and less than 1 mm for other samples. Finally, nanocomposite with 5% nHA exhibited adequate properties to overcome the drawbacks of calcium hydroxide cements.

Abstract: A three-dimensional finite element model has been created to study the change rules of temperature field during the laser sintering process of nano-hydroxyapatite powder. The numerical simulation of temperature distribution has been achieved based on the equivalence between the sintering time and the sintering speed. The simulation results show that the temperature declines gradually along the radial direction of the laser spot. At the same time, there was the largest temperature gradient at the edge of the laser spot. The temperature of sintering layer rises with the increase of laser power linearly when the other process parameters are the same. The maximum sintering temperature is 1320°C with laser power of 8.75W, laser spot diameter of 4mm, sintering time of 5s and layer thickness of 0.2mm. The test results verify that nano-hydroxyapatite powder could be sintered under this process condition. It shows that the finite element model can be used to simulate the temperature field during the laser sintering process.