Yan Yu-hua

Morphology and formation mechanism of hydroxyapatite whiskers from moderately acid solution

Hydroxyapatite (HA) whiskers with uniform morphology and good crystallinity were successfully prepared by a precipitation-hydrolysis method in moderately acid solution at 85-95 °C for 48-120 h, their lengths were in the range of 50-150 mm and aspect ratios (length/diameter) in the range of 40-100. The precipitates formed at each stage of the synthesis were characterized by XRD, FTIR, TEM and SEM. The morphology and crystallinity of the precipitates depended on the synthesis temperature and time as well as the concentrations of soluble calcium and phosphate ions. The HA whiskers were formed by the hydrolysis of precursors produced during the reactions and took over the morphology of fibrous octacalcium phosphate (OCP). The stoichiometric HA whiskers were improved with the increase of pH value of solution, the synthetic temperature and the duration.

Apoptosis of Cancer Cells Induced by HAP Nanoparticles

To confirm apoptosis is one of the hepatoma cells death pathways after HAP nanoparticles absorption, hepatoma cells were collected for ultrathin sections preparation and examined under a transmission electron microscope (TEM) after 1 h incubation with HAP nanoparticle. Apoptosis was detected by TUNEL technique. After absorption, some vacuoles with membrane containing HAP nanoparticles were found in cytoplasma. The nuclear envelope shrinked, and some are pullulated from nucleus. The karyotin became pycnosis and assembled at the edge. An apoptosis body was found. And the data of IOD and numbers of the positive apoptosis signals in nuclear area of slides could illustrate much more apoptosis in the HAP group than those in the control group. (P<0.001). The experimental results that the HAP nanoparticles can induce cancer cells apoptosis.

Selective anti-hepatoma treated with titanium oxide nanoparticlesin vitro

Effects of titanium oxide (TiO2) nanoparticles on Bel-7402 human hepatoma hepatoma cells and L-02 human hepatocytes at different times were observed. Using cell culture, cell growth curves of Bel-7402 cells and L-02 cells treated with TiO2 nanoparticles were examined by MTT assay, and the cellular ultrastructure was observed by an analytical transmission electron microscope (ATEM). It is found that OD value of Bel-7402 cell treated with TiO2 nanoparticles for 48–144h is obviously lower than that of control group (p<0.01). However the growth curve of L-02 cells is almost not affected by TiO2 nanoparticles. ATEM and energy dispersive X-ray (EDX) analyses show that there are obvious vacuoles increased heterolysosome, and particles with high electron density which are confirmed to be TiO2 nanoparticles in Bel-7402 cytoplasm. More interestingly, it is alse found that TiO2 nanoparticle obviously inhibits the proliferation of hepatoma cells by altering lysosome activity and destroying cytoplasm structure. The inhibition on proliferation of hepatocytes by TiO2 nanoparticles is much slighter. The results demonstrate that TiO2 nanoparticle has different killing effects on cancer cell and normal cell.

Cytotoxinic mechanism of hydroxyapatite nanoparticles on human hepatoma cell lines

Stable and single-dispersed HAP nanoparticles were synthesized with chemical method assisted by ultrasonic treatment. HAP nanoparticles were surveyed by AFM and Zataplus. The effect on the Bel-7402 human hepatoma cell lines treated with HAP nanoparticles was investigated by the MTT methods and observation of morphology, and the mechanism was studied in changes of cell cycle and ultrastructure. The result shows that inhibition of HAP nanoparticles on the Bel-7402 human hepatoma cell lines is obviously in vitro. HAP nanoparticles the entered cancer cytoplasm, and cell proliferation is stopped at G1 phase of cell cycle, thus, cancer cells die directly.

Titanium dioxide nanoparticle absorbed by hepatoma cellsin vitro

It is reported that nanoparticles can be applied as carriers and anti-cancer medicines. But the interaction of nanoparticles and cells is unclear. The purpose of this study was to discuss whether inorganic crystal nanoparticles can get through cells with intact crystal. BEL7402 hepatoma cells and titanium dioxide (TiO2) nanoparticles were selected and incubated together in vitro. All specimens were prepared and observed under a transmission electron microscope (TEM). TiO2 nanoparticles were found not in the nuclear area but in the cytoplasma. TiO2 nanoparticles maintained the plate-like shape during absorbing. The result shows that hepatoma cells can endocytose the intact TiO2 crystal nanoparticles. It implies that novel nano-effect plays an important role in the biomedicinal application of inorganic crystal nanoparticles.

Biomedical image processing using FCM algorithm based on the wavelet transform

An effective processing method for biomedical images and the Fuzzy C-mean (FCM) algorithm based on the wavelet transform are investigated. By using hierarchical wavelet decomposition, an original image could be decomposed into one lower image and several detail images. The segmentation started at the lowest resolution with the FCM clustering algorithm and the texture feature extracted from various sub-bands. With the improvement of the FCM algorithm, FCM alternation frequency was decreased and the accuracy of segmentation was advanced.

The transformation of calcium phosphate bioceramicsin vivo

To study the transformation process of calcium phosphate bioceramic in vivo, biodegradable porous β-tricalcium phosphate ceramics (β-TCP) were used in this experiment. The materials (ø5×8mm) were implanted in the tibia of rabbits. The β-TCP ceramics with bone tissue were retrieved, and treated for histology, and then observed by using a scanning electron microscope (SEM) and an electron probe X-ray microanalyzer (EMPA) every month. The results show that β-TCP ceramics bond to bone directly, new bones are forming and maturing with materials continuous degrading, and the materials are nearly replaced by the formed bone finally. Parts of the materials were degraded, absorpted and recrystallized, the others dispersped on the cancellous bone and the Haversian lamella with an irregular arrangement incorporating in bone formation directly by remodeling structure.

Influential factors on morphology of hydroxyapatite crystals

Needle-like hydroxyapatite crystals were synthesized by homogeneous precipitation method with water-soluble calcium salts and phosphates. The work focuses on the analysis of influencing factors on length and lengh/diameter ratio of hydroxyapatite crystals, which are main characteristics of reinforcement materials. The effects caused by system temperature, concentration of nutrient, and additives are discussed, and the optimum reacting condition is given.

Biodegradation of Absorbable Hydroxyapatite/Poly-DL-lactide Composites in Different Environment

To develop a new generation of absorbable fracture fixation devices with enhanced biocompatibility, the biodegradation mechanism and its influence on the cellular response at the tissue/implant interface of hydroxyapatite/poly-DL-lactide (HA/PDLIA) composites were investigated in vitro and in vivo. HA/PDLIA rods were immersed in phosphate-buffered saline, or implanted in muscle and bony tissue for 52 weeks. Scanning electron microscopic and histological studies were done. The degradation rate was the slowest in vitro, slower in muscle tissue and fast in bone. In vitro, the composites degraded heterogeneously and a hollow structure was formed. In bone, the limited clearing capacity leads to the accumulation of oligomeric debris, which contribute totally to the autocatalytic effect. So, the fastest degradation and intense tissue response were seen. In muscle tissue, oligomeric debris migrated into vicinal fibers over a long distance from the original implant cavity and the tissue reactions were, however, quite moderate. For the same size organic/inorganic composite, the environment where it was placed is the major factor in determining its biodegradation process and cellular reaction. In living tissue, factors such as cells, enzymes and mechanical stress have an obvious influence on the biodegradation and biological process at the tissue/implant interface. The biocompatibility of the HA/PDLIA composites is enhanced with the incorporating of the resorbable HA microparticles.

Formation of Apatite in Simulated Body Fluid

It is confirmed that the essential condition for glasses and glass-ceramics to bond to living bone is the formation of an apatite layer on their surfaces in the body. It is proposed that a hydrated silica formed on the surfaces of these materials in the body plays an important role in forming the surface apatite layer, which has noi been proved yet. It is shown experimentally that a pure hydrated silica gel can induce the apatite formation on its surface in a simulated body fluid when its starting pH is increased from 7.2 to 7.4.