The nanocrystalline Eu 3+ doped calcium phosphate was prepared by calcining precursors, which were got by precipitation method combined with ultrasound treatment and some polysaccharide. The existence of Eu 3+ inhibited the reaction of Na+ ion and SO 2-4 radical with apatite and resulted in the transformation of HAP to β-TCP by replacing the calcium ions. The strongest excitation peak was at 393nm, and other lower peaks were at 361 nm, 375 nm, 381 nm, 418 nm. The strongest emission spectrum appeared at about 618nm. The emission peak （579 nm） showed that Eu 3+ ions distributed on Ca 2+ sites of the apatitic structure.
Many particles are found in the cytoplasm area after the mixture of hydroxyapatite(HAP) nanoparticles and cultured cancer cells.The purpose of this study was to confirm whether these particles in cytoplasm are HAP nanoparticles exactly.BEL7402 cells were incubated in HAP sol for 8 hours.Then,the cells were collected for specimen preparation.Transmission electron microscope(TEM),energy dispersing spectrum (EDS)and electronic diffraction(ED)attached to TEM were used to detect the properties of the particles.It is found that many particles similar to HAP in shape are in the cytoplasm under TEM.By EDS analysis,they are the particles containing calcium(Ca)and phosphorus(P).The classic rings of HAP crystal appear in the ED pictures of these particles.So the particles are confirmed as HAP nanoparticles.Thus,it is concluded that HAP nanoparticles as the crystal particles can be absorbed by hepatoma cells.
The change of hydroxyapatite (HAP) nanoparticles in shape and crystal structure after endocytosis into cancer cells was studied. BEL7402 cells were incubated with HAP nanoparticles for 2 hour,8 hours,20 hours,respectively. Then,the cells were collected and viewed under a transmission electronic microscope (TEM). Electronic diffraction (ED) attached to TEM was used to detect the properties of the particles. The results show that HAP particles in the cytoplasm can be degraded in cytoplasm. The degradation process is prolonged by more than 20 hours. Thus,it is concluded that HAP nanoparticles would be degraded after kill cells or delivery gene.
The particle size has a strong impact on the interactions between nanoparticles and cells. However, the synthesis process of nanoparticles limits the range of achievable average particle sizes. When biocompatible hydroxyapatite nanoparticles (HAP) are doped with the luminescent rare earth element Europium (Eu), the particle size becomes larger compared to pure HAP. Hence, a particle size reduction is necessary to achieve similar experimental conditions when substituting pure HAP with luminescent HAP:Eu nanoparticles to investigate particle-cell-interactions in cell culture experiments. While the sedimentation process of particles in liquids and gels has been well described in literature, the separation of particles in dispersed colloids has not been studied, yet. In this study, the size depending separation and particle size reduction of a homogeneous dispersed nanoparticle sol by gravity and centrifugation were investigated. As the results showed, shorter time of centrifugation at higher speed can reduce the average particle size compared to the decline of the particle concentration in the upper sol layer most efficiently. This centrifugation method has some similarity to the overspeeding technique which is commonly used to lower the transient time to reach the equilibrium of sedimentation.
Inorganic nanoparticles were used to treat cancer cells as well as normal cells. Ca9Sr（PO4）6（OH）2 nanoparticles were prepared through homogeneous precipitation method. Strontium hydroxide, calcium hydroxide solution and monocalcium phosphate were used as initial materials. The strontium-doped hydroxyapatite nanoparticles were characterized by XRD, PCS and AFM. The nanoparticles were applied to interact with human hepatocellular carcinoma cells Bel-7402 and normal liver cells L-02. Experimental results revealed that nano strontium-strontium apatite has different bioeffects on proliferation of these two kinds of cells.
The co-precipitation method followed by ultrasound and heat treatment is a common way to prepare below 100 nm sized hydroxyapatite nanoparticles for biomedical studies and applications. The size and pH value of the obtained calcium phosphate nanoparticles in aqueous sol have a strong impact on the interactions with cells and tissue. The physical and chemical properties of material samples for in vitro and in vivo studies are often assumed to remain constant from the time after fabrication to the actual use. Only little attention is paid to eventual changes of the material over time or due to the different in vitro conditions. In this study, the physical and chemical transformation of calcium phosphate nanoparticles after preparation and in vitro was investigated. As the result showed, dispersed nano sized amorphous calcium phosphate precipitation as well as crystallized hydroxyapatite nanoparticles continue to crystallize even when kept at 4 ℃ leading to declining pH values and particle sizes. Due to the pH buffer in the medium the pH value of the cell culture remained stable after adding 20% nanoparticle sol in vitro. However, hydroxyapatite nanoparticles immediately became unstable in the presents of cell culture medium. The resulting loose agglomerations showed a size of above 500 nm.
