Nano hydroxyapatite particles (n-HA) have been reported to promote osteogenic activities of bone-related cells, while inhibiting tumor cell growth, and the biological effects of n-HA are related with the particle size, dose, culture time and cell type. In this work, we prepared n-HA with a strictly controlled rod-like shape and adjustable sizes without any surface chemical contaminations. Using the prepared n-HA, we investigated the size and dose effect of the nano particles on pre-osteoblasts for up to 7 days. We probed cell proliferation and gene expression in the presence of n-HA, the cellular uptake pathways of n-HA particles, as well as the extracellular and intracellular [Ca2+] ([Ca2+]i) changes caused by the particles, in order to get a better understanding of the biological effects of n-HA of various sizes. The n-HA exhibited size- and dose-dependent impacts on MC3T3-E1 proliferation, intracellular reactive oxygen species (ROS) generation, mitochondrial membrane potential, and osteogenic gene expression. 40 nm n-HA caused the slowest MC3T3-E1 growth, the highest intracellular ROS concentration, the largest mitochondrial membrane potential loss and the lowest level of osteogenic gene expression among the samples. The cytotoxicity of 40 nm n-HA increased with the dose and culture time. 70 nm n-HA showed beneficial effects on MC3T3-E1 growth, but the positive effect disappeared at the highest concentration on day 7. 100 nm n-HA promoted cell growth and the promoting effect increased with the dose. Cells cultured with 100 nm n-HA expressed the highest level of osteogenic gene expression among the experimental groups. We discovered that the presence of n-HA increased [Ca2+]i but did not elevate extracellular [Ca2+]. The [Ca2+]i increased as the n-HA size decreased. We also found that n-HA may enter cells through two pathways and that the amount of engulfed particles depended on the particle size. The internalized n-HA particles located in the cytosol, endosomes, lysosomes and nuclei. The particles dissolved in lysosomes and raised [Ca2+]i, which correlated with the cell death and osteogenic gene expression. In conclusion, the particle size, dose, and culture time influenced the biological effects of n-HA on ME3T3-E1 cells, probably by changing the [Ca2+]i in the cells instead of the extracellular [Ca2+].

The effects of poly(ethylene glycol) (PEG) molecular weights on nano hydroxyapatite (n-HA) crystal growth were studied, and a possible mechanism was proposed. n-HA crystals were synthesized in the presence of PEG with different molecular weights via hydrothermal method. Transmission electron microscopy (TEM) analysis showed that the presence of PEG increased the size of n-HA crystals; PEG with larger molecular weights produced larger n-HA crystals. High-resolution TEM observation indicated that all of the n-HA crystals tended to grow along the ⟨002⟩ axis. X-ray diffraction patterns showed that all of the samples consisted of only the HA phase. Besides, PEG increased the crystallinity of n-HA crystals, and this effect was more significant for PEGs with larger molecular weights. Fourier transform infrared results further revealed that all of the crystals were carbonated HA. Thermogravimetry/differential scanning calorimetry analysis detected PEG residues on n-HA particles. To thoroughly study the modulating mechanism of PEGs on n-HA crystal growth, n-HA samples heat-treated for various times were prepared in the presence of PEG20000, and a possible mechanism in which PEG modulated the growth of n-HA crystals was discussed.

Perovskite-type oxide LaFeO3 powder was prepared using a stearic acid combustion method. Its phase structure, electrochemical properties and hydrogen storage mechanism as negative electrodes for nickel/metal hydride (Ni/MH) batteries have been investigated systematically. The results of X-ray diffraction (XRD) analysis show that both the calcined powder and the charged/discharged samples after 10 cycles have orthorhombic structures. The discharge capacity, whose maximum value appeared at the first cycle, is 530.3 mA h g−1 at 333 K and increases with an increase in temperature. The discharge capacity decreases distinctly during the first three cycles and then stays steady at about 80 mA h g−1, 160 mA h g−1 and 350 mA h g−1 at 298 K, 313 K and 333 K, respectively. The hydrogen storage mechanism is studied by XRD, X-ray photoelectron spectroscopy (XPS) and mass spectrometry (MS), coupled with pressure–composition–temperature (PCT) methods. Hydrogen atoms may be intercalating into the oxide lattice and forming a homogeneous solid solution during the charging process.

Perovskite-type oxide La0.4Sr0.6FeO3 powder was prepared by a stearic acid combustion method, and its phase structure, kinetic characteristics, and electrochemical properties were systematically investigated as the negative electrode for Ni/MH batteries. X-ray diffraction (XRD) shows that the as-prepared powder consists of a single phase with rhombohedral structure. After 20 cycles, perovskite-type structure still remains in the electrode sample. The electrochemical test shows that the reaction at the La0.4Sr0.6FeO3 electrode is reversible. With an increase in temperature from 298 K to 333 K, its initial discharge capacities increase from 153.4 mA h g−1 to 502.6 mA h g−1 at 31.25 mA g−1, and from 56.0 mA h g−1 to 279.6 mA h g−1 at 125 mA g−1, respectively. At a discharge current density of 125 mA g−1, its capacities keep steady at about 80.0 mA h g−1, 195 mA h g−1 and 370 mA h g−1 at 298 K, 313 K and 333 K, respectively. Both the exchange current density and the proton diffusion coefficient of the La0.4Sr0.6FeO3 oxide electrode also increase with temperature in a manner similar to the discharge capacity.

Nano hydroxyapatite particles (n-HA) have been reported to promote osteogenic activities of bone-related cells, while inhibiting tumor cell growth, and the biological effects of n-HA are related with the particle size, dose, culture time and cell type. In this work, we prepared n-HA with a strictly controlled rod-like shape and adjustable sizes without any surface chemical contaminations. Using the prepared n-HA, we investigated the size and dose effect of the nano particles on pre-osteoblasts for up to 7 days. We probed cell proliferation and gene expression in the presence of n-HA, the cellular uptake pathways of n-HA particles, as well as the extracellular and intracellular [Ca2+] ([Ca2+]i) changes caused by the particles, in order to get a better understanding of the biological effects of n-HA of various sizes. The n-HA exhibited size- and dose-dependent impacts on MC3T3-E1 proliferation, intracellular reactive oxygen species (ROS) generation, mitochondrial membrane potential, and osteogenic gene expression. 40 nm n-HA caused the slowest MC3T3-E1 growth, the highest intracellular ROS concentration, the largest mitochondrial membrane potential loss and the lowest level of osteogenic gene expression among the samples. The cytotoxicity of 40 nm n-HA increased with the dose and culture time. 70 nm n-HA showed beneficial effects on MC3T3-E1 growth, but the positive effect disappeared at the highest concentration on day 7. 100 nm n-HA promoted cell growth and the promoting effect increased with the dose. Cells cultured with 100 nm n-HA expressed the highest level of osteogenic gene expression among the experimental groups. We discovered that the presence of n-HA increased [Ca2+]i but did not elevate extracellular [Ca2+]. The [Ca2+]i increased as the n-HA size decreased. We also found that n-HA may enter cells through two pathways and that the amount of engulfed particles depended on the particle size. The internalized n-HA particles located in the cytosol, endosomes, lysosomes and nuclei. The particles dissolved in lysosomes and raised [Ca2+]i, which correlated with the cell death and osteogenic gene expression. In conclusion, the particle size, dose, and culture time influenced the biological effects of n-HA on ME3T3-E1 cells, probably by changing the [Ca2+]i in the cells instead of the extracellular [Ca2+].