Cytotoxicity Of Hydroxyapatite Nanoparticles With Different Characteristics To Human Gastric Carcinoma Cells

Due to its excellent biocompatibility, hydroxyapatite has been extensively applied in biomedical field. Recently, it has been reported that hydroxyapatite nanoparticles (HAPNs) can inhibit growth of various human cancer cells, showing antitumor activity. However, the effect of particle properties such as size, shape, surface charge and area on cytotoxicity of HAPNs is still largely unknown.Diverse HAPN samples were synthesized by precipitation or microwave irradiation-assisted precipitation, and MTT assay was used to evaluate their cytotoxicity to human gastric cancer cells (MGC80-3). For microwave irradiation-assisted precipitation, under the conditions tested, changing microwave power, lyophilized time, and heat treatment could affect the cytotoxicity of HAPNs, while different drying methods and varying crystallinity didn't have an obvious effect on their cytotoxicity. For precipitation, no significant differences of cytotoxicity were observed with different washing solutions or addition of PEG, but calcination enhanced the cytotoxicity of HAPNs.HAPN samples L200, M300, and C200 were chosen to study the effect of material properties on antitumor activity. L200 and M300 were synthesized with the microwave power of 200 W and 300 W respectively, and obtained by freeze drying. C200 was prepared with the microwave power of 200 W and calcined at 550?. The basic material properties of these three samples, such as particle size, morphology, specific surface area and polydispersity, were found be different from each other. In vitro studies revealed these three HAPNs could inhibit proliferation of MGC80-3 cells, and L200 showed the highest toxicity. Morphological changes of nucleus and apoptosis assay using Annexin V-FITC/PI demonstrated these HAPNs could induced apoptosis, with the highest apoptosis proportion induced by L200. MGC80-3 cells could internalize L200 more quickly and efficiently compared with C200 and M300. It appeared that the uptake of these HAPNs was energy-dependent, and mainly through caveolin dependent endocytosis. Using laser-scanning confocal microscopy, we found that all the HAPNs were lodged in cytoplasm, while part of L200 was transported into nucleus. In addition, these HAPNs could cause a more than 40% increase in intracellular calcium levels compared to the untreated control, and the highest increase(1.8-fold) was observed with L200.According to these results, the properties of HAPNs are strongly interconnected. These properties had an effect on the interaction between nanoparticles and cancer cells, which would influence the cellular uptake, intracellular trafficking and metabolism, finally resulted in different degrees of apoptosis and cytotoxicity.