Antitumor activity of spherical nanoparticles GdYVO4:Eu3+ depends on pre-incubation time

The significance of tumor cells incubation with spherical nanoparticles based on orthovanadates of rare-earth elements activated by europium GdYVO4:Eu3+ in the effectiveness of Ehrlich carcinoma growth inhibition was shown. Ehrlich carcinoma cells were incubated with nanoparticles for 1, 2, 3, and 4 h; afterwards, their accumulation in cells using a LSM 510 META confocal laser microscope (Carl Zeiss, Germany), changes in mitochondrial function and apoptotic/necrotic cells were assessed. Even from the 1st hour of incubation, there was observed an increase in mean fluorescence intensity, indicating the beginning of nanoparticles accumulation inside the cells. By the third hour of incubation, the fluorescence values of total Ehrlich carcinoma population reached the maximum values. At the same time, the appearance of single cells with ultra-high level of fluorescence was established; the number of those did not exceed 5%. By the third hour of incubation with nanoparticles, there was a significant mitochondrial dysfunction of Ehrlich carcinoma cells and a convincing increase in the proportion of cells in the late apoptosis (An(+)/PI+) and necrosis (An(-)/PI+) compared to the control. The aforesaid changes in the Ehrlich carcinoma cells after 3-h pretreatment with nanoparticles contributed to the highest decrease in intensity of tumor growth in vivo down to 41.80%. Thus, the successful implementation of an antitumor effect of nanoparticles based on orthovanadates of rare earth elements activated by europium GdYVO4:Eu3+ implies their penetration and accumulation inside the cells as well as associated with impaired mitochondrial function and induction of apoptotic and necrotic changes in tumor cells.