Rare earth oxide nanocrystals as a new class of autophagy inducers.

Functional interaction of nanomaterial with autophagy, a fundamental biological process for cellular degradation, is of great interest to nanobiology. Rare earth nanomaterials hold tremendous potential for a variety of diagnostic and therapeutic applications and have also been reported to protect cells against bacterial, viral and oxidative stress. In a brief communication we report that both light and heavy classes of rare earth oxide nanocrystals (REOs) elicit an autophagic response in HeLa cells, a human cancer cell line, in a dose- and time-dependent manner. The autophagy induced by REOs is complete and is accompanied by vacuolization within the cytoplasm. Autophagy induction may help explain some of the biological effects caused by REOs, and at the same time raises a special point of consideration for this type of nanomaterial, with regard to both safety assessment and application exploration.