Additive effects of green LED light and cerium oxide nanoparticles on the planarian's regeneration

Nanotechnology makes it possible to design advanced materials being able to effectively modulate radiation effects on a cell, depending on the radiation intensity, wavelength, and type. Today, one of the most promising UV and X-ray protective biomaterials is nanocrystalline cerium oxide (CeO$_2$), which has a unique redox activity due to its surface reducibility. Meanwhile, the modulating properties of CeO$_2$ nanoparticles when the cells are exposed to visible light remain completely unexplored. Here, we analyzed the impact of CeO$_2$ nanoparticles on the process of planarian regeneration after exposure to low-intensity green LED light. It was found that a one-time exposure (10 or 25 min) of regenerating planarians with low-intensity green light reduced head blastema growth rate by up to 20%. At the same time, the preliminary treatment of planaria with CeO$_2$ nanoparticles in nanomolar concentrations (10 – 11 M) ensures the restoration of the neoblasts activity and a significant acceleration of blastema regeneration. Thus, we have firstly demonstrated that the planarian regeneration process can be promoted by cerium oxide nanoparticles even under adverse action of low-intensity green light radiation.