Physicochemical properties and biological activity of novel cerium oxide nanoparticles modified with pyrroloquinoline quinone

Nanoscale cerium oxide (CeO$_2$) is a bioavailable inorganic nanozyme exhibiting pronounced redox activity and capable of acting as a delivery system for bioactive compounds. We have synthesized and characterized novel CeO$_2$ nanoparticles modified with pyrroloquinoline quinone (CeO$_2$@PQQ). TEM analysis revealed the diameter of the CeO$_2$@PQQ NPs to be approximately 4 nm, with a hydrodynamic diameter of 62 nm (DLS). Furthermore, the zeta potential was found to be -38 mV (ELS), and FTIR analysis confirmed the adsorption of PQQ on the surface of CeO$_2$ NPs. The results demonstrated that CeO$_2$@PQQ NPs exhibited no cytotoxic effects on L929 cells within the concentration range of 0.1 – 10 $\mu$M and did not adversely affect the mitochondrial function of the cells. It was demonstrated that CeO$_2$@PQQ NPs exhibited protective effects against L929 cells when induced with oxidative stress (200 $\mu$M H$_2$O$_2$), leading to preservation of cell mitochondrial potential levels up to 76% of control and cell viability up to 78% before and after incubation with CeO$_2$@PQQ NPs. The results indicate that CeO$_2$@PQQ NPs can be regarded as a novel hybrid nanosystem that exhibits mitochondrial-directed control of oxidative stress.