Cardiac effects of acute exposure to titanium dioxide nanoparticles: electrophysiological characterization

The potential adverse effects of titanium dioxide nanoparticles (TiO2-NPs) on cardiovascular system are still largely unknown. The aim of this study is to investigate the direct effects of acute exposure to TiO2-NPs on cardiac electrical function, at cellular and organ level. Single ventricular cardiomyocytes were enzymatically isolated from rat hearts, brought in patch clamp whole-cell configuration in order to measure in controls and TiO2-NPs treated cells 1) membrane capacitance (Cm), 2) membrane resting potential (Vr) and action potential duration (APD). Multiple epicardial electrograms were also recorded in vivo on the ventricular surface or rat hearts after 4h tracheal instillation of vehicle (control) or TiO2-NPs solution (2mg/Kg), during normal sinus rhythm and ventricular pacing. TiO2-NPs did not modify Cm and Vr values; however, in cells incubated with TiO2-NPs, 30 sec recordings of Vr showed a significant increase of Vr variability. The treatment with TiO2-NPs induced also a significant shortening in plateau and late phase of repolarization of APs. Electrophysiological parameters from epicardial mapping revealed that PQ, QRS and QT durations were significantly reduced, while excitability and anisotropy ratio were increased. In conclusion, the TiO2-NPs induced decrease in cellular APD and in electrographic QT intervals associated with an increase of cardiac excitability, could be responsible for a cardiac substrate more prone to arrhythmia development.