Real-time investigation of acute toxicity of ZnO nanoparticles on human lung epithelia with hopping probe ion conductance microscopy.

Recent studies have proved that zinc oxide nanoparticles (nZnO) can cause acute lung epithelial inflammation and respiratory toxicity; however, the mechanism of such acute negative effect on lung epithelia is still unclear. In this study, early responses of living human alveolar epithelial A549 cells after exposure to nZnO were investigated by noncontact hopping probe ion conductance microscopy (HPICM) that was combined with the patch-clamp technique. Continuous repetitive high-resolution HPICM scannings observed that 100 μg/mL nZnO treatment caused acute damage to A549 cell membrane within 1.5 h. Such membrane damage was reflected in a significantly elevated lactate dehydrogenase (LDH) level in cell culture medium after 3 h of nZnO exposure. The combined HPICM and patch-clamp technique can easily perform whole-cell patch-clamp recordings, which demonstated that nZnO treatment even could inhibit the activities of ion channels in A549 cells within 15 min. The HPICM technique is shown to be capable of detecting the acute toxicity of nZnO on living cells in real time and helping to elucidate the mechanism of its action.