Helium Ion Microscopy to address relevant questions in the impact of nanomaterials on lung epithelium – correlative microscopy approach

Helium Ion Microscopy (HIM) has not been thoroughly exploited for biological studies addressing relevant questions that range from the cellular to the subcellular level. One of the benefits of HIM compared to other high-resolution imaging techniques is definitely the large depth of focus, sub-nm resolution, nm surface sensitivity, and especially that no sample coating is needed that can change the nanostructure morphology on the surface. The prerequisite to getting the most from the technique is thus the appropriate sample preparation. Besides, to get the most from understanding the addressed biological question, a successful correlative microscopy approach is necessary. This is best shown in our recently published study (H Kokot, Advanced Materials, 2020), where we have addressed one of the most critical issues in toxicology, that is the poor understanding of chronic inflammation initiation in lung tissue caused by inhaled nanoparticles, with the correlative microscopy approach using advanced multimodal optical microscopy and HIM. HIM nicely revealed the TiO2 nanotube organization and passivation on the cell surface and confirmed lipid and protein binding to the TiO2 surface (Figure below), identified as well by in silico simulations. In brief, HIM is an extremely powerful technique for the surface, and in the case of porous samples also in-depth morphology characterization on an nm scale. In combination with complementary imaging techniques and proper sample preparation, many relevant biological questions can be addressed and solved. Still, there are many limitations and challenges in cell preparation and imaging using helium ions, such as imaging of internal structures, definitely pursuing discussions and new developments in the future.