Correlative liquid phase electron microscopy and optical microscopy of biological phenomena

Jungwon Park

Molecular structures, reactions, interactions of bio-molecules including proteins, ribosomes, bacteria, and viruses require understanding in molecular, and sometimes, atomic level. Microscopic studies have greatly facilitated structural analysis as well as direct observation of real-time phenomena that occur in a live cell. My research focuses on developing a new type of microscopic method for studying biological sample in high-resolution and applying it to comprehensively understand 3D structure, function, reactivity, and role of bio-molecules in realistic conditions.

Recent development of micro-fabricated liquid cells just opened a new era of studying liquid samples in high-resolution which had not been achievable by other existing analytic tools. I have recently developed a new type of liquid cell for in-situ high-resolution transmission electron microscopy based on entrapment of a liquid film between layers of graphene. This graphene liquid cell was successfully applied in studying colloidal nanocrystal growth and diffusion in liquid in an atom-resolved resolution. 

Figure 1. (a) TEM image of influenza viruses in an aqueous state, (b) correlative STORM and SEM image of actin filaments in macrophage, (c) TEM image of polystyrene particle endocytosis by an epithelial cell.

The first step of my research is to develop a new type of graphene liquid cells to trap aqueous biological samples such as proteins, bacteria, viruses, and cells. Graphene windows minimize electron beam scattering and maintain liquid phase in a harsh imaging condition; thus, they will provide high resolution and contrast of aqueous biological specimens at lower electron voltage while preserving reliable sample stability.

These graphene liquid cells will be compatible both with optical microscopy (such as confocal microscopy and super-resolution fluorescence microscopy) and liquid phase electron microscopy.  I expect that we can achieve high contrast (from fluorescent labeling in optical microscopy) and spatial resolution (from electron microscopy) of biological samples in liquid. We hope to generalize this analytical tool in studying many biological reactions in-situ.