Liquid Phase TEM for Structure Elucidation and Property Prediction of Dynamic Biomaterials

Organic, soft materials with nanoscale structures inherent to their solvated state, such as emulsions, hydrogels, biomaterials and thermally responsive materials, provide fertile ground for investigation via direct imaging using liquid phase transmission electron microscopy (LPTEM). With key advances having been made in the past decade, including improved sample preparation protocols, image capture technologies, and image analysis, LPTEM has gained in utility to the point where we are able to investigate materials that are otherwise difficult or impossible to directly image by other methods with nanoscale resolution. This workflow consists of (1) modelling electron beam-solvent interactions, (2) studying electron beam-sample interactions via LCTEM coupled with post-mortem analysis, (3) construction of “damage plots” displaying sample integrity under varied imaging and sample conditions, (4) optimized LCTEM imaging, (5) image processing, and (6) correlative analysis via X-ray or light scattering. Herein, we describe this workflow for the examination of biomolecular hydrogels including their dynamics and assembly in the solvated state. The insight gained has provided an exciting window into these materials that eludes cryogenic TEM, which is necessarily disruptive of these structures. We present our efforts in this space, and in the correlative methods used to verify, or support the structural information found. This includes the use of LPTEM to define gel parameters including persistence length and mesh sizes, which has led to the prediction of properties in thermally responsive gels. We will also give some perspective on how we leverage these capabilities for other materials with relevance to biomedical materials we are developing in regenerative medicine, cancer, dermatology and neurodegenerative disease.