Interface Visualization of Bio-material Interaction Via Cryo-AEM Using the Biosynthesis of Iron-Based Nanoparticles as a Model.

Although interaction between organisms and nonorganisms is vital in environmental processes, it is difficult to characterize at nanoscale resolution. Biosynthesis incorporates intracellular and extracellular processes involving crucial interfacial functions and electron and substance transfer processes, especially on the inorganic-organic interface. This work chooses the biosynthesis of iron-based nanoparticles ( n Fe) as a model for biomaterial interaction and employs Cryo-AEM (i.e., S/TEM, EELS, and EDS analysis based on sample preparation with cryo-transfer holder system), combined with CV, Raman, XPS, and FTIR to reveal the inorganic-organic interface process. The inorganic-organic interactions in the biosynthesis of iron-based nanoparticles by Shewanella oneidensis MR-1 (M- n Fe) were characterized by changes in electron cloud density, and the corresponding chemical shifts of Fe and C EELS edges confirm that M- n Fe acquires electrons from MR-1 on the interface. Capturing intact filamentous-like, slightly curved, and bundled structure provides solid evidence of a "circuit channel" for electron transfer between organic and inorganic interface. CV results also confirm that adding M- n Fe can enhance electron transfer from MR-1 to ferric ions. A mechanism for the synthesis of M- n Fe with MR-1 based on intracellular and extracellular conditions under facultative anaerobic was visualized, providing a protocol for investigating the organic-inorganic interface.