Ultra-microstructures and mechanics of plant mucilage functional interfaces investigated via atomic force microscopy in liquid

Abstract

<p indent="0mm">Mucus plays an important role in regulating biological activities. Accordingly, investigating the structures and properties of mucus can be beneficial for providing a better understanding of physiological and pathological changes. Due to a lack of adequate observation tools, the ultra-microstructures of native mucus functional interfaces are not yet fully understood. Atomic force microscopy (AFM) provides a novel and powerful tool for investigating the structures and properties of biomaterials in their native states. Nevertheless, to date, studies of biomaterials using AFM are commonly performed in air, which cannot faithfully reflect the structures of biomaterials in liquids. In this paper, by adopting the mucilage secreted by the carnivorous sundew plant as an example, high-resolution AFM imaging and analysis of mucous nanostructures in aqueous conditions were achieved. Sundew mucilage was coated onto the surface of a glass slide or mica, and the subsequent AFM imaging of the mucilage-coated substrates in pure water revealed that a large number of nanoparticles were contained in the sundew mucilage. In contrast, AFM imaging of sundew mucilage-coated substrates in air showed that dried mucilage contained a large number of nanofibers. This underscored the structural differences in sundew mucilage in the air and in a solution. Furthermore, AFM multiparametric imaging was employed to visually characterize the mechanical properties of sundew mucilage nanostructures in pure water and showed significant differences in the mechanics between nanoparticles and nanofibers. This study provides a novel approach for investigating the ultra-microstructures and mechanics of mucus’ functional interfaces in their native states <italic>in situ</italic>, which has fundamental impacts on research focused on biomaterials.