Nanoscale organization and functional analysis of carnivorous plant mucilage by atomic force microscopy

Uncovering the underlying mechanisms guiding the behaviors of natural sticky glue is of important significance for developing novel biomimetic or bioinspired materials to regulate cellular activities. Carnivorous plants secrete adhesive mucilage to capture insects, but the nanoscale organizations of the mucilage are still not fully understood. In particular, the advent of atomic force microscopy (AFM) provides a powerful tool for investigating the structures and properties of biological samples in their native states with unprecedented spatial resolution, offering novel possibilities for the studies of characterizing biomaterials. In this work, AFM was utilized to reveal the nanostructures of mucilage secreted by carnivorous plant (Pinguicula and Sarracenia) for promoting cell growth. AFM imaging of the mucilage-coated substrates in air showed that nanostructures (nanoparticles and nanofibers) with different assembly behaviors were significantly observed in mucilage, which were confirmed by electron microscopy imaging. AFM in situ imaging in liquids remarkably revealed that nanoparticles were contained in native mucilage. The mechanical properties of individual nanofibers were visualized and quantified by AFM indenting assays. The elemental organizations of the mucilage were analyzed, and the experiments of cells grown on mucilage-coated substrates indicated that carnivorous plant mucilage could facilitate cell growth. The research provides novel insights into the nanostructures and mechanical properties as well as biological functions of mucilage secreted by carnivorous plants, which will have potential impacts on the studies of biomaterials for tuning cell behaviors.