In situ imaging and analysis of the nanostructures in natural hydrogels from carnivorous plants by atomic force microscopy

Abstract

Natural hydrogels have been widely applied in the field of biomedicine for their biocompatible and biodegradable characteristics. However, due to the lack of adequate observation tools, so far the detailed organizations and structures of native natural hydrogels at the nanoscale are still not fully understood. The advent of atomic force microscopy (AFM) provides a novel powerful tool for characterizing biomaterials, but studies about utilizing AFM to investigate the nanostructures of native natural hydrogels are still scarce. In this paper, AFM in situ high-resolution imaging was used to reveal the nanoscopic fine structures of the natural hydrogels secreted by four types of carnivorous plants (Drosera capensis, Pinguicula cyclosecta, Sarracenia rubra, and Dionaea muscipula). Mucilage secreted by Drosera capensis or Pinguicula cyclosecta was coated on the surface of mica, and the subsequent AFM imaging of the mucilage-coated mica in air clearly revealed that both the mucilage secreted by Drosera capensis and Pinguicula cyclosecta contained a large number of nanofibers which had diverse self-assembly behaviors. Nectar secreted by Sarracenia rubra or Dionaea muscipula was coated on the surface of glass slides, and AFM images of the nectar-coated glass slide recorded in deionized water showed that both the nectar secreted by Sarracenia rubra and Dionaea muscipula considerably contained nanoparticles. Statistical results showed that the size of nanoparticles in the nectar of Dionaea muscipula was significantly larger than that of nanoparticles in the nectar of Sarracenia rubra. The study improves our understanding of the natural hydrogels secreted by carnivorous plants and provides a novel approach for characterizing the nanostructures of natural biomaterials in their native states, offering new possibilities for the studies of supramolecular biomaterials.