Sundew adhesive: a naturally occurring hydrogel

Abstract

Bioadhesives have drawn increasing interest in recent years, owing to their ecofriendly, biocompatible and biodegradable nature. As a typical bioadhesive, sticky exudate observed on the stalked glands of sundew plants aids in the capture of insects and this viscoelastic adhesive has triggered extensive interests in revealing the implied adhesion mechanisms. Despite the significant progress that has been made, the structural traits of the sundew adhesive, especially the morphological characteristics in nanoscale, which may give rise to the viscous and elastic properties of this mucilage, remain unclear. Here, we show that the sundew adhesive is a naturally occurring hydrogel, consisting of nanonetwork architectures assembled with polysaccharides. The assembly process of the polysaccharides in this hydrogel is proposed to be driven by electrostatic interactions mediated with divalent cations. Negatively charged nanoparticles, with an average diameter of 231.9 + 14.8 nm, are also obtained from this hydrogel and these nanoparticles are presumed to exert vital roles in the assembly of the nano-networks. Further characterization via atomic force microscopy indicates that the stretching deformation of the sundew adhesive is associated with the flexibility of its fibrous architectures. It is also observed that the adhesion strength of the sundew adhesive is susceptible to low temperatures. Both elasticity and adhesion strength of the sundew adhesive reduce in response to lowering the ambient temperature. The feasibility of applying sundew adhesive for tissue engineering is subsequently explored in this study. Results show that the fibrous scaffolds obtained from sundew adhesive are capable of increasing the adhesion of multiple types of cells, including fibroblast cells and smooth muscle cells, a property that results from the enhanced adsorption of serum proteins. In addition, in light of the weak cytotoxic activity exhibited by these scaffolds towards a variety of mammal cells, evidence is sufficient to propose that sundew adhesive is a promising nanomaterial worth further exploitation in the field of tissue engineering.

Sticky mucilages and exudates of plants: putative microenvironmental design elements with biotechnological value

“…Despite their name, extrafloral nectars are not involved in attracting pollinators but rather entice invertebrates such as ants or wasps to protect the plants from herbivorous predators (Gaume & Forterre, 2007;Llhan et al, 2007) or to supplement their diet with nitrogen by trapping insects or cultivating microbial symbionts (Adlassnig et al, 2010;Deynze et al, 2018). So far, only the mucilage of Drosera has been subjected to an analysis of its polysaccharide composition and was shown to contain predominantly highmolecular-weight substances that resemble pectins (Tables 1, 2) (Huang et al, 2015). 2b) or butterworts (genus Pinguicula) possess trichomes with terminal glands, which produce the mucilage in small droplets on their upper leaf surface (Adlassnig et al, 2010) while pitcher plants secrete larger volumes of their mucilage in special leaves formed like a cone (Gaume & Forterre, 2007).…”

“…Sundew (genus Drosera) ( Fig. The architecture of the mucilage appears to have a higher order nanostructure that changes depending on the presence or absence of tensile forces (Huang et al, 2015). So far, only the mucilage of Drosera has been subjected to an analysis of its polysaccharide composition and was shown to contain predominantly highmolecular-weight substances that resemble pectins (Tables 1, 2) (Huang et al, 2015).…”

“…A very promising approach that has yielded major breakthroughs in recent years is the use of techniques enabling visualisation of nanostructures (Huang et al, 2015(Huang et al, , 2016. Some molecules present in these mucilages possess naturally adhesive properties that have potential biotechnological and biomedical value in the form of glues or wound coversalthough the precise bioadhesive molecules present in the secretions have rarely been identified.…”

“…Huang et al (2015); 2,Schaffner (1976); 3, Llhan et al (2007); 4, Deynze et al (2018); 5, Gowda (1984); 6, Gedalovich-Shedletzky et al (1989). Ó 2019 The Authors New Phytologist Ó 2019 New Phytologist Trust New Phytologist (2020) 225: 1461-1469 www.newphytologist.com…”

Slippery when sticky: Lubricating properties of thin films of Taxus baccata aril mucilage

“…), where mucilage exudes are used to attract and capture prey via its dew-like appearance which are highly sticky in nature. 3,4 Engineering these adhesive properties of mucilage is beneficial largely in its pharmaceutical applications, such as binding agent in tablets, 5 gelling agent, 6 demulcent, on mucosa membrane, 7 and industrial applications as in glues for bonding paper items. 8 Recently, lubricity of mucilage, a seemingly opposite characteristic to its adhesive properties, has drawn an increasing interest.…”