Advances in nanotechnology and molecular biology have promoted material development using bio-inspired approaches [1]. Nano-defined self-assemblies derived from biological systems have been used as an inspiration for the innovative development of materials, such as bio-adhesives that could work efficiently in water using cross-linked non-toxic components. Some animals and plants produce adhesive secretions for prey capture, defence, prevention of dehydration, and camouflage, among other things; and have been used as the inspiration for the design of new adhesives to be applied in the medical, bio-electronical, textile and cosmetics industries [ 2, 3]. Recent examples include mussels, frogs, ivy plants, sandcastle worms, geckos, sea cucumbers and tubeworms [4-12]. Each organism has its own features and the physicochemical characterization of biological derivate secretions is challenging. In general, these secretions are composed mainly of mixtures of proteins, carbohydrates, surfactants, peptides, water and some ions like Ca 2+. Natural adhesives usually consist of complex biopolymer blends, forming in many cases extracellular nanometric structures that play a key role in the adhesion mechanism. Some of the functions of the extracellular nanostructures are attributed to the enhancement of energy dissipation, as it is frequently found in climbing animals that produce fibrillary structures. These structures are thought to be responsible for a mechanism analogous to the molecular stretching of polymeric chains and also, through their nanostructures, to influence the contact points with the target surfaces to minimize crack length and propagation [10].

Silica in plant tissues has been suggested as a component for enhancing mechanical properties, and as a physical barrier. Pineapples present in their shell and bracts rosette-like microparticles that could be associated to biogenic silica. In this study, we show for the first time that silica-based microparticles are co-purified during the extraction process of nanocellulose from pineapple (Ananas comosus). This shows that vegetable biomass could be an underappreciated source, not only for nanocellulose, but also for a highly valuable sub-product, like 10 µm biogenic rosette-like silica-based microparticles. The recovery yield obtained was 7.2 wt.%; based on the dried initial solid. Due to their size and morphology, the microparticles have potential applications as reinforcement in adhesives, polymer composites, in the biomedical field, and even as a source of silica for fertilizers.

Slime expelled by velvet worms entraps prey insects within seconds in a hardened biopolymer network that matches the mechanical strength of industrial polymers. While the mechanic stimuli-responsive nature and building blocks of the polymerization are known, it is still unclear how the velvet worms’ slime hardens so fast. Here, we investigated the slime for the first time, not only after, but also before expulsion. Further, we investigated the slime’s micro- and nanostructures in-depth. Besides the previously reported protein nanoglobules, carbohydrates, and lipids, we discovered abundant encapsulated phosphate and carbonate salts. We also detected CO2 bubbles during the hardening of the slime. These findings, along with further observations, suggest that the encapsulated salts in expelled slime rapidly dissolve and neutralize in a baking-powder-like reaction, which seems to accelerate the drying of the slime. The proteins’ conformation and aggregation are thus influenced by shear stress and the salts’ neutralization reaction, increasing the slime’s pH and ionic strength. These insights into the drying process of the velvet worm’s slime demonstrate how naturally evolved polymerizations can unwind in seconds, and could inspire new polymers that are stimuli-responsive or fast-drying under ambient conditions.