Evidence that gecko setae are coated with an ordered nanometre-thin lipid film

Abstract

The fascinating adhesion of gecko to virtually any material has been related to surface interactions of myriads of spatula at the tips of gecko feet. Surprisingly, the molecular details of the surface chemistry of gecko adhesion are still largely unknown. Lipids have been identified within gecko adhesive pads. However, the location of the lipids, the extent to which spatula are coated with lipids, and how the lipids are structured are still open questions. Lipids can modulate adhesion properties and surface hydrophobicity and may play an important role in adhesion. We have therefore studied the molecular structure of lipids at spatula surfaces using near-edge X-ray absorption fine structure imaging. We provide evidence that a nanometre-thin layer of lipids is present at the spatula surfaces of the tokay gecko ( Gekko gecko ) and that the lipids form ordered, densely packed layers. Such dense, thin lipid layers can effectively protect the spatula proteins from dehydration by forming a barrier against water evaporation. Lipids can also render surfaces hydrophobic and thereby support the gecko adhesive system by enhancement of hydrophobic–hydrophobic interactions with surfaces.

High Performance Marine and Terrestrial Bioadhesives and the Biomedical Applications They Have Inspired

“…It has been proposed that interactions between anionic intermediate filament keratins and positively charged CBPs produce resilient flexible corneous assemblies, disulphide bonding may also stabilize these structures. Protein-lipid interactions may also contribute to the pliability of these structures providing compliant properties to the setae improving their adhesion to irregular adhesive surfaces [131]. Nuclear Magnetic Resonance (NMR) spectroscopy also confirms the presence of lipid-keratin structures in the Gecko foot setae [132].…”

Ecologically‐related variation of digit morphology in Cyrtodactylus (Gekkota, Squamata) reveals repeated origins of incipient adhesive toepads

“…These scales are underpinned by modified muscles, tendons, bones, and other tissues which function to fine‐tune the control of the scansors during locomotion, allowing for their correct placement onto—and removal from—the substratum (Russell, 1975, 2002; Russell & Gamble, 2019). The ultimate agents of adhesion are microfibrillar stalks (setae) arising from the “Oberhäutchen”—the outermost layer of the epidermis (Autumn, 2007; Hiller, 1968; Maderson, 1970), which generate adhesion via van der Waals forces (Autumn, 2006; Autumn & Peattie, 2002), probably acting in concert with electrostatic interactions (Izadi et al., 2014; Song et al., 2022) and surface chemistry (Rasmussen et al., 2022; Singla et al., 2021).…”

Characterization of Morphologically Distinct Components in the Tarsal Secretion of Medauroidea extradentata (Phasmatodea) Using Cryo-Scanning Electron Microscopy

“…Tree frogs similarly, but convergently, produce an adhesive liquid in their mucus glands to strengthen their attachment [ 17 , 18 ]. Geckos do not produce large amounts of tarsal secretion, but it has been shown that a nanometer thin lipid film covers the surface of their adhesive setae [ 19 ]. Especially in marine environments, other depletion mechanisms are found: Echinoderms, for example, secrete a two-phase secretion, where the first phase generates the adhesion and the second phase dissolves the first phase [ 20 , 21 , 22 , 23 ].…”