title: Nanospherical arabinogalactan proteins are a key component of the high-strength adhesive secreted by English ivy.
abstract: Over 130 y have passed since Charles Darwin first discovered that the adventitious roots of English ivy (Hedera helix) exude a yellowish mucilage that promotes the capacity of this plant to climb vertical surfaces. Unfortunately, little progress has been made in elucidating the adhesion mechanisms underlying this high-strength adhesive. In the previous studies, spherical nanoparticles were observed in the viscous exudate. Here we show that these nanoparticles are predominantly composed of arabinogalactan proteins (AGPs), a superfamily of hydroxyproline-rich glycoproteins present in the extracellular spaces of plant cells. The spheroidal shape of the AGP-rich ivy nanoparticles results in a low viscosity of the ivy adhesive, and thus a favorable wetting behavior on the surface of substrates. Meanwhile, calcium-driven electrostatic interactions among carboxyl groups of the AGPs and the pectic acids give rise to the cross-linking of the exuded adhesive substances, favor subsequent curing (hardening) via formation of an adhesive film, and eventually promote the generation of mechanical interlocking between the adventitious roots of English ivy and the surface of substrates. Inspired by these molecular events, a reconstructed ivy-mimetic adhesive composite was developed by integrating purified AGP-rich ivy nanoparticles with pectic polysaccharides and calcium ions. Information gained from the subsequent tensile tests, in turn, substantiated the proposed adhesion mechanisms underlying the ivy-derived adhesive. Given that AGPs and pectic polysaccharides are also observed in bioadhesives exuded by other climbing plants, the adhesion mechanisms revealed by English ivy may forward the progress toward understanding the general principles underlying diverse botanic adhesives.
authors.affiliation: Department of Biomedical Engineering, College of Engineering, The Ohio State University, Columbus, OH 43210; Interdisciplinary Biophysics Graduate Program, The Ohio State University, Columbus, OH 43210; Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH 43210;
authors.forename: Yujian
authors.initials: Y
authors.lastname: Huang
authors.affiliation: Department of Biomedical Engineering, College of Engineering, The Ohio State University, Columbus, OH 43210; Interdisciplinary Biophysics Graduate Program, The Ohio State University, Columbus, OH 43210; Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH 43210;
authors.forename: Yongzhong
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Complex Carbohydrate Research Center, University of Georgia, Athens, GA 30602; DOE BioEnergy Science Center, University of Georgia, Athens, GA 30602;
authors.forename: Li
authors.initials: L
authors.lastname: Tan
authors.affiliation: Department of Biomedical Engineering, College of Engineering, The Ohio State University, Columbus, OH 43210; Interdisciplinary Biophysics Graduate Program, The Ohio State University, Columbus, OH 43210; Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH 43210;
authors.forename: Leming
authors.initials: L
authors.lastname: Sun
authors.affiliation: Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH 43210;
authors.forename: Jennifer
authors.initials: J
authors.lastname: Petrosino
authors.affiliation: Department of Biomedical and Diagnostic Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37996.
authors.forename: Mei-Zhen
authors.initials: MZ
authors.lastname: Cui
authors.affiliation: Department of Biomedical and Diagnostic Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37996.
authors.forename: Feng
authors.initials: F
authors.lastname: Hao
authors.affiliation: Department of Biomedical Engineering, College of Engineering, The Ohio State University, Columbus, OH 43210; Interdisciplinary Biophysics Graduate Program, The Ohio State University, Columbus, OH 43210; Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH 43210; zhang.4882@osu.edu.
authors.forename: Mingjun
authors.initials: M
authors.lastname: Zhang
mesh_terms: D000269:Adhesives / Q000737:chemistry*; D000595:Amino Acid Sequence; D001483:Base Sequence; D002118:Calcium / Q000737:chemistry; D003432:Cross-Linking Reagents; D018744:DNA, Plant / Q000235:genetics; D035981:Hedera / Q000737:chemistry* / Q000235:genetics; D018625:Microscopy, Atomic Force; D008958:Models, Molecular; D015394:Molecular Structure; D009088:Mucoproteins / Q000737:chemistry* / Q000235:genetics / Q000648:ultrastructure; D054118:Nanospheres / Q000737:chemistry / Q000648:ultrastructure; D010368:Pectins / Q000737:chemistry; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000648:ultrastructure; D017155:Wettability
chemical_list: D000269:Adhesives; D003432:Cross-Linking Reagents; D018744:DNA, Plant; D009088:Mucoproteins; D010940:Plant Proteins; C006619:arabinogalactan proteins; D010368:Pectins; D002118:Calcium
keywords: adhesion mechanism; arabinogalactan protein; ivy adhesive; ivy nanoparticle; reconstructed adhesive