Microscopic and infrared spectroscopic comparison of the underwater adhesives produced by germlings of the brown seaweed speciesDurvillaea antarcticaandHormosira banksii

Abstract

Adhesives from marine organisms are often the source of inspiration for the development of glues able to create durable bonds in wet environments. In this work, we investigated the adhesive secretions produced by germlings of two large seaweed species from the South Pacific, Durvillaea antarctica, also named 'the strongest kelp in the word', and its close relative Hormosira banksii. The comparative analysis was based on optical and scanning electron microscopy imaging as well as Fourier transform infrared (FTIR) spectroscopy and principal component analysis (PCA). For both species, the egg surface presents peripheral vesicles which are released soon after fertilization to discharge a primary adhesive. This is characterized by peaks representative of carbohydrate molecules. A secondary protein-based adhesive is then secreted in the early developmental stages of the germlings. Energy dispersive X-ray, FTIR and PCA indicate that D. antarctica secretions also contain sulfated moieties, and become cross-linked with time, both conferring strong adhesive and cohesive properties. On the other hand, H. banksii secretions are complemented by the putative adhesive phlorotannins, and are characterized by a simple mechanism in which all constituents are released with the same rate and with no apparent cross-linking. It is also noted that the release of adhesive materials appears to be faster and more copious in D. antarctica than in H. banksii. Overall, this study highlights that both quantity and quality of the adhesives matter in explaining the superior attachment ability of D. antarctica.

Analysis of the Effect of Processing Conditions on Physical Properties of Thermally Set Cellulose Hydrogels

“…This is indicative of conformational changes of urea molecules, which transition from a relatively constrained state surrounding the cellulose chains (before gelation), to a more disordered state in a free solution after gelation. Finally, minor spectral changes are present in the 1150–950 cm −1 region (νCO, δCOC, νCC, νCOH and ring vibrations in polysaccharides), indicative of a change from preferred cellulose–solvent interaction to cellulose–cellulose interactions mediated by physical cross-links (Figure 5B) [17,59].…”

Involvement of sulfated biopolymers in adhesive secretions produced by marine invertebrates

“…Sulfate moieties are one of the chemical groups proposed to be involved in the underwater adhesion of marine organisms ( Stewart et al, 2011 ; Petrone, 2013 ). However, algae are the only organisms in which the involvement of sulfates in the adhesion process has been demonstrated through spectroscopic investigations of their secreted adhesive holdfast ( Chiovitti et al, 2008 ; Petrone et al, 2011 ; Dimartino et al, 2016 ). In metazoans, the occurrence of sulfate groups in the adhesive material generally remains speculative because, in many cases, they have only been detected in gland cells by histochemical methods.…”

Phlorotannin and its Derivatives, a Potential Antiviral Molecule from Brown Seaweeds, an Overview

“…In the FTIR (Fourier Transfer Infrared) spectrum, the intensity of the absorption frequencies (cm -1 ), representing particular function groups (C=C, O-H, C-H) reveals the presence of phenolic compounds. The marine brown algae Durvillaea antarctica and Hormosira banksii were analyzed for the presence of phenolic compounds using FTIR [24]. The FTIR spectrum of kelp phenolic compounds was determined to evaluate the presence of phlorotannins [8].…”