Investigation of the adhesive from Hormosira banksii germlings and its performance over different material surfaces and topographies

Adhesives produced by marine organisms possess the ability to adsorb robustly and under water to a range of substrates, in a range of environmental conditions and undergo curing under water. In the present work, the bioadhesive produced by germlings of a large brown seaweed, Hormosira banksii, is investigated to assess its adhesive performance. The production of the adhesive secretions was monitored using microscopy and staining experiments, while the attachment strength over substrates of varied chemistry and topography was indirectly evaluated through flow channel experiments. H. banksii germlings displayed a two-stage development of the adhesive, with an initial uniform production around the entire germling, followed by localized production in the rhizoidal tip. Germlings were found to exhibit a settlement-time dependent increase in adhesion strength across all of the substrates investigated, including glass, stainless steel, poly(methyl methacrylate) (PMMA), polytetrafluoroethylene (PTFE) and polydimethylsiloxane (PDMS). Conversely, any substrate-dependent variation in the adhesive strength was not observed, suggesting H. banksii germlings are able to produce an adhesive able to interact with a range of substrate types. On substrates with simple, defined topographies, H. banksii zygotes were found to adhere most effectively to a surface with a feature size slightly larger than the size of the zygote. A feature size smaller than the zygote resulted in a minor disruption of adhesion strength that diminished with settlement time.