The barnacle adhesive plaque: morphological and chemical differences as a response to substrate properties

Abstract

This paper reports the differences in structure and composition of the adhesive plaque biosynthesized by the barnacle, Balanus improvisus, growing on poly(methylmethacrylate) (PMMA) and polydimethylsiloxane (PDMS). Barnacles growing on the low surface energy, low modulus PDMS synthesized a thick rubbery adhesive plaque with granular morphology, as determined with atomic force microscopy, which should be compared with the hard, continuous adhesive plaque produced by barnacles growing on the medium surface energy, glassy PMMA polymer. Calcium was detected in the PMMA adhesive plaque with electron probe microanalysis and infrared spectroscopy showed that calcium was incorporated as calcite, one of the crystal polymorphs of CaCO 3. In comparison, no calcium could be detected in the PDMS adhesive plaque. Three distinct proteins and some minor polypeptides were found with sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis when the adhesive plaque from PDMS was dissolved in a buffer containing 0.5 M dithiothreitol and 7 M guanidine hydrochloride. No proteins could be dissolved when adhesive plaque from PMMA was treated in the same buffer used for PDMS plaque.