posted on 2016-01-19, 00:00authored byJoel P. Golden, Daniel
K. Burden, Kenan P. Fears, Daniel E. Barlow, Christopher R. So, Justin Burns, Benjamin Miltenberg, Beatriz Orihuela, Daniel Rittshof, Christopher M. Spillmann, Kathryn J. Wahl, Leonard M. Tender
Surface plasmon resonance
imaging (SPRI) and voltammetry were used
simultaneously to monitor Amphibalanus (=Balanus) amphitrite barnacles reattached and grown on gold-coated glass slides in artificial
seawater. Upon reattachment, SPRI revealed rapid surface adsorption
of material with a higher refractive index than seawater at the barnacle/gold
interface. Over longer time periods, SPRI also revealed secretory
activity around the perimeter of the barnacle along the seawater/gold
interface extending many millimeters beyond the barnacle and varying
in shape and region with time. Ex situ experiments using attenuated
total reflectance infrared (ATR-IR) spectroscopy confirmed that reattachment
of barnacles was accompanied by adsorption of protein to surfaces
on similar time scales as those in the SPRI experiments. Barnacles
were grown through multiple molting cycles. While the initial reattachment
region remained largely unchanged, SPRI revealed the formation of
sets of paired concentric rings having alternately darker/lighter
appearance (corresponding to lower and higher refractive indices,
respectively) at the barnacle/gold interface beneath the region of
new growth. Ex situ experiments coupling the SPRI imaging with optical
and FTIR microscopy revealed that the paired rings coincide with molt
cycles, with the brighter rings associated with regions enriched in
amide moieties. The brighter rings were located just beyond orifices
of cement ducts, consistent with delivery of amide-rich chemistry
from the ducts. The darker rings were associated with newly expanded
cuticle. In situ voltammetry using the SPRI gold substrate as the
working electrode revealed presence of redox active compounds (oxidation
potential approx 0.2 V vs Ag/AgCl) after barnacles were reattached
on surfaces. Redox activity persisted during the reattachment period.
The results reveal surface adsorption processes coupled to the complex
secretory and chemical activity under barnacles as they construct
their adhesive interfaces.