Adhesion force measurement of live cypris tentacles by scanning probe microscopy in seawater

Abstract

The adhesion force of the tentacle of a live cypris on a glass surface covered with polymer brush was directly measured by scanning probe microscopy. Polymer brushes were prepared on the cover glass and silicon wafers by surface-initiated atom transfer radical polymerization of 3-(N-2-methacryloyloxyethyl-N,N-dimethyl)ammonatopropanesulfonate (MAPS) or 2-hydroxyethyl methacrylate (HEMA). A small amount of glue was placed at the edge of a tipless cantilever supported by the piezo motion control system of the scanning probe microscope and monitored by using an optical microscope. A live cypris swimming in seawater was held down on the slide glass by the cantilever for 30 min until the glue cured. The tentacles of the live cypris immobilized on the cantilever were forced to make contact with the surface-modified cover glass. The adhesion force was determined by the torsion of the cantilever when the tentacle was detached from the cover glass surface. The adhesion force between the cypris and the propylsilane-modified glass surface increased from 1.6 to 40 μN with the increase in age of the cypris larva from 3 to 21 days after metamorphosis from the nauplius larva. Poly(MAPS) and poly(HEMA) brush surfaces exhibited extremely low adhesion to the cypris larva during 21 days in seawater, indicating the effective antifouling property of hydrophilic polymer brushes. The adhesion force between the tentacle of a live cypris and polymer brushes on the sidewall of cover glass was directly measured by scanning probe microscopy in seawater. The cypris was immobilized on the cantilever with glue, and then forced to make contact with the modified surface. When the tentacle was detached by moving the cantilever away from the surface, the torsion of the cantilever caused the laser deflection on the photodiode corresponding to the adhesion force. Polymer brush surfaces exhibited extremely low adhesion to the cypris larva.