Reciprocation of micro-objects by contraction and extension of <i>Vorticella convallaria</i> using polylysine as adhesive material

Abstract

Integration of bioactuators in engineered microstructures is expected to be beneficial to further miniaturize and functionalize microelectromechanical systems. However, it is difficult to achieve reciprocation of micro-objects with common biological motors, although reciprocating movement is an important mechanism in constructing micromechanical systems. The ciliate protozoan Vorticella convallaria possesses a contractile filamentous stalk approximately 100 µm long, of which the contraction-extension cycle has the potential of being used as a linear reciprocating machine. In this study, we used polylysine (PLL) to attach micro-objects to Vorticella convallaria with the purpose of reciprocating the objects by contracting and extending the Vorticella cells. Two types of micro-objects, namely, polystyrene microspheres and glass grits, were coated with positively charged PLL and attached by electrostatic interaction to negatively charged V. convallaria. We characterized the adhesive performance and analyzed the movement of the objects by optical microscope observation. Microspheres of diameter 21 µm were moved back and forth by the contraction and extension of V. convallaria. Comparison of the adhesiveness of PLL-coated and COOH-terminated spheres confirmed the effectiveness of our attachment and actuation method. The grits were actuated in various ways depending on their size, the point of attachment to V. convallaria, and the number of cells. The typical motions were linear and rotational and were propelled by a few cells. V. convallaria cells displaced thin glass grits of thickness up to tens of micrometers. The adhesive force and the drag forces were estimated hydrodynamically. The implemented reciprocating motion can be applied to biohybrid microfluidic systems.

Vorticella: A Protozoan for Bio-Inspired Engineering

“…However, little is known about what types of taxis responses Vorticella shows. Instead, it seems more probable to use magnetic particles and magnetic field to control Vorticella , as applied for controlling a ciliate protozoan Tetrahymena pyriformis [ 163 ], because such particles can be attached to or engulfed by Vorticella [ 147 , 148 ]. Controlling the stalk contraction of Vorticella is also critical for utilizing the animal as a bioactuator.…”

“…Additionally, micro-objects were successfully attached to live Vorticella using biocompatible glues such as streptavidin-biotin binding [ 147 ] and poly- l -lysine coating [ 148 ], and their reciprocal motion was achieved from the stalk motion of Vorticella . Therefore, such binding methods prove that harnessing live Vorticella for microsystem application is feasible.…”

Rotibot: Use of Rotifers as Self‐Propelling Biohybrid Microcleaners

“…A major challenge in the field is to translate and scale up these microrobotic applications to relevant environmental settings by addressing limitations associated with toxic chemical fuels, short time span, and the small domain operation of externally‐actuated microrobots . One plausible solution is to develop biohybrid microrobots that integrate self‐propelling microorganisms with functionalized synthetic nanostructures. The current generation of biohybrid platforms is based primarily on flagellated microorganisms which survive only in delicate living conditions and may not provide sufficient fluid mixing for enhancing decontamination processes.…”

Fluid dynamic estimation of the effective spring constant of the relaxing stalk of Vorticella convallaria

“…The spasmoneme of V. convallaria has been studied for actuators in microscale engineering systems [1]. For instance, V. convallaria was incorporated in microfluidic systems to operate the reciprocal motion of microfluidic valves or micro-objects [15][16][17]. In these applications, controlling the stalk contraction cycle of V. convallaria is crucial, which requires characterizing the relaxation phase.…”