2016 Volume 2 Pages 16-00445
Biohybrid systems, constructed by combining biological cells and artificial components, have the potential to resolve the current technical limits of traditional microactuators. The aim of this study is to bring poly(ethylene glycol) diacrylate (PEG-DA) movable components, formed by microfluidic in situ photolithography, into biohybrid Vorticella-based systems. This paper reports conditions for integrating PEG-DA hydrogels and actuators of Vorticella convallaria (V. convallaria). PEG-DA hydrogels were formed in a polydimethylsiloxane (PDMS) microfluidic channel by in-situ photolithography techniques. Basic photopolymerization properties of PEG-DA hydrogels in a PDMS microchannel were studied by changing the magnification of an objective lens and light intensity. To incorporate a PEG-DA structure with V. convallaria, we studied two possible integration methods: 1) hydrogel formation after cell placement and 2) cell placement after hydrogel formation. To examine the integration methods, we evaluated the viability of V. convallaria in a PEG-DA solution mixed with photoinitiators or in a buffer after the formation of a PEG-DA hydrogel. A viability assay in a PEG-DA solution revealed that lower concentrations of PEG-DA and photoinitiator improved cellular viability. To establish the second integration method, we designed and fabricated a microfluidic device to transport a V. convallaria cell to a microchamber containing a polymerized PEG-DA structure. Cell viability in a microchamber was evaluated after replacing a PEG-DA solution with a culture medium. Vorticella was active and generated a flow, which was characterized by particle image velocimetry (PIV). A higher molecular weight PEG-DA increased V. convallaria viability. The conditions for forming a hydrogel structure while maintaining Vorticella activity were clarified as a method for incorporating a movable component into biohybrid systems.
