This study presents the high-precision microinjection of fluorescent micro-gel beads into Caenorhabditis elegans trapped in a suction microchannel. In our previous works, we demonstrated survival microinjection by a conventional micromanipulation technique. However, the focal planes differed between the tip of the microinjection tool and the target axon inside the C. elegans body. To resolve this problem, we here propose a suction microchannel that traps C. elegans during the microinjection operation. The focal plane of the target nerve axon matches that of the fluorescent microbead in the microinjection tool, enabling high-precision microinjection into the interior of the C. elegans body under a microscopic view. In an experimental evaluation, the positioning accuracy of the injection into C. elegans was within the target accuracy (15 μm). The head-flrst navigation alignment of C. elegans along the microchannel was controlled by electrotaxis. Injection of the fluorescent micro-gel bead into the C. elegans body was quantitatively confirmed by confocal microscopy.

This study presents the survival microinjection into Caenorhabditis elegans (C. elegans) with in vivo observation based on micromanipulation. The microinjections were achieved with micro-gel beads which are enable to encapsulate chemicals for injection. In this study, a fluorescent material was used to evaluate the injection positional precision inside the C. elegans. The fluorescent microbead was picked up at the tip of a micropipette injection tool and injected by a piezo actuated microinjector. The distance between the injected micro-gel bead and closest nerve axon was measured as 20.3 μm and 16.5 μm by in vivo observation of a confocal microscopy. The two types of pipette tools were used to evaluate the success and survival rates of microinjection, and the smaller pipette (pipette A, 0.8 μm in diameter) showed higher rates as 50 % and 67 % respectively.