Simultaneous Loading and Injection Chip to Automate Single-cell Injections for Bovine Oocytes

In order to simplify and automate the microinjection process, we propose a new microinjection chip for 100- to 150-µm-size spherical cells, which integrates a novel rack-pinion loader and a previously developed bubble injector. Microinjection has always been the backbone of intracellular cargo delivery owing to its reliability for applications ranging from gene injection to intracellular drug delivery. Unfortunately, the conventional microinjection method is no longer sufficient as it requires highly skilled operators and is time-consuming. To solve these problems, we propose a novel reliable and reusable rack-pinion-based loader combined with a bubble injector for in-chip injection. Here, the rack-pinion loader was tested for its strength, precision, and loading capability, while the bubble injector was tested for its intercellular delivery capability. The rack-pinion-based loader has high performance under an external magnetic field, loading up to 42 particles per min. Furthermore, the pinion can be accurately positioned within 3ºand produces a 40 mN force to deliver cells and overcome friction. The bubble injector entails a simple procedure with an 80 to 87.5% successful injection rate. Overall, the chip has a competitive throughput of at least 6 cells per min, including both the loading and injection processes.