A multimodal holographic system for optical manipulation and injection of developing embryos

Transgenic animals are an essential means for investigating genetic processes in vivo, and depend on efficient delivery techniques to introduce exogenous genetic material into the organism, often at the zygote stage. In this study, we demonstrate an optical approach to microinjection based on a holographic system using a spatial light modulator and a Ti: Sapphire laser. This integrated system is capable of both optical orientation and injection of 60- μm diameter Pomatoceros lamarckii (P.lamarckii) embryos. Individual blastomeres of P. lamarckii embryos were optoinjected with varying sizes of dextran molecules and Propidium iodide using an 800-nm femtosecond laser with controlled dosage. We also show that the technique is able to deliver materials to cells located deep within a welldeveloped embryo. As a visual confirmation of successful optoinjection, the presence of gas bubbles was observed as a function of laser power and exposure time. Small gas bubbles, less than 5-μm in diameter, were found to be tolerated by the irradiated embryo. Furthermore, when switched to the continuous wave mode, the laser could exert optical forces upon the embryo. This facilitated computer-controlled handling and orientation of P. lamarckii embryos without compromising viability. Our multimodal optical platform offers a sterile, non-contact and robust alternative to traditional microinjection. This work is a step towards applications in developmental biology such as cell lineage mapping and formation of transgenic animals using an optical approach.