The tip of a needle is closed when made by a puller (see M7-2) . The tip of the needle needs to be opened just before injection (refer to Appendix 7-2).
1. Injection solution is loaded into the needle before its tip is broken, using a thin micropipette tip (for example, an Eppendorf Microloader #5242 956.003).
2. Further layer with mineral oil using a stainless steel fine needle to fill the needle (for example, a HAMILTON 90131). Be sure not to allow any air bubbles to remain.
3. Set the needle to a needle holder.
4. Focus the microscope on the surface of the egg holder and gradually lower the needle to the glass bottom.
5. When the tip of the needle touches the glass bottom, the tip would be broken and opened, which is confirmed by leakage of injection solution from the tip of the needle.