I've mostly used Eppendorf FemtoJet + FemtoTip for microinjecting siRNA or sgRNA/Cas9 (cocktail) into cytoplasm of mammalian embryos. Recently I'm trying to establish mouse prenuclear injection for producing KI mice, and want to use piezo assisted microinjection with oil control microinjector (Eppendorf CellTram) instead of FemtoJet. The problem is that loading cocktail into needle is challenging by backloading since the needle's tip is too tiny. I can see capillary phenomenon when I put the needle into liquid, so the tip must be opened. I prefer not to break back the tip because it usually makes tip rough and too opened, but I want to try if anyone knows good ways of it. Could anyone share how to do this for me?

Any comments, suggestions and advices are appreciated.

Thank you,