Numerically controlled electrochemical etching of tungsten nano-needles for penetrating the tough yeast cell wall

The effective transfer of foreign macromolecules into yeast cells has been a challenge for decades due to the tough yeast cell wall. Existing transfer methods involve cell wall removal or cell wall permeability alteration, which causes serious damage to the cell structure and affects their further budding proliferation. Traditional microinjection has been successfully applied to animal cells but is not viable for yeast cells due to the low stiffness of the glass micro-pipette tip, which is inadequate to penetrate the tough yeast cell wall. In this study, a tungsten nano-needle with an optimized tip profile was fabricated using a numerically controlled electrochemical etching platform. We successfully penetrated the tough yeast cell wall using our customized tungsten nano-needle. The experiment results confirmed the possibility of mechanically penetrating the yeast cell wall using nano-needles. This method paves a new promising way for further microinjection of foreign substances into yeast cells.