Good question. I have done some experimentation with the Neon device (see here: https://jeltsch.org/neon_electroporation), but the buffer composition is unknown. PBS without ions would essentially be distilled water, which your cells (what cells are you transfecting?) will not like. Which of the two buffers do you want to replace with home-made one? R or T? We have leftover buffer T which we probably never will need... Most conventional electroporation is done in buffers that are similar to the growth medium of the cells. Just make a couple of experiments trying out several options: 150mM NaCl, D-MEM +/- 10%FCS, serum-free medium, 1xHBS, 1xPBS, 0.75xPBS, 0.5xPBS, etc. Since you use the same DNA, you can use one tip and many experiments. Figuring out a good buffer replacement would benefit everybody and could be fun!
Looks like you can use a sucrose based buffer, see the reference below: 250 mM sucrose and 1 mM MgCl2 in DPBS [Dulbecco’s phosphate-buffered saline, Gibco cat. no. 14190
ref:
Anal Biochem. 2014 Dec 1;466:49-50. doi: 10.1016/j.ab.2014.08.017. Epub 2014 Aug 27.
A cost-effective approach to microporate mammalian cells with the Neon Transfection System.