I’ve been trying to find an OS electroporator and after several failures with some posted like electro pen I had to try to create one.
At this point it should work but it either does not or occasionally gets 2 or 3 colonies.
I’m using a DIY “cuvette” with 2 aluminum bars glued to a microscope slide like seen in several papers.
I’m using the simple wash with water 4 times and store in 10 glycerol all in ice water to produce the Electro competent cells.
Based on my measurements I deliver about 2kV on a 1 mm gap and probably a 8=9 ms decay.
Here’s a comparison between results using my competent made cells using the chemical CaCl2 method and using the “ElectroCompetent” cells.
Bottom: almost a month old lab produced electrocompetent cells zapped with the above built electroporator.
Top: lab produced electrocompetent cells washed 4 times using the same DNA in the same quantity and the same recovery protocol after shocking.
Here’s the ‘pulse’ captured on an oscilloscope(currently the hight is about 2000V not 1.6KV as in the image)
:
I did maybe a dozen of tests with the best getting maybe 3 colonies after a looong time like 2 days.
Argh
I used both “Room temperature electrocompetent bacterial cells improve DNA transformation and recombineering efficiency | Scientific Reports” hot prep and the classic cold protocol:
“Prep: all on ice.cool fridge/freezer. cool rotor, Cts, ice cold ddWater and work on ice
Grow in shaker 15h@33C until OD=04, 0.5, 0.6
Cool flask 10-15 min. Fill #0 2 mL CTs spin 1 @3000-4000 G (~7k RPM) for 6 min, discard super, refill 1, spin 2 again, refill 2 and spin 3 and resuspend with 1mL ice cold ddWater
Repeat wash with 1mL water 4 times for spin 4, 5,6 and spin 7 which produces last pellet
Discard super, add 50uL 10% glycerol. Can try water instead of glycerol
so mine 6 mL->50uL so 6000/50 about < 120x”
Recovery and plating are the same as for the chemical transformation works most of the times with dozens / hundreds of colonies after 12-15 hours. I do freeze the DIY cuvette before zapping.
A lot of info was based on https://www.bio-rad.com/webroot/web/pdf/lsr/literature/M1652098.pdf
If you have further ideas or interested to make one (maybe a functional one 
please let me know. I’m convinced it will work some day hopefully better than the chem transformation and I hope the prepared competent cells will last much longer at -20C.
Thank you,
Adrian