Re: [DIYbio] diy electroporation so far?

On 07/30/2014 12:49 PM, Jeswin wrote:
> What's become of the diy electroporation using the piezo starters? How exactly would one go about this?

I've been talking with Nathan and some others about electroporation and it seems
to range far and wide. The recipes you find usually quote using name brand equipment
with specific settings that are not in basic units of time, volts and impedance,
but a few things come out of it: 2kV is enough. Time at 2kV or falling exponentially
from it can be as brief as a millisecond and get results. Resistance of a cuvette
is about 40 kOhms in a 1mm between electrodes x 10mm x10mm cuvette.
for cultured cells in broth without adding extra salt.

It seems valid to get results
with several short pulses rather than needing long pulses.

So, here's a method for very roughly calibrating your piezo sparker:

.25 inches of spark in air is about 10k Volts at sea level. Try to find out
How long a spark your piezo zapper makes in air. If it is .4 inches, then
the Volts are: 16 kV so, to get 2kV divide by 8. For a cuvette resistance of
40k Ohms, it can be the 1:8 ratio with other resistors in series = 280 k Ohms total,
all of them rated for voltage they will carry. You could not do it with little chip resistors
that measure 2mm across for example. A way that would work OK would be 1/4 Watt resistors
of 100k, 100k, 80k Ohms where each one is about 7 mm long. Such low wattage resistors would
need short pulses only, or get hot -- higher wattage is better, but more work to find and buy.
Ordering from Digikey with a prepaid check is a good way -- they will send those orders
for zero shipping charge.

After that, just vary the number of sparks. Also you could add salinity to go below 40k Ohms
for a 1mm spacing cuvette resistance, which
would pull the volts down and spread the current through the dissolved salt as well as
the cells suspended. Both of those effects would be less volts at a any one cell,
(in case the zap is too strong -- killing them).

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