An electroporator applies a controlled electrical pulse that makes a membrane transiently permeable, which is how DNA, RNA and protein are delivered to cells that chemical reagents will not transfect and how a large plasmid or a library is put into bacteria at high efficiency. The instruments differ in the pulse they can produce, and that is what a protocol is really naming when it quotes a voltage and a time.
Exponential decay against square wave
An exponential decay pulse discharges a capacitor through the sample, so the field falls away with a time constant set by capacitance and resistance, and it is the classical setting for bacteria and yeast. A square wave holds the field for a set time and can deliver several pulses, which is gentler on mammalian and primary cells and gives independent control of voltage and duration. An instrument that does only one of the two will run half the protocols in the literature, which is worth checking before the purchase rather than after.
Cuvettes, gaps and cartridges
Field strength is voltage divided by the electrode gap, so a one millimetre cuvette at 1,800 volts and a two millimetre cuvette at 2,500 volts are different experiments, and a protocol that names volts without the gap is incomplete. Bacterial work uses one and two millimetre cuvettes; mammalian work uses four millimetre cuvettes or the maker's own cartridges and plates, which are consumables tied to that instrument. Reusing cuvettes is possible with careful cleaning and is a false economy where arcing has pitted an electrode.
What arcing tells you
An arc is a short circuit through the sample and it destroys the cells and often the cuvette. The usual causes are salt in the DNA or the cell suspension, bubbles in the cuvette, too high a voltage for the gap, and a warm sample. The fixes are mechanical rather than electrical: dialyse or precipitate the DNA out of salt, wash the cells into a low conductivity medium or a maker's buffer, tap out the bubbles, and keep everything on ice. A recorded time constant well below the expected value is the warning before an arc.
Where a chemical method is better
Electroporation is harsh: viability falls, the sample is handled in a small volume and the instrument has to be by the bench. Where a cell line transfects well with a lipid or polymer reagent, the chemical route is cheaper, gentler and easier to scale across a plate. Electroporation earns its place with primary and suspension cells, with large constructs and libraries where efficiency per microgram matters, with protein and ribonucleoprotein delivery, and wherever a reagent's own toxicity would confound the readout.
A protein transfection reagent and what it delivers
A protein transfection reagent carries a protein rather than a nucleic acid across the membrane, which is how a nuclease, an antibody or a labeled protein is delivered without expression, and the chemistry differs from a lipid built for DNA. Efficiency is measured by a functional readout rather than by fluorescence, since surface bound protein looks identical to delivered protein in an image.
ipsc derived neurons and what the protocol produces
ipsc derived neurons are a population rather than a cell type, so the useful description is the differentiation route, the days in culture and the marker panel that identifies what was made and what else is in the dish. Maturity is the recurring limitation, since electrophysiology takes weeks to resemble adult tissue. Batch to batch variation makes the differentiation run part of the record.
ht22 cells and what they are used for
ht22 cells are an immortalised mouse hippocampal line used mostly for oxidative stress and glutamate toxicity work, and they are not a substitute for neurons: they divide, lack mature synapses and respond by a non receptor mediated mechanism. That mechanism is exactly why they are used, so a paper's claim has to be about the pathway rather than about neuronal biology.
A podocyte culture and the phenotype it loses
A podocyte in culture dedifferentiates and loses the foot processes and the slit diaphragm proteins that define it, which is why conditionally immortalised lines are grown at one temperature to proliferate and shifted to another to differentiate. The marker panel after differentiation, rather than the line's name, is what says the culture is worth interpreting.
egf human, and the recombinant growth factor order
An order for egf human is a specification: the sequence's residue range, the expression host, whether it is carrier free, the endotoxin limit and the specific activity in a named assay. Mass alone means nothing because an inactive preparation weighs the same. Because the factor is used continuously in culture media, the cost per active unit at scale is the number to compare.
Questions people ask about electroporator
Square wave or exponential decay?
Exponential decay for bacteria and yeast, square wave for mammalian and primary cells, where independent control of duration and multiple pulses protects viability.
Why does the same protocol fail in a different cuvette?
Field strength depends on the electrode gap, so the voltage has to be recalculated when the gap changes. A protocol without the gap is incomplete.
What causes arcing?
Salt carried in with the DNA or the cells, bubbles, too high a field for the gap, or a warm sample. Wash into a low conductivity buffer and keep everything cold.