ElectroPen: An ultra-low–cost, electricity-free, portable electroporator
(a) Fluorescence output due to expression of GFP from a transformed plasmid is similar between a commercial electroporator and the ElectroPen, confirming successful transformation and GFP expression. Here, [−] plasmid control refers to electroporation with no plasmid DNA as a reference measurement for fluorescence. Data represent N = 3 trials (see S1 Text). (b) Transformation efficiencies for the commercial electroporator (Bio-Rad MicroPulser) and ElectroPen are within an order of magnitude (see inset). Data from N = 4 for electroporator and N = 7 for ElectroPen. A negative control of the same plasmid DNA and electrocompetent cells without electroporation yielded zero colonies on selective media for all attempts. For a and b, the lines represents the median of the data set; the edges of the box represent the quartiles, with the bottom representing 25th and top representing 75th percentiles; the whiskers extend to the most extreme data points not considered outliers; and for normally distributed data, whiskers correspond to approximately ±2.7σ, where σ is the standard deviation. (c) Image of a commercial electroporator alongside ElectroPens. (d) Image of cuvette being inserted into electroporator for usage alongside usage of the ElectroPen (with hardwired connections). The data for a and b can be found on GitHub under the S3 Data file, under the sheets titled Fig 4A and 4B, respectively. a.u., arbitrary unit; GFP, green fluorescent protein; OD, optical density.