Mapping of bionic array electric field focusing in plasmid DNA-based gene electrotransfer

Abstract

Molecular medicine through gene therapy is challenged to achieve targeted action. This is now possible utilizing bionic electrode arrays for focal delivery of naked (plasmid) DNA via gene electrotransfer. Here, we establish the properties of array-based electroporation affecting targeted gene delivery. An array with eight 300 μm platinum ring electrodes configured as a cochlear implant bionic interface was used to transduce HEK293 cell monolayers with a plasmid-DNA green fluorescent protein (GFP) reporter gene construct. Electroporation parameters were pulse intensity, number, duration, separation and electrode configuration. The latter determined the shape of the electric fields, which were mapped using a voltage probe. Electrode array-based electroporation was found to require ~100 × lower applied voltages for cell transduction than conventional electroporation. This was found to be due to compression of the field lines orthogonal to the array. A circular area of GFP-positive cells was created when the electrodes were ganged together as four adjacent anodes and four cathodes, whereas alternating electrode polarity created a linear area of GFP-positive cells. The refinement of gene delivery parameters was validated in vivo in the guinea pig cochlea. These findings have significant clinical ramifications, where spatiotemporal control of gene expression can be predicted by manipulation of the electric field via current steering at a cellular level.

Neurotrophin gene augmentation by electrotransfer to improve cochlear implant hearing outcomes

“…3B, Fig. 4) confirmed the efficacy of this tandem electrode configuration (Browne et al, 2016;Pinyon et al, 2014) (Fig. 3B, C; Fig.…”

“…Here it was shown that the tandem gene delivery array configuration caused a substantial compression of the electric field centre around the null between the ganged anodes and cathodes. As such, the absolute voltage in the solution in this zone was found to be very low relative to other regions around the array, but the local voltage differential (change in voltage over distance = electric field strength) was found to be equivalent to fields requiring many hundreds of volts under conventional open-field electroporation where the tissue was located between a pair of electrodes (Browne et al, 2016). This has been modelled ( Fig.…”

Cochlear Implant Close-Field Electroporation

“…(a) 40 V pulses (5) at 50 ms duration; (b) 40 V pulses (2) at 100 ms duration; (c) 20 V pulses (5) at 50 ms duration; (d) 20 V pulses (2) at 100 ms duration configurations (below). Both these array configurations produced substantially greater gene electrotransfer than the single pairs of electrodes with the minimum (300 μm separation), with further rapid attenuation of gene transfer efficiency with increasing separation of the pairs of electrodes (Browne et al 2016). Such studies, particularly those using the higher efficiency tandem configuration, demonstrated that transduction efficiency improved as pulse duration was extended, with maximum transduction efficiency around 100 ms (Figs.…”

“…The principal parameters underlying bionic array-based CFE have been characterized using a high-throughput human embryonic kidney (HEK293) cell monolayer bioassay (Browne et al 2016). Such bioassays have been effective in the past for analysis of electric fields for gene electrotransfer (Rebersek et al 2007).…”

“…The proof of principle of CFE gene delivery was established using cochlear implant electrode arrays (Browne et al 2016;Pinyon et al 2014a). These "bionic ear" arrays are the neural interface that enables restoration of hearing to people with profound sensorineural hearing loss.…”