Delivery of nucleic acids to ex vivo porcine airways using electrospray

Nucleic acid-based therapies have the potential to provide clinically meaningful benefit across a wide spectrum of lung disease. However, in vivo delivery remains a challenge. Here we examined the feasibility of using electrospray to deliver nucleic acids to both porcine tracheal tissue sections and whole lung ex vivo.

The effect of electrospray solution, emitter gauge, flow rate and voltage on plasmid DNA integrity was examined by analyzing supercoiled:open circle structure ratio by gel electrophoresis. Optimal parameters were used to deliver luciferase DNA and mRNA and siRNA-FITC to tracheal tissue sections. Luciferase mRNA was delivered to whole porcine lungs ex vivo using a catheter and bronchoscope system. Luciferase activity and fluorescence were analyzed by luminometry and microscopy respectively.

The incidence of DNA plasmid nicking was greatest in a low salt solution without ethanol compared with 1% and 20% ethanol with salt. From a range of emitters tested, a 32 gauge emitter produced the best supercoiled:open circle structure ratio, likely because less voltage was required to produce a stable electrospray with this emitter. Lower flow rates also showed a trend towards reduced DNA nicking. GFP DNA electrosprayed at 5 kV and 6 kV resulted in lower levels of GFP expression in A549 lung cells following lipofection compared with 3 kV and 4 kV. Optimised parameters of 20% ethanol solution, 32 gauge emitter, low flow rates and voltages of 3-5 kV, nucleic acid molecules were successful for delivery of luciferase DNA and mRNA as well as siRNA-FITC to porcine tracheal tissue sections and for delivery of luciferase mRNA to whole porcine lungs via bronchoscope.

We report ex vivo delivery of nucleic acids to porcine lung tissue via electrospray and bronchoscopic electrospray delivery of nucleic acid to an ex vivo porcine lung model.