Novel suction-based in vivo cutaneous DNA transfection platform

Abstract

This work reports a suction-based cutaneous delivery method for in vivo DNA transfection. Following intradermal Mantoux injection of plasmid DNA in a rat model, a moderate negative pressure is applied to the injection site, a technique similar to Chinese báguàn and Middle Eastern hijama cupping therapies. Strong GFP expression was demonstrated with pEGFP-N1 plasmids where fluorescence was observed as early as 1 hour after dosing. Modeling indicates a strong correlation between focal strain/stress and expression patterns. The absence of visible and/or histological tissue injury contrasts with current in vivo transfection systems such as electroporation. Specific utility was demonstrated with a synthetic SARS-CoV-2 DNA vaccine, which generated host humoral immune response in rats with notable antibody production. This method enables an easy-to-use, cost-effective, and highly scalable platform for both laboratorial transfection needs and clinical applications for nucleic acid–based therapeutics and vaccines.

Fig. 1.. GFP expression under dermal suction.

(A) Schematic of experimental setup; suction follows Mantoux injection. (B) Suction is induced via a disposable cup (6 mm inner diameter at opening) attached to a vacuum pump. (C) Skin after suction treatment (65 kPa, 30 s) showed both the injection bleb and the mark by cup rim; no bruising was observed. (D) Top view expression pattern for control (injection only) and (E) suction-treated skin at 1, 2, 4, 12, 24, 36, and 48 hours after treatment, respectively. (F) Top view fluorescence quantification at different time points (n = 3). a.u., arbitrary units. Photo credit: Emran Lallow, Rutgers University.

Fig. 2.. Dependence of expression on pressure, treatment time, DNA amount, and device type.

(A) Normalized fluorescence intensity and (B) normalized expression area as functions of suction pressure; treatment time is 30 s, n = 7. (C) Normalized fluorescence intensity and (D) normalized expression area as functions of treatment time, all at 65 kPa. n = 6 for 5, 10, and 20 s; n = 9 for 30 s; n = 3 for 60, 120, and 300 s. (E) Normalized fluorescence intensity and (F) normalized expression area for 100, 25, and 5 μg of GFP plasmid in 50 μl of solution, all at 65 kPa for 30 s (n = 3). (G) Normalized fluorescence intensity and (H) normalized expression area across different device types, all at 65 kPa for 30 s. Device 1, n = 7; device 2, n = 17; device 3, n = 7. *P ≤ 0.05; **P ≤ 0.01.

Fig. 3.. Simulation results.

(A) 3D view of the color-mapped strain magnitude within the skin layer. (B to F) Cross-sectional views [in the rz plane in the axisymmetric geometry, see arrow in (A)] of the strain magnitude about the focal region at 20, 45, 65, 80, and 90 kPa, respectively. (G) Volume quantification within the skin layer for strain magnitude above the various thresholds from 0.2 to 0.7. (H) Strain magnitude from simulation using a human skin model at 65 kPa; the cross section shows a thicker skin layer of 2 mm. The strain distribution is quantitatively similar to that within a rat skin despite the anatomical differences.

Fig. 4.. Induction of humoral response to a SARS-CoV-2 DNA vaccine candidate.

(A) An integrated device used to apply suction for vaccine administration. (B) The geometric mean titer (GMT) for IgG against the SARS-CoV-2 S1 protein as determined by ELISA. n = 5, *P ≤ 0.05. The bars represent the endpoint titer geometric mean of all five animals for each group; the error bars are the 95% confidence interval (CI). The dashed line at 25 represents the cutoff threshold. Photo credit: Emran Lallow, Rutgers University.

Fig. 5.. Histology of skin cross sections via H&E staining 24 hours after DNA delivery.

(A) A representative histological image of a section across the injection bleb from skin that received DNA injection only. (B) A representative histological image of a section of a skin area that received DNA injection followed by suction at 65 kPa for 30 s.