Dissolving microneedles for DNA vaccination: Improving functionality via polymer characterization and RALA complexation

Abstract

DNA vaccination holds the potential to treat or prevent nearly any immunogenic disease, including cancer. To date, these vaccines have demonstrated limited immunogenicity in vivo due to the absence of a suitable delivery system which can protect DNA from degradation and improve transfection efficiencies in vivo. Recently, microneedles have been described as a novel physical delivery technology to enhance DNA vaccine immunogenicity. Of these devices, dissolvable microneedles promise a safe, pain-free delivery system which may simultaneously improve DNA stability within a solid matrix and increase DNA delivery compared to solid arrays. However, to date little work has directly compared the suitability of different dissolvable matrices for formulation of DNA-loaded microneedles. Therefore, the current study examined the ability of 4 polymers to formulate mechanically robust, functional DNA loaded dissolvable microneedles. Additionally, complexation of DNA to a cationic delivery peptide, RALA, prior to incorporation into the dissolvable matrix was explored as a means to improve transfection efficacies following release from the polymer matrix. Our data demonstrates that DNA is degraded following incorporation into PVP, but not PVA matrices. The complexation of DNA to RALA prior to incorporation into polymers resulted in higher recovery from dissolvable matrices, and increased transfection efficiencies in vitro. Additionally, RALA/DNA nanoparticles released from dissolvable PVA matrices demonstrated up to 10-fold higher transfection efficiencies than the corresponding complexes released from PVP matrices, indicating that PVA is a superior polymer for this microneedle application.

DNA vaccination for cervical cancer: Strategic optimisation of RALA mediated gene delivery from a biodegradable microneedle system

“…24 h following transfection cells were supplemented with 10% CellTiter 96 Aqueous One Solution Reagent (MTS) (Promega, UK), and percentage toxicity was determined as previously described. [22] For transfection studies NCTC-929 cells were seeded into 24 well plates (100,000 cells/well) and treated with NPs as above, with a total of 5 µg of pDNA/well. Cells were treated with F-NPs, L-NPs or L-NPs which had been resuspended and dried in PVA.…”

“…A piece of sticky tape was placed over the flat side of the baseplate of MNs loaded with NP (NP-MN) or pDNA (DNA-MN), and MNs were subsequently placed onto the SC surface, inserted into the skin using manual thumb pressure, and held in place for 30 s. 2D images of needle penetration were obtained using an EX1301 OCT microscope (Michelson Diagnostics Ltd, UK) and Image J software (National Institutes of Health, USA) was used to analyse images of penetration as previously described. [22]…”

“…[19,20] As such dissolvable arrays may be more suitable for DNA vaccination as the cargo may be incorporated throughout the entire matrix of the MN thereby increasing potential loading capacity. [21,22] Dissolvable MN arrays further remove the inherent danger of needle buckling or breakage within the skin, minimise the risk of abuse or reuse, and provide a means to visually confirm dosage delivery. [17] Previously, we reported on the design of a dissolvable Poly(Vinyl Pyrrolidine) (PVP) MN system incorporating pDNA cargo complexed to the cationic cell-penetrating peptide, RALA, to aid intra-cellular uptake.…”

“…[24] By thoroughly screening a range of dissolvable polymers for the MN fabrication process, this device has been further optimised to increase cargo transfection efficacies and payload. [22] Despite these improvements, increasing the quantity of pDNA vaccine delivered from dissolvable MNs remains a considerable challenge. Therefore, the current study was designed to determine whether lyophilisation could be used to facilitate increased loading of the RALA/pDNA nanoparticle (NP) cargo within the dissolvable MN matrix, without compromising needle integrity or functionality.…”

Microneedle‐Mediated Vaccine Delivery to the Oral Mucosa

“…Many different vaccine biologics can be formulated into microneedles due to the abundance of materials and designs that are available. Vaccine compositions have included virus‐like particles, DNA polyplexes, protein subunit, and viral vectors . Vaccine components can be formulated onto solid microneedles as coatings through a variety of dry and wet coating techniques, and these coatings can be further layered to incorporate both antigen and adjuvant .…”