PMC

Handheld motorized microneedle array device. (a) The inner reservoir of the motorized microneedle array cartridge contains 300 µl of a red dye solution for visualization. (b) The needles can be adjusted for penetration depth and are set here at 0.1 mm to protrude slightly beyond the edge of the chamber. (c) Channels located between the needles allow flow of solution onto the surface of the skin during treatment.

Confocal fluorescence imaging of Cy3-labeled sd-siRNA in human skin.Following motorized microneedle array delivery (30–60 minutes) of 100 µl of 0.5 mg/ml Cy3-labeled sd-siRNA (in phosphate-buffered saline) to excised human facial skin, siRNA distribution was imaged (reflectance and red fluorescence) with a modified Lucid VivaScope (see Materials and Methods). (a) Reflectance imaging at 29-µm depth shows the primary penetration site for this individual needle (note arrow). (b) Fluorescence imaging at 59-µm depth shows the diffusion of labeled sd-siRNA through the epidermis. (c) Magnification of the boxed region in (b) shows the interaction of the labeled sd-siRNA with individual cells. Scale bar = 100 µm.

Cy3-labeled sd-siRNA distribution in mouse and human skin. Mouse or human skin was treated with the motorized microneedle array device loaded with 50 µl of 0.1 mg/ml Cy3-labeled sd-siRNA and intradermally injected as described below. After a 1-hour incubation, skin was collected, frozen in optimum cutting temperature (OCT) compound, and sectioned (10 µm). (a) Sections of hairless mouse flank skin in which breaches in the epidermis are shown in their entirety using a ×5 objective. Intradermally injected skin (16 µl of 0.1 mg/ml Cy3-labeled sd-siRNA) was sectioned to the center of the injection site and similarly displayed. The individual images were stitched together using ICE software. (b) Magnification (×10) of treated skin. (c) Further magnification of images from (b) shows diffusion of the Cy3-labeled sd-siRNA in the epidermis originating from the needle penetration site (arrow). Left panels: 4′,6-diamidino-2-phenylindole and Cy3 overlay; right panels: Cy3 alone. (d) Distribution of fluorescently labeled sd-siRNA in human abdominoplasty skin. Skin breaches due to penetration of the motorized microneedles are seen in their entirety using a ×5 objective. Intradermally injected skin (50 µl of 0.1 mg/ml Cy3-labeled sd-siRNA) was similarly sectioned and imaged. (e) Magnification of treated skin. (f) Further magnification of the images from (e) shows diffusion of the Cy3-labeled sd-siRNA in the epidermis originating from the needle penetration site (arrow), whereas low levels of fluorescence are observed in the epidermis following intradermal injection. Left panels: 4′,6-diamidino-2-phenylindole, and Cy3 overlay; right panels: Cy3 alone. Nuclei are visualized by DAPI (blue). Scale bar = 200 µm.

Delivery of sd-siRNA strongly inhibits targeted reporter gene expression. Hairless tg-CBL/hMGFP mouse flank skin (n = 3) was treated on days 0, 2, 4, 6, 8, and 10 with the MMNA device loaded with 100 µl of 5 mg/ml CBL3 sd-siRNA or nonspecific control sd-siRNA (sd-TD101). The mouse skin was marked to allow the same area of the flank to be treated for each administration. On day 11, the mice were killed and the treated skin was excised for RTqPCR analysis and fluorescence imaging. (a) Total RNA was isolated from the epidermis of the excised skin, reverse transcribed, and reporter (CBL/hMGFP) mRNA levels (relative to K14) were quantified in triplicate by qPCR. Bars indicate standard error. (b) Representative fluorescence images (bottom) with bright field overlay (top) of frozen skin sections (10 µm) prepared from treated mice show inhibition of hMGFP fluorescence signal in the skin treated with specific sd-siRNA over control sd-siRNA. Nuclei are visualized by DAPI (blue). Scale bar is 100 µm.