Fig. 6: The diffusion of drugs under the skin is controlled by the gas-producing behavior of microbial engines.

a Confocal microscopy imaging of the release and diffusion over time of dye-simulated drugs at different depths beneath the skin. Scale bar, 500 μm. b, c The average fluorescence intensity of dye-simulated drugs diffusing over time at different depths beneath the skin. d The curves show the average fluorescence intensity of drug diffusion over time at different depths, and the curves depict gas production by microneedles over time. e A schematic diagram illustrating the gradual dissolution and diffusion of dye-simulated drugs under the skin due to gas production by microneedles, penetrating into deeper tissues. Created with BioRender.com/u33l993. A representative image of four biologically independent samples from each group is shown in (a).