Suction-mediated cutaneous DNA uptake yielded high in vivo efficiency and thus provides an alternative transfection platform.

Intradermal (ID) injection is a technique widely used in laboratorial and clinical applications. The boundary of the dome-like bleb formed during injection is assumed to represent the lateral extent of the injected material. This work systematically characterizes cargo molecule distribution (puddle) as a function of injection volume and molecular/particle size in rat skin post ID injection. In general, results indicate that the puddle forms a subdomain laterally contained within the bleb, with an area inversely correlating to the molecular size of the injected material. For 50 μL and 100 µL injections, the average area of the bleb was 40.97 ± 6.30 mm2 and 55.64 ± 8.20 mm2, respectively, regardless of the molecular/particle size. On the other hand, the area of the puddle was dependent on the molecular size and ranged between 45.38 ± 8.29 mm2 and 6.14 ± 4.50 mm2 for 50 µL injections, and 66.64 ± 11.22 mm2 and 11.50 ± 9.67 mm2 for 100 µL injections. The lateral distribution appears to have no time-dependency up to 10 min post injection. The trend in the depth of cargo penetration is also similar, with smaller particles extending deeper into the dermis and subcutaneous fat layers. Because the area of puddle can be significantly less than that of the bleb, establishing base characterization is essential to understand cellular interactions with the injected biological substances.

Electrospray deposition (ESD) is a promising technique for depositing micro-/nano-scale droplets and particles with high quality and repeatability. It is particularly attractive for surface coating of costly and delicate biomaterials and bioactive compounds. While high efficiency of ESD has only been successfully demonstrated for spraying surfaces larger than the spray plume, this work extends its utility to smaller surfaces. It is shown that by architecting the local “charge landscape”, ESD coatings of surfaces smaller than plume size can be achieved. Efficiency approaching 100% is demonstrated with multiple model materials, including biocompatible polymers, proteins, and bioactive small molecules, on both flat and microneedle array targets. UV-visible spectroscopy and high-performance liquid chromatography measurements validate the high efficiency and quality of the sprayed material. Here, we show how this process is an efficient and more competitive alternative to other conformal coating mechanisms, such as dip coating or inkjet printing, for micro-engineered applications.