(a) Schematic of the ePatch fabrication. A patterned mask is layered on a silicone substrate. After depositing a conductive hydrogel ink and UV crosslinking, the mask is removed. Next, CaCl2 solution is added to generate a double-crosslinked network. (b) Schematic of AgNW-MAA ink formula and the double-crosslinked network. A uniform mixture of MAA and AgNW network system is generated. The ePatch was applied to a wound created on the back of a model rat with the indicated electric parameters. (c) Illustration of the biological activities of the ePatch during the healing process: (i) acceleration of fibroblast migration and proliferation; (ii) suppression of bacterial growth; (iii) promotion of angiogenesis; (iv) down-regulation of immune cell activities; (v) improved re-epithelization and tissue remodeling.
(a) Schematic of the ePatch fabrication. A patterned mask is layered on a silicone substrate. After depositing a conductive hydrogel ink and UV crosslinking, the mask is removed. Next, CaCl2 solution is added to generate a double-crosslinked network. (b) Schematic of AgNW-MAA ink formula and the double-crosslinked network. A uniform mixture of MAA and AgNW network system is generated. The ePatch was applied to a wound created on the back of a model rat with the indicated electric parameters. (c) Illustration of the biological activities of the ePatch during the healing process: (i) acceleration of fibroblast migration and proliferation; (ii) suppression of bacterial growth; (iii) promotion of angiogenesis; (iv) down-regulation of immune cell activities; (v) improved re-epithelization and tissue remodeling.

A flexible electrical patch based on a hydrogel impregnated with naturally antibacterial silver nanowires dramatically speeds up wound healing [Wang et al., Biomaterials 285 (2022) 121479, https://doi.org/10.1016/j.biomaterials.2022.121479 ]. The device, ‘ePatch’, uses electrical stimulation to promote healing, enhance cell growth and angiogenesis, and mediate immune response.

In the US alone, around 300,000 patients are hospitalized each year with wound healing issues. If left untreated, or in conditions like diabetes or vascular disease, even minor wounds can become chronic, taking months to heal. The ability to accelerate wound healing would not only be highly beneficial in clinical situations but also in the event of emergencies such as war or natural disasters.

Electrical field (EF) stimulation is already used to boost wound healing, but existing devices based on metallic electrodes are rigid and bulky, with the lack of conformability to the skin often causing inflammation and distress for patients. Instead, an international team of researchers led by Wujin Sun at Virginia Tech and Ali Khademhosseini at the University of California, Los Angeles have designed conformable hydrogel electrodes that can deliver electrical stimulation to the site of a wound comfortably for the patient. The ePatch is also cheap and easy to fabricate, using simple components that can be printed from biocompatible materials.

The materials used in the ePatch are FDA-approved wound dressing materials: methacrylated alginate (MAA) and silver nanowires (AgNWs). Together these components form a double-crosslinked network that forms the basis of the novel conductive material. The relative proportions of the two components can be tailored to form a printable ink. The team used mask-based printing to produce electrodes 5 µm thick with a uniformly distributed network of AgNW to ensure high conductivity.

In tests, the electrically-stimulated ePatch not only boosts expression of cellular growth factors associated with wound migration and tissue remodeling, but also improves the proliferation and migration of cells. In vivo mouse tests reveal that ePatch reduces wound healing from 20 days, without any treatment, to just 7, while minimizing scarring.

The researchers believe that ePatch holds great promise for wound treatment, as well as reducing the adverse effects of implants.

“This approach provides a biomimicking way to accelerate wound healing,” says Sun. “Compared with other wound care approaches, this has minimal side effects and is highly simple.”

Although the ePatch currently requires a power module, the researchers hope to explore self-powered designs incorporating solar cells or nanogenerators in the future.