The team at the Terasaki Institute for Biomedical Innovation (TIBI) in California believe their so-called ePatch also offers ‘uniquely advantageous features’ for wound healing.
Electric field (EF) dressings activate the migration of skin and other granulation cells to the wound site, inducing blood vessel formation and controlling excessive inflammation. However, the bulkiness and inflexibility of their electrodes can result in conformational incompatibility with the wound.
For their ePatch solution the team chose silver nanowire electrodes that provide antibacterial properties and deliver high conductivity under strain. The electrodes are embedded in alginate, a gelatinous substance which maintains good moisture levels and biocompatibility and is presently used in absorbent surgical dressings.
Through a chemical modification of the alginate and the addition of calcium, the team produced a material increased electrode stability and function. Further adjustment of the silver nanowire/modified alginate ratio gave the team a flexible, precisely printable gel (bio-ink), which would produce a patch with customisable conformity to various wound shapes and sizes. In addition, the calcium added to the mix induced cell proliferation and migration to the wound site, promoting the formation of blood vessels.
To fabricate the e-Patch, a template was layered onto a silicone sheet and the bio-ink was deposited onto the template. The template was removed when the bio-ink solidified.
In a statement, TIBI researcher Han-Jun Kim, PhD, DVM said: “By careful selection of the materials and optimisation of our gel formulation, we were able to develop a multifunctional, easy to make, and cost-effective e-Patch which will greatly facilitate and accelerate wound healing.”
According to TIBI, mechanical tests demonstrated that the e-Patch exhibited improved electrode stability and conductivity, and strain tests results showed good tolerance on a level needed for normal skin deformation.
Tests conducted on cells cultured on the e-Patch showed that e-Patches pulsed with EF stimulation exhibited significantly faster cellular proliferation, migration, aggregation and alignment, as well as an increased secretion of growth factors, all contributing to faster wound healing.
Animal model studies on rats showed that ‘significantly accelerated’ wound healing results were obtained with the e-Patch. The EF stimulated e-Patch exhibited more rapid progression of the wound-healing steps and there was more directional healing process, resulting in minimal scarring, deposition of normal skin layers and hair growth following wound closure.
Other experiments confirmed the antibacterial properties of the silver nanowire electrodes, and that this property was independent of the amount of EF stimulation applied.
Further experiments tested cellular adherence to the silicone component of the e-Patch, and it was found that the silicone provided an effective, non-stick surface for cells. This feature helps to ensure that there is less skin damage and excessive scarring.
“Our ePatch offers an unprecedented combination of optimum features for accelerated wound healing,” said TIBI director and CEO Ali Khademhosseini, PhD.
The team’s findings are published in Biomaterials.