Application of biodegradable piezoelectric PLLA nanofibers on a wound in combination with external ultrasound to produce controllable surface charge for wound healing and prevention of bacterial infection. The biocompatible scaffold facilitates tissue ingrowth for skin healing and prevents bacterial infections. Reproduced with permission from: Das et al., Biomaterials 301 (2023) 122270.
Skin cells grown in the nanofiber scaffold. Courtesy of Thanh D. Nguyen.A novel wound dressing scaffold material exploits the piezoelectric effect to stimulate healing and protect against bacterial infection [Das et al., Biomaterials 301 (2023) 122270, http://doi.org/10.1016/j.biomaterials.2023.122270].
Large or chronic skin wounds can be difficult to treat, requiring dressings that provide a physical barrier, prevent bacterial infection, absorb fluids while keeping tissue moist, and support the regrowth of skin. Conventional bandages and more recent biomaterials such as polyurethane and hydrogel membranes struggle to meet all these requirements.
Instead, a team from the University of Connecticut, Boston University, and New York University led by Thanh D. Nguyen turned to nanofibrous materials, which have a large surface-to-volume ratio, absorb fluids, are permeable to moisture, and flexible enough to conform to the skin and stretch with the movement of muscles. They identified piezoelectric nanofibers made from poly-L-lactic acid (PLLA) as a suitable skin-wound scaffold material.
“Our lab had developed a nanofiber PLLA scaffold, which had strong piezoelectric properties. We wanted to see if [this] piezoelectric PLLA membrane could be used to heal skin wounds and prevent infection when activated by ultrasound,” explain first author Ritopa Das and Nguyen.
The biocompatible, biodegradable PLLA scaffold is activated by external ultrasound stimulation, which produces surface charges to either promote skin regeneration (positive) or suppress bacterial growth (negative). Both in vitro and in vivo studies in mice reveal that ultrasound-activated piezoelectric PLLA scaffolds encourage the attachment and proliferation of skin cells, promote new skin formation including the hair follicles and blood vessels, and exhibit an antibacterial effect against common strains including S. aureus and P. aeruginosa.
“Our… piezoelectric PLLA scaffolds under ultrasound activation enhance gene expression and cell proliferation in fibroblasts and epithelial cells in vitro, produce reactive oxygen species that can kill bacteria, and accelerate wound closure as well as promote healthy skin formation in mice in vivo,” point out Das and Nguyen.
Not only does the ultrasound-activated piezoelectric PLLA scaffold improve the rate of wound healing, but the nanofibers also degrade naturally inside the body as the skin heals, eliminating the need for replacement or removal, which can be invasive and painful for patients.
“The PLLA scaffold is integrated with the skin and biodegrades to facilitate tissue ingrowth, avoiding the need of frequent dressing replacements, which are damaging to the healed skin and prone to infection,” they add.
The researchers now plan to test the scaffold material in larger animal models and improve the anti-inflammatory/bacterial effect with other biodegradable components.