Image: PLLA biodegradable polyester nanosheets (Photo courtesy of Tokai University).
A new nanometric biomaterial coating hugs body contours like cling-wrap, preventing bacteria from colonizing wounds.
Researchers at Tokai University (Tokyo, Japan) developed the nanosheets from poly-L lactic acid (PLLA), a biodegradable polyester that when centrifuged with water breaks up into small pieces. When poured onto a flat surface, the PLLA emulsion dries into a patchwork that forms as a single nanosheet. The researchers then tested the nanosheets’ ability to coat small and irregular shapes by dipping various objects into the mixture, including a mouse’s paw. The nanosheet patchwork effectively covered the surface of the mouse’s digits, and after it dried, it clung in place.
The researchers then tested the nanosheets on burn wounds, and found that the PLLA dressing could protect wounds against the common bacteria Pseudomonas aeruginosa
for three continuous days. With an additional coating, the nanosheets kept bacteria at bay for a total of six days, which suggests that its use could also reduce the number of dressing changes needed. In preparation for projected human clinical trials, the researchers are currently planning large-scale animal and safety tests.
In addition to PLLA nanosheets, the researchers have recently started developing a novel set of similar, super-flexible, patchwork coatings composed of polymers with a phosphorylcholine group, a range of materials that are compatible with blood and could thus act as coatings for medical devices, such as catheters. The study describing nanosheets and its application as a burn wound dressing was presented at the national meeting & exposition of the American Chemical Society (ACS), held during August 2014 in San Francisco (CA, USA).
“Existing wound dressings work well when it comes to treating burns on relatively flat and broad areas. But the human body has curves, wrinkles and ridges that present problems for these dressings,” said lead author and study presenter Yosuke Okamura, PhD. “The nanosheets can adhere not only to flat surfaces, but also to uneven and irregular surfaces without adding any adhesives.”
PLLA is a biodegradable, thermoplastic, aliphatic polyester derived from renewable resources, such as corn starch, tapioca roots, or sugarcane. It can be processed by extrusion, injection molding, casting, and spinning, providing access to a wide range of materials. Since it is biodegradable, PLLA is used as medical implants in the form of anchors, screws, plates, pins, rods, and as a mesh, breaking down inside the body within 6 months to 2 years.