Indian researchers have developed a smart wound-healing nanofibrous mat that interacts with the body to help it heal faster and without scarring.
The mat is made of a non-protein polymer (PVA) mixed with silk protein and coated with an antibiotic and epidermal growth factor. It heals wounds that have all the layers of the skin removed and are as big as 6 mm in diameter.
While conventional dressing materials only absorb fluids and blood, the smart material expedites the healing process. It will be a big boon for diabetics, for whom wound-healing is very slow. The results were published recently in the journal Acta Biomaterialia.
A team led by Prof. Biman B. Mandal from the Department of Biosciences and Bioengineering, Indian Institute of Technology (IIT) – Guwahati, and the corresponding author of the paper evaluated the potential of non-mulberry silk (wild silk) and mulberry silk (domesticated silk).
While complete wound healing took 21 days in control, it was just 10-11 days in the case of mats made of wild silk.
When wound healing takes place normally, body cells in and around the wound along with progenitor cells are brought to the wound site for repair. But the recruitment of the cells to the wound site is slow and hence the healing takes time. “But in our case, the wild silk has an amino acid sequence (RGD – arginine glycine aspartate), which possibly attracts more cells thus accelerating the healing process and also allowing the cells to attach better. Mulberry silk does not have this amino acid sequence and so the healing is comparatively slower,” he says.
While the epidermal growth factor promotes the development of cells, the antibiotic Ciprofloxacin inhibits the growth of commonly seen bacteria. “Generally, antibiotics have a short life span. So we embedded the antibiotic in the matrix so that the drug gets released for up to 80 hours or more,” Prof. Mandal says.
The researchers used the protein taken from two different types of wild non-mulberry silk (commonly known as muga and eri) to synthesise the nanofibrous mat and compared its performance with mats synthesised using mulberry silk, PVA (a polymer approved by the U.S. Food and Drug Administration) and control.
While complete wound healing took 21 days in control, it was 18 days in the case of PVA, 15 days for mats with mulberry silk and 10-11 days for mats made of wild silk. “We have started studying the wound healing property of the mats made of wild silk in diabetic wounds and have got encouraging results,” says Prof. Mandal. The results on diabetic wounds are yet to be published.
In rabbits, the healing process followed the same pathway of normal healing despite the wound being critical in size and full-thickness; there was no scarring. The mat was tested on mice to understand the inflammatory response, while the wound healing studies were carried out on rabbits. The silk mats (mulberry and non-mulberry) did not cause any inflammation and were found to be biocompatible in mice.
Complete skin regeneration was seen when the wounds in rabbits were treated with wild silk mats. “Besides well-formed collagen bundles, the healed wounds had sebaceous glands and hair follicles when wild silk mats were used. Mulberry silk mats too closed the wound but sebaceous glands and hair follicles were significantly fewer in number. Also, we could see sebaceous glands and hair follicles as early as 14 days when wild silk mats were used,” says Dimple Chouhan from IIT Guwahati and the first author of the paper.