Smart bandage a fix for hard-to-heal wounds

A smart bandage that integrates a sensor can accelerate the healing of chronic wounds by real-time monitoring of moisture levels without removing the dressing, as shown in a study.

Developed by a team of researchers from the University of Bologna in Italy, the sensor is based on a conductive polymer, known as poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS). Applied onto a gauze using the screen printing technique, PEDOT:PSS measures the electrical activity caused by changes in the moisture level of the wound in real time.

“PEDOT:PSS is an organic semiconducting polymer that can be easily deposited on several substrates as a standard ink,” according to lead researcher Dr Marta Tessarolo in a commentary released by Frontiers Science News.

Aside from the sensor, a cheap, disposable, and bandage-compatible RFID tag, similar to those used for clothing security tags, is also added onto the gauze. The tag facilitates wireless communication of moisture level data through a smartphone. This way, healthcare staff are alerted when a bandage needs to be changed, Tessarolo pointed out.

“The final device results in a low-cost, user friendly, disposable, and wirelessly connected patch,” she said.

Maintaining optimal moisture levels

“The healing process of a wound depends on several factors such as moisture level, pH, temperature, uric acid, lactate and glucose levels, as well as infection status. Among them, the most relevant is the moisture,” according to Tessarolo. [Bioeng Biotechnol 2018;6:47]

When too dry, the tissue dries out. Conversely, the tissue becomes white and wrinkly in the presence of too much moisture. Both conditions can slow down the healing process. [Adv Skin Wound Care 2007;20:39-53]

“In daily practices, wound assessment is mainly based on a visual inspection. The clinicians perform a qualitative assessment of the wound’s status by removing the dressing, with the consequence of disturbing the healing process. A quantitative analysis of exudate is obtained by measuring the weight of the dressing before and after use,” Tessarolo said. J Wound Care 2006;15:149–53]

The possibility of noninvasively monitoring the moisture level of a wound in real-time, that is without removing the dressing, had been the impetus behind the development of Tessarolo and colleagues’ smart bandage. The team believed that it could significantly improve the quality of wound management, avoiding unnecessary dressing changes and personalized therapies.

Gauze–absorption layer combos

In designing the sensor and performance testing, the researchers found that the sensor response and behaviour were mainly influenced by the composition of the textile substrate or the kind of material the sensor was integrated onto. [Front Phys 2021;doi:10.3389/fphy.2021.722173]

Based on these results, the researchers used different materials to design a smart bandage composed of three different stacked layers. The first layer was a thin gauze that would be directly in contact with the wound, while the second layer was the gauze that contained the moisture sensor. The third layer was the absorbing layer, which functioned to guide the exudate flux through the sensing area, avoid stagnation, collect the total amount of exudate, and protect the wound from external impact.

When exposed to artificial wound exudate (ie, the liquid that seeps from wounds), the bandage proved to be sensitive and was able to distinguish between a dry, moist, and wet wound.

“A proper combination of gauze and absorption layer can thus be used to obtain an entirely passive smart bandage able to give an RFID tamper alarm when the wound switches from wet to dry and vice-versa,” Tessarolo pointed out.

“When a low amount of exudate is present on the wound, the gauze rayon (ie, mix of rayon and polyethylene fibres with a thickness of 0.71 mm) with the absoption layer C (ie, polyurethane foam attached under a cellulose-based mesh fabric) represents a better combination to monitor the wound healing progression,” she said.

On the other hand, when dealing with chronic wounds or blisters that exude considerable amounts of fluid, the gauze PET (ie, an open mesh fabric based on polyethylene terephthalate with a thickness of 0.25 mm) plus absorption layer PE (ie, a thick layer of nonwoven cotton with an absorption capability of 10 g/g) is a more suitable combination, since it is able to store a large amount of fluid, according to Tessarolo.