Advanced hydrogels for wound dressings?


Novel bio-materials could form a new class of medical dressing, aiding in recovery

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Image by Marco Verch

By Emily Jones

THINK OF A time when you injured yourself – maybe you grazed your knee on the concrete, or burned your hand grasping a still-hot baking tray. A first aider would cover your injury with a dressing. However, what often happens is, as the body attempts to heal, the gauze dries out and gets stuck to the newly forming scab. This means when it’s time for fresh dressing, the new skin cells are (often painfully) removed and the vulnerable flesh is once again exposed to the elements. This makes gauze and other currently available barrier-type wound dressings somewhat counterproductive in helping to heal.

Now, imagine a future where a child comes home from school after a graze on the knee or elbow, but this time, their wound has been treated with a skin-like sheet produced by bacterial cell cultures. A group at the University of Wolverhampton, led by Dr. Abhishek Gupta, has been making this a reality through investigating the use of cellulose hydrogels as wound coverings.

Hydrogels are long protein chains which have hydrophilic properties, meaning they can bond to water-based liquids. This arises from their electrically-charged groups, held in a 3D structure by crosslinks between ions or hydrogen. This means hydrogels are non-adhesive – and therefore are easy to remove – and are designed to apply intensive moisture to the wound, which expedites the healing process and causes a therapeutic soothing and cooling effect.

The bacteria which produce these hydrogels are known as Gluconacetobacter xylinus, the most effective known producer of bacterial cellulose – a strong structural material also found in plant cell walls. Changing the size and shape of the vessel containing the bacterial culture allows researchers to create tailor-made dressings in suitable shapes for the patient’s body and wound. Due to their 3D network structure, these dressings can be loaded with active ingredients to further aid healing. The Wolverhampton group has been exploring the loading of curcumin and silver into the fibrous cellulose structure. Curcumin is a naturally occurring bioactive compound found in turmeric, famed for its anti-inflammatory benefits, while silver is a well-known anti-microbial agent.

Together, these ingredients can massively boost the hydrogel’s already impressive healing power; researchers have shown that this combination can fight off three of the most common infection-causing germs – Staphylococcus aureus, Pseudomonas aeruginosa, and Candida auris.

Ring-shaped sugars called cyclodextrins were used to increase the solubility of curcumin, so these molecules can travel via the moist hydrogel barrier directly to the site of the wound and prevent infection.

To obtain increased control over the release of silver, a two-part system was created within the structure involving two key compounds: silver zeolites and silver nitrate. Zeolites are effective cage-like holders for a therapeutic agent, which have various pore sizes and structures, suiting them to contain different molecules. Silver nitrate is commonly used to effectively cauterise burns by forming a barrier to infection.

Hydrogels, along with all the previously described benefits, can also be formulated to have a stimuli-responsive release system. Earlier studies investigated the use of poly(2-hydroxyethyl methacrylate), a gel first used in soft contact lenses, which can selectively form bonds with a photo-active, nitrogen-based molecule. In other words, shining a light on this dressing induces the release of antimicrobials, making an antiseptic that could be controlled by light – even by the torch on your phone.

Whether these innovative solutions will be on the market anytime soon remains uncertain, but they do give us a glimpse of a future for our NHS where chronic wounds, such as those in patients with diabetes which would otherwise be considered for amputation, could instead be successfully and economically treated to prevent further complications, improving patient outcomes and NHS efficiency.