Photothermal surgical dressing prevents skin cancer recurrence

Photothermal surgical dressing
Photothermal therapy: A novel surgical dressing promotes tissue healing and prevents tumour recurrence by eliminating residual melanoma cells. It could also enable smaller surgical resections than standard procedures. (Courtesy: University of Nottingham/Adv. Functional Mater. 10.1002/adfm.202205802)

A highly effective surgical dressing designed for patients with skin cancer could speed up the healing process after surgery. Developed by researchers in the UK and China, the dressing also exploits photothermal effects to prevent tumours from reappearing.

Photothermal therapy (PTT) has emerged as a promising technique for treating skin cancer. It involves injecting tumours with conductive nanomaterials that convert light into heat, and then illuminating them with specific wavelengths to kill cancer cells. For large tumours, this treatment must be carried out in combination with surgery, leaving wounds that must be treated with surgical dressings to prevent infection.

Recently, more advanced treatment methods have been proposed in which PTT is integrated directly into the surgical dressings. The hope is that these materials could promote healing in the skin, while preventing tumours from re-emerging after treatment. The theorized designs for these dressings are based around the photothermal material reduced graphene oxide (rGO). This material can be synthesized by bonding oxygen-containing groups to single-layer graphene sheets, and then subjecting them to a process that reduces their oxygen content.

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Currently, this technique faces a major roadblock: rGO is toxic to living cells, meaning it can’t be used directly in surgical dressings. Before the reduction process, graphene oxide can be made more biocompatible by combining it with biomolecules like peptides and proteins. However, in order to enhance its photothermal response, the material must then endure a harsh reduction process: carried out in a sealed reactor at temperatures exceeding 180°C, in an environment of pure ethanol. While reducing the material’s graphene oxide, this also destroys the more delicate biomolecular structures attached to it.

The team, led by Yuanhao Wu at the University of Nottingham, has now developed a new technique that allows the reduction process to occur at lower temperatures. It involves an assembly of graphene oxide flakes, encased in a protein biopolymer named “elastin-like recombinamer” (ELR), which is known for its ability to promote skin repair and heal wounds. By controlling the molecular interactions between these structures, the team produced a multi-layered graphene oxide core, surrounded by an ELR shell.

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Afterwards, the researchers exposed this structure to a disinfectant containing 70% ethanol. Typically, this liquid would penetrate straight through bacteria and the protein shells of viruses. In this case, it passed straight through the ELR shell to interact with the pure graphene oxide inside. This allowed the team to trigger the reduction process at far lower temperatures of 85°C, while leaving the ELR’s structure intact.

Altogether, the final structure combined the high PTT efficiency of rGO with the capacity to promote tissue regeneration. As an added bonus, the material was sterilized through its treatment with ethanol.

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The researchers validated their approach using in vivo experiments in mice, demonstrating that the dressings could prevent tumour recurrence and promote wound healing after tumour resection. The material only needed 15 s exposure to near-infrared light every 48 hr to be effective.

Wu’s team hopes that the unique dressings could lead to practical post-surgery treatments that patients with skin cancer could deliver at home: both speeding up the healing of their surgical wounds, and preventing tumours from re-emerging as their skin regenerates.

The study is described in Advanced Functional Materials.