Can Microscopic Needles Help Treat Skin Cancer?

Drug–loaded dissolving microneedles may offer an effective, convenient alternative treatment for patients with the most common type of skin cancer.

About eight out of 10 skin cancers are basal cell carcinomas (BCC). These tumours start in the top layer of the skin and are often related to sun exposure. Among the different subtypes, superficial BCCs usually present as flat red patches on top of the skin while nodular BCCs are translucent pearly–white lumps located deeper below the surface.

Because BCCS tend to grow slowly, most are curable if they are detected and treated early. Surgery is the most common treatment, but some patients will opt for alternatives that can administer themselves and may improve cosmetic outcomes.

One of the most effective non–surgical treatments is a cream called imiquimod, which works by boosting the body’s immune response against the cancer cells. But despite its effectiveness, the drug has limited ability to permeate into the skin – and is currently only used in patients with early superficial BCCs. 

Developing new ways to get imiquimod the drug into the lower layers of the skin could help widen its therapeutic potential to patients with nodular BCCs.

A New Type of Drug Delivery

Microneedles are a promising new drug delivery system that work by generating transient channels that promote the entry of medicines into and across the skin.

Many formulations currently under investigation are based on solid stainless–steel microneedles. But these are limited by the short time that the channels remain open, reducing the amount of drug that can be delivered to the tumour. So researchers are also investigating the potential of dissolving microneedle systems, which could offer a more effective strategy.

In a new study, published in the International Journal of Pharmaceutics, researchers explore the delivery of imiquimod using polymer-based dissolving microneedles for treating nodular BCC.

Reaching Deeper Skin Layers

The researchers developed polyvinylpyrrolidone–co–vinyl acetate (PVPVA) microneedles loaded with imiquimod. They then carried out a series of experiments to evaluate the skin–penetrating ability of the new formulation compared with a cream that is already used in the clinic to treat superficial BCCs.

The team used high-performance liquid chromatography (HPLC) to measure the levels of the drug that permeated through full-thickness pieces of pig skin over 24 hours. Both formulations showed similar results – despite the microneedles having six-fold lower drug loading. Further experiments demonstrated that the drug reached the lower layers of skin through microneedle–based delivery, whereas it largely remained within the upper layer after the cream application.

The researchers used ultrapure water from an ELGA PURELAB® laboratory water purification system for their experiments, minimising the risk of introducing contaminants that may affect their results.

Promising Potential

This study suggests that imiquimod–loaded PVPVA microneedle systems could provide a useful new approach for targeted drug delivery into the skin. The next steps will involve in vivo and clinical studies to explore its potential effectiveness at treating nodular BCC.

Such microneedle–based formulations could one day provide an effective, convenient alternative for patients with this common type of skin cancer who would prefer a non–surgical treatment. 

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Reference:

1. Sabri, A.H. et al. Intradermal delivery of imiquimod using polymeric microneedles for basal cell carcinoma. Int J Pharm. 2020;119808 doi: 10.1016/j.ijpharm.2020.119808

Dr Alison Halliday
After completing an undergraduate degree in Biochemistry & Genetics at Sheffield University, Alison was awarded a PhD in Human Molecular Genetics at the University of Newcastle. She carried out five years as a Senior Postdoctoral Research Fellow at UCL, investigating the genes involved in childhood obesity syndrome. Moving into science communications, she spent ten years at Cancer Research UK engaging the public about the charity’s work. She now specialises in writing about research across the life sciences, medicine and health.