pH Sensing of Interstitial Skin Fluid with Non-Invasive Hydrogel Patches Can Improve Sensitivity of Skin Cancer Diagnosis in Primary Care

Background: Cancers of the skin are the most common of all cancers and affect almost equally women and men. The number of cases is increasing rapidly, including for melanoma, one of the deadliest forms.

Other skin cancer types such as basal cell carcinoma (BCC) and cutaneous squamous cell carcinoma (cSCC) are less deadly but also much more common.

They too require fast intervention and are notoriously hard to diagnose, especially at an early stage, without the help of a biopsy.

Skin cancer diagnosis is most commonly derived from visual or digital inspection of a skin lesion by a trained professional, ideally including dermoscopy.

Identification of suspicious skin lesions in primary care are typically followed by an urgent referral, leading to a skin biopsy and histopathological examination.

Whilst primary care clinicians are generally accurate at recognising suspicious skin lesions, and despite promising improvements in sensitivity when using artificial intelligence and machine learning algorithms, only around 15% of urgent referrals result in a malignancy diagnosis.

This low positive predictive value is responsible for a large number of skin biopsies performed unnecessarily which is distressing to the patient (long time-to-result and morbidities) and costly to the NHS which spends >£35M every year on unnecessary diagnostic procedures for skin cancer only.

With extracellular pH of tumour interstitial fluid being abnormally acidic compared to that of healthy tissue, we reasoned that measuring pH in interstitial skin fluid (ISF) from suspicious skin lesions could improve skin cancer diagnosis.

Aims: Our solution is to develop a novel, non-invasive, pH-sensing skin patch to be used alongside visual inspection to improve skin cancer patient triage accuracy in primary care or community settings.

Methods: Bespoke hydrogel-based microneedle patches will be used to electrochemically interrogate, both in vitro and in vivo, the pH of ISF within/around skin lesions in a rapid and painless manner.

These patches will be used on a cSCC mouse model to accurately monitor, in vivo, local changes in ISF pH from the first appearance of pre-cancerous lesions.

How the results of this research will be used: This multidisciplinary project will (1) validate pH in ISF as a clinically useful biomarker for the early diagnosis of skin cancers and (2) deliver a medical device prototype to measure it non-invasively and at the point-of-care.

Results will enable us to apply for larger scale follow-on funding to further validate both the biomarker and the technology on human skin biopsies.