Non-invasive methods for early diagnosis of skin cancer are highly valued. One possibleapproach is to monitor relevant biomarkers such as tryptophan (Trp) and kynurenine (Kyn), onthe skin surface. The primary aim of this in vitro investigation was, therefore, to examine whetherreverse iontophoresis (RI) can enhance the extraction of Trp and Kyn, and to demonstrate how theTrp/Kyn ratio acquired from the skin surface reflects that in the epidermal tissue. The study alsoexplored whether the pH of the receiver medium impacted on extraction efficiency, and assessedthe suitability of a bicontinuous cubic liquid crystal as an alternative to a simple buffer solution forthis purpose. RI substantially enhanced the extraction of Trp and Kyn, in particular towards thecathode. The Trp/Kyn ratio obtained on the surface matched that in the viable skin. Increasingthe receiver solution pH from 4 to 9 improved extraction of both analytes, but did not significantlychange the Trp/Kyn ratio. RI extraction of Trp and Kyn into the cubic liquid crystal was comparableto that achieved with simple aqueous receiver solutions. We conclude that RI offers a potential fornon-invasive sampling of low-molecular weight biomarkers and further investigations in vivo aretherefore warranted.
- Bicontinuous cubic liquid crystals
- Cancer-related biomarkers
- Non-invasive extraction
- Tryptophan-to-kynurenine ratio
ASJC Scopus subject areas
- Pharmaceutical Science