Non-invasive skin sampling: optimization of sample collection and extraction; Enhancing cytokine recovery by the modification of extraction solvents and the use of alternative sampling methods

Abstract

Cytokines are a group of proteins that play a crucial role in cell communication within the immune system and are frequently studied as biomarkers for assessing skin condition. However, many inflammatory cytokines of interest are present at levels too low to be detected in skin surface samples. The aim of this master’s thesis was to refine a non-invasive skin sampling technique, enhancing cytokine recovery by optimizing both the sample collection method and the cytokine extraction solvent. Improved cytokine recovery leads to more accurate analysis of the skin condition. This clinical study involved two rounds of skin sample collection from test participants. In the first round, samples were collected using the tape stripping method, and cytokines were extracted from the tapes using combinations of two buffers and three detergents at three different concentrations. In the second round, samples were collected via tape stripping and skin swabbing. The samples were extracted using the most effective solvents identified in the first round, allowing for a comparison of the performance of the collection methods. Cytokine analysis was conducted using ELISA (enzyme-linked immunosorbent assay), complemented by the Micro BCA Protein Assay to determine the total soluble protein concentration of the samples. Statistical evaluations were carried out using ANOVA (analysis of variance). The results indicate that Tris-HCl combined with 0.5% Triton X-100 and 0.5% β- dodecyl maltoside achieved the highest recovery of the cytokines IL-1α and IL-1RA, with swab being the most effective sampling method. For TNF-α, the optimal extraction solvent was Tris-HCl with 0.005% Tween 20, and the optimal collection method proved to be Leukofix tape, which was also true for IL-8. However, IL-8 and IL-6 levels were generally at or below the detection limit, which is why no definitive conclusions could be drawn from those data.