Optimization of protein extraction from skin tape strips for biomarker assessment

Stratum corneum tape-stripping is a non-invasive alternative to biopsies for biomarker analysis in inflammatory skin diseases, but low-abundance protein detection is challenging. High extraction yield is therefore crucial, yet extraction protocols vary. Because total protein collected on the tapes is commonly used for biomarker normalization, factors influencing its measurement can impact data interpretation. We sought to investigate how extraction conditions such as buffer type, volume, and sonication time affect both total protein and cytokine biomarker yield. Sequential tape strips were collected from lesional skin of 19 patients with chronic hand eczema and matched skin sites in 13 healthy controls. Tapes were cut for equal allocation across experimental conditions. Total protein was measured by the Micro BCA assay and biomarkers by the ELISA and MSD immunoassays, with blank tapes and buffers as controls. T-PER buffer with protease inhibitor CAA yielded higher cytokine levels than PBS or PBS-Tween ± CAA, but also increased BCA assay background levels. Longer sonication and smaller extraction volumes exacerbated background without improving cytokine yield. Hence, normalization of biomarker levels may be confounded by these methodological factors. Considering the buffer, its volume, sonication time, and the inclusion of negative controls is therefore instrumental when designing studies.