Development of an improved method for quantitative analysis of skin blotting: increasing reliability and applicability for skin assessment

Objective A novel skin assessment tool named 'skin blotting' has been recently developed, which can easily predict the skin status to avoid its deterioration. The aim of this study was to propose a normalization method for skin blotting to compensate for individual differences that can hamper the quantitative comparisons and clinical applications. Methods To normalize individual differences, we utilized a total protein as a 'normalizer' with calibration curves. For evaluation, we performed a simple simulation experiment, in which the same concentration of a protein of interest [tumour necrosis factor (TNF)-α] was applied at different volumes as a virtual individual difference. Moreover, to demonstrate the applicability of this normalization, male volunteers were recruited for skin blotting followed by the estimation of TNF-α with normalization. Results We obtained good calibration curves for total protein (R² = 0.995) and TNF-α (R² = 0.997), both of which were necessary for an exact quantification. In the simulation experiment, we estimated the exact concentration of TNF-α regardless of the applied volume, demonstrating the applicability of this normalization method in skin blotting. Further, skin blotting on human subjects showed a wide range of variation in the total protein content, although the normalization was thought to reduce such individual variations. Conclusion This study has proposed total protein normalization for skin blotting with calibration curves. This method may strengthen the quantitative performance of skin blotting, which may expand the applicability of this method as a skin assessment tool in broader fields, such as nursing and cosmetology.