Quantification of dermis sodium concentration in skin layers by power spectral density drop of square-wave electrical impedance spectroscopy (PSDd-sEIS)

Abstract

Assessing dermis sodium concentration in skin is essential since an excessive amount of sodium is associated with vascular function disorders. In this research, dermis sodium concentration has been quantified by the power spectral density drop of square-wave electrical impedance spectroscopy (PSDd-sEIS). PSDd-sEIS is composed of three stages: (1) dermis voltage measurement, (2) PSDd calculation, and (3) dermis sodium quantification. In the 1st stage, three electrodes are arranged to measure voltage under the constant current of square-wave. In the 2nd stage, is evaluated by the first and third harmonic frequency from . In the 3rd stage, is quantified by the developed linear regression. To obtain the highest sensitivity between c and four measurement factors (square-wave frequency duty-cycle , electrode distance d, and electrode diameter ø) were optimized using numerical simulations of a skin model. Experiments on multi-layered skin under various c in the range of 5 nM–50 mM were conducted by PSDd-sEIS hardware with optimized measurement factors of , , , and . As the results, the quantification of c has a good accuracy with the normalized sensitivity =0.87 and determination coefficient R2 = 0.92. The measurement factors of and affect the power of square-wave excitation to pass through the high resistivity barrier of the stratum corneum, while the measurement factors of d and ø affect the stability of current flow in the dermis.