Admittance Relaxation Time Distributions (aRTD) for Quantification of Protein Concentration

• Published in: IEEE sensors journal 2024-12, p.1-1
• Main Authors: Wicaksono, Arbariyanto Mahmud, Kawashima, Daisuke, Takei, Masahiro
• Format: Article
• Language: English
• Subjects: Admittance; Admittance relaxation time distributions; Circuits; Electrical spectroscopy; Equivalent circuits; Fitting; Frequency measurement; Impedance; Impedance measurement; Protein concentration quantification; Proteins; Sensors; Spectroscopy
• ISSN: 1530-437X
• DOI: 10.1109/JSEN.2024.3512482

The admittance relaxation time distributions (aRTD) has been proposed for the quantification of protein (albumin and ɣ-globulin) concentration c . The aRTD extracts peaks of distribution function ɣ [S] at relaxation times τ [s] from measured admittance τ [S]. In order to clarify the relationship between ɣ, τ, and c , aRTD was performed on solutions and porcine subcutaneous adipose tissue (SAT) with an injected current frequency f from 10Hz to 1MHz under the albumin concentration Alb c of 0.80 g/dL to 2.30 g/dL, the ɣ-globulin concentration Glo c of 0.40 g/dL to 1.15 g/dL, and protein mixtures PM c . As the results, two peaks (P 1 and P 2 ) of ɣ P1 at τ P1 from 0.014 s to 0.083 s and ɣ P2 at τ P2 from 0.98 μs to 1.27 μs were extracted, which changes alongside an increase in Alb c , Glo c , and PM c . In order to evaluate the predictability and accuracy of aRTD, the aRTD ɣ P1 and aRTD τ P1 extracted by aRTD are compared with iRTD ɣ P1 and iRTD τ P1 extracted by typical impedance RTD (iRTD). Regression line analysis shows c is linearly proportional to aRTD ɣ P1 and inversely proportional to aRTD τ P1 with a coefficient of determination R 2 above 0.8, which is much larger than R 2 between c and P 1 extracted by iRTD. The aRTD on SAT provides additional correlation through ɣ P2 at τ P2 , which increases proportionally to Glo c and inversely proportional to Alb c and PM c . Moreover, the average fitting error ϵ of aRTD is smaller than ϵ of iRTD by 12%, which highlights aRTD accuracy in the fitting.