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

• Published in: IEEE sensors journal Vol. 25; no. 3; pp. 4135 - 4142
• Main Authors: Wicaksono, Arbariyanto Mahmud, Kawashima, Daisuke, Takei, Masahiro
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.02.2025; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Adipose tissue; Admittance; Admittance relaxation time distribution (aRTD); Albumins; Circuits; Distribution functions; Electrical impedance; Equivalent circuits; Fitting; Frequency measurement; Impedance; Impedance measurement; protein concentration quantification; Proteins; Relaxation time; Sensors; Spectroscopy
• ISSN: 1530-437X; 1558-1748
• DOI: 10.1109/JSEN.2024.3512482

The admittance relaxation time distribution (aRTD) has been proposed for the quantification of protein (albumin and ɣ-globulin) concentration <inline-formula> <tex-math notation="LaTeX">c </tex-math></inline-formula>. The aRTD extracts peaks of distribution function ɣ [S] at relaxation times <inline-formula> <tex-math notation="LaTeX">\tau </tex-math></inline-formula> [s] from measured admittance <inline-formula> <tex-math notation="LaTeX">Y </tex-math></inline-formula> [S]. In order to clarify the relationship between ɣ, <inline-formula> <tex-math notation="LaTeX">\tau </tex-math></inline-formula>, and <inline-formula> <tex-math notation="LaTeX">c </tex-math></inline-formula>, aRTD was performed on solutions and porcine subcutaneous adipose tissue (SAT) with an injected current frequency <inline-formula> <tex-math notation="LaTeX">f </tex-math></inline-formula> from 10 Hz to 1 MHz under the albumin concentration <inline-formula> <tex-math notation="LaTeX">^{\text {Alb}} {c} </tex-math></inline-formula> of 0.80-2.30 g/dL, the ɣ-globulin concentration <inline-formula> <tex-math notation="LaTeX">^{\text {Glo}} {c}~{R} ^{{2}} </tex-math></inline-formula> above 0.8, which is much larger than <inline-formula> <tex-math notation="LaTeX">{R} ^{{2}} </tex-math></inline-formula> between <inline-formula> <tex-math notation="LaTeX">c </tex-math></inline-formula> and P1 extracted by iRTD. The aRTD on SAT provides additional correlation through ɣP2 at <inline-formula> <tex-math notation="LaTeX">\tau _{\text {P2}} </tex-math></inline-formula>, which increases proportionally to <inline-formula> <tex-math notation="LaTeX">^{\text {Glo}} {c} </tex-math></inline-formula> and inversely proportional to <inline-formula> <tex-math notation="LaTeX">^{\text {Alb}} {c} </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">^{\text {PM}} {c} </tex-math></inline-formula>. The average fitting error <inline-formula> <tex-math notation="LaTeX">\epsilon </tex-math></inline-formula> of aRTD is, moreover, smaller than <inline-formula> <tex-math notation="LaTeX">\epsilon </tex-math></inline-formula> of iRTD by 12%, which highlights aRTD accuracy in the fitting.