Study of the dielectric function of aqueous solutions of glucose and albumin by THz time-domain spectroscopy

Abstract

We report a study of aqueous solutions of glucose and bovine serum albumin using THz time-domain spectroscopy. To describe the permittivity of the solutions of these substances, we use a simplified model being applicable in the frequency range of 0.05-2.7 THz. On the assumption that most of the water molecules become bound at high concentrations of glucose and protein in the solution, the changes in water characteristics are investigated. To improve the reliability of the results, the measurements are performed by two independent methods: the method of attenuated total internal reflection and the transmission method. Combination of the results obtained by these two methods allows expanding the spectral range towards lower frequencies.

Terahertz spectroscopy for diabetes diagnostics

“…We have previously shown the insertion of glucose into water leads only to an increase of relaxation time τ 1 of the slow Debye process of this solution. The increasing of protein albumin concentration in the solution results in a decrease of the amplitude ∆ε 1 of the slow Debye relaxation process [5]. This explains observed sensitivity of THz skin reflection spectra and blood plasma properties.…”

“…Our THz time-domain apparatus was described previously [4,5]. We used the radiation of a Ti:sapphire laser with a wavelength of 790 nm, a pulse duration of 90 fs with 1 Wt average power.…”

Spectroscopy of solutions in the low frequency extended THz frequency range

“…For the high THz frequencies, the attenuated total reflection (ATR) measurement approach is preferable, since it does not suffer from strong water absorption and implies measurements of a bulk sample; thus, eliminating an error of layer thickness measurements. Actually, these methods have considerable overlap of the spectral operation range; thus, we combine the results obtained by transmission and reflection in order to achieve a broader spectral operation range and more reliable data for water solution spectroscopy [1].…”

“…(1) to describe permittivity of such biological media as aqueous solutions. To detect small-scale changes in solutions we have normalized the transmittance (and reflectance) of the solution T BSA to that of water - To identify the reasons for the THz transmission changes of BSA solutions we have compared the experimental spectra to the relative transmission of modified model of water [1]. Such a simplified approach, implying variation of a single parameter ∆ε 1 (C), describes well the experimental spectra of aqueous solutions (particularly, of sugars and proteins) in the frequency range of at least 0.03 to 3.2 THz, which is important for practical applications of THz-TDS systems.…”

“…Slow relaxation shift of bounded water spectra.To fit dielectric function of water a well-known model with Debye-type relaxation and over-dumped oscillator components is usually applied[1][2][3][4].…”