Biophysics Characteristic of Human Hair Keratin by Impedance Spectroscopy

Havrylyak V. V., Iaremkevych O. S.

METHODS AND METHODOLOGIES

Scentific article

Impedance spectroscopy, based on electrical impedance measuring of various objects, including biological, is analytical technique that has found widespread use in biology and medicine. It has been known that impedance of biological tissue reflects its biophysical properties in the frequencies range from 1 Hz to 100 kHz. Today the electric impedances used in a wide range of clinical trials, particularly for the differentiation of various types of cancer, tomography and the analysis of the body content. The literature data inform about impedance characteristics of the epidermis, skin and nails but little attention has been paid to studies the dielectric properties of human hair. The main purpose of this research is to examine the biophysical characteristics of human hair by impedance spectroscopy in response to chemical factors after the action of the alternating current at a frequency from 1 Hz to 100 kHz. In the experiment human hair with an average diameter of d = 67,3 µm were used. Hair treatment with 10 % aqueous solution of thioglicolic acid at 37° C during 15 min was designed. The alternating current of varying fre- quency passed through the human hair and bioimpedance Z (Ohm) and angle (degree) were measured. Structural changes in the surface of the untreated and chemically treated hair were evaluated by scanning elec- tron microscopy. The destruction of cuticle layer of human hair after the influence of thioglicolic acid was observed. It should be noted that the reliable differences in bioimpedance of untreated and chemically treated hair are ob- served only in the low-frequency range. These changes, perhaps, are related to the dielectric properties of cuticle layer of hair, while impedance in the high-frequency range is associated with cortex. It has been shown that the electric impedance of keratin fibers depends linearly on the frequency of the alternat- ing current. Obtained results show that impedance of the untreated hair at current frequency from 1 Hz to 40 kHz is significantly higher compared to chemically treated hair. The lowest value of bioimpedance both untreated and chemically treated hair was fixed at a frequency of 10 kHz (3. 59 Ohm and 1. 77 Ohm, P 2264 > 0,01 respectively). Lower impedance of chemically treated hair is apparently due to the rupture of disulfide and hydrogen links between polypeptide chains of keratin. It has been detected that the phase angle of permittivity of chemically treated hair, regardless of the alternating current frequency, is lower compared to the untreated hair and its lowest value was fixed at a frequency of 40 kHz (-73. 87° and -61. 25° respectively, P 2264 > 0,01). These changes are obviously related to the capacitive characteristics of keratin fibers, which depend on the mo- lecular mobility of -keratin chains, while their conductivity depends on the mobility of water molecules associated with the polar groups of the keratin molecules. Thus, hair treatment with aqueous solution of thioglicolic acid affects the structure of cell-membrane complexes, primarily by changing their polarization properties. It was concluded that the human hair is characterized by dielectric dispersion and impedance components – conductivity and capacitance depend on the state of the keratin fibers.

human hair, electrical impedance, angle , structure, thioglicolic acid

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