Premium
Dielectric properties of alginate beads and bound water relaxation studied by electrorotation
Author(s) -
Esch Mandy,
Sukhorukov Vladimir L.,
Kürschner Markus,
Zimmermann Ulrich
Publication year - 1999
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/(sici)1097-0282(199909)50:3<227::aid-bip1>3.0.co;2-y
Subject(s) - conductivity , dielectric , chemistry , dispersion (optics) , relaxation (psychology) , permittivity , electrical resistivity and conductivity , self healing hydrogels , relative permittivity , materials science , analytical chemistry (journal) , polymer chemistry , chromatography , optics , optoelectronics , psychology , social psychology , physics , electrical engineering , engineering
The electrical and dielectric properties of Ba 2+ and Ca 2+ cross‐linked alginate hydrogel beads were studied by means of single‐particle electrorotation. The use of microstructured electrodes allowed the measurements to be performed over a wide range of medium conductivity from about 5 mS/m to 1 S/m. Within a conductivity range, the beads exhibited measurable electrorotation response at frequencies above 0.2 MHz with two well‐resolved co‐ and antifield peaks. With increasing medium conductivity, both peaks shifted toward higher frequency and their magnitudes decreased greatly. The results were analyzed using various dielectric models that consider the beads as homogeneous spheres with conductive loss and allow the complex rotational behavior of beads to be explained in terms of conductivity and permittivity of the hydrogel. The rotation spectra could be fitted very accurately by assuming (a) a linear relationship between the internal hydrogel conductivity and the medium conductivity, and (b) a broad internal dispersion of the hydrogel centered between 20 and 40 MHz. We attribute this dispersion to the relaxation of water bound to the polysaccharide matrix of the beads. The dielectric characterization of alginate hydrogels is of enormous interest for biotechnology and medicine, where alginate beads are widely used for immobilization of cells and enzymes, for drug delivery, and as microcarriers for cell cultivation. © 1999 John Wiley & Sons, Inc. Biopoly 50: 227–237, 1999