Dielectric spectroscopy of chemically stabilized pericardium tissue at sub-zero temperatures

In this paper dielectric spectroscopy is used as a tool for the investigation of crosslinking processes in chemically modified collageneous tissues. Measurements in the frequency range of 10/sup -1/ to 10/sup 7/ Hz and at temperatures 180, 200 and 220 K have been performed for collageneous porcine pericardium tissues, crosslinked with glutaraldehyde (GA) and dimethyl suberimidate (DMS) reagents for exposure times ranging from 15 min to 2 h. The dielectric loss spectra allowed detection of a shift of the main relaxation process to lower frequencies upon GA or DMS treatment. The observed increase of relaxation times can be interpreted as a result of the crosslinking-induced changes in dipolar polarization of collagen bound water as well as in water-assisted polarization of polar sidegroups in collagen polypeptide chains. It has been found that the relaxation time reaches a maximum value after 1 h of chemical treatment for both reagents. This result can support earlier findings, which have shown that the major part of crosslinks in collagen is created over the first hour of the chemical modification.