Mechanical properties of the porcine pericardium extracellular matrix cross-linked with glutaraldehyde and tannic acid

Purpose The aim of study was to determine the influence of factors such as temperature and glutaraldehyde (GA) concentration on the mechanical properties of porcine pericardia, and to propose the recommended optimal conditions for a cross-linking process. It was also to verify whether tannic acid (TA), a natural cross-linking agent that stabilizes collagenous tissues by different mechanism than GA, may positively influence the strength of pericardium. Methods The samples were incubated at various temperatures (4, 22, and 37°C) and GA concentration solutions (0.6%, 1.5%, 3%) for 7 days. Three series were selected and additionally cross-linked with 0.3% TA for another 7 days. Mechanical properties of cross-linked pericardium samples, i.e. ultimate tensile strength (UTS) and elastic modulus (E), were measured in uniaxial tensile testing. The hyperelastic model for incompressible materials – isotropic by Ogden and anisotropic by Fung was utilized to describe the mechanical behaviour of treated pericardium. Results The temperature has influence on cross-linking effects; the lowest values of UTS were reported for specimens cross-linked at 22°C, while the mechanical properties of series treated at 4°C or 37°C were comparable. At a particular temperature of incubation, the GA concentrations have not affected the mechanical properties of tissues. The dependence between mechanical parameters and agent concentration was only observed for specimens treated with GA at 37°C. Conclusions The conditions of the cross-linking process affect the mechanical properties of the porcine pericardium. Room temperature (22°C) and the concentration of 1.5% GA were ineffective. The mechanical properties of GA-treated pericardium were improved by an additional TA cross-linking.