Development of mechanically stable alginate/chondrocyte constructs: effects of guluronic acid content and matrix synthesis.

The purpose of this study was to investigate factors which enhanced the compressive properties of alginate/chondrocyte constructs. Firstly, we studied the effect of biochemical composition (high, mid and low guluronic acid content) and sterilization method on alginate properties. Secondly, we studied the biosynthetic characteristics of chondrocytes in three different alginate compositions and performed mechanical tests to determine whether the synthesis of cartilage matrix components could significantly enhance the compressive properties. 2% alginate solutions containing an initial cell density of 4 x 10(6) cells/ml were cast into cylinders and cultured for seven weeks. Compression tests, biochemistry, immunohistochemistry and electron microscopy were performed at fixed intervals during the seven-week culture period. The dynamic modulus, peak strain, and peak stress were maximum for alginate with the highest guluronic acid content. The presence of cells and their respective matrix components enhanced the equilibrium modulus of the constructs for all types of alginate, though this effect was small. Alginate containing the middle amount of guluronic acid resulted in constructs which were both mechanically stable and which promoted synthesis of cartilage matrix proteins. In experiments and applications in which the mechanical integrity of the alginate is important, the composition and purity of the alginate and its method of sterilization should be selected with care.