Bonding of cartilage blocks after treatment with surface-degrading reagents and subsequent cross-linking. Adhesive strength as a measure of bonding was determined immediately after cross-linking with (a) glutaraldehyde, (b) 1-Ethyl-3-diaminopropyl-carbodiimide (EDC)/N-hydroxysuccinimide (NHS), (c) genipin, or (d) transglutaminase. Before cross-linking, cartilage blocks were pre-treated with either trypsin, pepsin, or guanidine, or blocks were cross-linked without pre-treatment ('no pre-treatment'). In the control group, neither pre-treatment nor cross-linking were performed. Bars represent the mean with standard error of the mean of 20 samples derived from 4 independent experiments, each with 5 replicates per group. P values are from Mann Whitney-U test for pairwise comparisons.