Changes in serum conditioning profiles of glutaraldehyde-crosslinked collagen sponges after their treatment with calcification inhibitors

The purpose of this study was to evaluate the effects of the calcification inhibitors FeCl₃ and sodium dodecyl sulfate (SDS) on the morphology of glutaraldehyde-crosslinked type I collagen sponges and on their serum conditioning. Scanning electron microscopy (SEM) showed that the morphology of the sponges, already modified by glutaraldehyde crosslinking, underwent further changes after treatment of the hydrogels with inhibitors. Coral-like structures were found to branch from the bulk of the material especially in the case of SDS-treated samples. The composition and morphology of the conditioning layers was characterized after 48 h incubation in serum by SDS-polyacrylamide gel electrophoresis-immunoblot of the adsorbed proteins, by energy-dispersive X-ray analysis of the elements (EDX), and by SEM of the conditioned surfaces. All the samples showed the adsorption of proteins with molecular weights ranging from 10 to 203 kD. However, the peculiar adsorption of an approximately 10-kD band (complement C3 fragment) and of fibronectin were detected in the case of glutaraldehyde-crosslinked collagen. On the other hand, glutaraldehyde-crosslinked collagen treated with 0.1M FeCl₃ showed the remarkable adsorption of a 29-kD band. The glutaraldehyde-crosslinked hydrogels showed the massive precipitation of crystals on their exposed surfaces, whereas a disordered network structure surrounding the collagen fibrils was found in the case of the samples pretreated with inhibitors. A predominant precipitation of sodium and chloride was detected in all the sponges, although the ratio between the peaks changed from one hydrogel to another. The results reported in this article clearly indicate that the treatments with SDS and FeCl₃ change the surface conditioning of collagen sponges, suggesting a possible role of deposited serum solutes in affecting mineralization processes on bioprosthesis.