Sepiolite, a magnesium silicate, binds collagen resulting in a complex which has a gel-like structure when hydrated. The binding of the protein to the clay decreases its degradability by collagenase, and no degradation was observed after treatment of the complex with glutaraldehyde. Extracts of both the untreated and the glutaraldehyde-treated complex are biocompatible for fibroblast growth. Based on its properties, this material should be considered in the design of biomaterials.