Abstract: The present invention relates to a process for cross-linking a proteinaceous material. The process comprises: i) soaking the material to be cross-linked in an agueous solution of high osmolality; ii) incubating the material in an agueous buffer including an amount of a photooxidative catalyst sufficient to catalyze photooxidation of the material; and iii) irradiating the material and the catalyst of step (i) with light that includes a range of wavelengths selectively absorbed by the catalyst. Irradiation is effected under conditions such that cross-linking of the material occurs. In a further embodiment, the present invention relates to a cross-linked product produced by the above-described method.