Collagen cross linking agents: design and development of a multifunctional cross linker.

A new cross linking reagent based on the first-generation polyamidoamine dendrimer (G.1 PAMAM) has been synthesized by reaction of the PAMAM with eight equivalents of p-nitrophenyl diazopyruvate. The resulting water-soluble octadiazopyruvoyl PAMAM (8G.1 DAP, 1.3) was shown to undergo Wolff rearrangements upon photolysis in methanol at λ > 300 nm to yield the methyl esters of the ketenes formed from the loss of nitrogen. 8G.1 DAP also forms strong bonds with dehydrated collagen with glass as high as 36 N cm -2 . Collagen to collagen bonds with tensile strengths as high as 92 N cm -2 were observed with fully dehydrated tissues. The bonding decreased rapidly with increasingly hydrated tissue possibly due to the increased distance between the collagen fibrils and the competition of H 2 O for the free ketene functions.