Photochemical cross-linking of type I collagen with hydrophobic and hydrophilic 1,8-naphthalimide dyes

This study extends our previous studies of the photochemical cross-linking of collagen and bonding of collagenous sheets of dura mater using the hydrophobic 1,8-naphthalimide N,N'- bis-(2-({hexylamino)-5-bromo-1H-benz [de]isoquinolin-1,3(2H)-dion-6- yl]amino}ethyl)hexanediamide. We have obtained hydrophilic forms of the bifunctional molecule introducing a spacer and ligands containing alternating carbon-oxygen bonds (polyethers) wherein the oxygen moieties form hydrogen bonds. Additional hydrophilicity is attained by incorporating of an amino group (positive charge) at the end of each ligand. Ongoing studies with these forms of the bifunctional 1,8 naphthalimides have demonstrated welding of meniscal cartilage, articular cartilage, and cornea. These results suggest that the hydrophilic form of the dyes is able to penetrate readily the anionically charged proteoglycan matrix of these tissues and cross-link collagen molecules and possibly the protein cores of the proteoglycans. Gel electrophoretic studies have been performed to assess the photochemical cross-linking of these connective tissue proteins with these new forms of the paththalimide dyes.