FN1 and atrial fibrillation: GAGs doubly modified by oxidation and methacrylation can covalently bind interpenetrating network (IPN) hydrogels composed of fibronectin and polyethene glycol diacrylate (PEGDA) to natural AF tissue, which produces a higher lap shear bond strength than riboflavin cross-linked and genipin cross-linked fibronectin hydrogels.