Photochemical crosslinking improves the physicochemical properties of collagen scaffolds

Collagen is a natural biomaterial with excellent biocompatibility. However, unprocessed collagen has low stability and weak mechanical strength, which limits its application in tissue engineering. The current study aimed to improve the physicochemical properties of collagen scaffolds by using photochemical crosslinking. Collagen gel was reconstituted and photochemically crosslinked by using laser irradiation in the presence of a photosensitizer. Scanning electron microscope was used to characterize the surface and cross-sectional morphology. Stress-strain relationship and other mechanical properties were determined by uniaxial tensile tests. Thermostability and water-binding capacities also were analyzed by using differential scanning calorimetry and swelling ratio measurements, respectively. Photochemically crosslinked porous structures showed fine microstructure with interconnected micron-sized pores, whereas uncrosslinked controls only showed macrosheet-like structures. The stabilizing effect of photochemical crosslinking also was revealed by retaining the three-dimensional lamellae-like structures after thermal analysis in crosslinked membranes but not in the controls. Photochemical crosslinking also significantly reduced the swelling ratio, improved the stress-strain relationship, peak load, ultimate stress, rupture strain, and tangent modulus of collagen membranes. The current study showed that an innovative photochemical crosslinking process was able to produce collagen scaffolds with fine microstructures; to strengthen, stiffen, and stabilize collagen membranes; and to modify their swelling ratio. This may broaden the use of collagen-based scaffolds in tissue engineering, particularly for weight-bearing tissues.