Enzymatically crosslinked porous composite matrices for bone tissue regeneration

Three-dimensional porous hydroxyapatite/collagen (HA/Coll) composites with a random pore structure were obtained by freeze-drying and crosslinked by an enzymatic treatment using microbial transglutaminase (mTGase). The procedure resulted in improved mechanical strength and thermal stability of the scaffolds. The scaffolds were characterized in terms of their stability (Coll release, swelling, collagenase-mediated degradation), thermal properties (thermogravimetric analysis, differential scanning calorimetry), mechanical behavior under compression and cell compatibility. Enzymatic treatment stabilized the sponges to water vapors, with measurable swelling ratio between 100% for HA/Coll/mTGase 0/100 to 5% for HA/Coll/mTGase 80/20. Weight loss in water due to Coll release was between 2 and 10% in mTGase-crosslinked samples and decreased with increasing HA content. Cultures of MG63 osteoblast-like cells and human umbilical vein endothelial cells (HUVEC) showed good adhesion and proliferation on the scaffolds, good viability (through MTT test, 100-150% of control), and good differentiation (alkaline phosphatase, up to 40 UI/L with respect to 35 UI/L for control).