Biomimetic polyurethane/TiO₂ nanocomposite scaffolds capable of promoting biomineralization and mesenchymal stem cell proliferation

Scaffolds with extracellular matrix-like fibrous morphology, suitable mechanical properties, biomineralization capability, and excellent cytocompatibility are desired for bone regeneration. In this work, fibrous and degradable poly(ester urethane)urea (PEUU) scaffolds reinforced with titanium dioxide nanoparticles (nTiO₂) were fabricated to possess these properties. To increase the interfacial interaction between PEUU and nTiO₂, poly(ester urethane) (PEU) was grafted onto the nTiO₂. The scaffolds were fabricated by electrospinning and exhibited fiber diameter of < 1 μm. SEM and EDX mapping results demonstrated that the PEU modified nTiO₂ was homogeneously distributed in the fibers. In contrast, severe agglomeration was found in the scaffolds with unmodified nTiO₂. PEU modified nTiO₂ significantly increased Young's modulus and tensile stress of the PEUU scaffolds while unmodified nTiO₂ significantly decreased Young's modulus and tensile stress. The greatest reinforcement effect was observed for the scaffold with 1:1 ratio of PEUU and PEU modified nTiO₂. When incubating in the simulated body fluid over an 8-week period, biomineralization was occurred on the fibers. The scaffolds with PEU modified nTiO₂ showed the highest Ca and P deposition than pure PEUU scaffold and PEUU scaffold with unmodified nTiO₂. To examine scaffold cytocompatibility, bone marrow-derived mesenchymal stem cells were cultured on the scaffold. The PEUU scaffold with PEU modified nTiO₂ demonstrated significantly higher cell proliferation compared to pure PEUU scaffold and PEUU scaffold with unmodified nTiO₂. The above results demonstrate that the developed fibrous nanocomposite scaffolds have potential for bone tissue regeneration.