Tough and biodegradable polyurethane-silica hybrids with a rapid sol-gel transition for bone repair

Inorganic-organic hybrid materials have promising properties for bone repair because of the covalent bonding between their inorganic and organic phases. This desirable interaction allows the limitations of composite materials, such as inhomogeneous biodegradation rates and nonbiointeractive surfaces, to be overcome. In this study, a polycaprolactone (PCL)-based polyurethane (PU) with an organosilane functional group was synthesized for the first time. Thereafter, a biodegradable PU-silica hybrid was produced through the sol-gel process. The PU-silica hybrid was not only flexible and fully biodegradable but also possessed shape memory ability. In addition, allophanate bonding enabled the silane coupling agent to induce increased crosslinking between the polymer and silica network, as well as between polymer and polymer. Accordingly, the sol-to-gel gelation time required to produce the hybrids was very short, which allowed the production of 3D porous hybrid scaffolds through a simple salt-leaching process. A hybrid scaffold with a 30 wt. % silica composition was the most ideal bone regenerative scaffold since it was able to withstand thermal deformation with promising mechanical properties. Moreover, the hybrid scaffold induced osteogenic differentiation and angiogenesis to accelerate bone regeneration.