Use of thioglycerol on porous polyurethane as an effective theranostic capping agent for bone tissue engineering.

Thiolated biodegradable polyurethane (TG-DPU) was synthesized using a one-pot reaction with thioglycerol adopted as a functionalized chain extender. After characterization of the chemical structure of TG-DPU using proton nuclear magnetic resonance spectroscopy, bone morphogenetic protein (BMP-2) was loaded in the TG-DPU under oxidative conditions to form disulfides between the free thiol of TG-DPU and BMP-2. The interaction between TG-DPU and BMP-2, so-called bioconjugates, was investigated using X-ray photoelectron spectroscopy analysis; the appearance of disulfide (S-S) linkage indicated the formation of a polymer/growth factor conjugate system. The covalently linked bioconjugates provided stability with minimal loss during the drug delivery with prolonged release performance in in vitro release tests. The effects of the drugs delivered by TG-DPU were also confirmed by in vitro alkaline phosphatase tests using pre-osteoblasts and in vivo bone regeneration tests. The drugs effectively induced cell differentiation and promoted mature bone recovery.