Porous biodegradable polyurethane nanocomposites: preparation, characterization, and biocompatibility tests

A porous biodegradable polyurethane nanocomposite based on poly(caprolactone) (PCL) and nanocomponents derived from montmorillonite (Cloisite®30B) was synthesized and tested to produce information regarding its potential use as a scaffold for tissue engineering. Structural and morphological characteristics of this nanocomposite were studied by infrared spectroscopy (FTIR), X-ray diffraction (XRD), small angle X-ray scattering (SAXS) and scanning electron microscopy (SEM). The reaction between polyurethane oligomers with isocyanate endcapped chains and water led to the evolution of CO2, which was responsible for building interconnected pores with sizes ranging from 184 to 387 μm. An in vitro cell-nanocomposite interaction study was carried out using neonatal rat calvarial osteoblasts. The ability of cells to proliferate and produce an extracellular matrix in contact with the synthesized material was assessed by an MTT assay, a collagen synthesis analysis, and the expression of alkaline phosphatase. In vivo experiments were performed by subcutaneously implanting samples in the dorsum of rats. The implants were removed after 14, 21, and 29 days, and were analyzed by SEM and optical microscopy after tissue processing. Histology crosssections and SEM analyses showed that the cells were able to penetrate into the material and to attach to many location throughout the pore structure. In vitro and in vivo tests demonstrated the feasibility for polyurethane nanocomposites to be used as artificial extracellular matrices onto which cells can attach, grow, and form new tissues.