Characterization of the physical properties and biocompatibility of polybenzoxazine-based aerogels for use as a novel hard-tissue scaffold

The process to successfully synthesize polybenzoxazine (PBO)-based aerogels has recently been optimized; however, the biocompatibility of these materials has never been investigated. PBO is synthesized from bisphenol A and aniline, which are both precursors to many commonly used biomaterials, including polyurethane. Surface-wise these new aerogels resemble the innate extracellular matrix of bone and if these new aerogels exhibit acceptable biocompatibility, they may be used as a scaffold for bone tissue engineering. Here, we aimed to characterize some of the physical properties of PBO aerogels, PBO aerogels co-polymerized with resorcinol and formaldehyde (RF) and their conversion to carbon aerogel, while determining the compatibility of all of these materials towards human osteoblasts. Biocompatibility was determined with a live/dead cell cytotoxicity assay, a metabolic activity assay, alkaline phosphatase activity and osteocalcin production, after incubation with PBO-based aerogels for up to 5 days. PBO aerogels co-polymerized with RF tended to have a low density, porosity and elastic modulus and provided the weakest substrate for bone cell growth. PBO-derived carbon aerogels tended to have a high density, a large porosity and improved mechanical properties and provided the best substrate for bone cell growth. These results suggest that PBO based carbon aerogels have a suitable biocompatibility towards osteoblasts and that they may be able to be used for bone tissue engineering scaffolds.