Phosphate modified graphene oxide: Long–term biodegradation and cytocompatibility

The application of functional graphenic materials (FGMs) in medicine has been limited due to insufficient knowledge of long–term degradation and cytocompatibility. Degradation studies that match the timeframe of clinical treatments are difficult to perform due to the limited timeframe in which in vitro studies can be conducted and the short lifespan of in vivo animal models. Here, we have designed an ex vivo experimental approach, where the degradation of FGMs can be monitored indefinitely and sampled at any point during the degradation process. We used this approach to study the aqueous and enzymatic degradation of phosphate graphenes (PGs), which are promising materials for biodegradable bone implants. We found that PGs chemically degrade through cation elution and basal plane scission of polyphosphates, and degradation timeframes are dependent on cation identity. Further, PGs also undergo physical degradation indicated by reduction of particle size. The pathways and timeframes of physical degradation of PGs are different for aqueous and enzymatic conditions. PG degradation was related to structure, which according to kinetic studies of the synthesis, could be manipulated to tune degradation. Nevertheless, all PGs and the resulting degradation byproducts are cytocompatible, opening the door for long–term biomedical applications, such as synthetic bone graft implants. [Display omitted]