Engineered tissue with a dense extracellular matrix, such as bone or cartilage, can exhibit cell necrosis at the centre of the tissue mass. This is attributed to restricted oxygen diffusion, and as a result, the problem is exacerbated when engineering large, clinically relevant tissue constructs. We have addressed this issue through the development of a novel cell-functionalisation technology based on the construction of hybrid protein-surfactant nanoconstructs. Specifically, we have primed adult human mesenchymal stem cells (hMSCs) with myoglobin to act as an oxygen reservoir capable of alleviating hypoxic stress during the engineering of large cartilage constructs.
The nanoconstructs exhibited near-native protein structure and function, while the amphiphilic surfactant corona facilitated the association of the bioconjugate with the cytoplasmic membrane of the hMSCs. The process is non-cytotoxic, the cells remain labelled for up to a week in culture, and retain their ability to proliferate and differentiate. We primed a population of hMSCs with myoglobin-surfactant nanoconstructs and used the functionalised cells to engineer large constructs (5 mm x 6 mm) of hyaline cartilage. When compared to control samples grown from untreated stem cells, the myoglobin-primed cells produced tissue constructs with a superior biochemical composition, and crucially, a significant reduction in cell necrosis and tissue degradation at the centre of the engineered cartilage.