Thermal stability and rheological properties of the 'non-stick' Caf1 biomaterial

The ability to culture cells in three-dimensions has many applications, from drug discovery to wound healing. 3D cell culture methods often require appropriate scaffolds that mimic the cellular environments of different tissue types. The choice of material from which these scaffolds are made is of paramount importance, as its properties will define the manner in which cells interact with the scaffold. Caf1 is a protein polymer that is secreted from its host organism, Yersinia pestis, to enable escape from phagocytosis. In vitro, cells adhere poorly to the protein unless adhesion motifs are specifically introduced. Caf1 is a good candidate biomaterial due to its definable bioactivity, economical production and its ability to form hydrogels, through the use of cross-linkers. In this study, the thermostability of Caf1 was tested over a range of chemical conditions, and an initial characterisation of its rheological properties conducted in order to assess the suitability of Caf1 as a biomedical material. The results show that Caf1 retains its high thermostability even in harsh conditions such as extremes of pH, high salt concentrations and the presence of detergents. In solution, the concentrated polymer behaves as a complex viscous liquid. Due to these properties, Caf1 polymers are compatible with 3D bioprinting technologies and could be made to form a stimuliresponsive biomaterial that can alter its macrorheological properties in response to external factors. Caf1 biomaterials could therefore prove useful as 3D cell scaffolds for use in cell culture and wound repair.