Phosphatase responsive peptide surfaces

The development of interactive surfaces able to respond to biological cues is of interest for the development of next generation biomaterials. We report the design, synthesis and characterisation of an enzyme responsive peptide based surface whose chemical properties change upon catalytic action of alkaline phosphatase (AP). AP is a membrane-anchored enzyme involved in osteogenesis (bone formation), making it a suitable biomolecule to facilitate interactivity between the cell and the biomaterial surface. Surface analysis is used to follow dephosphorylation and a phosphate assay is used to determine the amount of phosphate removed by the enzyme. This analysis reveals significant differences in the dephosphorylation rate at the surface compared to that in solution. The ability of the surface to respond to native enzymes expressed by mesenchymal stem cells (MSCs) was indirectly explored by assessing the response of the cells to phosphorylated, non-phosphorylated and enzymatically dephosphorylated surfaces. No differences were found between the surfaces, suggesting that cell expressed enzymes are able to dephosphorylate the peptide surfaces rapidly. This work presents the first phosphatase responsive surfaces whose phosphorylation state can be altered by native enzymes provided by the cells.