(739h) Biosensor Coatings from Protein-Polymer Complex Coacervates

Engineering proteins into functional catalysts enables their application as biosensors and green catalysts. The biocatalyst must maintain mechanical integrity, protein stability and longevity, and access to the protein active site in order to be a viable technology. In addition, high protein density is needed to achieve high catalytic activity. The self-assembly of proteins in solid-state materials has the ability to achieve each of these requirements. Templating protein assembly with block copolymers offers a simple bottom-up method for the three-dimensional nanoscale patterning of proteins. Using ionic interactions between the protein and block copolymer, known as complex coacervation, to drive the self-assembly enables all aqueous processing of the two components. The enzyme alkaline phosphatase was immobilized via ionic interactions with a neutral-cationic block copolymer. The complex coacervate was flow coated on substrates, photo-crosslinked to immobilize the film, and assayed for enzyme activity. The immobilized phosphatase maintained activity over several cycles and was used to detect heavy metal contaminants. The nanostructure of the films before and after crosslinking was evaluated by AFM. Previous work has demonstrated that even though many proteins do not readily form coacervates in their native state, increasing the surface charge on proteins results in coacervation. While alkaline phosphatase did form a coacervate with polycations, the effect of protein surface charge on activity, loading in the films, and stability was evaluated.