Electropolymerized tyrosine-based thin films: Selective cell binding via peptide recognition to novel electropolymerized biomimetic tyrosine RGDY films

We have created thin films by cyclic voltammetry (CV) electropolymerizations of the following phenolic functional group-based monomers: phenol; tyrosineamide; the tetrapeptide RGDY-containing the integrin membrane adhesion protein recognition tripeptide RGD; RDGY, a nonsense control tetrapeptide; and 1:3 mixtures of tyrosineamide with the two tetrapeptide monomers. The film formation process and description of the film properties were obtained by repetitive CV cycling using the oscillating quartz frequency shift, Δf, and motional resistance shift, ΔR, parameters obtained with the electrochemical quartz crystal microbalance technique. Only the poly(phenol) film exhibited close chain packing-based self-limiting behavior, where all film synthesis ceased after approximately 7 CV cycles. All other films continued to form by electropolymerization with successive CV cycles out to the maximum cycle number (30 cycles) we measured. All of the films exhibited little energy dissipation behavior. Using the quartz crystal microbalance, we next compared the time course of cell attachment with the washed films and demonstrated that cells bound best to films in the following order: RGDY sense peptide:tyrosineamide films > RDGY nonsense peptide:tyrosineamide films = tyrosineamide films > phenol films. Cell enumeration after washing and trypsinization revealed firm protein-based cell attachment to the underlying extracellular matrix for the RGDY-containing films. These sense peptide films bound and retained two- to fivefold as many cells as the other films, with cells exhibiting a normal morphology. These results suggest the operation of specific cell attachment to the electropolymerized films via the RGD binding site for cellular integrin membrane proteins. The electropolymerization method we studied here forms a cassette system for creating electropolymerized films tailored to specific attachment of different cell types by varying the electropolymerized Y(tyrosine)-containing recognition peptide.