Influence of polydopamine functionalization on the rapid protein immobilization by alternating current electrophoretic deposition

Biomolecule immobilization onto implant surfaces is an interesting approach which allows fine-tuning the biological response upon implantation. However, the relatively low adsorption rates seen in current methodologies typically lead to long processing times, which can affect the activity of the biomolecules. Here, we investigate the effect of combining a bioinspired polydopamine (PDA) functionalization strategy with alternating current electrophoretic deposition (AC-EPD) for the immobilization of bovine serum albumin (BSA) on Ti6Al4V. PDA films introduce a high density of functional groups on the metal surface for the permanent attachment, while AC-EPD has the potential to actively concentrate biomolecules at the implant surface within a short time. First, PDA films were optimized in terms of the dopamine (DA) starting concentration. Next, amine-rich PDA-functionalized Ti6Al4V substrates served as electrodes during AC-EPD of BSA. While an improved deposition yield could already be observed for the PDA and AC-EPD strategies individually, significant merit lays in their combination, as was revealed by thicker proteinaceous deposits on the PDA-functionalized Ti6Al4V serving as anode during the high-amplitude half cycle of the AC signal. This provides a proof-of-concept for the synergistic effect of a PDA coupling chemistry in combination with AC electrophoresis as a time-efficient coating methodology for the proteins.