Polydopamine modification of polydimethylsiloxane for multifunctional biomaterials: Immobilization and stability of albumin and fetuin-A on modified surfaces.

The surface of polydimethylsiloxane (PDMS) can be modified to immobilize proteins; however, most existing approaches are limited to complex reactions and achieving multifunctional modifications is challenging. This work applies a simple technique to modify PDMS using polydopamine (PDA) and investigates immobilization of multiple proteins. The surfaces were characterized in detail and stability was assessed, demonstrating that in a buffer solution, PDA modification was maintained without an effect on surface properties. Bovine serum albumin (BSA) and bovine fetuin-A (Fet-A) were used as model biomolecules for simultaneous or sequential immobilization and to understand their use for surface backfilling and functionalization. Based on 125I radiolabeling, amounts of BSA and Fet-A on PDA were determined to be close to double that were obtained on control PDMS surfaces. Following elution with sodium dodecyl sulfate, around 67% of BSA and 63% of Fet-A were retained on the surface. The amount of immobilized protein was influenced by the process (simultaneous or sequential) and surface affinity of the proteins. With simultaneous modification, a balanced level of both proteins could be achieved, whereas with the sequential process, the initially immobilized protein was more strongly attached. After incubation with plasma and fetal bovine serum, the PDA-modified surfaces maintained over 90% of the proteins immobilized. This demonstrates that the biological environments also play an important role in the binding and stability of conjugated proteins. This combination of PDA and surface immobilization methods provides fundamental knowledge for tailoring multifunctional PDMS-based biomaterials with applications in cell-material interactions, biosensing, and medical devices.