Dual-Function Nanofilm Coatings with Diffusion Control and Protein Resistance

To date, limited examples of polyelectrolyte multilayers (PEMs) can be found that truly exploit the power of layer-by-layer nanoassembly to combine multiple functions into a complex multilayer. We demonstrate that PEMs can be designed as optimized coatings for implantable biosensors, exhibiting both diffusion control and protein resistance. PEM coatings comprising strong weak and weak weak pairs were evaluated, resulting in decreases in glucose diffusivity up to 5 orders of magnitude compared to water. Addition of poly(ethylene glycol) (PEG)-grafted terminal layers on the base diffusion-controlling multilayers substantially improved resistance to albumin adsorption relative to unmodified PEMs. For transport-controlling films comprising strong weak polyelectrolyte pairs, the consistent diffusivity was observed even after exposure to protein-containing solutions, indicating minimal effects of biofouling. In contrast, the transport behavior of weak weak polyelectrolyte pairs was susceptible to alteration by protein exposure, resulting in large variation in diffusivity, even when protein-resistant outer layers were employed.