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.