Humidity-Triggered Self-Healing of Microporous Polyelectrolyte Multilayer Coatings for Hydrophobic Drug Delivery

Layer-by-layer (LbL) self-assemblies have inherent potential as dynamic coatings because of the sensitivity of their building blocks to external stimuli. Here, humidity serves as a feasible trigger to activate the self-healing of a microporous polyethylenimine/poly(acrylic acid) multilayer film. Microporous structures within the polyelectrolyte multilayer (PEM) film are created by acid treatment, followed by freeze-drying to remove water. The self-healing of these micropores can be triggered at 100% relative humidity, under which condition the mobility of the polyelectrolytes is activated. Based on this, a facile and versatile method is suggested for directly integrating hydrophobic drugs into PEM films for surface-mediated drug delivery. The high porosity of microporous film enables the highest loading (≈303.5 μg cm −2 for a 15-bilayered film) of triclosan to be a one-shot process via wicking action and subsequent solvent removal, thus dramatically streamlining the processes and reducing complexities compared to the existing LbL strategies. The self-healing of a drug-loaded microporous PEM film significantly reduces the diffusion coefficient of triclosan, which is favorable for the long-term sustained release of the drug. The dynamic properties of this polymeric coating provide great potential for its use as a delivery platform for hydrophobic drugs in a wide variety of biomedical applications.