Antifibrinogen, Antireflective, Antifogging Surfaces with Biocompatible Nano-Ordered Hierarchical Texture Fabricated by Layer-by-Layer Self-Assembly

Endoscopic surgery is a minimally invasive approach that is widely used in various clinical departments, including digestive surgery, thoracic surgery, and urology, because it can minimize the burden on patients. To perform more elaborate procedures, highly functional coatings that enhance the operation efficiency of the related equipment are required; for example, coatings to improve the visibility through endoscope lenses are needed. In this study, we designed multifunctional surfaces that displayed antithrombogenicity, antireflection, and antifogging by controlling nano-ordered hierarchical structures fabricated via layer-by-layer self-assembly. The coatings were composed of polyelectrolyte multilayers prepared from blends of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA) that were deposited in alternating layers with blends of poly(allylamine hydrochloride) (PAH), PVA, and PAA. Although mixing cationic PAH and anionic PAA solutions generally causes polyelectrolyte-polyelectrolyte complexes (PECs) to form through electrostatic interactions, we found that PAH and PAA hardly formed PECs when PVA was present in the solution containing PAA. Consequently, PAA behaved differently in cationic and anionic solutions, resulting in the formation of coatings with hierarchical texture. The structures possessed antireflective properties with a graded refractive index and >95% transmittance. The coatings also displayed resistance to protein adsorption derived from free hydroxyl groups and antifogging performance caused by hydrophilicity combined with the strong hydrogen bonding ability of PVA. The results of this study would be valuable for the development of innovative biomedical devices through a simple and environmentally friendly approach.