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.

Antithrombogenic films with high durability were fabricated in a wet process. Antithrombogenicity was achieved with polyelectrolyte multilayer thin film prepared from poly(vinyl alcohol)-poly(acrylic acid) (PVA-PAA) blends, deposited in alternate layers with poly(allylamine hydrochloride) (PAH). Film durability, assessed by abrasion resistance and water resistance, was enhanced by forming cross-links via amide bonds induced by heat treatment of the film. The film was found to be resistant to protein adsorption, as measured by the amount of fibrinogen adsorbed from an aqueous solution. The antithrombogenic efficacy was assessed in ex vivo experiments by the ability of stainless steel mesh, coated with the polyelectrolyte and inserted into a pig blood vessel, to inhibit thrombus formation. Mesh coated with the polyelectrolyte did not reduce blood flow over a period of 15 min, whereas with uncoated mesh blood flow stopped within 6 min because of blood vessel blockage by thrombus formation.

The development of cyclic peptides that exhibit pHsensitive membrane permeation is a promising strategy for tissueselective drug delivery. We investigated the pH-dependent interactions of designed cyclic peptides bearing noncanonical amino acids of long acidic side chains with lipid membranes, including surface binding, insertion, and translocation across the membrane. As the length of the side chain of acidic amino acid increased, the binding affinity of the peptides to phosphatidylcholine bilayer surfaces decreased, while the pH for the 50% insertion of the peptides into the bilayers increased. The pH for membrane permeation of the peptides increased with the side chain length, resulting in specific membrane permeation at pH ∼6.5. The longer side chain of acidic amino acids improved the maximum rate of membrane permeation at low pH, where both entropic and enthalpic contributions affected the permeation. Our peptide also showed intracellular delivery of cargo molecules into living cells in a pHdependent manner.

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