The external region of a cell membrane, known as the glycocalyx, is dominated by glycosylated molecules, which direct specific interactions such as cell-cell recognition and contribute to the steric repulsion that prevents undesirable non-specific adhesion of other molecules and cells. Mimicking the non-adhesive properties of a glycocalyx provides a potential solution to the clinical problems, such as thrombosis, that are associated with implantable devices owing to non-specific adsorption of plasma proteins. Here we describe a biomimetic surface modification of graphite using oligosaccharide surfactant polymers, which, like a glycocalyx, provides a dense and confluent layer of oligosaccharides. The surfactant polymers consist of a flexible poly(vinyl amine) with dextran and alkanoyl side chains. We show that alkanoyl side chains assemble on graphite through hydrophobic interaction and epitaxial adsorption. This constrains the polymer backbone to lie parallel to the substrate, with solvated dextran side chains protruding into the aqueous phase, creating a glycocalyx-like coating. The resulting biomimetic surface is effective in suppressing protein adsorption from human plasma protein solution.

Quantum confined materials have been extensively studied for photoluminescent applications. Due to intrinsic limitations of low biocompatibility and challenging modulation, the utilization of conventional inorganic quantum confined photoluminescent materials in bio-imaging and bio-machine interface faces critical restrictions. Here, we present aromatic cyclo-dipeptides that dimerize into quantum dots, which serve as building blocks to further self-assemble into quantum confined supramolecular structures with diverse morphologies and photoluminescence properties. Especially, the emission can be tuned from the visible region to the near-infrared region (420 nm to 820 nm) by modulating the self-assembly process. Moreover, no obvious cytotoxic effect is observed for these nanostructures, and their utilization for in vivo imaging and as phosphors for light-emitting diodes is demonstrated. The data reveal that the morphologies and optical properties of the aromatic cyclo-dipeptide self-assemblies can be tuned, making them potential candidates for supramolecular quantum confined materials providing biocompatible alternatives for broad biomedical and opto-electric applications.

A series of novel surfactant polymers: poly(N-vinyldextran aldonamide-co-N-vinylhexanamide) (PNVDA-co-PNVH), in which hydrophilic dextran oligosaccharides and hydrophobic hexanoyl groups were incorporated simultaneously on to poly(vinylamine) (PVAm), were synthesized, and characterized by FTIR and 1 H NMR spectroscopy. Structurally well-defined poly(vinylamine) was prepared by hydrolysis of poly(N-vinylformamide), which was obtained by free radical polymerization of N-vinylformamide. Dextran molecules (Mw ) 1600) were attached to poly(vinylamine) by reacting amine groups with dextran lactone, while hexanoyl groups were attached by reacting amine groups with N-(hexanoyloxy)succinimide. By adjustment of the feed ratio, surfactant polymers with different hydrophilic/hydrophobic balances were prepared. Surface activity of the surfactants at an air/water interface was demonstrated by significant reductions in water surface tension. Surface activity at a solid surface/water interface was demonstrated by atomic force microscopy of surfactant molecules adsorbed onto a highly oriented pyrolytic graphite. The synthetic approach described in this report provides a route to prepare a variety of oligosaccharide surfactant polymers with well-defined structures and hydrophilic/hydrophobic balances, by selecting different combinations of oligosaccharide and alkanoyl groups or by adjusting feed ratio of the oligosaccharide to alkanoyl groups.

N-Alkylmaltonamide nonionic diblock surfactants of varying hydrophobic segment lengths were synthesized, and their surface active properties on highly oriented pyrolytic graphite were characterized by atomic force microscopy (AFM). The N-alkylmaltonamide surfactants are composed of maltose, a hydrophilic disaccharide, with amide-linked alkyl groups of varying length, from octyl to octadecyl. All the surfactants readily adsorb uniformly onto the hydrophobic graphite surface from solution. Surfactants with alkyl lengths of 10 or more carbons exhibit epitaxial adsorption on graphite, forming ordered hemicylinders with a diameter that increases with increasing surfactant length. The solution concentration necessary for inducing surface ordering decreases with increasing alkyl chain length. N-Octadecylmaltonamide, which is insoluble in water, adsorbed from methanol solution without ordering and upon solvent replacement with water, assembled into hemicylinders. Once formed, the surfactant structures appeared stable in pure water and under high scanning forces. The effects of alkyl chain length on surfaceinduced assembly and molecular packing are discussed from the viewpoint of surfactant composition and adsorbed configurations.

A series of oligomaltose surfactant polymers were prepared by the simultaneous coupling of hydrophilic maltolactone [of 2(M2), 7(M7), or 15(M15) glucose units] and hydrophobic N-(hexanoyloxy)succinimide (Hex) groups to the amino groups of a poly(vinyl amine) backbone. The surfactants were characterized by FTIR and 1H-NMR spectroscopies for purity and composition. Contact-angle and AFM measurements confirmed full monolayer adsorption for all surfactants on a model surface, highly oriented pyrolitic graphite, while full coverage was observed on polyethylene only for PVAm (M7:Hex) due to the optimal M7:Hex ratio and Hex chain density. On graphite, protein resistance increased with increasing coating thickness from 81.4 to 85.8 to 95.8% for the M2, M7, and M15 surfactants, respectively. Additionally, static platelet adhesion on all three surfactants dropped substantially to 15% (M2), 17% (M7), and 16% (M15)compared to glass (adhesion normalized to 100%) and a polyurethane (24%) surface. Protein- and platelet-resistant properties of the controlled oligomaltose layers are discussed by analysis of molecular modeling, oligomaltose and hexanoyl chain densities, and surfactant stability.