Biotin chain-terminated glycopolymers were generated by cyanoxyl-mediated free-radical polymerization using a biotin-derivatized arylamine initiator with high conversion (75%) and low polydispersity (1.30). Streptavidin-biotinylated glycopolymer binding was verified by SDS-PAGE gel shift assay and patterned glycocalyx-mimetic surfaces successfully fabricated.

A stabilized, phosphatidylcholine-containing polymeric surface was produced by in-situ polymerization of a self-assembled lipid monolayer on an alkylated substrate. The phospholipid monomer 1-palmitoyl-2-[12-(acryloyloxy)dodecanoyl]-sn-glycero-3-phosphorylcholine was synthesized, prepared as unilamellar vesicles, and fused onto alkylated glass. Free-radical polymerization was carried out in aqueous solution at 70 °C and characterized using either the water-soluble initiator 2,2‘-azobis(2-methylpropionamidine) dihydrochloride (AAPD) or an oil-soluble initiator 2,2‘-azobis(isobutyronitrile) (AIBN). Under optimized conditions, the supported monolayer displayed advancing and receding water contact angles of 64 and 44°, respectively. Angle-dependent ESCA results confirmed the presence of phosphorus and nitrogen and were consistent with theoretical predictions for close-packed monolayer formation with near-normal alignment of lipid chains. In the absence of network formation, polymeric films demonstrated acceptable stability under static conditions in water and air, as well as in the presence of a high shear flow environment. Blood compatibility was assessed in a baboon arteriovenous shunt model, which revealed miminal platelet deposition over a 2 h observation period.

Glycopolymer-polypeptide triblock copolymers of the structure, poly(l-alanine)-b-poly(2-acryloyloxyethyl-lactoside)-b-poly(l-alanine) (AGA), have been synthesized by sequential atom transfer radical polymerization (ATRP) and ring-opening polymerization (ROP). Controlled free radical polymerization of 2-O-acryloyl-oxyethoxyl-(2,3,4,6-tetra-O-acetyl-beta-d-galactopyranosyl)-(1-4)-2,3,6-tri-O-acetyl-beta-d-glucopyranoside (AEL) by ATRP with a dibromoxylene (DBX)/CuBr/bipy complex system was used to generate a central glycopolymer block. Telechelic glycopolymers with diamino end groups were obtained by end group transformation and subsequently used as macroinitiators for ROP of l-alanine N-carboxyanhydride monomers (Ala-NCA). Gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR) spectroscopy analysis demonstrated that copolymer molecular weight and composition were controlled by both the molar ratios of the Ala-NCA monomer to macroinitiator and monomer conversion and exhibited a narrow distribution (Mw/Mn = 1.06-1.26). FT-IR spectroscopy of triblock copolymers revealed that the ratio of alpha-helix/beta-sheet increased with poly(l-alanine) block length. Of note, transmission electron microscopy (TEM) demonstrated that selected amphiphilic glycopolymer-polypeptide triblock copolymers self-assemble in aqueous solution to form nearly spherical aggregates of several hundreds nanometer in diameter. Significantly, the sequential application of ATRP and ROP techniques provides an effective method for producing triblock copolymers with a central glycopolymer block and flanking polypeptide blocks of defined architecture, controlled molecular weight, and low polydispersity.

Differences observed between the various barrier prostheses are likely attributable to the chemical composition of the barrier or the conditions required for resorption and metabolism of the barrier components. It is likely that the components of these barriers incite a wide range of inflammatory responses resulting in the range of adhesion coverage and tenacity observed in the preclinical and clinical studies reviewed. Clinical trials are needed to more appropriately define the clinical effectiveness of these barriers.

A stable, substrate-supported phospholipid film was created by in-situ photopolymerization of an acrylate functionalized lipid assembly. The lipid film was generated on alkylated substrates by vesicle fusion and polymerized by irradiation with visible light, using eosin Y/triethanolamine as the photoinitiating species. Optimal experimental conditions were determined with respect to vesicle fusion time and duration of irradiation. The resulting polymeric lipid film was characterized by contact angle measurements, angle-resolved ESCA, and polarized external reflectance infrared spectroscopy. Static stability and desorption studies indicate enhanced stability of the photopolymerized system when compared with a heat-initiated analogue prepared by classical free-radical techniques.

A stabilized, membrane-mimetic film was produced on a polyelectrolyte multiplayer (PEM) by in-situ photopolymerization of an acrylate functonalized phospholipid assembly at a solid-liquid interface. The phospholipid monomer was synthesized, prepared as unilamellar vesicles, and fused onto close-packed octadecyl chains as part of an amphiphilic terpolymer anchored onto the PEM by electrostatic interactions. The lipid film displayed an advancing contact angle of ∼ 60°, elemental composition, as determined by X-ray photoelectron spectroscopy, was in agreement with that anticipated for a lipid membrane. Data obtained from both high-resolution scanning electron microscopy and ellipsometry were consistent with the formation of a supported lipid monolayer. In addition, polarized external reflection infrared spectroscopy revealed significant acyl chain ordering induced on lipid fusion and polymerization. Doping the lipid assembly with a fluorescein terminated polymerizable lipid provided visible confirmation of film formation and its stability under a variety of conditions, including shear rates of 2000 sec -1 . Transport studies demonstrated that the addition of a lipid film significantly reduced barrier permeability for compounds in excess of 70 kD. The ability to coat microbeads (d ∼ 300 µm) with a robust membrane-mimetic film, while preserving encapsulated cell viability is illustrated, thereby establishing a new strategy for modulating the physiochemical and biological properties of immunoisolation barriers for cell transplantation.

A novel class of biomimetic glycopolymer–polypeptide triblock copolymers [poly(L‐glutamate)–poly(2‐acryloyloxyethyllactoside)–poly(L‐glutamate)] was synthesized by the sequential atom transfer radical polymerization of a protected lactose‐based glycomonomer and the ring‐opening polymerization of β‐benzyl‐L‐glutamate N‐carboxyanhydride. Gel permeation chromatography and nuclear magnetic resonance analyses demonstrated that triblock copolymers with defined architectures, controlled molecular weights, and low polydispersities were successfully obtained. Fourier transform infrared spectroscopy of the triblock copolymers revealed that the α‐helix/β‐sheet ratio increased with the poly(benzyl‐L‐glutamate) block length. Furthermore, the water‐soluble triblock copolymers self‐assembled into lactose‐installed polymeric aggregates; this was investigated with the hydrophobic dye solubilization method and ultraviolet–visible analysis. Notably, this kind of aggregate may be useful as an artificial polyvalent ligand in the investigation of carbohydrate–protein recognition and for the design of site‐specific drug‐delivery systems. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5754–5765, 2004

Neutron reflectivity measurements were performed on a cell membrane mimic system, developed by Liu et al., consisting of a polyelectrolyte multilayer plus synthetic terpolymer plus a phospholipid layer (PE + TER + PC) assembly, at all of the intermediate steps in the assembly of the composite, to obtain neutron scattering length density depth profiles. 1 The polyelectrolyte multilayer functions as a soft, water-containing "cushion" for the membrane mimic, formed by the synthetic terpolymer and the phospholipid layer. The assemblies were studied dry and in 92% humidity using a phase-sensitive neutron reflectometry technique. By use of two water conditions (D2O and H2O mixtures) on the PE + TER + PC assembly, the distribution of water in the layers was obtained. It was found that under 92% humidity conditions, the supported membrane mimic has 40% water content in the "cushion" polyelectrolyte multilayer and 10% water content in the terpolymer-phospholipid region. The overall thickness change, due to water uptake, was found to be 20 Å. Because fusing phospholipid vesicles onto the polyelectrolyte multilayer plus synthetic terpolymer assembly shows an overall 30 Å increase in thickness of the composite, it can be inferred that a phospholipid monolayer was formed.