Surface Ligand Density Switches Glycovesicles between Monomeric and Multimeric Lectin Recognition

Carbohydrate-protein interactions define a multitude of cellular recognition events. We present herein synthetic glycovesicles as cell-surface mimics in order to switch the nature of lectin recognition. The covalent glycovesicles, constituted with diacetylene monomers of various ligand densities at their surfaces, are prepared through photo-polymerization. Vesicles with sparsely imbedded ligands engage in a lectin interaction leading to the formation of a dense, crosslinked multimeric complex. On the other hand, vesicles with many ligands, or completely covered with them, switch the lectin interaction to form a fully soluble monomeric complex, without crosslinking. Nanomolar dissociation constants govern these interactions, as assessed by a ligand-displacement assay. The study demonstrates the switching nature – between monomeric and multimeric – of the interaction as a function of ligand density in the vesicles; the results are directly relevant to understanding such a phenomenon occurring at cell surfaces.     

Study on microstructure and mechanical properties of polydiacetylene composite biosensors

10,12-Pentacosadiynoic acid (PCDA) monomers were mixed with polyurethane (PU) or poly(ethylene oxide) (PEO) and the mixtures were electrospun to obtain composite nanofibers that were then photopolymerized via ultraviolet radiation, resulting polydiacetylene (PDA) in the nanofibers. The PDA demonstrated color-changing properties in the presence of Escherichia coli, which exhibited potential for developing flexible colorimetric biosensors for medical textiles. Phase separation was found in the PEO–PDA fibers, resulting in amorphous PEO accumulation at the fiber surface. In contrast, the PU–PDA fibers demonstrated a homogeneous microstructure throughout the fibers. Tensile test results suggested a molecular orientation in the PU–PDA fibers that significantly improved the mechanical properties of the fibers. The presence of PDA in the matrix polymer reduced the overall strength and breaking elongation of both composite nanofibers in comparison to 100% PEO and PU fibers. A single PU–PDA fiber showed significantly higher stiffness and modulus than a single PEO–PDA fiber. Force–distance curve analysis suggested that the PU–PDA fibers exhibited an elastic deformation. In a comparison, the PEO–PDA fibers were brittle and showed low modulus. The results of structural and mechanical properties suggest that the PU–PDA nanofibers are a promising composite for developing nonadherent, durable, and flexible colorimetric biosensors used in medical textiles. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47877.     

Surface Density of Ligands Controls In-Plane and Aggregative Modes of Multivalent Glycovesicle-Lectin Recognitions

Glycovesicles are ideal tools to delineate finer mechanisms of the interactions at the biological cell membranes. Multivalency forms the basis which, in turn, should surpass more than one mechanism in order to maintain multiple roles that the ligand-lectin interactions encounter. Ligand densities hold a prime control to attenuate the interactions. In the present study, mannose trisaccharide interacting with a cognate receptor, namely, Con A, is assessed at the vesicle surface. Synthetic (1→3)(1→6)-branched mannose trisaccharides tethered with a diacetylene monomer and glycovesicles of varying sugar densities were prepared. The polydiacetylene vesicles were prepared by maintaining uniform lipid concentrations. The interactions of the glycovesicles with the lectin were probed through dynamic light scattering and UV-Vis spectroscopy techniques. Binding efficacies were assessed by surface plasmon resonance. Aggregative and in-plane modes of interactions show ligand-density dependence at the vesicle surface. Vesicles with sparsely populated ligands engage lectin in an aggregative mode (trans-), leading to a cross-linked complex formation. Whereas glycovesicles embedded with dense ligands engage lectin interaction in an in-plane mode intramolecularly (cis-). Sub-nanomolar dissociation constants govern the intramolecular interaction occurring within the plane of the vesicle, and are more efficacious than the aggregative intermolecular interactions.     

Synthesis and Polymerization Behavior of Tridentate Diacetylene Hosts

The synthesis of three new tridentate ligands capable of forming large cavities for encapsulation of organoiodides is described. Each compound consists of a central heterocyclic “base unit” linked by acetylenes to two heterocyclic “arm” units. The base and the arm unit are each either a 2,6-disubstituted pyridine or a 2,5-disubsituted thiophene ring. The terminal end of each arm unit is connected to a (butoxycarbonyl)methylurethanyl (BCMU) moiety by way of a diacetylene linkage. This serves as a polymerogenic group that helps align the diacetylenes for topotactic polymerization. The triaryl ring systems are constructed through a series of aryl bromide/protected acetylene coupling steps, followed by deprotection and further coupling. Two of the compounds polymerize photochemically and all three polymerize thermally.     

非线性光学材料聚二乙炔及其衍生物的制备及应用

非线性光学材料聚二乙炔及其衍生物的研究已引起国内外的广泛关注。本文总结了近年来聚二乙炔及其衍生物的合成方法 ,综述了聚二乙炔及其生物在非线性光学方面的研究进展 ,并且对聚二乙炔及其衍生物在非线性光学领域的进一步应用提出了展望。     

Towards a Universal Method for the Stable and Clean Functionalization of Inert Perfluoropolymer Nanoparticles: Exploiting Photopolymerizable Amphiphilic Diacetylenes

Highly fluorinated materials are being widely investigated due to a number of peculiar properties, which are potentially useful for various applications, including use as lubricants, anti‐adhesive films, and substitutes for biological fluids for biomedical utilization. However, at present such potential is still poorly exploited. One of the major drawbacks that hampers the rapid development of nanoscale fluoro‐hybrid devices is the remarkable inertness of perfluoropolymeric materials that lack reactive functionalities, as they do not offer any functional groups that can be employed to covalently anchor organic molecules on their surface. In this paper, a convenient method for the stable biofunctionalization of strongly unreactive perfluoropolymer nanoparticles (PnPs) is reported. PnPs are easily coated with newly synthesized asymmetric diacetylenic monomer compounds (ADMs), thanks to PnP’s high propensity to interact with hydrophobic moieties. Once monomerically adsorbed onto PnPs, such suitably designed ADMs enable the formation of a robust polymeric shell around the perfluoroelastomer core via a clean UV‐promoted localized photopolymerization. Given the peculiar optical characteristics of PnPs, the coating of the particles can be monitored step by step using light scattering, which also allows estimation of the fraction of reacted monomers by competitive adsorption with smaller particles. The potential of this method for the biofunctionalization of PnPs is demonstrated with representative proteins and carbohydrates. Among them, the extension to avidin–biotin technology may broaden the scope and applicability of this strategy to potentially a large number of molecules of biomedical interest.     

Molecular structure modulated properties of azobenzene-substituted polydiacetylene LB films: Chirality formation and thermal stability

Langmuir-Blodgett (LB) films of three novel azobenzene-substituted diacetylene monomers (DA1, DA2 and DA3) were fabricated and their optical and chiroptical properties were investigated in detail by ultraviolet-visible (UV-vis) spectra and circular dichroism (CD) spectra. Achiral DA1 molecules could form chiral LB films through overcrowded packing of the azobenzene moiety, while achiral DA2 and DA3 molecules not. When exposed to left-or right-handed circular polarized UV light (CPUL), striking left- or right-handed (opposite) CD signals for azobenzene chromophores and polydiacetylene chains were observed for the polymerized DA1 (PDA1) and DA2 (PDA2) LB films. However, DA3 LB films could hardly be polymerized in this case, and only striking opposite CD signals for azobenzene chromophores could be observed. It was demonstrated that the intermolecular steric hindrance and irregular arrangement of azobenzene chromophores were not favorable for the topo-polymerization and chirality formation of polydiacetylenes backbone. Further, the effects of thermal treatment on the supramolecular chirality of above three LB films were studied. Strong collective noncovalent interactions (π-π stacking) were believed to be responsible for the thermal stability of chiral supramolecular assemblies.     

Electric field depolarization in high aperture focusing with emphasis on annular apertures

Electromagnetic focusing theory of light predicts that at high apertures field components arise that are polarized perpendicular to the initial polarization. Although vectorial depolarization has received considerable attention in focusing theory, no evidence has been presented as to its relevance in experiments. We measure the intensity of the perpendicularly orientated field in the focal region by utilizing monomolecular, fluorescent polydiacetylene layers whose transition dipoles are orientated in a single direction. For a 1.4 numerical aperture oil objective lens illuminated with linearly x -polarized light, we find that the integral of the modulus squared of the y -polarized focal field amounts to 1.5% of its x -polarized counterpart. In particular, we show here that the depolarization increases when using annular apertures. Annuli formed by a central obstruction with a diameter of 89% of that of the entrance pupil raise the integral to 5.5%. This compares well with the value of 5.8% predicted by electromagnetic focusing theory; however, the depolarization is also due to imperfections connected with focusing by refraction. Besides fluorescence microscopy and single molecule spectroscopy, the measured intensity of the depolarized component in the focal plane is relevant to all forms of light spectroscopy combining strong focusing with polarization analysis.