A detailed study on understanding glycopolymer library and Con A interactions

Synthetic glycopolymers are important natural oligosaccharides mimics for many biological applications. To develop glycopolymeric drugs and therapeutic agents, factors that control the receptor-ligand interaction need to be investigated. A library of well-defined glycopolymers has been prepared by the combination of copper mediated living radical polymerization and CuAAC click reaction via post-functionalization of alkyne-containing precursor polymers with different sugar azides. Employing Concanavalin A as the model receptor, we explored the influence of the nature and densities of different sugars residues (mannose, galactose, and glucose) on the stoichiometry of the cluster, the rate of the cluster formation, the inhibitory potency of the glycopolymers, and the stability of the turbidity through quantitative precipitation assays, turbidimetry assays, inhibitory potency assays, and reversal aggregation assays. The diversities of binding properties contributed by different clustering parameters will make it possible to define the structures of the multivalent ligands and densities of binding epitopes tailor-made for specific functions in the lectin-ligand interaction. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2588–259

Self-Assembling Hydrogels Based on a Complementary Host-Guest Peptide Amphiphile Pair

Supramolecular polymer-based biomaterials play a significant role in current biomedical research. In particular, peptide amphiphiles (PAs) represent a promising material platform for biomedical applications given their modular assembly, tunability, and capacity to render materials with structural and molecular precision. However, the possibility to provide dynamic cues within PA-based materials would increase the capacity to modulate their mechanical and physical properties and, consequently, enhance their functionality and broader use. In this study, we report on the synthesis of a cationic PA pair bearing complementary adamantane and β-cyclodextrin host–guest cues and their capacity to be further incorporated into self-assembled nanostructures. We demonstrate the possibility of these recognition motifs to selectively bind, enabling noncovalent cross-linking between PA nanofibers and endowing the resulting supramolecular hydrogels with enhanced mechanical properties, including stiffness and resistance to degradation, while retaining in vitro biocompatibility. The incorporation of the host–guest PA pairs in the resulting hydrogels allowed not only for macroscopic mechanical control from the molecular scale, but also for the possibility to engineer further spatiotemporal dynamic properties, opening opportunities for broader potential applications of PA-based materials

Single-chain glycopolymer folding via host-guest interactions and its unprecedented effect on DC-SIGN binding

Reversible self-folding actions of natural biomacromolecules play crucial roles for specific and unique biological functions in Nature. Hence, controlled folding of single polymer chains has attracted significant attention in recent years. Herein, reversible single-chain folded glycopolymer structures in α-shape with different density of sugar moieties in the knot were created. The influence of folding as well as the sugar density in the knot was investigated on the binding capability with lectins, such as ConA, DC-SIGN and DC-SIGNR. The synthesis of triblock glycocopolymers bearing β-CD and adamantane for the host-guest interaction and also mannose residues for the lectin interaction was achieved using the reversible addition-fragmentation chain transfer (RAFT) polymerization technique. The reversible single-chain folding of glycopolymers was achieved under a high dilution of an aqueous solution and the self-assembled folding was monitored by 2D nuclear overhauser enhancement spectroscopy (NOESY) NMR and dynamic light scattering. The lectin binding profiles consistently provided an unprecedented effect of single chain folding as the single-chain folded structures enhanced greatly the binding ability in comparison to the unfolded linear structures

Hyperbranched poly(2-oxazoline)s via bisfunctional crosslinker

Hyperbranched polymers are an interesting type of polymeric structure as they possess useful features for a range of applications. They have been used for small molecule storage and transport owing to the existence of their large number of end groups that can be used for further functionalisation. In this study, we introduce a bisfunctional 2-oxazoline based crosslinker to synthesise hyperbranched poly(2-oxazoline)s with molar mass ranging from 3.2 kDa to 22 kDa. Furthermore, to control the degree of crosslinking, an end-capping agent was added at the beginning of the polymerisation in order to prevent uncontrolled branching and subsequent gelation. Moreover, advanced viscosity gel permeation chromatography was used to compare the degree of branching present in each polymer, and the lower critical solution temperature of each branched polymer was measured, with transition temperatures ranging from 44 °C to 70 °C

Ugi multicomponent reaction to prepare peptide–peptoid hybrid structures with diverse chemical functionalities

Monodisperse sequenced peptides and peptoids present unique nano-structures based on their self-assembled secondary and tertiary structures. However, the generation of peptide and peptoid hybrid oligomers in a sequence-defined manner via Ugi multicomponent reaction has not yet been studied. Herein, we report a synthetic strategy that enables both the modification of peptides as well as the generation of sequence-defined peptide–peptoid hybrid structures. Our synthetic methodology rests on the fusion of solid phase peptide synthesis with Ugi multicomponent reactions. We evidence that a diversity of chemical functionalities can be inserted into peptides or used in the design of peptide–peptoid hybrids exploiting a wide functional array including amines, carboxylic acids, hydrocarbons, carbohydrates as well as polymers, introducing a sequence-defined synthetic platform technology for precision peptoid hybrids

Detailed GPC analysis of poly(N-isopropylacrylamide) with core cross-linked star architecture

Core cross-linked star shaped polymers possess unique physical properties that can be utilized as drug transporters for biomedical applications. However, detailed analysis of these polymer structures is not straightforward. Herein, we employ multi-detector gel permeation chromatography (GPC) to elucidate structural features of cross-linked stars prepared from the polymerisation of NIPAM via Cu(0)-mediated Reversible Deactivation Radical Polymerisation. Furthermore, we aim to show how varying the arm length and the core size of the star polymers can not only affect their structural properties but also their capacity to encapsulate drug-like molecules

Poly(2-oxazoline) with pendant hydroxyl groups via a silyl ether-based protecting group

The introduction of a functionality onto a poly(2-oxazoline) (POx) chain has been widely explored, yet reports of POx bearing hydroxyl side chains in a well-defined manner have not. Here, we report a simple yet elegant approach for the synthesis of POx with pendant hydroxyl groups through use of silyl protecting groups. First, a hydroxyl group containing 2-oxazoline monomer was synthesized from ε-caprolactone, which on its own results in poorly defined polymers. Moreover, protecting the hydroxy group with silyl ether-based protecting group led to well-defined polymers with free hydroxyl groups on the side chains upon deprotection. Finally, copolymers with 2-ethyl-2-oxazoline resulted in polymers with tunable hydrophilicity, and copolymers with 2-n-propyl-2-oxazoline resulted in polymers with tunable thermoresponsive behavior in water

Thermoresponsive polymers in non-aqueous solutions

Thermoresponsive polymers are gaining increasing interest for numerous applications especially in the biomedical and nanotechnology fields. The thermoresponsive behaviour of polymers has been extensively studied in pure water or water/organic solvent systems, however, temperature-induced phase transitions in other organic solvents are less common. Polymers in organic solvents exhibit a broad range of temperature-driven solution behaviours, from LCST and UCST, to sol–gel transitions, to micellization processes, among others, with potential applications as smart materials in electronics, in the lubricant industry, and in the biomedical field. This review article will focus on the thermoresponsive behaviour of polymers in different classes of organic solvents and mixtures thereof to emphasize and demonstrate the versatility and potential of these polymers

Controllable degradation kinetics of POSS nanoparticle-integrated poly(ε-caprolactone urea)urethane elastomers for tissue engineering applications.

Biodegradable elastomers are a popular choice for tissue engineering scaffolds, particularly in mechanically challenging settings (e.g. the skin). As the optimal rate of scaffold degradation depends on the tissue type to be regenerated, next-generation scaffolds must demonstrate tuneable degradation patterns. Previous investigations mainly focussed on the integration of more or less hydrolysable components to modulate degradation rates. In this study, however, the objective was to develop and synthesize a family of novel biodegradable polyurethanes (PUs) based on a poly(ε-caprolactone urea)urethane backbone integrating polyhedral oligomeric silsesquioxane (POSS-PCLU) with varying amounts of hard segments (24%, 28% and 33% (w/v)) in order to investigate the influence of hard segment chemistry on the degradation rate and profile. PUs lacking POSS nanoparticles served to prove the important function of POSS in maintaining the mechanical structures of the PU scaffolds before, during and after degradation. Mechanical testing of degraded samples revealed hard segment-dependent modulation of the materials' viscoelastic properties, which was attributable to (i) degradation-induced changes in the PU crystallinity and (ii) either the presence or absence of POSS. In conclusion, this study presents a facile method of controlling degradation profiles of PU scaffolds used in tissue engineering applications