Publications
Article
Tumor-Targeting Polymer–Drug Conjugate for Liver Cancer Treatment In Vitro
Abstract
Bufalin (buf) has poor solubility in aqueous solution, poor tumor targeting, and many non-specific toxic and side effects. The advantages of high-molecular-weight polymer conjugates are that they can improve the water solubility of buf, prolong plasma half-life, and reduce non-specific toxicity. A novel water-soluble polymer–drug conjugate with buf and fluorescein pendants was prepared by the combination of reversible addition-fragmentation transfer (RAFT) polymerization and click chemistry. Its anticancer performance and cellular uptake behavior against liver cancer were investigated in vitro. The polymer–buf conjugates exhibit controlled release and tumor-targeting capabilities, showing promise for clinical applications.
Oxidative Degradation of Thermosets Based on Thioketal Cleavable Linkages in Aqueous Environment
Abstract
Thermosets are rigid, infusible, and unmolded materials containing three-dimensional (3D) cross-linked structures. They are considered a fundamental pillar in the international economy, which are produced by 65 million tons annually. The responsive cross-linking moieties provide the thermosets characterized with outstanding physicochemical properties such as stiffness, degradability, and chemical and thermal resistance. We prepared degradable thermoset materials using thioketal (TK) cross-linkers, which underwent main-chain or side change degradation in the presence of hydrogen peroxide in water. TK cross-linkers at different concentrations (5, 10, and 20% wt %) were polymerized with 2-hydroxyethyl acrylate (HEA) or with 2-hydroxyethyl methacrylate (HEMA) and 1-vinyl-2-pyrrolidone (PD) to produce cross-linked poly(HEA) and poly(HEMA-PD) by free radical polymerization, respectively. The resultant polymer materials completely degraded in hydrogen peroxide/water (3–30%, vol). Using isophorone diisocyanate, we also produced degradable polyurethane based on TK-bearing diol. We prepared a 3D degradable thermoset using the Direct-Ink-Writing (DIW) 3D printing technology, which was charged by diethylene glycol diacrylate (15%, wt %) and a prepolymer (isophorone diisocyanate terminated by acrylate moieties) containing diol-thioketal linkage (15%, wt %). Finally, we found that TK-poly(HEA) underwent microbial degradation by Lactobacillus jensenii at 37 °C, which indicates a benign eco-friendly effect.
A nanomedicine enables synergistic chemo/photodynamic therapy for pancreatic cancer treatment
Abstract
Pancreatic cancer is one of the leading causes of cancer-related deaths worldwide. Gemcitabine (Gem) has been a key chemotherapy agent for pancreatic cancer treatment by suppressing cell proliferation and inducing apoptosis. However, the overexpression of inhibitors of apoptosis (IAP) family of proteins during the carcinogenesis of pancreatic cancer can develop resistance to chemotherapy treatment and result in poor efficacy. To achieve the synergistic combinations of multiple strategies for this dismal disease, we developed a robust nanomedicine system, consisting of a photodynamic therapeutic agent (chlorine e6, Ce6) and a pro-apoptotic peptide–Gem conjugate. To have spatiotemporally controlled drug release, the pro-apoptotic peptide–Gem conjugate was designed to have a vinyldithioether linker that was sensitive to reactive oxygen species (ROS). The nanomedicine was fabricated by the direct self-assembly of the pro-apoptotic peptide–Gem conjugate with Ce6. After being delivered into tumors, the nanomedicine disassembled and rapidly released Gem, Ce6, and the pro-apoptotic peptide upon light illumination (660 nm). Both in vitro and in vivo studies in pancreatic cancer models confirmed the tumor inhibition efficacy with low systemic toxicity to animals.
Aggregation-Induced Emission Luminogen Catalyzed Photocontrolled Reversible Addition–Fragmentation Chain Transfer Polymerization in an Aqueous Environment
Abstract
A robust aggregation-induced emission luminogen photocatalyst, 5,6-bis(4′-(diphenylamino)-[1,1′-biphenyl]-4-yl)pyrazine-2,3-dicarbonitrile (DCDPP-2TPA), for photoinduced electron transfer-reversible addition–fragmentation chain transfer (PET-RAFT) polymerization was investigated. A variety of well-defined polymers with narrow polydispersities (Đ < 1.20) were prepared using the donor–acceptor (D–A) type aggregation-induced emission luminogen as a photocatalyst (as low as 5 ppm with respect to monomers) under visible light at ambient temperature. The use of ppm level of metal- or organo-photocatalysts for PET-RAFT polymerization has been investigated before, but mainly in organic solvents, and very much fewer studies were reported in aqueous environments. The polymerization strategy was successfully demonstrated in water with or without oxygen-free conditions and resulted in structure-controlled polymers. We observed that the fluorescence of DCDPP-2TPA was intensified linearly with an increase in the degree of polymerization.
Controlled Intracellular Polymerization for Cancer Treatment
Abstract
Numerous prodrugs have been developed and used for cancer treatments to reduce side effects and promote efficacy. In this work, we have developed a new photoactivatable prodrug system based on intracellular photoinduced electron transfer–reversible addition–fragmentation chain-transfer (PET–RAFT) polymerization. This unique polymerization process provided a platform for the synthesis of structure-predictable polymers with well-defined structures in living cells. The intracellularly generated poly(N,N-dimethylacrylamide)s were found to induce cell cycle arrest, apoptosis, and necroptosis, inhibit cell proliferation, and reduce cancer cell motilities. This polymerization-based “prodrug” system efficiently inhibits tumor growth and metastasis both in vitro and in vivo and will promote the development of targeted and directed cancer chemotherapy.
Supramolecular Self-Assembly in Living Cells
Abstract
Supramolecular interactions rely on non-covalent forces, such as hydrophobic effects, hydrogen-bonding, and electrostatic interactions, which govern many intracellular biological pathways. In cellulo supramolecular self-assembly is mainly based on host–guest interactions, changes in pH, enzymes, and polymerization-induced self-assembly to accurately induce various unnatural reactions without disturbing natural biological processes. This process can produce synthetic biocompatible macromolecules to control cell properties and regulate biological functions, such as cell proliferation and differentiation. This Minireview focuses on the latest reports in the field of in cellulo supramolecular self-assembly and anticipates future advances regarding its activation in response to internal and external stimuli, such as pH changes, reactive oxygen species, and enzymes, as well as external light illumination.
Harnessing Focal Adhesions to Accelerate p53 Accumulation and Anoikis of A549 Cells Using Colloidal Self-Assembled Patterns (cSAPs)
Abstract
Extracellular matrix (ECM) of the tumor microenvironment (TME), including topography and biological molecules, is crucial in cancer cell attachment, growth, and even the sensitivity to the chemo and cell drugs treatment. This study hypothesizes that mimic ECM structures can alter the attachment and drug sensitivity of cancer cells. A family of artificial ECM called colloidal self-assembled patterns (cSAPs) was fabricated to mimic tumor ECM structures. Cell adhesion, proliferation, and drug sensitivity of the A549 non-small cell lung cancer (NSCLC) cells were studied on 24 cSAPs, named cSAP#1–cSAP#24, where surface topography and wettability were distinct. The results showed that cell adhesion and cell spreading were generally reduced on cSAPs compared to the flat controls. In addition, the synergistic effect of cSAPs and several chemo drugs on cell survival was investigated. Interestingly, A549 cells were more sensitive to the combination of doxorubicin and cSAP#4. Under this condition, the focal adhesion kinase (FAK) signaling was downregulated while p53 signaling was upregulated, confirmed by real-time PCR and western blot analysis. It indicates that the specific surface structure could induce higher drug sensitivity and in vitro anoikis of A549 cells. A serum alternative, human platelet lysate (hPL), and different cSAPs were examined to verify our hypothesis. The result further confirmed that cell adhesion strongly affected the drug sensitivity of A549 cells. This study demonstrates that the tumor ECM is vital in cancer cell activity and drug sensitivity; therefore, it should be considered in drug discovery and therapeutic regimens.
Switching on prodrugs using radiotherapy
Abstract
Chemotherapy is a powerful tool in the armoury against cancer, but it is fraught with problems due to its global systemic toxicity. Here we report the proof of concept of a chemistry-based strategy, whereby gamma/X-ray irradiation mediates the activation of a cancer prodrug, thereby enabling simultaneous chemo-radiotherapy with radiotherapy locally activating a prodrug. In an initial demonstration, we show the activation of a fluorescent probe using this approach. Expanding on this, we show how sulfonyl azide- and phenyl azide-caged prodrugs of pazopanib and doxorubicin can be liberated using clinically relevant doses of ionizing radiation. This strategy is different to conventional chemo-radiotherapy radiation, where chemo-sensitization of the cancer takes place so that subsequent radiotherapy is more effective. This approach could enable site-directed chemotherapy, rather than systemic chemotherapy, with ‘real time’ drug decaging at the tumour site. As such, it opens up a new era in targeted and directed chemotherapy.
C=C Bond Oxidative Cleavage of BODIPY Photocages by Visible Light
Abstract
Photocages for protection and the controlled release of bioactive compounds have been widely inves-tigated. However, the vast majority of these photocages employ the cleavage of single bonds and high-energy ultraviolet light. The construction of a photo activation system that uses visible light to cleave unsaturated bonds still remains a challenge. Herein, we report a regioselective oxidative cleavage of C=C bonds from a boron-dipyrrole-methene (BODIPY) - based photocage by illumination at 630 nm, resulting in a free aldehyde and a thiol fluorescent probe.This strategy was demonstrated in live HeLacells, and the generatedα-formyl - BODIPY allowed real-time monitoring of aldehyde release in the cells.In particular, it is shown that a man nose -functionalized photocage can target HepG2cells.
Light-controlled, living radical polymerisation mediated by fluorophore-conjugated RAFT agents
Abstract
Photoinduced electron transfer-reversible addition−fragmentation chain-transfer (PET-RAFT) polymerisation allows the controlled synthesis of polymers and provides an alternative to transition metal-based photoinitiators. Here, fluorophore-conjugated RAFT agents, containing either 5-carboxyfluorescein or a “boron-dipyrromethene” (BODIPY) moiety attached to a thiocarbonylthio group, were synthesised. Both agents enabled light-controlled (470 nm, 0.4 mW/cm2) “on/off” polymerisation yielding polymers with a Mw/Mn < 1.50. The BODIPY-based RAFT agent showed excellent photostability and gave polymers that contained a single fluorophore per polymer chain, providing an expedient route to homogeneous fluorescently labelled polymers. This agent was compatible with multiple acrylamide/acrylate monomers with a range of functional groups, with the thiocarbonylthio terminating group enabling further polymer chain extension and the formation of fluorescent block copolymers, as demonstrated by the synthesis of BODIPY-labelled poly(N,N-dimethylacrylamide)-block-poly (3-acrylamidophenyl)boronic acid).
Reinforcing the Combinational Immuno-Oncotherapy of Switching “Cold” Tumor to “Hot” by Responsive Penetrating Nanogels
Abstract
Although immuno-oncotherapy in clinic has gained great success, the immunosuppressive tumor microenvironment (TME) existing in the “cold” tumor with insufficient and exhausted lymphocytes may result in a lower-than-expected therapeutic efficiency. Therefore, a properly designed synergistic strategy that can effectively turn the “cold” tumor to “hot” should be considered to improve the therapeutic effects of immuno-oncotherapy. Herein, TME-responsive penetrating nanogels (NGs) were developed, which can improve the delivery and penetration of the co-loaded resiquimod (R848) and green tea catechin (EGCG) in tumors by a nano-sized controlled releasing system of the soluble cyclodextrin-drug inclusion complex. Consequently, the NGs effectively promoted the maturation of dendritic cells, stimulated the cytotoxic T lymphocytes (CTLs), and decreased the PD-L1 expression in tumors. The combination of NGs with the OX40 agonist (αOX40) further synergistically enhanced the activation and infiltration of CTLs into the deep tumor and inhibited the suppression effects from the regulatory T cells (Tregs). As a result, an increased ratio of active CTLs to Tregs in tumors (20.66-fold) was achieved with a 91.56% tumor suppression effect, indicating a successful switch of “cold” tumors to “hot” for an immunologically beneficial TME with significantly improved anti-tumor immune therapeutics. This strategy could be tailored to other immuno-oncotherapeutic approaches to solve the urgent efficiency concerns of the checkpoint-based treatment in clinic.
Bioorthogonal Swarming: In Situ Generation of Dendrimers
Abstract
With the aid of bioorthogonal chemistry, we demonstrate the fabrication of synthetic dendrimers in situ around living cells. Using tetrazine dienophile and aminooxyl/hydrazide aldehyde chemistries, the density of functional groups on the dendrimers exponentially amplified intensities of fluorescent markers in antibody-targeted live cell imaging. This novel “swarming” approach highlights the power of bioorthogonal chemistry and provides a route to non-natural chemical structures on cells, paving the way for the generation of various artificial cellular nanostructures and scaffolds.
BODIPY based realtime, reversible and targeted fluorescent probes for biothiol imaging in living cells
Abstract
Real-time live cell imaging and quantification of biothiol dynamics are important for understanding pathophysiological processes. However, the design and synthesis of rational probes that have reversible and real-time capabilities is still challenging. In this work, we have prepared boron-dipyrrolemethene (BODIPY) based fluorescent molecules as ratiometric probes that allow the real-time biothiol dynamics to be observed in living cells. The Michael reaction between a-formyl-BODIPY (BOD-JQ) and GSH exhibited a reversible fluorogenic mechanism with fluorescent emission shifting from 592 nm to 544 nm with t1/2 = 16 ms. In particular, we showed that the probes with targeting agents are capable of detecting biothiols in mitochondria and the endoplasmic reticulum (ER) with high temporal resolution.
Multifunctional, histidine-tagged polymers: antibody conjugation and signal amplification
Abstract
A polymer scaffold, with multiple reactive centres, was synthesised by RAFT polymerisation and conjugated to the antibody herceptin. A hexahistidine RAFT agent enabled the rapid and simple purification of polymer–protein conjugates, while the tetrazine conjugation strategy allows myriad cargos to be attached and amplified.
Photo-controlled one-pot strategy for the synthesis of asymmetric three-arm star polymers
Abstract
A rapid photo-controlled one-pot strategy for the synthesis of asymmetric star polymers was developed using two different wavelengths of light to allow spatial and temporal control of the synthesis of the star polymers with controlled structures and narrow polydispersities. Several asymmetric star structures were successfully synthesised and the simultaneous photo-induced ATRP and RAFT polymerisation was demonstrated using this procedure.
Radical polymerization inside living cells
Abstract
Polymerization reactions conducted inside cells must be compatible with the complex intracellular environment, which contains numerous molecules and functional groups that could potentially prevent or quench polymerization reactions. Here we report a strategy for directly synthesizing unnatural polymers in cells through free radical photopolymerization using a number of biocompatible acrylic and methacrylic monomers. This offers a platform to manipulate, track and control cellular behaviour by the in cellulo generation of macromolecules that have the ability to alter cellular motility, label cells by the generation of fluorescent polymers for long-term tracking studies, as well as generate a variety of nanostructures within cells. It is remarkable that free radical polymerization chemistry can take place within such complex cellular environments. This demonstration opens up a multitude of new possibilities for how chemists can modulate cellular function and behaviour and for understanding cellular behaviour in response to the generation of free radicals.
Rapid Polymer Conjugation Strategies for the Generation of pH-Responsive, Cancer Targeting, Polymeric Nanoparticles
Abstract
The combination of controlled living polymerization in association with rapid and highly efficient macromolecule conjugation strategies provides a powerful tool for the synthesis of novel polymeric materials. Here functional block copolymers were rapidly and quantitatively conjugated using an efficient reaction between polymers containing a phenolic group and the 4-phenyl-3H-1,2,4-triazole-3,5(4H)-dione (PTAD) moiety and used to generate nanoparticles that encapsulated drugs. pH responsive amphiphilic block copolymers, which self-assemble into nanoparticles, were fabricated using our novel polymer conjugation strategy with the resulting system designed to promote drug release within the acidic milieu of the cancer microenvironment. The conjugation strategy also enabled the direct tagging of the nanoparticles with a range of fluorophores, targeting assets, or both with cargo release demonstrated in cancer cells.
Combinatorial delivery of bioactive molecules by a nanoparticle-decorated and functionalized biodegradable scaffold
Abstract
The combination of supportive biomaterials and bioactive factors to stimulate endogenous progenitor cells is of key interest for the treatment of conditions in which intrinsic bone healing capacities are compromised. To address this need a “scaffold-decoration platform” was developed in which a biocompatible, biotin-functionalised 3D structural polymer network was generated through a solvent blending process, and used to recruit avidin modified nanoparticles within its 3D structure through biotin–avidin conjugation. This was enabled via the generation of a suite of poly(lactic-co-glycolic acid) (PLGA) nanoparticles, encapsulating two bioactive factors, vascular endothelial growth factor (VEGF) and L-ascorbic acid 2-phosphate (AA2P) and conjugated to streptavidin to allow attachment to the bone generating scaffold. The levels of encapsulated and released VEGF and AA2P were tailored to fall within the desired range to promote biological activity as confirmed by an increase in endothelial cell tubule formation and collagen production by osteoblast cells in response to nanoparticle release of VEGF and AA2P, respectively. The release of VEGF from the scaffolds produced a significant effect on vasculature development within the chick chorioallantoic membrane (CAM) angiogenic assay. Similarly, the scaffolds showed strong biological effects in ex vivo assays indicating the potential of this platform for localised delivery of bioactive molecules with applications in both hard and soft tissue engineering.
An Approach to the High-Throughput Fabrication of Glycopolymer Microarrays through Thiol–Ene Chemistry
Abstract
The fabrication of microarrays consisting of well-defined glycopolymers is described. This was achieved by postfunctionalization of an immobilized poly(allyl glycidyl ether) using unprotected thiol-modified carbohydrates through thiol–ene conjugation chemistry. This enabled the fabrication of glycopolymer microarrays in which the density and composition of the carbohydrate moieties varied along each of the polymer chains displayed across the array. These glycopolymer microarrays were applied in the evaluation of multivalent ligand–protein interactions with the determination of surface dissociation constants (KD) with concanavalin A and Ricinus communis agglutinin I for surface immobilized mannose-, glucose-, and galactose-containing glycopolymers and validated in solution with ITC.
Understanding Polymer-Cell Attachment
Abstract
The development of polymeric materials with cell adhesion abilities requires an understanding of cell–surface interactions which vary with cell type. To investigate the correlation between cell attachment and the nature of the polymer, a series of random and block copolymers composed of 2-(dimethylamino)ethyl acrylate and ethyl acrylate are synthesized through single electron transfer living radical polymerization. The polymers are synthesized with highly defined and controlled monomer compositions and exhibited narrow polydispersity indices. These polymers are examined for their performance in the attachment and growth of HeLa and HEK cells, with attachment successfully modeled on monomer composition and polymer chain length, with both cell lines found to preferentially attach to moderately hydrophobic functional materials. The understanding of the biological-material interactions assessed in this study will underpin further investigations of engineered polymer scaffolds with predictable cell binding performance.
Nanoparticle “switch-on” by tetrazine triggering
Abstract
This work describes how a small-molecule chemical trigger, reacting through the mediatory of an inverse electron demand Diels–Alder reaction, results in enhanced cellular uptake and selective nanoparticle disintegration and cargo liberation, via gross polymeric morphological alterations. The power of these responsive nanoparticles is demonstrated through encapsulation of the anti-cancer agent doxorubicin and its triggered release, allowing controlled cell death in response to a small-molecule chemical trigger.
Tetrazine-Mediated Postpolymerization Modification
Abstract
A new and highly efficient polymer, postpolymerization, modification platform based on an inverse electron demand Diels–Alder reaction is reported. Well-defined polymers were synthesized from allyl glycidyl ether and glycidol by anionic ring-opening polymerization with postpolymerization modifications conducted with a number of tetrazine derivatives that carried functional groups spanning from carboxylates and esters to primary amines. Analysis of polymerization kinetics by real-time 1H NMR, and GPC revealed a rapid and high degree of side-chain conversion (>99%), with the generation of well-defined functional polymers, in both organic and aqueous solvents, without the need for additives or catalysts.
Supramolecular Peptide Amphiphile Vesicles through Host–Guest Complexation
Abstract
Tricky triggering: Supramolecular peptide amphiphiles were prepared by host–guest complexation of pyrene-labeled peptides and viologen lipid with cucurbit[8]uril. They self-assemble into vesicles, which are responsive to a variety of external triggers. Both “switching on” and “switching off” of fluoresence and cytotoxicity is demonstrated in vitro.
A detailed study on understanding glycopolymer library and Con A interactions
Abstract
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.
One-Step Fabrication of Supramolecular Microcapsules from Microfluidic Droplets
Abstract
Although many techniques exist for preparing microcapsules, it is still challenging to fabricate them in an efficient and scalable process without compromising functionality and encapsulation efficiency. We demonstrated a simple one-step approach that exploits a versatile host-guest system and uses microfluidic droplets to generate porous microcapsules with easily customizable functionality. The capsules comprise a polymer-gold nanoparticle composite held together by cucurbit[8]uril ternary complexes. The dynamic yet highly stable micrometer-sized structures can be loaded in one step during capsule formation and are amenable to on-demand encapsulant release. The internal chemical environment can be probed with surface enhanced Raman spectroscopy.
A supramolecular route towards core–shell polymeric microspheres in water via cucurbit[8]uril complexation
Abstract
Core–shell polymeric microspheres with a cleavable shell were prepared in water using cucurbit[8]uril to bring together functional polymeric microspheres and functional polymers. This supramolecular approach was employed to switch the cytotoxicity of the polymeric microspheres, leading to potential applications in the eradication of cancer cells.
Controlled Alternate Layer-by-Layer Assembly of Lectins and Glycopolymers Using QCM-D
Abstract
Layer-by-layer (LBL) assembly of concanavalin A (Con A), peanut agglutinin (PNA) plant lectins, and well-defined synthetic glycopolymers via their biological affinities have been prepared using a quartz crystal microbalance with dissipation monitoring (QCM-D). We demonstrate the use of mannose/galactose glycopolymers as lectin binders due to their selective binding to Con A/PNA, respectively. A detailed analysis of the adsorption processes and the adsorbed layer are provided and tuning the composition of multilayers using a series of well-defined glycopolymers differing only in the pendant sugar ratio is discussed.
Supramolecular Glycopolymers in Water: A Reversible Route Toward Multivalent Carbohydrate–Lectin Conjugates Using Cucurbit[8]uril
Abstract
Supramolecular self-assembly and reversible switching has been demonstrated for the first time between monovalent and multivalent carbohydrate ligands and the multivalency effect on lectin binding has been investigated. The self-assembly process is mediated through noncovalent interactions between pendant moieties on a polymer scaffold and a monosaccharide-functionalized viologen with cucurbit[8]uril (CB[8]) acting as a “supramolecular handcuff”. The rate of binding of the tetrameric lectin Concanavalin A (Con A) to a mannose-containing supramolecular glycopolymer was investigated through a standard turbidimetric assay.
Peptide Separation through a CB[8]-Mediated Supramolecular Trap-and-Release Process
Abstract
We demonstrate a supramolecular peptide separation approach by the selective immobilization of peptides bearing an N-terminal tryptophan onto a CB[8]-modified gold substrate, followed by electrochemical release. The CB[8]-stabilized heteroternary complexes were characterized by 1H NMR, ESI-MS, UV/vis, and fluorescence spectroscopy and cyclic voltammetry. Micropatterned CB[8]-modified gold substrates were found to trap only the recognizable N-tryptophan-containing peptides from a peptide mixture that could be visualized as green peptide arrays under fluorescence microscopy. Subsequently, the bound peptides were released from the modified substrates by the controlled single-electron reduction of viologen. The fully reversible trap-and-release process was repeated for 13 cycles, and the cumulative release profile of the dye−peptide conjugate was monitored by fluorescence spectroscopy, indicating that no degradation occurred.
High-Affinity Glycopolymer Binding to Human DC-SIGN and Disruption of DC-SIGN Interactions with HIV Envelope Glycoprotein
Abstract
Noncovalent interactions between complex carbohydrates and proteins drive many fundamental processes within biological systems, including human immunity. In this report we aimed to investigate the potential of mannose-containing glycopolymers to interact with human DC-SIGN and the ability of these glycopolymers to inhibit the interactions between DC-SIGN and the HIV envelope glycoprotein gp120. We used a library of glycopolymers that are prepared via combination of copper-mediated living radical polymerization and azide−alkyne [3+2] Huisgen cycloaddition reaction. We demonstrate that a relatively simple glycopolymer can effectively prevent the interactions between a human dendritic cell associated lectin (DC-SIGN) and the viral envelope glycoprotein gp120. This approach may give rise to novel insights into the mechanisms of HIV infection and provide potential new therapeutics.
An Aqueous Supramolecular Side-Chain Polymer Designed for Molecular Loading
Abstract
Hydrophilic copolymers containing recognition motifs based on 2-naphthol moieties in their side chains for the self-assembly with cucurbit[8]uril (CB[8]), have been prepared by reversible addition–fragmentation chain transfer polymerization. Self-assembly of the copolymer with both redox sensitive hydrophilic and hydrophobic viologen derivatives in the presence of CB[8] has been investigated.
Site-Selective Immobilization of Colloids on Au Substrates via a Noncovalent Supramolecular “Handcuff”
Abstract
We have examined hierarchical supramolecular structure in the formation of colloidal arrays by immobilizing monodispersed naphthalene-functionalized colloids onto Au substrates bearing viologen moieties using the macrocyclic host molecule cucurbit[8]uril as a supramolecular “handcuff”. Naphthalene-functionalized poly(methyl methacrylate)- and polystyrene-based colloids were synthesized by soap-free emulsion polymerization and characterized by dynamic light scattering and scanning electron microscopy to realize the colloidal arrays and to facilitate direct macroscopic imaging. The formation of host-stabilized ternary complexes on the surface of naphthalene-functionalized microspheres in colloidal suspension was verified by titration of a preformed viologen−CB[8] complex and followed by zeta potential measurements. Patterned self-assembled monolayers of a viologen derivative on Au substrates were formed by backfilling viologen-modified thiols after spontaneous chemisorption of “protective” alkylthiols by microcontact printing. After the initial complexation of CB[8] onto the viologen derivative on the Au substrates, monolayers of colloids with both 1D and 2D patterns could be formed and characterized by contact angle measurement, optical microscopy, and scanning electron microscopy. Control experiments indicated that no colloids were attached to the Au substrate after moderate washing by water if (1) CB[8] was replaced by a smaller analogue of the macrocyclic host, CB[6] or CB[7], (2) colloids without naphthalene-functionalities on the periphery were employed, or (3) alkanethiol was used entirely instead of viologenthiol to protect the Au substrate. These results suggest that the supramolecular ternary complexes were key to successfully bind the colloids onto the Au substrates with the CB[8] acts as a supramolecular “handcuff”. The fundamental expertise gained from the study of these materials is believed to facilitate progress in the field of smart materials and wet nanotechnology and lead to the preparation of controlled reversible architectures on surfaces.
Simultaneous Copper(I)-Catalyzed Azide–Alkyne Cycloaddition (CuAAC) and Living Radical Polymerization
Abstract
CuBr/iminopyridine systems can catalyze simultaneously both copper(I)-catalyzed azide–alkyne cycloaddition (CuAAC, “click”) and living radical polymerization (LRP) processes (see scheme). The relative rate of the two processes can be tailored by a judicious choice of the reaction conditions (solvent, temperature, [CuBr]0) leading to the development of a potentially very efficient synthetic route to well-defined functional polymers.
Tunable thermoresponsive water-dispersed multiwalled carbon nanotubes
Abstract
Polymers containing poly(ethylene glycol) methacrylate and 2-(2-methoxyethoxy)ethyl methacrylate have been synthesized by Cu(0)-mediated radical polymerisation for use as thermoresponsive water-dispersants for carbon nanotubes.
Site-Directed Conjugation of “Clicked” Glycopolymers To Form Glycoprotein Mimics: Binding to Mammalian Lectin and Induction of Immunological Function
Abstract
Synthesis of well-defined neoglycopolymer−protein biohybrid materials and a preliminary study focused on their ability of binding mammalian lectins and inducing immunological function is reported. Crucial intermediates for their preparation are well-defined maleimide-terminated neoglycopolymers (Mn = 8−30 kDa; Mw/Mn = 1.20−1.28) presenting multiple copies of mannose epitope units, obtained by combination of transition-metal-mediated living radical polymerization (TMM LRP) and Huisgen [2+3] cycloaddition. Bovine serum albumin (BSA) was employed as single thiol-containing model protein, and the resulting bioconjugates were purified following two independent protocols and characterized by circular dichroism (CD) spectroscopy, SDS PAGE, and SEC HPLC. The versatility of the synthetic strategy presented in this work was demonstrated by preparing a small library of conjugating glycopolymers that only differ from each other for their relative epitope density were prepared by coclicking of appropriate mixtures of mannopyranoside and galactopyranoside azides to the same polyalkyne scaffold intermediate. Surface plasmon resonance binding studies carried out using recombinant rat mannose-binding lectin (MBL) showed clear and dose-dependent MBL binding to glycopolymer-conjugated BSA. In addition, enzyme-linked immunosorbent assay (ELISA) revealed that the neoglycopolymer−protein materials described in this work possess significantly enhanced capacity to activate complement via the lectin pathway when compared with native unmodified BSA.
Well-Defined Poly(N-glycosyl 1,2,3-triazole) Multivalent Ligands: Design, Synthesis and Lectin Binding Studies
Abstract
Glycopolymers have been synthesised by post-functionalisation of well-defined alkyne-functional polymers with sugar azides to yield N-glycosyl 1,2,3-triazole functional polymers. The Cu(I)-catalysed Huisgen cycloaddition was used to attach α-mannoside, β-galactoside and β-lactoside derivatives via an azide functionality bound directly to the sugar anomeric carbon. Three different catalytic systems were investigated for the click reactions; [(PPh3)3Cu(I)Br], TBTA/Cu(I)Br and bathophenanthrolinedisulphonic acid disodium salt/Cu(I)Br. The latter of these was found to be the most efficient for the attachment of the larger/more sterically hindered disaccharide lactose moiety. The interaction of the lactose- and galactose-bearing glycopolymers with Ricinus Communis Agglutinin (RCA I) lectin was investigated by affinity HPLC analysis. The rate of the interaction between mannose polymer and concanavalin A (Con A) lectin was assessed by turbidimetry. The results from the lectin conjugation studies indicate that the glycopolymers prepared in this work are able to function as multivalent ligands, further suggesting that the attachment of the triazole directly to the sugar anomeric carbon has no significant effect on the interaction of these glycopolymers with Con A and RCA I.
A Modular Click Approach to Glycosylated Polymeric Beads: Design, Synthesis and Preliminary Lectin Recognition Studies
Abstract
Covalent immobilization of a range of carbohydrate derivatives onto polymeric resin beads is described. Copper-catalyzed Huisgen [2 + 3] cycloaddition (often termed click chemistry) was used to graft mannose-containing azides to complementarily functionalized alkyne surfaces, namely (a) Wang resin or (b) Rasta particles consisting of a clickable alkyne polymer loose outer shell and a Wang resin inner core. For the second approach, Wang resin beads were first converted into immobilized living radical polymerization initiators with subsequent polymerization of trimethylsilanyl-protected propargyl methacrylate followed by deprotection with TBAF to yield the desired polyalkyne clickable scaffold. The appropriate α-mannopyranoside azide was then clicked onto the bead to give a mannose functionalized Rasta resin. IR, gel-phase 1H NMR, and elemental analysis have been used to characterize the modified resins. The binding abilities of these d-mannose-modified particles were subsequently tested using fluorescein-labeled Concanavalin A (Con A), a lectin that binds certain mannose-containing molecules. Preliminary results indicated that the novel glyco-hybrid materials presented in this work are able to efficiently recognize mannose-binding model lectins such as Con A, opening the way for their potential application in affinity chromatography, sensors, and other protein recognition/separation fields.
Bioconjugation of biotinylated PAMAM dendrons to avidin
Abstract
The biotin-terminated PAMAM dendron has been synthesized and the asymmetric dendron used to modify the protein avidin via non-covalent bioconjugation.
