Block Glycopolymers Research Articles

Dual-Responsive Glycopolymers for Intracellular Codelivery of Antigen and Lipophilic Adjuvants.

Traditional approaches to vaccines use whole organisms to trigger an immune response, but they do not typically generate robust cellular-mediated immunity and have various safety risks. Subunit vaccines composed of proteins and/or peptides represent an attractive and safe alternative to whole organism vaccines, but they are poorly immunogenic. Though there are biological reasons for the poor immunogenicity of proteins and peptides, one other key to their relative lack of immunogenicity could be attributed to the poor pharmacokinetic properties of exogenously delivered proteins and peptides. For instance, peptides often aggregate at the site of injection and are not stable in biological fluids, proteins and peptides are rapidly cleared from circulation, and both have poor cellular internalization and endosomal escape. Herein, we developed a delivery system to address the lack of protein immunogenicity by overcoming delivery barriers as well as codelivering immune-stimulating adjuvants. The glycopolymeric nanoparticles (glycoNPs) are composed of a dual-stimuli-responsive block glycopolymer, poly[2-(diisopropylamino)ethyl methacrylate]-b-poly[(pyridyl disulfide ethyl methacrylate)-co-(methacrylamidoglucopyranose)] (p[DPA-b-(PDSMA-co-MAG)]). This polymer facilitates protein conjugation and cytosolic release, the pH-responsive release of lipophilic adjuvants, and pH-dependent membrane disruption to ensure cytosolic delivery of antigens. We synthesized p[DPA-b-(PDSMA-co-MAG)] by reversible addition-fragmentation chain transfer (RAFT) polymerization, followed by the formation and physicochemical characterization of glycoNPs using the p[DPA-b-(PDSMA-co-MAG)] building blocks. These glycoNPs conjugated the model antigen ovalbumin (OVA) and released OVA in response to elevated glutathione levels. Moreover, the glycoNPs displayed pH-dependent drug release of the model hydrophobic drug Nile Red while also exhibiting pH-responsive endosomolytic behavior as indicated by a red blood cell hemolysis assay. GlycoNPs coloaded with OVA and the toll-like receptor 7/8 (TLR-7/8) agonist Resiquimod (R848) activated DC 2.4 dendritic cells (DCs) significantly more than free OVA and R848 and led to robust antigen presentation of the OVA epitope SIINFEKL on major histocompatibility complex I (MHC-I). In sum, the dual-stimuli-responsive glycopolymer introduced here overcomes major protein and peptide delivery barriers and could vastly improve the immunogenicity of protein-based vaccines.

Random versus Block Glycopolymers Bearing Betulin and Porphyrin for Enhanced Photodynamic Therapy.

Porphyrins and their derivatives, representing the second-generation photosensitizers, can generate reactive oxygen species (ROS) and kill tumors upon light irradiation. To compensate for the fluorescence quenching and reduced ROS production caused by aggregation and rigid inherent hydrophobicity of porphyrins, a series of comparable random and block glycopolymers bearing betulin and porphyrin were prepared via RAFT polymerization. Betulin was introduced into the copolymers to decrease aggregation-induced quenching of porphyrins and to improve the photodynamic therapy (PDT) efficiency of copolymers. The characteristics, self-assembly, and photophysical chemistry properties of these copolymers were systemically studied. The effect of polymer structure on photophysical chemistry properties and cellular interaction was investigated as well to demonstrate their potential targeting for PDT applications.

Preparation of Developing Biotinylated PH-Responsive Glycopolymers as Delivery Nanocarriers for Controlling Release of Bortezomib

To develop biotinylated pH-responsive glycopolymers and investigate their performances as anticancer drug delivery nanocarriers, bromide-terminated biotin was synthesized and then used to initiate the polymerization of D-gluconamido ethyl methacrylate (GAMA) and 2-(diethylamino)ethyl methacrylate (DEA) monomers via atom transfer radical polymerization (ATRP). Two biotinylated pH-responsive copolymers with similar degree polymerization (DP) chain segments, Biotin-P(GAMA-b-DEA) and Biotin-P(GAMA-co-DEA), were prepared by block or random architectures, respectively. The chemical compositions and self-assembly behavior of glycopolymers were characterized. The results show that the block glycopolymer self-assembles in water medium into core-shell structure assembly containing PGAMA shell and PDEA core with the 28 nm in diameter, while the random glycopolymer remains water-soluble state above pH 7.4. Both glycopolymers possess the loading ability of the BTZ with encapsulation efficiency (EE %) and loading capacity (LC %) of 83.7% and 8.4%, 78.7% and 7.9%, and the release behavior was kept at low constants with 20% and 26% cumulative amount even after 24 hours at pH 7.4, respectively. The study is expected to give the light to the development of new intelligent drug carrier system with excellent biological compatibility.

Highly Branched Gradient Glycopolymer: Enzyme-Assisted Synthesis and Enhanced Bacteria-Binding Ability.

A one-pot strategy was applied to synchronize enzymatic monomer transformation with reversible addition fragmentation chain transfer (RAFT) polymerization for the synthesis of glycopolymers with highly branched gradient architectures. Also, the linear analogues, block glycopolymers, and gradient glycopolymers were also synthesized for comparison. The binding ability of glycopolymers toward bacteria was then studied by optical density (OD) test, confocal laser scanning microscopy (CLSM), and quartz crystal microbalance with dissipation (QCM-D). The results show that the highly branched gradient glycopolymers have the most remarkable bacteria-binding ability compared with the two linear analogues, gradient glycopolymers, and block glycopolymers. The highly branched glycopolymers were further used as inhibitors in the anti-infection test, demonstrating a significant inhibitory effect on preventing bacteria from infecting the cells.

A Bioadhesive Nanoplatform Enhances the Permeation of Drugs Used to Treat Diabetic Macular Edema

The management of diabetic macular edema (DME), a condition that leads to an irreversible and severe visual impairment, remains a substantial challenge worldwide. In this study, we developed a bioadhesive nanoplatform with enhanced drug penetration to explore alternative treatment modalities for DME. This nanoparticulate formulation consisted of a sequence of an amphiphilic phenylboronic acid-based block and random glycopolymer with a high loading capacity for dexamethasone (DEX) of up to 20% and sustained drug release in vitro at a clinically relevant dose. The bioadhesive nanocarriers penetrated the sclera and choroid and were distributed in the retina under the action of phenylboronic acid to further promote drug permeation and retention in target lesions. The pathological analysis, electroretinography examination and immunofluorescence staining revealed that the nanoformulation of DEX much more markedly reduced the symptoms of and inflammation associated with DME than the drug alone, without affecting the function of the retina. Bioadhesive drug delivery systems are expected to be a feasible approach to treat DME and other fundus diseases.

Galactose-functionalized GlycoAuNR as a photothermal conversion complex: Its binding to lectin RCA120 and hepatoma-targeting therapy

Glycopolymer-grafted gold nanorods (GlycoAuNRs) were designed and fabricated as a heptoma-targeting phototherapy nanoparticles. The block glycopolymer, poly (diethyleneglycol methacrylate)-block-poly(6-O-vinyladipoyl-α-D-galactose) (PDEGMA-b-POVNGA), was synthesized by RAFT polymerization and modified AuNRs with Au-S bonds via reducing the thioester at the end of glycopolymer to thiol (–SH). Galactose pendants of thermosensitive AuNRs@PDEGMA-b-POVNGA were exposed when the temperature of aqueous dispersion is above lower critical solution temperature, which was responsible for specific binding ability with ricinus communis agglutinin. In vitro experiment indicated that the synthesized glycopolymer could significantly improve cytocompatibility of AuNRs and target to hepatocellular carcinoma cells, owing to the galactose moiety that recognized the overexpressed asialoglycoprotein receptor on the hepatocellular carcinoma cells. Interestingly, the addition of ricinus communis agglutinin could inhibit the growth of the hepatocellular carcinoma cells in some extent. Furthermore, the photothermal therapy assay proved that glycoAuNRs-ricinus communis agglutinin could realize highly effective photothermal treatment for the tumor cells in vitro upon laser irradiation by cooperative effect.

Aggregation of a double hydrophilic block glycopolymer: the effect of block polymer ratio.

Double hydrophilic block glycopolymers (DHBGs) composed of glycopolymers and polyethylene glycol (PEG) aggregate in aqueous solution. However, there are no guidelines to direct and design DHBG aggregation. Herein, we investigated the effect of the ratio of glycopolymer length to PEG length on the structure, and report that structure size could be influenced by the block polymer ratio. Nine kinds of DHBG with different glycopolymers and PEG lengths were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. The aggregation capability of DHBG was investigated by transmission electron microscopy (TEM) and dynamic light scattering (DLS). In all cases, the DHBGs formed the spherical structures, even when the PEG and glycopolymer lengths were quite different. The size of the structure was controlled by the ratio of the PEG length to the glycopolymer length. The aggregation of the DHBGs was induced by hydrogen bonding between the sugar moieties. The aggregation of the DHBG was affected by temperature and concentration.

Preparation of multifunctional glycopolymers using double orthogonal reactions and the effect of electrostatic groups on the glycopolymer–lectin interaction

We investigated synthetic biomacromolecules to control molecular interactions. Multifunctional glycopolymers for molecular recognition were prepared via living radical polymerization and post-click chemistry with orthogonal Huisgen and thiol-epoxy reactions. The synthesis of the polymer backbone and the subsequent side-chain introduction successfully proceeded in high yield. The multifunctional glycopolymers had a tri-block structure: the first and third blocks contained mannose, and the second block contained either a positively or negatively charged group or a neutral hydrophilic group. The molecular recognition of the glycopolymers toward lectin was evaluated via fluorescence quenching measurements. Because of the electrostatic interaction, the binding constant varied in the following order: positively charged glycopolymer (PT110) > negatively charged glycopolymer (NT110). The effect of the electrostatic interactions was modest compared with the effect of the carbohydrate–lectin binding. These results suggested that the carbohydrate–lectin interaction was an important factor in the molecular recognition of glycopolymers. This study provides guidelines for the preparation of multifunctional polymers, such as biomaterials. The block glycopolymers with specific arrangement of sugar ligand and electric charges were synthesized via RAFT living radical polymerization, where the block polymers were efficiently obtained using two orthogonal reactions of Huisgen and thiol-epoxy ring opening reactions. The molecular recognition abilities of the block glycopolymers was examined.

Synthesis and Self-Assembly of Double-Hydrophilic and Amphiphilic Block Glycopolymers.

In this report, we present double-hydrophilic block glycopolymers of poly(2-hydroxyethyl methacrylate)-b-poly(2-(β-glucosyloxy)ethyl methacrylate) (PHEMA-b-PGEMA) and amphiphilic block glycopolymers of poly(ethyl methacrylate)-b-PGEMA (PEMA-b-PGEMA) synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization. The block glycopolymers were prepared in two compositions of P(H)EMA macro-chain transfer agents (CTAs) and similar molecular weights of PGEMA. Structural analysis of the resulting polymers as well as the conversion of (H)EMA and GEMA monomers were determined by 1H NMR spectroscopy. Size exclusion chromatography measurements confirmed both P(H)EMA macro-CTAs and block glycopolymers had a low dispersity (Đ ≤ 1.5). The synthesized block glycopolymers had a degree of polymerization and a molecular weight up to 222 and 45.3 kg mol–1, respectively. Both block glycopolymers self-assembled into micellar structures in aqueous solutions as characterized by fluorescence spectroscopy, ultraviolet–visible spectroscopy, and dynamic light scattering experiments.

Investigation of pH-responsive block glycopolymers with different structures for the delivery of doxorubicin.

To understand the influence of the construction of pH-responsive glycopolymer carriers on loading and release behaviors of the drug, three types of block glycopolymers with similar compositions but different constructions, PEG-b-P(DEA-co-GAMA), PEG-b-PDEA-b-PGAMA and PEG-b-PGAMA-b-PDEA, were successfully synthesized via atom transfer radical polymerization (ATRP) method. The compositions and structures of the three glycopolymers were characterized using 1H NMR (nuclear magnetic resonance) and GPC (gel permeation chromatography), while the morphology and size of aggregates from pH-sensitive block glycopolymers were measured using TEM (transmission electron microscopy) and DLS (dynamic light scattering). The results indicated that the micelles prepared from PEG-b-PGAMA-b-PDEA had a more compact shell structure. The drug-loaded micelles were prepared using the diafiltration method at pH 10, and the loading content and loading efficiency were analyzed using a UV-visible spectrophotometer. DOX-loaded micelles formed by PEG-b-PGAMA-b-PDEA with the more compact shell construction showed the highest loading content and loading efficiency (12.0 wt% and 58.0%) compared with the other two micelles. Moreover, the DOX release tests of these micelles were carried out under two PBS conditions (pH 7.4 and pH 5.5), and the DOX release amount in a certain time was analyzed using a UV-visible spectrophotometer. The results showed that the more compact shell construction of the three layered micelle obstructed the diffusion of a proton into the PDEA core at pH 5.5 and delayed the drug from releasing under both conditions. Moreover the two-layered micelle with a PDEA and PGAMA mixed core showed a relatively high release amount owing to the porous core permitting unimpeded releasing at pH 7.4 and promoted the protonation of PDEA at pH 5.5. Insights gained from this study show that the structure of block copolymers, leading to different constructions of micelles, could adjust the drug loading and release behavior to certain extent, thus it may contribute to improving the design of desirable drug delivery systems.

Copolymers containing carbohydrates and other biomolecules: design, synthesis and applications.

Glycopolymers are synthetic polymers containing pendant carbohydrate groups. Other biological compounds can be incorporated into glycopolymers to prepare both random and block copolymers aimed at bio-related applications: boronic acid can be introduced as a functional group to obtain crosslinked hydrogels; cholesterol and bile acids can be introduced to render the polymers more hydrophobic for the formation of micelles. Sugar-containing block copolymers with biocompatible blocks such as polypeptides, poly(ethylene glycol), poly(lactic acid) and poly(ε-caprolactone) were also prepared for potential application in drug carriers. These glycopolymers interact with lectins or lectin-containing surfaces as natural carbohydrate mimics. This review highlights the recent progress in the synthesis of random or block glycopolymers. Examples of the applications of glycopolymers in the separation and removal of toxins and bacteria, tumor cell recognition and glucose-responsive insulin delivery are presented and discussed.

Novel block glycopolymers prepared as delivery nanocarriers for controlled release of bortezomib

To explore block glycopolymers as novel polymeric delivery nanocarriers for anticancer drug bortezomib (BTZ), three types of block glycopolymers, poly(ethylene glycol)-block-poly(gluconamido ethyl methacrylate) (PEG113-b-PGAMA20), poly(ethylene glycol)-block-poly(styrene)-block-poly(gluconamido ethyl methacrylate) (PEG113-b-PS50-b-PGAMA20), and poly(ethylene glycol)-block-poly(2-(diethyl amino) ethyl methacrylate)-block-poly(gluconamido ethyl methacrylate) (PEG113-b-PDEA50-b-PGAMA20), were synthesized via atom transfer radical polymerization (ATRP) using a PEG-based ATRP macroinitiator. Three glycopolymers possess the capacity to load BTZ via pH-induced dynamic covalent bonding and/or hydrophobic interaction with their specific self-assembly behaviors, and PEG113-b-PS50-b-PGAMA20 carrier maintains the sustain release behavior of BTZ due to the stable micellar structure; PEG113-b-PDEA50-b-PGAMA20 carrier realizes the abrupt release at pH 5.5 by collapse of micellar structure, while PEG113-b-PGAMA20 carrier exhibits the fastest release at studied solution pHs. This study would provide a light to develop novel block glycopolymer carrier for the delivery of anticancer drug bearing boronic acid groups.Graphical abstractᅟᅟ

Galactose-Functionalized Double-Hydrophilic Block Glycopolymers and Their Thermoresponsive Self-Assembly Dynamics.

Glycopolymers with large galactose units are attractive in biological processes because of their ability to selectively recognize lectin proteins. Recently, thermoresponsive double-hydrophilic block glycopolymers (TDHBGs) have been designed, which allow sugar residues to expose or hide via the lower critical solution temperature (LCST)-type phase transition. In this work, we first synthesize a new type of TDHBGs, composed of a thermoresponsive poly(di(ethylene glycol)methyl ether methacrylate) block and a galactose-functionalized, poly(6- O-vinyladipoyl-d-galactose) (POVNG) block. The LCST can be tuned by varying the size of the POVNG block. Then, we have systematically investigated their thermoresponsive self-assembly behavior, using static and dynamic light scattering techniques, combined with transmission electron microscopy (TEM) imaging. It is found that the TDHBGs possess both micellization and LCST-type transition, and there exist strong interactions between them, depending on the concentration and structure of the TDHBGs. It is particularly interesting that for the same type of TDHBGs under different conditions, such interactions result in rich morphologies of the formed micelles (or nanoparticles) such as spheres, hollow spheres, prolate ellipsoids, crystal-like, and so on, thus potentially enriching their biological applications by noting that they are hepatoma-targeting glycopolymers.

Self-Assembly of a Double Hydrophilic Block Glycopolymer and the Investigation of Its Mechanism.

We report the self-assembly of a double hydrophilic block glycopolymer (DHBG) via hydrogen bonding and coordinate bonding. This DHBG, composed of poly(ethylene)glycol (PEG) and glycopolymer, self-assembled into a well-defined structure. The DHBG was prepared through the controlled radical polymerization of trimethylsilyl-protected propargyl methacrylate using a PEG-based reversible addition-fragmentation chain transfer reagent, followed by sugar conjugation using click chemistry. The DHBG self-assembly capability was investigated by transmission electron microscopy and dynamic light scattering. Interestingly, the DHBG self-assembled into a spherical structure in aqueous solution. Hydrogen bonding and coordinate bonding with Ca2+ were identified as the driving forces for self-assembly.

Core Cross-linked Micelles Made of Glycopolymers Bearing Dopamine and Cholic Acid Pendants.

A series of block glycopolymers bearing galactose, dopamine, and cholic acid (CA) pendants have been synthesized by RAFT polymerization. These copolymers can self-assemble into micelles in water. The dopamine moieties, located near the interface of the core and shell of the micelles, can self-polymerize in a weakly basic solution, stabilizing the micelles in both water and organic solvent (DMSO). The cross-linked micelles are smaller in size than the uncross-linked precursors. Introducing more CA groups into the copolymers promotes the self-assembly to form larger aggregates, controls the cross-linking of the stabilized micelles, and facilitates the encapsulation of hydrophobic compounds such as Nile Red (NR). The amount of CA comonomers added also helps to control the cross-linking density, which affects the loading and release of NR. The core cross-linked micelles displayed a slow but sustained NR release and interact effectively with lectin (RCA120), demonstrating their potential use as a biocompatible multifunctional platform for targeted release of drugs.

A glucose-sensitive block glycopolymer hydrogel based on dynamic boronic ester bonds for insulin delivery

Hydrogels are good candidates to satisfy many needs for functional and tunable biomaterials. How to precisely control the gel structure and functions is crucial for the construction of sophisticated soft biomaterials comprising the hydrogels, which facilitates the impact of the surrounding environment on a unique biological function occurring. Here, glucose-responsive hydrogels comprised of 3-acrylamidophenyl boronic acid copolymerized with 2-lactobionamidoethyl methacrylate (p(APBA-b-LAMA)) were synthesized, and further evaluated as carriers for insulin delivery. The formation of (p(APBA-b-LAMA)) hydrogel was based on dynamic covalent bond using the association of boronic acid with diols. P(APBA-b-LAMA) hydrogel with the typical porous structure showed a rapid increase in equilibrium of swelling, which was up to 1856% after incubation with aqueous solution. Using insulin as a model protein therapeutic, p(APBA-b-LAMA) hydrogel exhibited high drug loading capability up to 15.6%, and also displayed glucose-dependent insulin release under physiological conditions. Additionally, the viability of NIH3T3 cells was more than 90% after treated with p(APBA-b-LAMA) hydrogel, indicating that the hydrogel had no cytotoxicity. Consequently, the novel p(APBA-b-LAMA) hydrogel has a practical application for diabetes treatment.

Synthesis of amphiphilic block copolymer consisting of glycopolymer and poly(l‐lactide) and preparation of sugar‐coated polymer aggregates

ABSTRACTThe block glycopolymer, poly(2‐(α‐d‐mannopyranosyloxy)ethyl methacrylate)‐b‐poly(l‐lactide) (PManEMA‐b‐PLLA), was synthesized via a coupling approach. PLLA having an ethynyl group was successfully synthesized via ring‐opening polymerization using 2‐propyn‐1‐ol as an initiator. The ethynyl functionality of the resulting polymer was confirmed by MALDI‐TOF mass spectroscopy. In contrast, PManEMA having an azide group was prepared via AGET ATRP using 2‐azidopropyl 2‐bromo‐2‐methylpropanoate as an initiator. The azide functionality of the resulting polymer was confirmed by IR spectroscopy. The Cu(I)‐catalyzed 1,3‐dipolar cycloaddition between PLLA and PManEMA was performed to afford PManEMA‐b‐PLLA. The block structure was confirmed by 1H NMR spectroscopy and size exclusion chromatography. The aggregating properties of the block glycopolymer, PManEMA16k‐b‐PLLA6.4k (Mn,PManEMA = 16,000, Mn,PLLA = 6400) was examined by 1H NMR spectroscopy, fluorometry using pyrene, and dynamic light scattering. The block glycopolymer formed complicated aggregates at concentrations above 21 mg·L−1 in water. The d‐mannose presenting property of the aggregates was also characterized by turbidimetric assay using concanavalin A. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 395–403

Thermoresponsive diblock glycopolymer by RAFT polymerization for lectin recognition

A thermoresponsive double-hydrophilic diblock glycopolymer, poly(diethyl- eneglycol methacrylate)-block-poly(6-O-vinyladipoyl-d-glucose) (PDEGMA-b-POVAG), was successfully prepared by a combination of enzymatic synthesis and reversible addition-fragment chain transfer (RAFT) polymerization protocols using poly(diethyl- eneglycol methacrylate) (PDEGMA) as macro-RAFT agent. The block glycopolymer was characterized by 1H NMR and GPC. UV–vis, DLS and TEM studies revealed that the glycopolymer PDEGMA-b-POVAG was thermoresponsive with LCST at 31.0°C, and was able to self-assemble into spherical micelles of various sizes in aqueous solution. The glucose pendants in the glycopolymer could interact with the lectin Concanavalin A (Con A), the average hydrodynamic diameters of glycopolymer micelles increased to 170nm from 110nm after recognizing Con A. The diblock glycopolymer micelles have excellent biocompatibility with pig iliac endothelial cells, as measured using the MTT assay, but micelles loaded with Con A could be used to induce apoptosis in human hepatoma SMMC-7721 cells.

Glyconanoparticles with controlled morphologies and their interactions with a dendritic cell lectin

Well-defined amphiphilic block glycopolymers with equal mannose content have been self-assembled in aqueous solution to form glyconanoparticles with different morphologies.

Block versus Random Amphiphilic Glycopolymer Nanopaticles as Glucose-Responsive Vehicles.

To explore the effect of polymer structure on their self-assembled aggregates and their unique characteristics, this study was devoted to developing a series of amphiphilic block and random phenylboronic acid-based glycopolymers by RAFT polymerization. The amphiphilic glycopolymers were successfully self-assembled into spherically shaped nanoparticles with narrow size distribution in aqueous solution. For block and random copolymers with similar monomer compositions, block copolymer nanoparticles exhibited a more regular transmittance change with the increasing glucose level, while a more evident variation of size and quicker decreasing tendency in I/I0 behavior in different glucose media were observed for random copolymer nanoparticles. Cell viability of all the polymer nanoparticles investigated by MTT assay was higher than 80%, indicating that both block and random copolymers had good cytocompatibility. Insulin could be encapsulated into both nanoparticles, and insulin release rate for random glycopolymer was slightly quicker than that for the block ones. We speculate that different chain conformations between block and random glycopolymers play an important role in self-assembled nanoaggregates and underlying glucose-sensitive behavior.