Carbohydrate-Conjugated Amino Acid-Based Fluorescent Block Copolymers: Their Self-Assembly, pH Responsiveness, and/or Lectin Recognition

A Review on Self-Assembly Driven Optoelectronic Properties of Polythiophene-Peptide and Polythiophene-Polymer Conjugates

Polythiophene (PT) is an important conducting polymer for its outstanding optoelectronic properties. Here, we delineate the self-assembly-driven optoelectronic properties of PT-peptide and PT-polymer conjugates, taking examples from recent literature reports. PT-peptide conjugates made by both covalent and noncovalent approaches are discussed. Poly(3-thiophene acetic acid) (P3TAA) covalently coupled with Gly-Gly-His tripeptide, C-protected and deprotected tripeptide H2N-F-F-V-OMe, etc. exhibits self-assembly-driven absorbance, fluorescence, photocurrent, and electronic properties. Noncovalent PT-peptide conjugates produced via ionic, H-bonding, and π-stacking interactions show tunable morphology and optoelectronic properties by varying the composition of a component. PT conjugated with Alzheimer's disease peptide (KLVFFAE, Aβ16-22) shows enhanced photocatalytic water splitting, cationic PT(CPT-I)-perylene bisimide-appended dipeptide (PBI-DY), and anionic PT-perylene diimide-appended cationic peptide (PBI-NH3+) conjugates and exhibits self-assembly-driven enhanced photoswitching and organic mixed electronic and ionic conductivity (OMEIC) properties. In the PT-polymer conjugates, self-assembly-driven optoelectronic properties of covalently produced PT-random copolymers, PT-block copolymers, PT-graft-random copolymers, and PT-graft-block copolymer conjugates are discussed. The HOMO-LUMO levels of hyperbranched polymers are optimized to obtain better power conversion efficiency (PCE) in the bulk heterojunction (BHJ) solar cell than in linear polymers, and P3TAA-ran-P3HT (43 mol % P3TAA) conjugated with MAPbI3 perovskite exhibits higher PCE (10%) than that with only P3TAA hole-transporting material. In the ampholytic polythiophene (APT), on increasing pH, the morphology changes from the vesicle to fibrillar network for the dethreading of the PT chain, resulting in a red shift of the absorbance peak, an enormous increase in PL intensity, lowering of the charge transfer resistance, and an induction of Warburg impedance for the release of quencher I- ions. The PT-g-(PDMAEMA-co-PGLU-HEM) graft copolymer self-assembles with Con-A lectin, causing fluorescence quenching, and acts as a sensor for Con-A with a LOD of 57 mg/L. Varying sequences of the block copolymer containing pH-responsive PDMAEMA and temperature-responsive PDEGMEM grafted to the PT backbone shows different self-assembly, optical, electronic, and photocurrent properties depending on the proximity and preponderance of the block sequence on the PT backbone.

Glycopolymer-Based Antiswelling, Conductive, and Underwater Adhesive Hydrogels for Flexible Strain Sensor Application

With the fast development of soft electronics, underwater adhesion has become a highly desired feature for various sensing uses. Currently, most adhesive hydrogels are based on catechol-based structures, such as polydopamine, pyrogallol, and tannic acid, with very limited structural variety. Herein, a new type of glycopolymer-based underwater adhesive hydrogel has been prepared straightforwardly by random copolymerization of acrylic acid, acetyl-protected/unprotected glucose, and methacrylic anhydride in dimethyl sulfoxide (DMSO). By employing a DMSO-water solvent exchange strategy, the underwater adhesion was skillfully induced by the synergetic effects of hydrophobic aggregation and hydrogen bonding, leading to excellent adhesion behaviors on various surfaces, including pig skins, glasses, plastics, and metals, even after 5 days of storage in water. In addition, the underwater adhesive hydrogels with simple and low-cost protected/unprotected carbohydrate compositions showed good mechanical and rheological properties, together with cytocompatibility and antiswelling behavior in water, all of which are beneficial for underwater adhesions. In application as a flexible strain sensor, the adhesive hydrogel exhibited stable and reliable sensing ability for monitoring human motion in real time, suggesting great potential for intelligent equipment design.

Polyisobutylene-based glycopolymers as potent inhibitors for in vitro insulin aggregation

A family of amphiphilic diblock copolymers containing a hydrophobic polyisobutylene (PIB, M_n = 1000 g mol^-1) segment and a hydrophilic block with sugar pendants has been synthesized by combining living cationic and reversible addition-fragmentation chain transfer (RAFT) polymerization techniques; to explore their potential in insulin fibrillation inhibition. The glucose content in the hydrophilic segment has been tailor-made from 20 to 57 units to prepare block copolymers. The removal of the acetates from the pendent glucose units resulted in amphiphilic block copolymers that generated micellar aggregates in aqueous media. The treatment of insulin with these block copolymers affected the fibril formation process which was demonstrated using an array of biophysical techniques, namely, thioflavin T (ThT) fluorescence, tyrosine (Tyr) fluorescence, Nile red (NR) fluorescence, isothermal titration calorimetry (ITC), etc. The Tyr fluorescence assay and NR fluorescence study revealed the crucial role of hydrophobic interaction in the inhibition process, whereas ITC measurements confirmed the importance of polar interaction. Thus, the block copolymers exhibit potent inhibition of insulin fibrillation owing to hydrophobic (from PIB segment) and glycosidic cluster effect (from sugar pendant block).

Tailor-made Glycopolymers via Reversible Deactivation Radical Polymerization: Design, Properties and Applications

Investigating the underlying mechanism of biological interactions using glycopolymer is becoming increasingly important owing to their unique recognition properties. The multivalent interactions between lectin and glycopolymer are significantly influenced by...

Supramolecularly cross-linked nanoassemblies of self-immolative polyurethane from recycled plastic waste: high encapsulation stability and triggered release of guest molecules

Stabilizing noncovalently encapsulated guest molecules inside a nanoassembly constructed from amphiphilic polymers has become a very challenging effort in the area of targeted drug delivery of biomedical applications. The unwanted...

Collaborative assembly of doxorubicin and galactosyl diblock glycopolymers for targeted drug delivery of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) patients suffer from severe pain due to the serious systemic side effects and low efficiency of chemotherapeutic drugs, and it is important to develop novel drug delivery systems to circumvent these issues. In this study, a series of galactose-based glycopolymers, poly(N-(prop-2-enoyl)-β-d-galactopyranosylamine)-b-poly(N-isopropyl acrylamide) (pGal(OH)-b-pNIPAA), were prepared through a sequential reversible addition-fragmentation chain transfer (RAFT) polymerization and tetrabutylammonium hydroxide (TBAOH)-mediated removal of acetyl groups. Hydrophilic doxorubicin hydrochloride was introduced to undergo collaborative assembly with poly(N-(prop-2-enoyl)-β-d-peracetylated galactosamine)-b-poly(N-isopropyl acrylamide) (pGal(Ac)-b-pNIPAA) via TBAOH treatment. pGal-b-pNIPAA/doxorubicin (DOX) delivery nanoparticles (GND NPs) formed by collaborative assembly were fully characterized by NMR, TEM and FT-IR, indicating the well-controlled formation of particles with uniform size and high efficiency in terms of drug loading and encapsulation compared with conventional adsorption methods. Meanwhile, the GND NPs were observed to be rapidly disintegrated under acidic conditions and resulted in an increased release of DOX. Cellular experiments showed that pGal-b-pNIPAA/DOX is apparently an asialoglycoprotein receptor (ASGPR)-mediated target of HCC, resulting in enhanced cellular uptake to HepG2 cells and anti-tumor efficacy in vitro. Furthermore, GND NPs III exerted more sustainable and effective anti-tumor effects compared to free DOX on a transgenic zebrafish TO(Kras^G12V) model in vivo. These results indicated that the biocompatible nanomaterials developed by collaborative assembly with galactosyl diblock glycopolymers and DOX may serve as a promising candidates for targeting therapy of HCC.

Uptake and Release of Species from Carbohydrate Containing Organogels and Hydrogels

Hydrogels are used for a variety of technical and medical applications capitalizing on their three-dimensional (3D) cross-linked polymeric structures and ability to act as a reservoir for encapsulated species (potentially encapsulating or releasing them in response to environmental stimuli). In this study, carbohydrate-based organogels were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization of a β-D-glucose pentaacetate containing methacrylate monomer (Ac-glu-HEMA) in the presence of a di-vinyl cross-linker; these organogels could be converted to hydrogels by treatment with sodium methoxide (NaOMe). These materials were studied using solid state ¹³C cross-polarization/magic-angle spinning (CP/MAS) NMR, Fourier transform infrared (FTIR) spectroscopy, and field emission scanning electron microscopy (FE-SEM). The swelling of the gels in both organic solvents and water were studied, as was their ability to absorb model bioactive molecules (the cationic dyes methylene blue (MB) and rhodamine B (RhB)) and absorb/release silver nitrate, demonstrating such gels have potential for environmental and biomedical applications.

Co-responsive smart cyclodextrin-gated mesoporous silica nanoparticles with ligand-receptor engagement for anti-cancer treatment

Combination of both internal- and external-stimuli responsive strategies in nanoplatforms can maximize therapeutic outcomes by overcoming drug efflux-mediated resistance and prolonging sustained release of therapeutic payloads in controlled and sequential manner. Here, we show a light/redox dual-stimuli responsive β-cyclodextrin (β-CD)-gated mesoporous silica nanoparticles (MSN) that can effectively load and seal the chemotherapeutics, doxorubicin (DOX), inside MSN with a dual-capped system. The primary gatekeeper was achieved by capping β-CD via a disulfide linkage. An azobenzene/galactose-grafted polymer (GAP) was introduced to functionalize the MSN surface through host-guest interaction. GAP not only served as a secondary non-covalent polymer-gatekeeper to further prevent molecules from leaking out, but also presented targeting ligand for engagement of the asialoglycoprotein receptor (ASGPR) on hepatocellular carcinoma (HepG2) cells. The controlled and stimuli release of DOX could be realized via dissociation of azobenzene moieties from β-CD cage upon UV-irradiation, followed by liberation with the endogenous glutathione. The in vitro studies verified the redox-sensitive DOX release behavior, and the UV irradiation could accelerate this process to trigger DOX burst from MSN-ss-CD/GAP. Notably, the DOX@MSN-ss-CD/GAP could more efficiently deliver DOX into HepG2 cells and demonstrate enhanced cytotoxicity as compared with HeLa and COS7 cells. The smart MSN-ss-CD/GAP delivery system holds the potential for universal therapeutic uses in both biomedical research and clinical settings.

Dual-Responsive Core Crosslinking Glycopolymer-Drug Conjugates Nanoparticles for Precise Hepatocarcinoma Therapy

Nanoparticles (NPs) have demonstrated a potential for hepatocarcinoma therapy. However, the effective and safe NP-mediated drug transportation is still challenging due to premature leakage and inaccurate release of the drug. Herein, we designed a series of core cross-linking galactose-based glycopolymer-drug conjugates (GPDs) NPs with both redox-responsive and pH-sensitive characteristics to target and program drug release. Glycopolymer is comprised of galactose-containing units, which gather on the surface of GPD NPs and exhibit specific recognition to hepatocarcinoma cells, which over-express the asialoglycoprotein receptor. GPD NPs are stable in a normal physiological environment and can rapidly release the drug in hepatocarcinoma cells, which are reductive and acidic, by combining disulfide bond cross-linked core, as well as boronate ester-linked hydrophilic glycopolymer chain and the hydrophobic drug.

Disassembly of Bacterial Biofilms by the Self-Assembled Glycolipids Derived from Renewable Resources

More than 80% of chronic infections of bacteria are caused by biofilms. It is also a long-term survival strategy of the pathogens in a nonhost environment. Several amphiphilic molecules have been used in the past to potentially disrupt biofilms; however, the involvement of multistep synthesis, complicated purification and poor yield still remains a major problem. Herein, we report a facile synthesis of glycolipid based surfactant from renewable feedstocks in good yield. The nature of carbohydrate unit present in glycolipid influence the ring chain tautomerism, which resulted in the existence of either cyclic structure or both cyclic and acyclic structures. Interestingly, these glycolipids self-assemble into gel in highly hydrophobic solvents and vegetable oils, and displayed foam formation in water. The potential application of these self-assembled glycolipids to disrupt preformed biofilm was examined against various pathogens. It was observed that glycolipid 6a disrupts Staphylococcus aureus and Listeria monocytogenes biofilm, while the compound 6c was effective in disassembling uropathogenic E. coli and Salmonella enterica Typhimurium biofilms. Altogether, the supramolecular self-assembled materials, either as gel or as surfactant solution could be potentially used for surface cleansing in hospital environments or the food processing industries to effectively reduce pathogenic biofilms.

Amino Acid Functional Polymers: Biomimetic Polymer Design Enabling Catalysis, Chiral Materials, and Drug Delivery

Amino acids are the natural building blocks for the world around us. Highly functional, these small molecules have unique catalytic properties, chirality, and biocompatibility. Imparting these properties to surfaces and other macromolecules is highly sought after and represents a fast-growing field. Polymers functionalized with amino acids in the side chains have tunable optical properties, pH responsiveness, biocompatibility, structure and self-assembly properties. Herein, we review the synthesis of amino acid functional polymers, discuss manipulation of available strategies to achieve the desired responsive materials, and summarize some exciting applications in catalysis, chiral particles, and drug delivery.

Self-assembly of well-defined fatty acid based amphiphilic thermoresponsive random copolymers

Side-chain stearic acid containing thermoresponsive and crystalline random copolymers are synthesized via RAFT technique, which self-assembled to spherical micellar structures in aqueous solution depending on stearate content in the copolymer.

Preparation and UCST-type phase behavior of glycopolypeptides in alcoholic solvents

Glycopolypeptides with mannose pendants exhibited a reversible UCST-type phase behavior in various alcoholic solvents. The solution phase transition temperature was related to the solvent, concentration, main-chain length, and side-chain composition.