Synthesis and Single-Chain Folding of Amphiphilic Random Copolymers in Water

Direct synthesis of acrylate monomers in heterogeneous continuous flow processes

An efficient, safe and convenient laboratory scale continuous flow process for synthesis of (meth)acrylate monomers is described.

Advances in Single-Chain Nanoparticles for Catalysis Applications

Enzymes are the most efficient catalysts known for working in an aqueous environment near room temperature. The folding of individual polymer chains to functional single-chain nanoparticles (SCNPs) offers many opportunities for the development of artificial enzyme-mimic catalysts showing both high catalytic activity and specificity. In this review, we highlight recent results obtained in the use of SCNPs as bioinspired, highly-efficient nanoreactors (3-30 nm) for the synthesis of a variety of nanomaterials (inorganic nanoparticles, quantum dots, carbon nanodots), polymers, and chemical compounds, as well as nanocontainers for CO₂ capture and release.

Improving the Folding of Supramolecular Copolymers by Controlling the Assembly Pathway Complexity

A family of amphiphilic, heterograft copolymers containing hydrophilic, hydrophobic, and supramolecular units based on Jeffamine M-1000, dodecylamine, and benzene-1,3,5-tricarboxamide (BTA) motifs, respectively, was prepared via a postfunctionalization approach. The folding of the copolymers in water into nanometer-sized particles was analyzed by a combination of dynamic and static light scattering, circular dichroism spectroscopy, and small-angle neutron scattering. The sample preparation protocol was crucial for obtaining reproducible and consistent results, showing that only full control over the structure and pathway complexity will afford the desired folded structure, a phenomenon similar to protein folding. The results revealed that relatively small changes in the polymer’s graft composition strongly affected the intra- versus intermolecular assembly processes. Depending on the amount of the hydrophobic grafts based on either dodecyl or BTA groups, pronounced behavioral differences were observed for copolymers that comprise similar degrees of hydrophobic content. A high number of BTA grafts (>10%) resulted in the formation of multichain aggregates comprising around six polymer chains. In contrast, for copolymers comprising up to 10% BTA grafts the folding results in nanoparticles that adopt open, sparse conformations and comprise one to two polymer chains. Interestingly, predominantly single-chain polymeric nanoparticles were formed when the copolymer comprised only Jeffamine or Jeffamine and dodecyl grafts. In addition, replacing part of the BTA grafts by hydrophobic dodecyl grafts while keeping the hydrophobic content constant promoted single-chain folding and resulted in the formation of a compact, globular nanoparticle with a more structured interior. Thus, the intra- and intermolecular self-assembly pathways can be directed by carefully tuning the polymer’s hydrophilic–hydrophobic balance in combination with the number of supramolecular grafts.

Rational Design of Single-Chain Polymeric Nanoparticles That Kill Planktonic and Biofilm Bacteria

Infections caused by multidrug-resistant bacteria are on the rise and, therefore, new antimicrobial agents are required to prevent the onset of a postantibiotic era. In this study, we develop new antimicrobial compounds in the form of single-chain polymeric nanoparticles (SCPNs) that exhibit excellent antimicrobial activity against Gram-negative bacteria (e.g., Pseudomonas aeruginosa) at micromolar concentrations (e.g., 1.4 μM) and remarkably kill ≥99.99% of both planktonic cells and biofilm within an hour. Linear random copolymers, which comprise oligoethylene glycol (OEG), hydrophobic, and amine groups, undergo self-folding in aqueous systems due to intramolecular hydrophobic interactions to yield these SCPNs. By systematically varying the hydrophobicity of the polymer, we can tune the extent of cell membrane wall disruption, which in turn governs the antimicrobial activity and rate of resistance acquisition in bacteria. We also show that the incorporation of OEG groups into the polymer design is essential in preventing complexation with proteins in biological medium, thereby maintaining the antimicrobial efficacy of the compound even in in vivo mimicking conditions. In comparison to the last-resort antibiotic colistin, our lead agents have a higher therapeutic index (by ca. 2-3 times) and hence better biocompatibility. We believe that the SCPNs developed here have potential for clinical applications and the information pertaining to their structure-activity relationship will be valuable toward the general design of synthetic antimicrobial (macro)molecules.

Synthesis and Solution-Phase Characterization of Sulfonated Oligothioetheramides

Nature has long demonstrated the importance of chemical sequence to induce structure and tune physical interactions. Investigating macromolecular structure and dynamics is paramount to understand macromolecular binding and target recognition. To that end, we have synthesized and characterized flexible sulfonated oligothioetheramides (oligo-TEAs) by variable temperature pulse field gradient (PFG) NMR, double electron-electron resonance (DEER), and molecular dynamics (MD) simulations to capture their room temperature structure and dynamics in water. We have examined the contributions of synthetic length (2-12mer), pendant group charge, and backbone hydrophobicity. We observe significant entropic collapse, driven in part by backbone hydrophobicity. Analysis of individual monomer contributions revealed larger changes due to the backbone compared to pendant groups. We also observe screening of intramolecular electrostatic repulsions. Finally, we comment on the combination of DEER and PFG NMR measurements via Stokes-Einstein-Sutherland diffusion theory. Overall, this sensitive characterization holds promise to enable de novo development of macromolecular structure and sequence-structure-function relationships with flexible, but biologically functional macromolecules.

Self-assembly of PEG/dodecyl-graft amphiphilic copolymers in water: consequences of the monomer sequence and chain flexibility on uniform micelles

Self-assembly of hydrophilic poly(ethylene glycol) and hydrophobic dodecyl-graft amphiphilic copolymers in water was investigated in detail, by focusing on the effects of the monomer sequence and chain flexibility on micelles.

Compartmentalization of an ABC triblock copolymer single-chain nanoparticle via coordination-driven orthogonal self-assembly

We present coordination-driven intramolecular orthogonal self-assembly of ABC triblock copolymer into protein-like compartmentalized SCNP, whose sub-10 nm ultrafine subdomains are discrete and can respond to aqueous surroundings individually.

Synthesis and self-assembly of polystyrene-based diblock and triblock coil–brush copolymers

Anionic coil–brush, brush–coil–brush and coil–brush–coil type polystyrene-based di- and tri-block copolymers were synthesized and their micellization behavior was compared.

Poly(ethylene glycol)-graft-poly(vinyl acetate) single-chain nanoparticles for the encapsulation of small molecules

Amphiphilic poly(ethylene glycol)-graft-poly(vinyl acetate) copolymers with a low degree of grafting undergo self-folding in water driven by hydrophobic interactions, resulting in single-chain nanoparticles (SCNPs) possessing a hydrodynamic radius of about 10 nm.

Photoresponsive liquid crystalline polymer single-chain nanoparticles

Single-chain nanoparticles prepared from a side-chain liquid crystalline polymer bearing azobenzene moieties can be multifunctional.

Unimolecular micelles from graft copolymer with binary side chains

A novel amphiphilic binary graft copolymer was synthesized and used to prepare unimolecular micelles by intramolecular association.

Stimuli-responsive single-chain polymeric nanoparticles towards the development of efficient drug delivery systems

Novel dynamic single-chain polymeric nanoparticles not only significantly improve drug transport efficiency in vitro but can also reside stably and facilitate precisely triggered drug-release in tumor-like microenvironments.

Protein storage with perfluorinated PEG compartments in a hydrofluorocarbon solvent

We report a novel storage technology of proteins with surface-perfluorinated poly(ethylene glycol) compartments in 2H,3H-perfluoropentane.

LCST-Type Phase Separation of Poly[poly(ethylene glycol) methyl ether methacrylate]s in Hydrofluorocarbon

Poly[poly(ethylene glycol) methyl ether methacrylate]s [poly(PEGMA)s] sharply and reversibly exhibited lower critical solution temperature (LCST)-type phase separation in 2H,3H-perfluoropentane (2HPFP). The cloud points decreased from 52 to 41 °C with increasing the PEG pendant length [-(CH₂CH₂O)_mCH₃: m = 4.5, 9, 19]. The cloud point was precisely controlled via the addition of perfluoroalkanes (e.g., perfluorooctane) to the 2HPFP solution: typically, it was inversely proportional to the amount of perfluorooctane in the mixture. The unique thermoresponsive solubility further afforded the temperature-mediated micellization of a block copolymer of PEG19MA and methyl methacrylate (MMA) in 2HPFP to uniquely give a PEG-core micelle with PMMA shell. Therefore, the LCST phase separation properties in the hydrofluorocarbon would open new vistas for thermoresponsive polymeric materials.

Surface water retardation around single-chain polymeric nanoparticles: critical for catalytic function?

A library of water-soluble dynamic single-chain polymeric nanoparticles (SCPN) was prepared using a controlled radical polymerisation technique followed by the introduction of functional groups, including probes at targeted positions. The combined tools of electron paramagnetic resonance (EPR) and Overhauser dynamic nuclear polarization (ODNP) reveal that these SCPNs have structural and surface hydration properties resembling that of enzymes.

Single Chain Polymeric Nanoparticles as Selective Hydrophobic Reaction Spaces in Water

A Ru(II)-based catalyst trapped within an amphiphilic, folded polymer is employed for the oxidation of secondary alcohols to their corresponding ketones using tBuOOH as the oxidant. Under the applied catalytic conditions, the polymer catalyst forms a compartmentalized structure with a hydrophobic interior. We selected secondary alcohols that differ in hydrophobicity, reactivity, and steric hindrance as substrates, with the aim to elucidate how this affects the rate and the end conversion of the oxidation reaction. Our investigations show that the Ru(II)-based catalyst is very efficient for oxidation reactions in water. Moreover, high selectivity toward the more hydrophobic substrate is observed, which originates from the hydrophobic interior of the compartmentalized catalyst system. This hydrophobic selectivity is also observed in the reverse reaction, the transfer hydrogenation.

Supramolecular Assembly Mediates the Formation of Single-Chain Polymeric Nanoparticles

A breakthrough innovation in water-based polymeric nanoparticles has enabled significant progress in mimicking the folding of natural proteins by generating novel "single-chain polymeric nanoparticles" (SCPNs) via supramolecular interactions. In this study, a practical approach to the living polymerization of functionalized oligo(ethylene glycol) methacrylate monomers allows the incorporation of self-constituted multiple hydrogen-bonded groups into physically cross-linked polymer networks, which enables the formation of highly functionalized SCPNs in an aqueous environment. The newly developed materials are particularly attractive from a practical point of view since they have a very low critical micellization concentration and uniform particle diameters of ca. 25 nm, making them extremely stable under dilute conditions. Concentration-dependent experiments showed that SCPNs formed at polymer concentrations up to 40 mg/mL with no significant change in morphology observed. Moreover, the formed SCPNs had a very high stability in an aqueous solution containing surfactant, suggesting potential for a wide variety of applications as a promising candidate nanocarrier for bioimaging, controlled release, and drug delivery systems.

Photodegradable and size-tunable single-chain nanoparticles prepared from a single main-chain coumarin-containing polymer precursor

A polyester bearing coumarin moieties in the main chain was used to prepare photodegradable single-chain nanoparticles (SCNPs) of variable sizes. While the intra-chain photodimerization of the chromophore determines the size of SCNPs, the photocleavage occurring under UV irradiation at a different wavelength breaks down the ultra-small nanoparticles.

Simulation guided design of globular single-chain nanoparticles by tuning the solvent quality

The control of primary and further structures of individual folded/collapsed synthetic polymers has received significant attention in recent years. However, the synthesis of single-chain nanoparticles (SCNPs) showing a compact, globular conformation in solution has turned out so far to be highly elusive. By means of simulations, we propose two methods for obtaining globular SCNPs in solution. The first synthesis route is performed in the bad solvent, with the precursor anchored to a surface. In the second route we use a random copolymer precursor with unreactive solvophilic and reactive solvophobic units, which form a single core-shell structure. Both protocols prevent intermolecular cross-linking. After recovering good solvent conditions, the swollen nanoparticles maintain their globular character. The proposed methods are experimentally realizable and do not require specific sequence control of the precursors. Our results pave the way for the synthesis via solvent-assisted design of a new generation of globular soft nanoparticles mimicking global conformations of native proteins in solution.