Formation of non-spherical polymersomes driven by hydrophobic directional aromatic perylene interactions

Faceted polymersomes: a sphere-to-polyhedron shape transformation

The creation of "soft" deformable hollow polymeric nanoparticles with complex non-spherical shapes via block copolymer self-assembly remains a challenge. In this work, we show that a perylene-bearing block copolymer can self-assemble into polymeric membrane sacs (polymersomes) that not only possess uncommonly faceted polyhedral shapes but are also intrinsically fluorescent. Here, we further reveal for the first time an experimental visualization of the entire polymersome faceting process. We uncover how our polymersomes facet through a sphere-to-polyhedron shape transformation pathway that is driven by perylene aggregation confined within a topologically spherical polymersome shell. Finally, we illustrate the importance in understanding this shape transformation process by demonstrating our ability to controllably isolate different intermediate polymersome morphologies. The findings presented herein should provide opportunities for those who utilize non-spherical polymersomes for drug delivery, nanoreactor or templating applications, and those who are interested in the fundamental aspects of polymersome self-assembly.

Re-designing materials for biomedical applications: from biomimicry to nature-inspired chemical engineering

Gathering inspiration from nature for the design of new materials, products and processes is a topic gaining rapid interest among scientists and engineers. In this review, we introduce the concept of nature-inspired chemical engineering (NICE). We critically examine how this approach offers advantages over straightforward biomimicry and distinguishes itself from bio-integrated design, as a systematic methodology to present innovative solutions to challenging problems. The scope of application of the nature-inspired approach is demonstrated via examples from the field of biomedicine, where much of the inspiration is still more narrowly focused on imitation or bio-integration. We conclude with an outlook on prospective future applications, offered by the more systematic and mechanistically based NICE approach, complemented by rapid progress in manufacturing, computation and robotics. This article is part of the theme issue 'Bioinspired materials and surfaces for green science and technology'.

Local dynamics in supramolecular polymer networks probed by magnetic particle nanorheology

Transient supramolecular polymer networks are promising candidates as soft self-healing or stimuli-sensitive materials. In this paper, we employ a novel nanorheological approach, magnetic particle nanorheology (MPN), in order to better understand the local dynamic properties of model supramolecular networks from a molecular point of view. Hence, the bond strength between four-arm star-shaped polyethylene glycol (PEG) functionalized at the four extremities with terpyridine ligands is tuned by implementing different metal ions with variable complexation affinities for the ligand. We show that MNP allows for the evaluation of the strength and connectivity of the polymer networks by the estimation of relaxation times, mesh size, and also the viscoelastic properties of these materials. These results are compared and complemented to former outcomes on these systems that were obtained by macroscopic analytical methods. A clear dependence between the strength of the metal-ligand complex and the local dynamics of the polymeric network is observed by the nanorheological approach, which is in good agreement with previous predictions related to the complex formation constants.

Non-spherical polymersomes: formation and characterization

This tutorial review summarizes recent efforts over the past decade to study the morphological transformation of conventionally spherical polymersomes into non-spherical polymersomes.

Correlation between polymer architecture and polyion complex micelle stability with proteins in spheroid cancer models as seen by light-sheet microscopy

Polyion complex (PIC) micelles are frequently used as a means to deliver biologics such as proteins.

Polymersomes: Breaking the Glass Ceiling?

Polymer vesicles, also known as polymersomes, have garnered a lot of interest even before the first report of their fabrication in the mid-1990s. These capsules have found applications in areas such as drug delivery, diagnostics and cellular models, and are made via the self-assembly of amphiphilic block copolymers, predominantly with soft, rubbery hydrophobic segments. Comparatively, and despite their remarkable impermeability, glassy polymersomes (GPs) have been less pervasive due to their rigidity, lack of biodegradability and more restricted fabrication strategies. GPs are now becoming more prominent, thanks to their ability to undergo stable shape-change (e.g., into non-spherical morphologies) as a response to a predetermined trigger (e.g., light, solvent). The basics of block copolymer self-assembly with an emphasis on polymersomes and GPs in particular are reviewed here. The principles and advantages of shape transformation of GPs as well as their general usefulness are also discussed, together with some of the challenges and opportunities currently facing this area.

Self-Assembly of Metallacages into Multidimensional Suprastructures with Tunable Emissions

Cubic metallacages were arranged into multidimensional (one-, two-, and three-dimensional) suprastructures via multistep assembly. Four new shape-controllable, hybrid metallacages with modified substituents and tunable electronic properties were prepared using dicarboxylate ligands with various substituents (sodium sulfonate, nitro, methoxyl, and amine), tetra-(4-pyridylphenyl) ethylene, and cis-(PEt3)2Pt(OTf)2. The as-prepared metallacages were used as building blocks for further assembly. Diverse suprastructures with tunable emissions (λmax from 451 to 519 nm) and various substituents (-SO3Na, -NO2, -OCH3, and -NH2) were prepared depending on the substituents and solvents used.

Development of Morphologically Discrete PEG-PDLLA Nanotubes for Precision Nanomedicine

Precise control over the morphological features of nanoparticles is an important requisite for their application in nanomedical research. Parameters such as size and shape have been identified as critical features for effective nanotherapeutic technologies due to their role in circulation, distribution, and internalization in vivo. Tubular PEG–PDLLA polymersomes (nanotubes) exhibit an interesting morphology with potential for immunotherapeutics, as the elongated shape can affect cell–particle interactions. Developing methodologies that permit control over the precise form of such nanotubes is important for their biomedical implementation due to the stringent physicochemical constraints for efficacious performance. Through careful control over the engineering process, we demonstrate the generation of well-defined nanotubes based on polymersomes as small as 250 and 100 nm, which can be successfully shape transformed. The quality of the resulting nanostructures was established by physical characterization using AF4-MALS and cryo-TEM. Moreover, we show the successful loading of such nanotubes with model payloads (proteins and drugs). These findings provide a promising platform for implementation in biomedical applications in which discrete structure and functionality are essential features.

The hallmarks of living systems: towards creating artificial cells

Despite the astonishing diversity and complexity of living systems, they all share five common hallmarks: compartmentalization, growth and division, information processing, energy transduction and adaptability. In this review, we give not only examples of how cells satisfy these requirements for life and the ways in which it is possible to emulate these characteristics in engineered platforms, but also the gaps that remain to be bridged. The bottom-up synthesis of life-like systems continues to be driven forward by the advent of new technologies, by the discovery of biological phenomena through their transplantation to experimentally simpler constructs and by providing insights into one of the oldest questions posed by mankind, the origin of life on Earth.

Bottom-Up Evolution of Vesicles from Disks to High-Genus Polymersomes

Polymersomes are vesicles formed by the self-assembly of amphiphilic copolymers in water. They represent one of the most promising alternatives of natural vesicles as they add new possibilities in the amphiphiles' molecular engineering of aqueous compartments. Here we report the design of polymersomes using a bottom-up approach wherein self-assembly of amphiphilic copolymers poly(2-(methacryloyloxy) ethyl phosphorylcholine)-poly(2-(diisopropylamino) ethyl methacrylate) (PMPC-PDPA) into membranes is tuned using pH and temperature. We report evolution from disk micelles, to vesicles, to high-genus vesicles (vesicles with many holes), where each passage is controlled by pH switch or temperature. We show that the process can be rationalized, adapting membrane physics theories to disclose scaling principles that allow the estimation of minimal radius of vesiculation as well as chain entanglement and coupling. This approach allows us to generate nanoscale vesicles with genus from 0 to 70, which have been very elusive and difficult to control so far.

Nonspherical Liquid Crystalline Assemblies with Programmable Shape Transformation

Liquid crystalline (LC) assemblies with tailored shape and programmable shape transformation were prepared via polymerization-induced self-assembly. The influence of polymerization temperature and solvent on the shape of the LC assemblies indicated that shape of the LC assemblies could be delicately regulated by the repulsive interaction among the solvophilic chains and LC ordering. Programmable shape transformation of ellipsoidal LC assemblies was achieved, taking advantage of the smectic-to-isotropic phase transition. The ellipsoidal assemblies could remain ellipsoids or transform to faceted spheres and spheres, depending on the temperature procedure used. Besides, the generated spheres could be reshaped to ellipsoids with high shape recovery ratio. Small angle X-ray scattering study indicated that the interplay of the reversible smectic-to-isotropic phase transition and kinetic trapping underpins the programmed shape transformation. As a general approach to LC assemblies with programmable shape transformation, our strategy would provide a reliable platform for nanoactuators, nanomotors, and adaptive colloidal devices.

Morphology Evolution of Stimuli-Responsive Triblock Copolymer Modulated by Polyoxometalates

Polyoxometalate (POM) H₃PMo₁₂O₄₀ was coassembled with stimuli-responsive triblock copolymer poly(ethylene oxide)- block-polystyrene- block-poly(2-(dimethylamino)ethyl methacrylate) (PEO- b-PS- b-PDMAEMA) by electrostatic interactions. Depending on the POM contents, the hybrid complexes can self-assemble into a series of morphologies: micelles, rods, toroids, and vesicles. Unlike traditional morphology transition of amphiphilic block copolymer derived from a broad range of hydrophobic volume fractions, POM-induced morphology transitions just occurred in a narrow range of volume fractions. The length of rod micelles exponentially decreased with solvent compositions (tetrahydrofuran/H₂O). The hybrid assemblies showed acid-base responsibility due to the PDMAEMA block. Rod micelles could further assemble and disassemble reversibly upon adding acid/base. Fluorescent polyoxometalate Na₉EuW₁₀O₃₆ was also complexed with PEO- b-PS- b-PDMAEMA to prepare fluorescent vesicles. The vesicles showed off-on switchable fluorescence behavior accompanied with reversible vesicle-to-micelle transformation in response to pH stimuli.

Morphological and mechanical determinants of cellular uptake of deformable nanoparticles

Understanding the interactions of nanoparticles (NPs) with cell membranes and regulating their cellular uptake processes are of fundamental importance to the design of drug delivery systems with minimum toxicity, high efficiency and long circulation time. Employing the procedure of coarse-graining, we built an elastically deformable NP model with tunable morphological and mechanical properties. We found that the cellular uptake of deformable NPs depends on their shape: an increase in the particle elasticity significantly slows the uptake rate of spherical NPs, slightly retards that of prolate NPs, and promotes the uptake of oblate NPs. The intrinsic mechanisms have been carefully investigated through analysis of the endocytic mechanisms and free energy calculations. These findings provide unique insights into how deformable NPs penetrate across cell membranes and offer novel possibilities for designing effective NP-based carriers for drug delivery.

Physical stimuli-responsive liposomes and polymersomes as drug delivery vehicles based on phase transitions in the membrane

This paper reviews liposomes with crystalline phase and polymersomes exhibiting crystalline and thermotropic liquid crystalline phases in the membrane. Intriguing morphologies of vesicles are described, including spherical, ellipsoidal and faceted vesicles, produced by a large variety of amphiphilic molecules and polymers with nematic phase, smectic phase or crystalline phase. It is highlighted how the phase transitions and the phase grain boundaries could be used ingeniously to destabilize the vesicular structure and to achieve cargo-release under the action of external stimulation. These liposomes and polymersomes are responsive to physical stimuli, such as temperature variation, shear stress, light illumination, and magnetic and electric fields. These stimuli-responsive properties make them promising candidates as new smart drug delivery systems.

Core-crosslinked diblock terpolymer micelles – taking a closer look on crosslinking efficiency

We present an in-depth study on the crosslinking of diblock terpolymer micellar cores.