Dynamic metastable polymersomes enable continuous flow manufacturing

Triblock Polyampholyte-Based Nanovesicles for Targeted Spleen Delivery

Polymeric vesicles are a promising platform for targeted drug delivery. In this study, nanovesicles are developed using triblock polyampholytes composed of neutral poly(ethylene glycol), cationic poly(L-lysine), and anionic poly(α,β-aspartic acid) segments (PEG-PLys-PAsp) poly(aspartate) segments. By controlling the polymerization degree of these cationic and anionic segments, narrowly distributed nanovesicles are successfully assembled with a hydrodynamic diameter of ≈140 nm. The membrane thickness of the nanovesicles is around 15 nm, corresponding to a uniform polyion complex layer. Cross-linking the membrane of the nanovesicles via amide bonds enhance their stability in physiological salt and temperature conditions. In vivo, the cross-linked nanovesicles exhibit prolonged blood circulation and selective accumulation in the spleen after intravenous injection in mice. This approach demonstrates the potential of polyampholyte-based nanovesicles (TPBV) for targeted drug delivery applications to the spleen.

Ultrathin Polymersomes with Controllable Light-Responsivity via Adjusting the Electronic Effect from Para-Substituents of Azobenzene

Achieving ultrathin polymersomes (UTPSs) with controllable light-responsive kinetics poses a prospective strategy to address the growing demands of intelligent and miniature systems, but it remains challenging. Herein, we reported the self-assembly of numerous side-chain-type amphiphilic alternating azocopolymers (AAACs) into a series of UTPSs with diameters spanning 210-270 nm and ultrathin vesicular thickness spanning 1.91-2.14 nm. The light-triggered reversible size transitions for these UTPSs are rendered by the photo-isomerization of azobenzene moiety upon alternating irradiation with UV and visible light. The systematical isomerization kinetic study proved that the light-responsive rate of distinct UTPSs was highly dependent on the electronic effect of para-substituents of azobenzenes within AAACs. Notably, the rate constant of electron-withdrawing nitro-modified UTPSs was 6.7 times greater than that of electron-donating hydroxyl-modified UTPSs. The proof-of-concept cargo release activity for different UTPSs was evaluated using a hydrophilic model drug of methylene blue (MB), with a light-controllable releasing performance that highly depended on the para-substituent-induced light-responsive kinetics. Our work offers an innovative strategy to fabricate stimuli-responsive UTPSs with a controllable responsive performance for the targeted applications in bionanotechnology.

Polymeric Nanoarchitectures: Advanced Cargo Systems for Biological Applications

Polymeric nanoarchitectures are crafted from amphiphilic block copolymers through a meticulous self-assembly process. The composition of these block copolymers is finely adjustable, bestowing precise control over the characteristics and properties of the resultant polymeric assemblies. These nanoparticles have garnered significant attention, particularly in the realm of biological sciences, owing to their biocompatibility, favorable pharmacokinetics, and facile chemically modifiable nature. Among the myriad of polymeric nanoarchitectures, micelles and polymersomes stand out as frontrunners, exhibiting much potential as cargo carrier systems for diverse bio-applications. This review elucidates the design strategies employed for amphiphilic block copolymers and their resultant assemblies, specifically focusing on micelles and polymersomes. Subsequently, it discusses their wide-ranging bio-applications, spanning from drug delivery and diagnostics to bioimaging and artificial cell applications. Finally, a reflective analysis will be provided, highlighting the current landscape of polymeric cargo carriers, and discussing the opportunities and challenges that lie ahead. With this review, it is aimed to summarize the recent advances in polymeric assemblies and their applications in the biomedical field.

Designing polymersomes with surface-integrated nanoparticles through hierarchical phase separation

Polymersomes with surface-integrated nanoparticles, in which a smaller sphere is attached to a larger capsule, are typically formed through complex processes like membrane deformation, polymerization, or membrane functionalization. This complexity restricts facile application of this unusual topology, for example in drug delivery or nanomotor science. Our study introduces a robust method for crafting polymersomes with surface-integrated nanoparticles using a hierarchical phase separation approach. By co-assembling block copolymers with aromatic aggregation-induced emission (AIE) moieties as side chains and photothermal-responsive guest molecules (PTM), spontaneous sequential phase separation processes occur that lead to their controlled formation. Polymer-rich liquid droplets form first, followed by internal phase separation of the guest molecules, which determines the formation of asymmetric morphology. This mechanism is elucidated in detail using liquid-phase transmission and cryogenic transmission electron microscopy (LP-TEM and cryo-TEM) and corroborated by theoretical simulations of the interaction forces between the block copolymers and guest molecules. Finally, the application potential of polymersomes with surface-integrated nanoparticles as nanomotors is demonstrated.

Unusual Endotaxy Growth of Hexagonal Nanosheets by the Self-Assembly of a Homopolymer

A classical crystallization usually grows epitaxially from a crystal nucleus. Presented in this study is an unusual endotaxy growth manner of a crystalline homopolymer to form hexagonal nanosheets. The amphiphilic homopolymer, poly(3-(4-(phenyldiazenyl)phenoxy)propyl methacrylate) (PAzoPMA), is first annealed in isopropanol to afford a hexagonal nut-like structure. Then, the PAzoPMA crystallizes from the inner wall to the center to form a thin bottom, which grows upwards along the bottom, leading to the formation of the evenly hexagonal nanosheets. The energy fluctuation by molecular dynamics (MD) simulation during self-assembly confirms the packing state of PAzoPMA chains in different solvents. In isopropanol, the total energy is the lowest, demonstrating the tight regular arrangement of polymer chains. In addition, the non-bonding interaction energy is also the lowest, leading to the favorable contact with solvent molecules and the formation of hexagonal nanosheets. Otherwise, nanowires and giant large compound micelles are formed in ethanol and n-butanol, respectively. Overall, an unusual endotaxy crystallization manner of an amphiphilic homopolymer is observed during the preparation of hexagonal nanosheets, which brings fresh insight for understanding the crystallization behavior of polymers and preparing functional soft nanomaterials.

Unlocking Intracellular Protein Delivery by Harnessing Polymersomes Synthesized at Microliter Volumes using Photo-PISA

Efficient delivery of therapeutic proteins and vaccine antigens to intracellular targets is challenging due to generally poor cell membrane permeation and endolysosomal entrapment causing degradation. Herein, these challenges are addressed by developing an oxygen-tolerant photoinitiated polymerization-induced self-assembly (Photo-PISA) process, allowing for the microliter-scale (10 µL) synthesis of protein-loaded polymersomes directly in 1536-well plates. High-resolution techniques capable of analysis at a single particle level are employed to analyze protein encapsulation and release mechanisms. Using confocal microscopy and super-resolution stochastic optical reconstruction microscopy (STORM) imaging, their ability to deliver proteins into the cytosol following endosomal escape is subsequently visualized. Lastly, the adaptability of these polymersomes is exploited to encapsulate and deliver a prototype vaccine antigen, demonstrating its ability to activate antigen-presenting cells and support antigen cross-presentation for applications in subunit vaccines and cancer immunotherapy. This combination of ultralow volume synthesis and efficient intracellular delivery holds significant promise for unlocking the high throughput screening of a broad range of otherwise cost-prohibitive or early-stage therapeutic protein and vaccine antigen candidates that can be difficult to obtain in large quantities. The versatility of this platform for rapid screening of intracellular protein delivery can result in significant advancements across the fields of nanomedicine and biomedical engineering.

Solvent Choice during Flow Assembly of Photocross-Linked Single-Chain Nanoparticles and Micelles Affects Cellular Uptake

Polymeric micelles have widely been used as drug delivery carriers, and recently, single-chain nanoparticles (SCNPs) emerged as potential, smaller-sized, alternatives. In this work, we are comparing both NPs side by side and evaluate their ability to be internalized by breast cancer cells (MCF-7) and macrophages (RAW 264.7). To be able to generate these NPs on demand, the polymers were assembled by flow, followed by the stabilization of the structures by photocross-linking using blue light. The central aim of this work is to evaluate how the type of solvent affects self-assembly and ultimately the structure of the final NP. Therefore, a library of copolymers with different sequences, including block copolymers (AB, ABA, BAB), and statistical copolymers (rAB and rAC) was synthesized using PET-RAFT with A denoting poly(ethylene glycol) methyl ether acrylate (PEGMEA), B as 2-hydroxyethyl acrylate (HEA), and C as 4-hydroxybutyl acrylate (HBA). The polymers were conjugated with a quinoline derivative to enable the formation of cross-linked structures by photocross-linking during flow assembly. Using water as the dispersant for photocross-linking led to the preassembly of these amphiphilic polymers into compact SCNPs and cross-linked micelles, resulting in a quick photoreaction. In contrast, acetonitrile led to fully dissolved polymers but a low rate of the photoreaction. These intramolecularly cross-linked polymers were then placed in water to result in more dynamic micelles and looser SCNPs. Small-angle X-ray scattering (SAXS), dynamic light scattering (DLS), and size exclusion chromatography (SEC) coupled with a viscosity detector show that cross-linking in acetonitrile results in better-defined NPs with a shell rich in PEGMEA. Cross-linking in acetonitrile led to NPs with significantly higher cellular uptake. Interestingly, passive transport was identified as the main pathway for the delivery of our NPs on MCF-7 cells, confirmed by the uptake of NPs on cells treated with inhibitors and by red blood cells. This work underscored the importance of the polymer precursor's structure and the choice of solvent during intramolecular cross-linking in determining the drug delivery efficiency and biological behavior of SCNPs.

Streamlined Formation and Manipulation of Charged Polymersomes

Charged polymersomes are attractive for advanced material applications due to their versatile encapsulation capabilities and charge-induced functionality. Although desirable, the pH-sensitivity of charged block copolymers adds complexity to its self-assembly process, making it challenging to produce charged polymersomes in a reliable manner. In this work, a flow approach to control and strike a delicate balance between solvent composition and pH for self-assembly is used. This allows for the identification of a phase window to reliably produce of charged polymersomes. The utility of this approach to streamline downstream processes, such as morphological transformation or in-line purification is further demonstrated. As proof-of-concept, it is shown that the processed polymersomes can be used for surface modifications facilitated by charge complexation.

Polymersomes with micellar patches

Hollow block copolymer particles called polymer vesicles (polymersomes) serve as versatile containers for compartmentalization in synthetic biology and drug delivery. Recently, there has been growing interest in using polymersomes as colloidal building blocks for creating higher-order clustered structures. Most reports thus far rely on the use of DNA base-pairing interactions to "glue" polymersomes with other colloidal components. In this study, we present two alternative electrostatically driven approaches to assemble polymersomes and model colloids (micelles) into hybrid clusters. The first approach uses pH to manipulate electrostatic interactions and effectively control the clustering extent of micellar subunits on polymersomes, while the second approach relies on the hydrolysis of an acid trigger, glucono delta-lactone (GDL), to introduce temporal control over clustering. We envisage our approaches and structures reported herein will help inspire the creation of new prospects for materials science and biomedical applications.

Kinetically Controlled and Nonequilibrium Assembly of Block Copolymers in Solution

Covalent polymers are versatile macromolecules that have found widespread use in society. Contemporary methods of polymerization have made it possible to construct sequence polymers, including block copolymers, with high precision. Such copolymers assemble in solution when the blocks have differing solubilities. This produces nano- and microparticles of various shapes and sizes. While it is straightforward to draw an analogy between such amphiphilic block copolymers and phospholipids, these two classes of molecules show quite different assembly characteristics. In particular, block copolymers often assemble under kinetic control, thus producing nonequilibrium structures. This leads to a rich variety of behaviors being observed in block copolymer assembly, such as pathway dependence (e.g., thermal history), nonergodicity and responsiveness. The dynamics of polymer assemblies can be readily controlled using changes in environmental conditions and/or integrating functional groups situated on polymers with external chemical reactions. This perspective highlights that kinetic control is both pervasive and a useful attribute in the mechanics of block copolymer assembly. Recent examples are highlighted in order to show that toggling between static and dynamic behavior can be used to generate, manipulate and dismantle nonequilibrium states. New methods to control the kinetics of block copolymer assembly will provide endless unanticipated applications in materials science, biomimicry and medicine.

Making the Complicated Simple: A Minimizing Carrier Strategy on Innovative Nanopesticides

The flourishing progress in nanotechnology offers boundless opportunities for agriculture, particularly in the realm of nanopesticides research and development. However, concerns have been raised regarding the human and environmental safety issues stemming from the unrestrained use of non-therapeutic nanomaterials in nanopesticides. It is also important to consider whether the current development strategy of nanopesticides based on nanocarriers can strike a balance between investment and return, and if the complex material composition genuinely improves the efficiency, safety, and circularity of nanopesticides. Herein, we introduced the concept of nanopesticides with minimizing carriers (NMC) prepared through prodrug design and molecular self-assembly emerging as practical tools to address the current limitations, and compared it with nanopesticides employing non-therapeutic nanomaterials as carriers (NNC). We further summarized the current development strategy of NMC and examined potential challenges in its preparation, performance, and production. Overall, we asserted that the development of NMC systems can serve as the innovative driving force catalyzing a green and efficient revolution in nanopesticides, offering a way out of the current predicament.

Polymersomes as the Next Attractive Generation of Drug Delivery Systems: Definition, Synthesis and Applications

Polymersomes are artificial nanoparticles formed by the self-assembly process of amphiphilic block copolymers composed of hydrophobic and hydrophilic blocks. They can encapsulate hydrophilic molecules in the aqueous core and hydrophobic molecules within the membrane. The composition of block copolymers can be tuned, enabling control of characteristics and properties of formed polymersomes and, thus, their application in areas such as drug delivery, diagnostics, or bioimaging. The preparation methods of polymersomes can also impact their characteristics and the preservation of the encapsulated drugs. Many methods have been described, including direct hydration, thin film hydration, electroporation, the pH-switch method, solvent shift method, single and double emulsion method, flash nanoprecipitation, and microfluidic synthesis. Considering polymersome structure and composition, there are several types of polymersomes including theranostic polymersomes, polymersomes decorated with targeting ligands for selective delivery, stimuli-responsive polymersomes, or porous polymersomes with multiple promising applications. Due to the shortcomings related to the stability, efficacy, and safety of some therapeutics in the human body, polymersomes as drug delivery systems have been good candidates to improve the quality of therapies against a wide range of diseases, including cancer. Chemotherapy and immunotherapy can be improved by using polymersomes to deliver the drugs, protecting and directing them to the exact site of action. Moreover, this approach is also promising for targeted delivery of biologics since they represent a class of drugs with poor stability and high susceptibility to in vivo clearance. However, the lack of a well-defined regulatory plan for polymersome formulations has hampered their follow-up to clinical trials and subsequent market entry.