Self-Assembled Block Copolymer Aggregates: From Micelles to Vesicles and their Biological Applications

Extracellular vesicles delivered rapamycin to improve the tumor microenvironment and enhance hepatocellular carcinoma immunotherapy

Hepatocellular carcinoma (HCC) is one of the most common and lethal malignancies worldwide with limited therapeutic options due to its tumor immunosuppressive microenvironment (TIME). Herein, we engineered extracellular vehicles (EVs) derived from hepatocellular carcinoma cells to encapsulate rapamycin-loaded nanoparticles (Rapa-EVs) for precision HCC therapy. The experimental results demonstrated that the Rapa-EVs improved water solubility and stability. Rapa-EVs showed a high cellular uptake rate and could effectively target tumor tissues, promote dendritic cell (DC) maturation, and thereby activated CD8 + T cells. They directly inhibited H22 cell proliferation, promoted macrophage M1 polarization. Rapa-EVs also normalized aberrant tumor vasculature to improve drug perfusion and immune cell infiltration, inhibited tumor metastasis. This design synergistically harnesses the natural tumor-targeting properties of EVs to achieve rapamycin-selective delivery, concurrently leveraging their intrinsic immunogenicity to prime antitumor immunity while coordinating rapamycin-mediated TIME remodeling. Through comprehensive in vitro and in vivo evaluations, our study establishes a paradigm for HCC therapy that integrates biomimetic drug delivery with microenvironmental modulation, offering a transformative approach to overcome treatment resistance and improve patient outcomes.

Emergent chiral and topological nanoarchitectonics in self-assembled supramolecular systems

The fabrication of structures with designated topologies at the nanoscale is an intriguing issue, attributed to the possibility of both imparting unique properties to functional materials and unravelling the codes that lie in many natural systems. As a significant bottom-up approach, the self-assembly strategy is potent in formulating various exquisite structures. While the building of common types of miniaturized structures such as tubes, twists and spheres has been investigated in depth to gain insight into the intrinsic principles that dictate their formation and functions, the preparation of peculiar topological nanostructures is still scattered and unsystematic. In parallel, chirality is among the most ubiquitous phenomena of fundamental significance in nature and is in close relationship with the origin of life. Essentially, chirality represents a type of orderliness and thus may interplay with peculiar topologies in an orchestrated and serendipitous way. In this review, we describe the development of constructing emergent chiral and topological nanoarchitectures via the self-assembly method, mainly focusing on structures including toroids, catenanes, Möbius strips, spirals and fractals. In addition, other types involving toruloids/kebabs, trumpets and bamboos, screws, dendritic and lamellar twists are also exemplified. The design of building blocks and various self-assembling strategies towards these target architectures are highlighted in this review, in an effort to provide an overview of the feasible approaches that facilitate the tailored construction of mesoscopic structures.

Polymersome-based nanomotors: preparation, motion control, and biomedical applications

Polymersome-based nanomotors represent a cutting-edge development in nanomedicine, merging the unique vesicular properties of polymersomes with the active propulsion capabilities of synthetic nanomotors. As a vesicular structure enclosed by a bilayer membrane, polymersomes can encapsulate both hydrophilic and hydrophobic cargoes. In addition, their physical-chemical properties such as size, morphology, and surface chemistry are highly tunable, which makes them ideal for various biomedical applications. The integration of motility into polymersomes enables them to actively navigate biological environments and overcome physiological barriers, offering significant advantages over passive delivery platforms. Recent breakthroughs in fabrication techniques and motion control strategies, including chemically, enzymatically, and externally driven propulsion, have expanded their potential for drug delivery, biosensing, and therapeutic interventions. Despite these advancements, key challenges remain in optimizing propulsion efficiency, biocompatibility, and in vivo stability to translate these systems into clinical applications. In this perspective, we discuss recent advancements in the preparation and motion control strategies of polymersome-based nanomotors, as well as their biomedical-related applications. The molecular design, fabrication approaches, and nanomedicine-related utilities of polymersome-based nanomotors are highlighted, to envisage the future research directions and further development of these systems into effective, precise, and smart nanomedicines capable of addressing critical biomedical challenges.

Regulating the Chiroptical Expression of Aggregated Solvophobic Core by Solvophilic Segments

The investigation of chiral supramolecular stacking is of essential significance for the understanding of the origin of homochirality in nature. Unlike structurally well-defined amphiphilic liposomes, it remains unclear whether the solvophilic segments of the amphiphilic block copolymer play a decisive role in the construction of asymmetric superstructures. Herein, insights are presented into the stacking patterns and morphological regulation in azobenzene-containing block copolymer assemblies solely by modulating the solvophilic chain length. The solvophilic poly(methacrylic acid) (PMAA) segments of different molecular weights could cause multi-mode chirality inversions involving stacking transitions between intra-chain π-π stacking, inter-chain H- and J-aggregation. Furthermore, the length of the solvophilic PMAA also affects the morphology of the chiral supramolecular assemblies; rice grain-like micelles, worms, nanofibers, floccules, and lamellae can be prepared at different solvophilic-solvophobic balance. The comprehensive mechanism is collectively revealed by utilizing various measurement methods, such as including circular dichroism (CD), small-angle X-ray scattering (SAXS), and wide-angle X-ray diffraction (WAXD). This study highlights the critical importance of fully dissolved solvophilic segments for the chiroptical regulation of the aggregated core, providing new insights into the arrangement of chiral supramolecular structures in polymer systems.

N-Amino Norbornene Imides as Scalable Monomers for Living Ring-Opening Metathesis Polymerization

Ring-opening metathesis polymerization (ROMP) is a well-established polymerization method that uses strained cyclic olefins to produce polymers with controlled molecular weight and dispersity suitable for aggregation in solution, leading to polymerization induced self-assembly (PISA). Herein, we report new norbornene-based monomers for the living ROMP that were synthesized on the multigram scale (20 g) starting from cis-5-norbornene-exo-2,3-dicarboxylic anhydride and hydrazine. Upon further reaction with carboxylic acid chlorides, non-hydrogen-bond-forming derivatives could be obtained. In the presence of Grubbs third generation catalyst (G3), the synthesized monomers could be polymerized to produce well-defined polymers with controlled molecular weights (Mn) and narrow dispersities (Đ). Furthermore, amphiphilic block copolymers were synthesized using a combination of acylated and nonacylated monomers, and the PISA behavior was investigated using dynamic light scattering (DLS). We believe that the self-assembly of the copolymers derived from the new norbornene-based monomers via the living ROMP method described here could be useful for developing advanced functional nanomaterials with various morphologies.

Ultra-pH-sensitive nanoplatform for precise tumor therapy

The emergence of precision cancer treatment has triggered a paradigm shift in the field of oncology, facilitating the implementation of more effective and personalized therapeutic approaches that enhance patient outcomes. The pH of the tumor microenvironment (TME) plays a pivotal role in both the initiation and progression of cancer, thus emerging as a promising focal point for precision cancer treatment. By specifically targeting the acidic conditions inherent to the tumor microenvironment, innovative therapeutic interventions have been proposed, exhibiting significant potential in augmenting treatment efficacy and ameliorating patient prognosis. The concept of ultra-pH-sensitive (UPS) nanoplatform was proposed several years ago, demonstrating exceptional pH sensitivity and an adjustable pH transition point. Subsequently, diverse UPS nanoplatforms have been actively explored for biomedical applications, enabling the loading of fluorophores, therapeutic drugs, and photosensitizers. This review aims to elucidate the design strategy and response mechanism of the UPS nanoplatform, with a specific emphasis on its applications in surgical therapy, immunotherapy, drug delivery, photodynamic therapy, and photothermal therapy. The potential and challenges of translating in the clinic on UPS nanoplatforms are finally explored. Thanks to its responsive and easily modifiable nature, the integration of multiple functional units within a UPS nanoplatform holds great promise for future advancements in tumor precision theranositcs.

Modular addition strategy-regulated polymerization-induced self-assembly: an in silico experiment

We propose a modular addition strategy-regulated polymerization-induced self-assembly (PISA) system to effectively control the reaction kinetics and self-assembly morphologies. We validated this strategy by performing in silico experiments on a well-established PISA system. Two categories of modular addition strategies, i.e., the multistep addition strategy and the constant rate addition strategy, were investigated. Results showed that the modular addition operation of macromolecular chain transfer agents (macro-CTAs) effectively regulated the width of the molecular weight distribution for the hydrophobic PSt block, which further led to an assembly of vesicle structures with irregular aspherical cavities. Besides, we found a new transition pathway for the formation of vesicles, which involved generation of small vesicles in the early stage followed by a gradual growth in the intermediate and late stages. In the constant rate addition strategy, with the increase in the addition rate of macro-CTA, we found that the morphology basically tended to change from a micellar structure to a vesicle structure. This study holds potential to inspire future work toward the improvement of experimental techniques in PISA-relevant systems.

Thermoresponsive Polymers as Viscosity Modifiers: Innovative Nanoarchitectures as Lubricant Additives

The world of lubricants is driven by the constant pursuit of improved performance in response of the requests of new engine generations. Engine oils play a critical role as lubricants in mitigating wear, reducing friction and ensuring optimal engine operation under diverse conditions. Modern commercial engine oils are complex formulations, comprising of a base oil, generally coming from petroleum sources, formulated with specific, important additives able to optimize the viscosity, thickening and shear stress in the operating temperature range. Such additives are produced in the thousand tons per year scale range. The most important class of additives for modern lubrication is made of organic polymers with variable architectures and topologies, generally referred as "viscosity modifiers" (VMs): they act as "moderators" of viscosity at different working temperatures. The tremendous advances in polymer science have been reflected in the realm of VMs, allowing the commercialization of products obtained by controlled polymerization techniques, and the experimentation of a broad variety of different macromolecular architectures and topologies as VMs. In this review we introduce the reader, together with the basic principles of viscosity modification and thermal-dependent rheological response, to the fascinating chemistry towards the improvement of VMs, through optimization of macromolecular design and architecture.

Fabrication of Hierarchical Nanostructures Featuring Amplified Asymmetry Through Co-Assembly of Liquid Crystalline Block Copolymer and Chiral Amphiphiles

The widespread presence of hierarchical asymmetric structures in nature has sparked considerable interest because of their unique functionalities. These ingenious structures across multiple scales often emerge from the transfer and amplification of asymmetry from chiral molecules under various synergistic effects. However, constructing artificial chiral asymmetric structures, particularly in developing hierarchical multicomponent structures analogous to those formed in nature through synergistic non-covalent interactions, still presents tremendous challenges. Herein, we propose a co-assembly strategy to fabricate hierarchical chiral mesostructures by combining a liquid crystalline block copolymer (LC-BCP) with a small molecular amphiphile containing chiral alanine or phenylalanine as a linker. Through a classic solvent-exchange process, chiral amphiphiles embedded within LC-BCP finely regulate the LC ordering effect and facilitate transfer and amplification of asymmetry. Consequently, various co-assembled structures with significant hierarchical chirality features are obtained through synergetic effects. Remarkably, subtle alterations to the side groups of amino acids in the amphiphiles effectively adjust the hierarchical morphology transition. Moreover, the covalent bonding sequence of amino acids in the amphiphiles emerges as a critical factor governing the formation of hierarchical nanofibers and multilayered vesicles exhibiting a superhelical sense.

Bicontinuous Nanoparticles from Spontaneous Self-Assembly of Block Copolymer Prodrug in Aqueous Medium for Potential Cancer Therapy

Despite having several advantages, bicontinuously structured polymeric nanoparticles (BSPNPs) are far less explored in the field of controlled drug delivery owing to the requirement of complex precursor copolymers and the associated multistep synthetic procedures. In this work, we report the synthesis of a redox-sensitive diblock copolymer (P1), which was subsequently utilized to prepare doxorubicin (DOX) containing a pH-labile prodrug (P2). P1 and P2 spontaneously self-assembled in aqueous media above their critical aggregation concentration, forming micellar nanoparticles with rare bicontinuous morphology that promotes loading of both hydrophobic and hydrophilic cargoes in different compartments. To the best of our knowledge, the formation of BSPNPs through direct self-assembly in aqueous media has not yet been reported. In vitro cellular studies asserted the higher safety profile of the nanoparticles against noncancerous cells (HEK293T) than free DOX, whereas they displayed higher drug-induced cytotoxicity against cancer cells (MCF-7) in comparison to free DOX, establishing them as promising cancer drug delivery systems.

Non-Biochemical Gradient Sequence-Controlled Polymers with Tuned Kinetics and Self-Assembled Morphologies

Two key challenges in the multidisciplinary field of sequence-controlled polymers are their efficient synthesis and the establishment of correlation with polymer properties. In this context, in this paper, gradient architecture in the hydrophobic tail of an amphiphile is implemented and synthesized for a fixed hydrophilic unit (polyethylene glycol, PEG), by means of two monomers (2-hydroxypropyl methacrylate, HPMA, and diacetone acrylamide, DAAM) of contrasting reactivities. The resulting non-biochemical gradient sequence-controlled polymers are generated from a one-pot, homogeneous mixture through a PET-RAFT-PISA (photoinduced electron/energy transfer-reversible addition-fragmentation chain transfer-polymerization-induced self-assembly) method. In addition, the initial concentration ratio of the monomers in the gradient is varied as an input for a set of fixed experimental parameters and conditions, and its correlation with kinetics, gradient and self-assembled morphologies is established, as the output of the process. These results are extensively corroborated via nuclear magnetic resonance (NMR) spectroscopy analysis, together with transmission electron microscopy (TEM) images, dynamic light scattering (DLS), and gel permeation chromatography (GPC) experiments. These results have implications for chemical computation carried out by PISA, programmable self-assembly, information storage, biomimetics, origins of life and synthetic protocell studies.

Nanoplatform for synergistic therapy constructed via the co-assembly of a reduction-responsive cholesterol-based block copolymer and a photothermal amphiphile

The goal of combination cancer therapy, including chemo-phototherapy, is to achieve highly efficient antitumor effects while minimizing the adverse reactions associated with conventional chemotherapy. Nevertheless, enhancing the contribution of non-chemotherapeutic strategies in combination therapy is often challenging because this requires multiple active ingredients to be encapsulated in a single delivery system. However, most commonly used photothermal reagents are challenging to be loaded in large quantities and have poor biocompatibility. Herein, we developed photothermal co-micelles through a co-assembly strategy using a cholesterol-based liquid crystal block copolymer (LC-BCP) with disulfide bonds in the side chain of the LC blocks and a croconaine-based amphiphile (CBA) containing a cholesterol moiety. This approach allowed the CBA to be effectively embedded within LC-BCPs, serving as the functional component of the drug-loaded carrier. These co-micelles could encapsulate doxorubicin (DOX), showed tunable reduction-responsive drug release, and enabled near-infrared laser-triggered photothermal therapy as well as in vivo fluorescence and photothermal imaging. Following laser irradiation, the photothermal activity of the co-micelles rapidly induced tumor cell death and accelerated drug release. In vitro and in vivo experiments demonstrated that the synergistic photo-chemotherapeutic effects of these drug-loaded co-micelles offer a promising avenue for synergistic precision photothermal-chemotherapy.

Self-assembly and phase behavior of Janus rods: Competition between shape and potential anisotropy

We characterize the self-assembly and phase behavior of Janus rods over a broad range of temperatures and volume fractions, using Langevin dynamics simulations and free energy calculations. The Janus rods consist of a line of fused overlapping spheres that interact via a soft-core repulsive potential, with the addition of an attractive pseudo-square-well tail to a fraction of the spheres (the coverage) ranging from 5% to 100% of sites. Competition between the stability of liquid crystal phases originating from shape anisotropy and assembly driven by directional interactions gives rise to a rich polymorphism that depends on the coverage. At low densities near the Boyle temperature, we observe the formation of spherical and tubular micelles at low coverages, while at higher coverages, randomly oriented monolayers form as the attractive parts of the rods overlap. At higher densities, bilayer structures appear and merge to form smectic and crystalline lamellar phases. All these structures gradually become unstable as the temperature is increased until eventually regular nematic and smectic phases appear, consistent with the hard rod limit. Our results indicate that the intermediate regime where shape-entropic effects compete with anisotropic attractions provided by site specificity is rich in structural possibilities and should help guide the design of rod-like colloids for specific applications.

Research Trends in the Development of Block Copolymer-Based Biosensing Platforms

Biosensing technology, which aims to measure and control the signals of biological substances, has recently been developed rapidly due to increasing concerns about health and the environment. Top-down technologies have been used mainly with a focus on reducing the size of biomaterials to the nano-level. However, bottom-up technologies such as self-assembly can provide more opportunities to molecular-level arrangements such as directionality and the shape of biomaterials. In particular, block copolymers (BCPs) and their self-assembly have been significantly explored as an effective means of bottom-up technologies to achieve recent advances in molecular-level fine control and imaging technology. BCPs have been widely used in various biosensing research fields because they can artificially control highly complex nano-scale structures in a directionally controlled manner, and future application research based on interactions with biomolecules according to the development and synthesis of new BCP structures is greatly anticipated. Here, we comprehensively discuss the basic principles of BCPs technology, the current status of their applications in biosensing technology, and their limitations and future prospects. Rather than discussing a specific field in depth, this study comprehensively covers the overall content of BCPs as a biosensing platform, and through this, we hope to increase researchers' understanding of adjacent research fields and provide research inspiration, thereby bringing about great advances in the relevant research fields.

Detailed Study of the Interactions between Glycopolymers in the Presence of Metal Ions through Quartz Crystal Microbalance Method

Polymer self-assemblies driven by enthalpic interactions, such as hydrogen bonding and electrostatic interactions, exhibit distinct properties compared to those driven by hydrophobic interactions. Carbohydrate-carbohydrate interactions, which are observed in physiological phenomena, also fall under enthalpic interactions. Our group previously reported on self-assemblies of methacrylate-type glycopolymers carrying mannose units in the presence of calcium ions; however, a detailed study of these interactions was lacking. In this work, we investigated the interactions between glycopolymers using the quartz crystal microbalance (QCM) method. Our quantitative analysis revealed that the interactions between the glycopolymers were influenced by the carbohydrate structures in the side chains, the types of divalent metal ions, and the structures of the polymer main chains. Notably, the strongest interaction was observed in the combination of methacrylate-type glycopolymers carrying mannose units and calcium ions, demonstrating their potential as a driving force for polymer self-assembly.

Designing Biomimetic Strain-Stiffening into Synthetic Hydrogels

Biological tissues are mechanoresponsive; that is, their properties dynamically change in response to mechanical stimuli. For example, in response to shear or elongational strain, collagen, fibrin, actin, and other filamentous biomaterials undergo dramatic strain-stiffening. Above a critical strain, their stiffness increases over orders of magnitude. While it is widely accepted that the stiffness of biological tissues impacts cell phenotype and several diseases, the biological impact of strain-stiffening remains understudied. Synthetic hydrogels that mimic the mechanoresponsive nature of biological tissues could serve as an in vitro platform for these studies. This review highlights recent efforts to mimic the strain-stiffening behavior of biological materials in synthetic hydrogels. We discuss the design principles for imparting synthetic hydrogels with biomimetic strain-stiffening, critically compare designs of strain-stiffening hydrogels that have been reported thus far, and discuss their use as in vitro platforms to probe how strain-stiffening impacts cell behavior, diseases, and other biological processes.

Dilute suspensions of Janus rods: the role of bond and shape anisotropy

Nanometer-sized clusters are often targeted due to their potential applications as nanoreactors or storage/delivery devices. One route to assemble and stabilize finite structures consists of imparting directional bonding patterns between the nanoparticles. When only a portion of the particle surface is able to form an inter-particle bond, finite-size aggregates such as micelles and vesicles may form. Building on this approach, we combine particle shape anisotropy with the directionality of the bonding patterns and investigate the combined effect of particle elongation and surface patchiness on the low density assembly scenario. To this aim, we study the assembly of tip-functionalised Janus hard spherocylinders by means of Monte Carlo simulations. By exploring the effects of changing the interaction strength and range at different packing fractions, we highlight the role played by shape and bond anisotropy on the emerging aggregates (micelles, vesicles, elongated micelles, and lamellae). We observe that shape anisotropy plays a crucial role in suppressing phases that are typical to spherical Janus nanoparticles and that a careful tuning of the interaction parameters allows promoting the formation of spherical micelles. These finite-size spherical clusters composed of elongated particles might offer more interstitials and larger surface areas than those offered by micelles of spherical or almost-spherical units, thus enhancing their storage and catalytic properties.

Monomer Composition as a Mechanism to Control the Self-Assembly of Diblock Oligomeric Peptide-Polymer Amphiphiles

Diblock oligomeric peptide-polymer amphiphiles (PPAs) are biohybrid materials that offer versatile functionality by integrating the sequence-dependent properties of peptides with the synthetic versatility of polymers. Despite their potential as biocompatible materials, the rational design of PPAs for assembly into multichain nanoparticles remains challenging due to the complex intra- and intermolecular interactions emanating from the polymer and peptide segments. To systematically explore the impact of monomer composition on nanoparticle assembly, PPAs were synthesized with a random coil peptide (XTEN2) and oligomeric alkyl acrylates with different side chains: ethyl, tert-butyl, n-butyl, and cyclohexyl. Experimental characterization using electron and atomic force microscopies demonstrated that the tail hydrophobicity impacted accessible morphologies. Moreover, the characterization of different assembly protocols (i.e., bath sonication and thermal annealing) revealed that certain tail compositions provide access to kinetically trapped assemblies. All-atom molecular dynamics simulations of micelle formation unveiled key interactions and differences in core hydration, dictating the PPA assembly behavior. These findings highlight the complexity of PPA assembly dynamics and serve as valuable benchmarks to guide the design of PPAs for a variety of applications, including catalysis, mineralization, targeted sequestration, antimicrobial activity, and cargo transportation.

Polyester nanoparticles delivering chemotherapeutics: Learning from the past and looking to the future to enhance their clinical impact in tumor therapy

Polymeric nanoparticles (NPs), specifically those comprised of biodegradable and biocompatible polyesters, have been heralded as a game-changing drug delivery platform. In fact, poly(α-hydroxy acids) such as polylactide (PLA), poly(lactide-co-glycolide) (PLGA), and poly(ε-caprolactone) (PCL) have been heavily researched in the past three decades as the material basis of polymeric NPs for drug delivery applications. As materials, these polymers have found success in resorbable sutures, biodegradable implants, and even monolithic, biodegradable platforms for sustained release of therapeutics (e.g., proteins and small molecules) and diagnostics. Few fields have gained more attention in drug delivery through polymeric NPs than cancer therapy. However, the clinical translational of polymeric nanomedicines for treating solid tumors has not been congruent with the fervor or funding in this particular field of research. Here, we attempt to provide a comprehensive snapshot of polyester NPs in the context of chemotherapeutic delivery. This includes a preliminary exploration of the polymeric nanomedicine in the cancer research space. We examine the various processes for producing polyester NPs, including methods for surface-functionalization, and related challenges. After a detailed overview of the multiple factors involved with the delivery of NPs to solid tumors, the crosstalk between particle design and interactions with biological systems is discussed. Finally, we report state-of-the-art approaches toward effective delivery of NPs to tumors, aiming at identifying new research areas and re-evaluating the reasons why some research avenues have underdelivered. We hope our effort will contribute to a better understanding of the gap to fill and delineate the future research work needed to bring polyester-based NPs closer to clinical application. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Microfluidic Controlled Self-Assembly of Polylactide (PLA)-Based Linear and Graft Copolymers into Nanoparticles with Diverse Morphologies

This study outlines the microfluidic (MF) controlled self-assembly of polylactide (PLA)-based linear and graft copolymers. The PLA-based copolymers (PLA-Cs) were synthesized through a convenient one-pot/one-step ROP/RAFT technique. Three distinct vinyl monomers-triethylene glycol methacrylate (TEGMA), 2-hydroxypropyl methacrylate (HPMA), and N-(2-hydroxypropyl) methacrylamide (HPMAA) were employed to prepare various copolymers: linear thermoresponsive polylactide-b-poly(triethylene glycol methacrylate) (PLA-b-PTEGMA), graft pseudothermoresponsive poly[N-(2-hydroxypropyl)] methacrylate-g-polylactide (PHPMA-g-PLA), and graft amphiphilic poly[N-(2-hydroxypropyl)] methacrylamide-g-polylactide (PHPMAA-g-PLA). The MF technology was utilized for the controlled self-assembly of these PLA-based BCs in a solution, resulting in a range of nanoparticle (NP) morphologies. The thermoresponsive PLA-b-PTEGMA diblock copolymer formed thermodynamically stable micelles (Ms) through kinetically controlled assemblies. Similarly, employing MF channels led to the self-assembly of PHPMA-g-PLA, yielding polymersomes (PSs) with adjustable sizes under the same solution conditions. Conversely, the PHPMAA-g-PLA copolymer generated worm-like particles (Ws). The analysis of resulting nano-objects involves techniques such as transmission electron microscopy, dynamic light scattering investigations (DLS), and small-angle X-ray scattering (SAXS). More specifically, the thermoresponsive behavior of PLA-b-PTEGMA and PHPMA-g-PLA nano-objects is validated through variable-temperature DLS, TEM, and SAXS methods. Furthermore, the study explored the specific interactions between the formed Ms, PSs, and/or Ws with proteins in human blood plasma, utilizing isothermal titration calorimetry.

Topology-Directed Coassembly of Linear and Cyclic Amphiphilic Diblock Copolymers: A Monte Carlo Study

The self-assembly behaviors of the mixtures composed of linear and cyclic AB diblock copolymers in A-selective solvents are investigated by means of Monte Carlo simulation. The simulation results indicate that a typical morphological transition of the aggregate from sphere to cylinder, to lamella, and then to vesicle can be achieved via solely adjusting the molar fraction of the cyclic diblock copolymers in the mixture. Furthermore, the simulation results show that under the condition that the pure cyclic and linear diblock copolymers can both form vesicles, the structure characteristics (e.g., the inner radius and hydrophobic membrane thickness of the vesicle) and the formation pathway of the vesicles formed by the mixtures can also be regulated via solely changing the molar fraction of the cyclic diblock copolymers in the mixture. It is worth noting that the inner radius of the vesicle can be considerably increased by increasing the molar fraction of the cyclic diblock copolymers in the mixture, which results in a remarkable increase in the inner capacity of the vesicle. This phenomenon has a unique significance in the field of drug delivery. Our simulation works can provide a new approach to the preparation of polymer materials with novel properties and functions.

Self-assembly of peptide nanocapsules by a solvent concentration gradient

Biological systems can create materials with intricate structures and specialized functions. In comparison, precise control of structures in human-made materials has been challenging. Here we report on insect cuticle peptides that spontaneously form nanocapsules through a single-step solvent exchange process, where the concentration gradient resulting from the mixing of water and acetone drives the localization and self-assembly of the peptides into hollow nanocapsules. The underlying driving force is found to be the intrinsic affinity of the peptides for a particular solvent concentration, while the diffusion of water and acetone creates a gradient interface that triggers peptide localization and self-assembly. This gradient-mediated self-assembly offers a transformative pathway towards simple generation of drug delivery systems based on peptide nanocapsules.

Association of Thermoresponsive Diblock Copolymer PDEGMA-b-PDIPAEMA in Aqueous Solutions: The Influence of Terminal Groups

Aqueous solutions of a thermoresponsive diblock copolymer poly(di-[ethylene glycol] methyl ether methacrylate)-b-poly(2-[diisopropylamino] ethyl methacrylate) (PDEGMA-b-PDIPAEMA) were studied by static, dynamic and electrophoretic light scattering, small-angle X-ray scattering and differential scanning calorimetry. Thermoresponsive behavior of PDEGMA-b-PDIPAEMA was investigated at two pH values, pH = 2, at which the terminal carboxylic group of the PDEGMA chain and the PDIPAEMA block are protonated, and pH = 7, where the carboxyl terminal group is ionized while the PDIPAEMA block is partially deprotonated and more hydrophobic. Both at pH = 2 and 7, PDEGMA-b-PDIPAEMA copolymer underwent extensive association (the size of the aggregates was between 100 and 300 nm), indicating strong interchain interactions. While the measurements confirmed thermoresponsive behavior of PDEGMA-b-PDIPAEMA at pH = 7, no changes in the association with temperature were observed at pH 2 as the thermoresponsivity of PDEGMA was suppressed by hydrogen bonding between carboxylic groups and PDEGMA segments, as well as due to the increased hydrophilicity of the PDIPAEMA block. Fluorescence measurements with pyrene as a fluorescent probe showed that both at pH = 2 and pH = 7 the associates were able to solubilize hydrophobic substances.

Effect of Micellar Morphology on the Temperature-Induced Structural Evolution of ABC Polypeptoid Triblock Terpolymers into Two-Compartment Hydrogel Network

We investigated the temperature-dependent structural evolution of thermoreversible triblock terpolypeptoid hydrogels, namely poly(N-allyl glycine)-b-poly(N-methyl glycine)-b-poly(N-decyl glycine) (AMD), using small-angle neutron scattering (SANS) with contrast matching in conjunction with X-ray scattering and cryogenic transmission electron microscopy (cryo-TEM) techniques. At room temperature, A100M101D10 triblock terpolypeptoids self-assemble into core-corona-type spherical micelles in aqueous solution. Upon heating above the critical gelation temperature (T gel), SANS analysis revealed the formation of a two-compartment hydrogel network comprising distinct micellar cores composed of dehydrated A blocks and hydrophobic D blocks. At T ≳ T gel, the temperature-dependent dehydration of A block further leads to the gradual rearrangement of both A and D domains, forming well-ordered micellar network at higher temperatures. For AMD polymers with either longer D block or shorter A block, such as A101M111D21 and A43M92D9, elongated nonspherical micelles with a crystalline D core were observed at T < T gel. Although these enlarged crystalline micelles still undergo a sharp sol-to-gel transition upon heating, the higher aggregation number of chains results in the immediate association of the micelles into ordered aggregates at the initial stage, followed by a disruption of the spatial ordering as the temperature further increases. On the other hand, fiber-like structures were also observed for AMD with longer A block, such as A153M127D10, due to the crystallization of A domains. This also influences the assembly pathway of the two-compartment network. Our findings emphasize the critical impact of initial micellar morphology on the structural evolution of AMD hydrogels during the sol-to-gel transition, providing valuable insights for the rational design of thermoresponsive hydrogels with tunable network structures at the nanometer scale.

Recent Progress in Polyion Complex Nanoparticles with Enhanced Stability for Drug Delivery

Polyion complex (PIC) nanoparticles, including PIC micelles and PICsomes, are typically composed of poly(ethylene glycol) block copolymers coupled with oppositely charged polyelectrolytes or therapeutic agents via electrostatic interaction. Due to a simple and rapid preparation process with high drug-loading efficiency, PIC nanoparticles are beneficial to maintaining the chemical integrity and high biological activity of the loaded drugs. However, the stability of PIC nanoparticles can be disrupted in high-ionic-strength solutions because electrostatic interaction is the DRIVING force; these disruptions can thus impair drug delivery. Herein, we summarize the advances in the use of PIC nanoparticles for delivery of charged drugs, focusing on the different chemical and physical strategies employed to enhance their stability, including enhancing the charge density, crosslinking, increasing hydrophobic interactions, forming hydrogen bonds, and the development of PIC-based gels. In particular, we describe the use of PIC nanoparticles to load peptide antibiotics targeting antibiotic-resistant and biofilm-related diseases and the use of nanoparticles that load chemotherapeutics and gaseous donors for cancer treatment. Furthermore, the application of PIC nanoparticles as magnetic resonance imaging contrast agents is summarized for the first time. Therefore, this review is of great significance for advances in the use of polymeric nanoparticles for functional drug delivery.

Stimuli-Responsive Control over Self-Assembled Nanostructures in Sequence-Specific Functional Block Copolymers

The precise sequence of a protein's primary structure is essential in determining its folding pathways. To emulate the complexity of these biomolecules, functional block copolymers consisting of segmented triblocks with distinct functionalities positioned in a sequence-specific manner are designed to control the polymer chain compaction. Triblock polymers P- b -C- b -F and P- b -F- b -C and random diblock copolymer P- b -C- r -F consist of a hydrophilic poly(ethylene oxide) (PEO) block and a hydrophobic block with coumarin (C) and ferrocene (F) moieties that are grafted in a sequence-specific or random manner onto the hydrophilic block. External stimuli such as UVB light, redox, and chemical cues influence the functional hydrophobic block to alter the packing parameters that are monitored with spectroscopic and scattering techniques. Interestingly, the positioning of the stimuli-responsive moiety within the hydrophobic block of P- b -C- b -F, P- b -F- b -C, and P- b -C- r -F affects the extent of the hydrophobic-hydrophilic balance in block copolymers that renders orthogonal control in stimuli-responsive transformation of self-assembled vesicles to micelles.

Hierarchical Design of Tissue-Mimetic Fibrillar Hydrogel Scaffolds

Most tissues of the human body present hierarchical fibrillar extracellular matrices (ECMs) that have a strong influence over their physicochemical properties and biological behavior. Of great interest is the introduction of this fibrillar structure to hydrogels, particularly due to the water-rich composition, cytocompatibility, and tunable properties of this class of biomaterials. Here, the main bottom-up fabrication strategies for the design and production of hierarchical biomimetic fibrillar hydrogels and their most representative applications in the fields of tissue engineering and regenerative medicine are reviewed. For example, the controlled assembly/arrangement of peptides, polymeric micelles, cellulose nanoparticles (NPs), and magnetically responsive nanostructures, among others, into fibrillar hydrogels is discussed, as well as their potential use as fibrillar-like hydrogels (e.g., those from cellulose NPs) with key biofunctionalities such as electrical conductivity or remote stimulation. Finally, the major remaining barriers to the clinical translation of fibrillar hydrogels and potential future directions of research in this field are discussed.

Self-Assembled Block Copolymers as a Facile Pathway to Create Functional Nanobiosensor and Nanobiomaterial Surfaces

Block copolymer (BCP) surfaces permit an exquisite level of nanoscale control in biomolecular assemblies solely based on self-assembly. Owing to this, BCP-based biomolecular assembly represents a much-needed, new paradigm for creating nanobiosensors and nanobiomaterials without the need for costly and time-consuming fabrication steps. Research endeavors in the BCP nanobiotechnology field have led to stimulating results that can promote our current understanding of biomolecular interactions at a solid interface to the never-explored size regimes comparable to individual biomolecules. Encouraging research outcomes have also been reported for the stability and activity of biomolecules bound on BCP thin film surfaces. A wide range of single and multicomponent biomolecules and BCP systems has been assessed to substantiate the potential utility in practical applications as next-generation nanobiosensors, nanobiodevices, and biomaterials. To this end, this Review highlights pioneering research efforts made in the BCP nanobiotechnology area. The discussions will be focused on those works particularly pertaining to nanoscale surface assembly of functional biomolecules, biomolecular interaction properties unique to nanoscale polymer interfaces, functionality of nanoscale surface-bound biomolecules, and specific examples in biosensing. Systems involving the incorporation of biomolecules as one of the blocks in BCPs, i.e., DNA-BCP hybrids, protein-BCP conjugates, and isolated BCP micelles of bioligand carriers used in drug delivery, are outside of the scope of this Review. Looking ahead, there awaits plenty of exciting research opportunities to advance the research field of BCP nanobiotechnology by capitalizing on the fundamental groundwork laid so far for the biomolecular interactions on BCP surfaces. In order to better guide the path forward, key fundamental questions yet to be addressed by the field are identified. In addition, future research directions of BCP nanobiotechnology are contemplated in the concluding section of this Review.

Using RAFT Polymerization Methodologies to Create Branched and Nanogel-Type Copolymers

This review aims to highlight the most recent advances in the field of the synthesis of branched copolymers and nanogels using reversible addition-fragmentation chain transfer (RAFT) polymerization. RAFT polymerization is a reversible deactivation radical polymerization technique (RDRP) that has gained tremendous attention due to its versatility, compatibility with a plethora of functional monomers, and mild polymerization conditions. These parameters lead to final polymers with good control over the molar mass and narrow molar mass distributions. Branched polymers can be defined as the incorporation of secondary polymer chains to a primary backbone, resulting in a wide range of complex macromolecular architectures, like star-shaped, graft, and hyperbranched polymers and nanogels. These subcategories will be discussed in detail in this review in terms of synthesis routes and properties, mainly in solutions.

Polymersomes in Drug Delivery─From Experiment to Computational Modeling

Polymersomes, composed of amphiphilic block copolymers, are self-assembled vesicles that have gained attention as potential drug delivery systems due to their good biocompatibility, stability, and versatility. Various experimental techniques have been employed to characterize the self-assembly behaviors and properties of polymersomes. However, they have limitations in revealing molecular details and underlying mechanisms. Computational modeling techniques have emerged as powerful tools to complement experimental studies and enabled researchers to examine drug delivery mechanisms at molecular resolution. This review aims to provide a comprehensive overview of the state of the art in the field of polymersome-based drug delivery systems, with an emphasis on insights gained from both experimental and computational studies. Specifically, we focus on polymersome morphologies, self-assembly kinetics, fusion and fission, behaviors in flow, as well as drug encapsulation and release mechanisms. Furthermore, we also identify existing challenges and limitations in this rapidly evolving field and suggest possible directions for future research.

Controlled node growth on the surface of polymersomes

Incorporating nucleobases into synthetic polymers has proven to be a versatile method for controlling self-assembly. The formation of strong directional hydrogen bonds between complementary nucleobases provides a driving force that permits access to complex particle morphologies. Here, nucleobase pairing was used to direct the formation and lengthening of nodes on the outer surface of vesicles formed from polymers (polymersomes) functionalised with adenine in their membrane-forming domains. Insertion of a self-assembling short diblock copolymer containing thymine into the polymersome membranes caused an increase in steric crowding at the hydrophilic/hydrophobic interface, which was relieved by initial node formation and subsequent growth. Nano-objects were imaged by (cryo-)TEM, which permitted quantification of node coverage and length. The ability to control node growth on the surface of polymersomes provides a new platform to develop higher-order nanomaterials with tailorable properties.

Self-assembly of rigid amphiphilic graft cyclic-brush copolymers to nanochannels using dissipative particle dynamics simulation

The synthesis of specific artificial nanochannels remains a formidable challenge in the field of nanomaterials and synthetic chemistry. In particular, the preparation of artificial nanochannels using amphiphilic graft cyclic-brush copolymers (AGCCs) as monomers has garnered substantial attention. Nevertheless, because of the constrained time and length scales inherent in traditional molecular dynamics simulations, a comprehensive theoretical understanding of the morphological regulation mechanism governing the self-assembly of AGCCs into nanochannels remains elusive. In this study, we employed the dissipative particle dynamics (DPD) method to explore the self-assembly mechanism considering factors such as the DPD interaction parameters, concentrations, and sizes of AGCCs. By calculating the phase diagrams, we predicted the emergence of four distinct nanochannel types: short independent, long independent, parallel, and disordered channels. Importantly, the formation of these nanochannels is highly contingent on specific environmental conditions. Furthermore, we extensively discussed self-assembly processes that lead to different types of nanochannels. The self-assembly of AGCCs is revealed as a multistep process primarily influenced by the interaction parameters. However, while the monomer size and concentration do not introduce novel self-assembly morphologies, they do influence the final aggregation state. The elucidation of the self-assembly mechanism presented in this study deepens our understanding of AGCC nanochannel formation. Consequently, this is a valuable guide for the preparation of copolymer materials with specific functionalities, offering insights into targeted copolymer material design.

Investigating microstructure evolution in block copolymer membranes

Block copolymer self-assembly in conjunction with nonsolvent-induced phase separation (SNIPS) has been increasingly leveraged to fabricate integral-asymmetric membranes. The large number of formulation and processing parameters associated with SNIPS, however, has prevented the reliable construction of high performance membranes. In this study, we apply dynamical self-consistent field theory to model the SNIPS process and investigate the effect of various parameters on the membrane morphology: solvent selectivity, nonsolvent selectivity, initial film composition, and glass transition composition. We examine how solvent selectivity and concentration of polymers in the film impact the structure of micelles that connect to form the membrane matrix. In particular, we find that preserving the order in the surface layer and forming a connection between the supporting and surface layer are nontrivial and sensitive to each parameter studied. The effect of each parameter is discussed, and suggestions are made for successfully fabricating viable block copolymer membranes.

Structure-Based Evaluation of Hybrid Lipid-Polymer Nanoparticles: The Role of the Polymeric Guest

The combination of phospholipids and block-copolymers yields advanced hybrid nanoparticles through the self-assembly process in an aqueous environment. The physicochemical features of the lipid/polymer components, like the lipid-polymer molar ratio, the macromolecular architecture of the block copolymer, the main transition temperature of the phospholipid, as well as the formulation and preparation protocol parameters, are some of the most crucial parameters for the formation of hybrid lipid/polymer vesicles and for the differentiation of their morphology. The morphology, along with other physicochemical nanoparticle characteristics are strictly correlated with the nanoparticle's later biological behavior after being administered, affecting interactions with cells, biodistribution, uptake, toxicity, drug release, etc. In the present study, a structural evaluation of hybrid lipid-polymer nanoparticles based on cryo-TEM studies was undertaken. Different kinds of hybrid lipid-polymer nanoparticles were designed and developed using phospholipids and block copolymers with different preparation protocols. The structures obtained ranged from spherical vesicles to rod-shaped structures, worm-like micelles, and irregular morphologies. The obtained morphologies were correlated with the formulation and preparation parameters and especially the type of lipid, the polymeric guest, and their ratio.

Kinetic pathway and micromechanics of fusion/fission for polyelectrolyte vesicles

Despite the wide existence of vesicles in living cells as well as their important applications like drug delivery, the underlying mechanism of vesicle fusion/fission remains under debate. Classical models cannot fully explain recent observations in experiments and simulations. Here, we develop a constrained self-consistent field theory that allows tracking the shape evolution and free energy as a function of center-of-mass separation distance. Fusion and fission are described in a unified framework. Both the kinetic pathway and the mechanical response can be simultaneously captured. By taking vesicles formed by polyelectrolytes as a model system, we predict discontinuous transitions between the three morphologies: parent vesicle with a single cavity, hemifission/hemifusion, and two separated child vesicles, as a result of breaking topological isomorphism. With the increase in inter-vesicle repulsion, we observe a great reduction in the cleavage energy, indicating that vesicle fission can be achieved without hemifission, in good agreement with simulation results. The force-extension relationship elucidates typical plasticity for separating two vesicles. The super extensibility in the mechanical response of vesicle is in stark contrast to soft particles with other morphologies, such as cylinder and sphere. Our work elucidates the fundamental physical chemistry based on intrinsic topological features of vesicle fusion/fission, which provides insights into various phenomena observed in experiments and simulations.

Determination of Reaction Kinetics by Time-Resolved Small-Angle X-ray Scattering during Polymerization-Induced Self-Assembly: Direct Evidence for Monomer-Swollen Nanoparticles

The kinetics of heterogeneous polymerization is determined directly using small-angle X-ray scattering (SAXS). This important advancement is exemplified for the synthesis of sterically-stabilized diblock copolymer nanoparticles by reversible addition-fragmentation chain transfer (RAFT) dispersion polymerization of benzyl methacrylate (BzMA) in mineral oil at 90 °C. The principle of mass balance is invoked to derive a series of equations for the analysis of the resulting time-resolved SAXS patterns. Importantly, there is a continuous change in the X-ray scattering length density for the various components within the reaction mixture. This enables the volume fraction of unreacted BzMA monomer to be calculated at any given time point, which enables the polymerization kinetics to be monitored in situ directly without relying on supplementary characterization techniques. Moreover, SAXS enables the local concentration of both monomer and solvent within the growing swollen nanoparticles to be determined during the polymerization. Data analysis reveals that the instantaneous rate of BzMA polymerization is proportional to the local monomer concentration within the nanoparticles. In principle, this powerful new time-resolved SAXS approach can be applicable to other heterogeneous polymerization formulations.

Multiresponsive Nanoscale Self-Assembly of Azurin-Elastin-like Polypeptide Fusion Protein for Enhanced Prostate Cancer Therapy

A fusion protein composed of a bacterial protein, azurin, having antineoplastic properties and a thermally responsive structural cationic elastin-like protein (ELP), is designed, cloned, expressed, and purified. A simple method of inverse transition cycle (ITC) is employed to purify the fusion protein azurin-ELP diblock copolymer (d-bc). The molecular weight of the azurin-ELP fusion protein is ∼32 kDa. Further, its self-assembly properties are investigated. Interestingly, the engineered azurin-ELP d-bc in response to increasing temperature shows a dual-step phase separation into biofunctional nanostructures. Around the physiological temperature, azurin-ELP d-bc forms stable coacervates, which is dependent on the concentration and time of incubation. These coacervates are formed below the lower critical solubility temperature (LCST) of the ELP block at physiological temperature. Above LCST, i.e., 50-55°C, micelles of size ranging from 25 to 30 nm are formed. The cytotoxicity of azurin-ELP d-bc depends on the size of the coacervates formed and their cellular uptake at physiological temperature. Further, MTT assay of azurin-ELP d-bc in the cross-linked micelles prepared ex situ shows > six times higher killing of LNCaP cells than the unimeric form of azurin-ELP at 5 μM concentration. The flow cytometric results of these micelles at 20 μM concentration show ∼97% LNCaP cells in the apoptotic phase. Thus, azurin-ELP cross-linked micelles have enhanced potential for anticancer therapy due to their higher avidity.

Synergetic Self-Assembly of Liquid Crystalline Block Copolymer with Amphiphiles for Fabrication of Hierarchical Assemblies

Novel functions and advanced structure, where each single component could not be produced individually, can exhibit from the collective and synergistic behavior of component systems. This synergetic strategy has been successfully demonstrated for co-assembly of polymer-polymer to construct hierarchical nanomaterials. However, differences in the natures of polymer and small molecules impose challenges in the construction of sophisticated co-assemblies with geometrical and compositional control. Herein, a synergetic self-assembly strategy is proposed to prepare organic-organic hybrid colloidal mesostructures by blending a liquid crystalline block copolymer (LC-BCP) with small molecular amphiphiles. Through a classic solvent-exchange process, amphiphiles embedded with LC-BCP realize multi-component nucleation and hierarchical assembly driven by anisotropic interaction from the LC ordering alignment of the core-forming block. 1D nanofibers with a periodic striped structure are formed by further LC component fusion and refinement. In addition, LC ordering effect of LC-BCP can be regulated by selecting appropriate solvents and leads to the formation of vesicular co-micelles. By means of the thermal-responsive behavior of amphiphiles, hexagonal pore arrays are finally generated on the surface of those vesicles.

Biomedical Application of Porphyrin-Based Amphiphiles and Their Self-Assembled Nanomaterials

Porphyrins have been vastly explored and applied in many cutting-edge fields with plenty of encouraging achievements because of their excellent properties. As important derivatives of porphyrins, porphyrin-based amphiphiles (PBAs) not only maintain the advanced properties of porphyrins (catalysis, imaging, and energy transfer) but also possess self-assembly and encapsulation capability in aqueous solution. Accordingly, PBAs and their self-assembles have had important roles in diagnosing and treating tumors and inflammation lesions in vivo, but not limited to these. In this article, we introduce the research progress of PBAs, including their constitution, structure design strategies, and performances in tumor and inflammation lesion diagnosis and treatments. On that basis, the defects of synthesized PBAs during their application and the possible effective strategies to overcome the limitations are also proposed. Finally, perspectives on PBAs exploration are updated based on our knowledge. We hope this review will bring researchers from various domains insights about PBAs.

Hierarchical assembly of foldable polymers and applications in organic optoelectronics and antibacterial or antiviral materials

Aggregation of amphiphilic polymers in block-selective solvents produces different nanostructures, which have been studied extensively for wide-ranging applications. Nevertheless, such immiscibility-driven aggregation does not endow them with the desired structural precision, predictability or surface functional group exposure, which significantly impact their functional applications. More recently, biomimetic folded structures of synthetic macromolecules (mostly oligomers) have come to the fore, but such studies have been limited to probe the secondary structures. In this article, we have collated hierarchical structures of foldamers, especially highlighting our recent contribution to the field of chain-folding regulated assembly of segmented polyurethanes (PUs) and their functional applications. A series of such PUs have been discussed, which contain a segmented hydrocarbon backbone and alternately placed pendant solvophilic groups. In either water or highly non-polar solvents (TCE, MCH), depending on the nature of the pendant group, they exhibit folded structures stabilized by intra-chain H-bonding. Hierarchical assembly of such folded chains by inter-chain H-bonding and/or π-stacking leads to the formation of well-defined nanostructures with functional applications ranging from organic optoelectronics to biomaterials. For example, a segmented PU with appended naphthalene-diimide (NDI) chromophores showed a pleated structure in MCH, which helped in organization of the NDI chromophores within π-stacking distance. Such folded polymer chains eventually produced nanotubular structures with excellent electron mobility. They also showed efficient intercalation of the pyrene (Py) donor by NDI-Py charge-transfer interaction and in this case the mixed nanotubular structure exhibited prominent room-temperature ferroelectricity. On the other hand, having cationic functionalities as the pendant groups such chain-folding regulated assembly produced unilamellar polymersomes with excellent antibacterial activity with very low minimum inhibitory concentrations (<10 μg mL-1). Replacing the pendant amine functionality with sulphate groups made these polyurethanes highly potent antiviral materials. In the absence of the alternating connectivity of the solvophobic and solvophilic segments or rigid hydrocarbon backbone, such folding propensity is destroyed, leading to structural collapse. While significant efforts have been made in correlating primary structures of wide-ranging polymers with their functional applications, this article demonstrates the direct correlation between the secondary structures of polymers and their functional properties.

Polypeptide-Based Systems: From Synthesis to Application in Drug Delivery

Synthetic polypeptides are biocompatible and biodegradable macromolecules whose composition and architecture can vary over a wide range. Their unique ability to form secondary structures, as well as different pathways of modification and biofunctionalization due to the diversity of amino acids, provide variation in the physicochemical and biological properties of polypeptide-containing materials. In this review article, we summarize the advances in the synthesis of polypeptides and their copolymers and the application of these systems for drug delivery in the form of (nano)particles or hydrogels. The issues, such as the diversity of polypeptide-containing (nano)particle types, the methods for their preparation and drug loading, as well as the influence of physicochemical characteristics on stability, degradability, cellular uptake, cytotoxicity, hemolysis, and immunogenicity of polypeptide-containing nanoparticles and their drug formulations, are comprehensively discussed. Finally, recent advances in the development of certain drug nanoformulations for peptides, proteins, gene delivery, cancer therapy, and antimicrobial and anti-inflammatory systems are summarized.

Self-Assembly of Symmetric Copolymers in Slits with Inert and Attractive Walls

Although the behavior of the confined semi-dilute solutions of self-assembling copolymers represents an important topic of basic and applied research, it has eluded the interest of scientists. Extensive series of dissipative particle dynamics simulations have been performed on semi-dilute solutions of A5B5 chains in a selective solvent for A in slits using a DL-MESO simulation package. Simulations of corresponding bulk systems were performed for comparison. This study shows that the associates in the semi-dilute bulk solutions are partly structurally organized. Mild steric constraints in slits with non-attractive walls hardly affect the size of the associates, but they promote their structural arrangement in layers parallel to the slit walls. Attractive walls noticeably affect the association process. In slits with mildly attractive walls, the adsorption competes with the association process. At elevated concentrations, the associates start to form in wide slits when the walls are sparsely covered by separated associates, and the association process prevents the full coverage of the surface. In slits with strongly attractive walls, adsorption is the dominant behavior. The associates form in wide slits at elevated concentrations only after the walls are completely and continuously covered by the adsorbed chains.

Polymersome Membrane Engineering with Active Targeting or Controlled Permeability for Responsive Drug Delivery

Polymersomes have been extensively investigated for drug delivery as nanocarriers for two decades due to a series of advantages including high stability under physiological conditions, simultaneous encapsulation of hydrophilic and hydrophobic drugs inside inner cavities and membranes, respectively, and facile adjustment of membrane and surface properties, as well as controlled drug release through incorporation of stimuli-responsive components. Despite these features, polymersome nanocarriers frequently suffer from nontargeting delivery and poor membrane permeability. In recent years, polymersomes have been functionalized for more efficient drug delivery. The surface shells were explored to be modified with diverse active targeting groups to improve disease-targeting delivery. The membrane permeability of the polymersomes was adjusted by incorporation of the stimuli-responsive components for smart controlled transportation of the encapsulated drugs. Therefore, being the polymersome-biointerface, tailorable properties can be introduced by its carefully modulated engineering. This review elaborates on the role of polymersome membranes as a platform to incorporate versatile features. First, we discuss how surface functionalization facilitates the directional journey to the targeting sites toward specific diseases, cells, or intracellular organelles via active targeting. Moreover, recent advances in the past decade related to membrane permeability to control drug release are also summarized. We finally discuss future development to promote polymersomes as in vivo drug delivery nanocarriers.

RE, Mocskos EE, Facelli JC, Pickholz M, Ferraro MB. Molecular dynamics study of the mechanical properties of drug loaded model systems: A comparison of a polymersome with a bilayer

In this work we implement a new methodology to study structural and mechanical properties of systems having spherical and planar symmetries throughout Molecular Dynamics simulations. This methodology is applied here to a drug delivery system based in polymersomes, as an example. The chosen model drug was the local anesthetic prilocaine due to previous parameterization within the used coarse grain scheme. In our approach, mass density profiles (MDPs) are used to obtain key structural parameters of the systems, and pressure profiles are used to estimate the curvature elastic parameters. The calculation of pressure profiles and radial MPDs required the development of specific methods, which were implemented in an in-house built version of the GROMACS 2018 code. The methodology presented in this work is applied to characterize poly(ethylene oxide)-poly(butadiene) polymersomes and bilayers loaded with the model drug prilocaine. Our results show that structural properties of the polymersome membrane could be obtained from bilayer simulations, with significantly lower computational cost compared to whole polymersome simulations, but the bilayer simulations are insufficient to get insights on their mechanical aspects, since the elastic parameters are canceled out for the complete bilayer (as consequence of the symmetry). The simulations of entire polymersomes, although more complex, offer a complementary approach to get insights on the mechanical behavior of the systems.

Stimuli-responsive viscosity modifiers

Stimuli responsive viscosity modifiers entail an important class of materials which allow for smart material formation utilizing various stimuli for switching such as pH, temperature, light and salinity. They have seen applications in the biomedical space including tissue engineering and drug delivery, wherein stimuli responsive hydrogels and polymeric vessels have been extensively applied. Applications have also been seen in other domains like the energy sector and automobile industry, in technologies such as enhanced oil recovery. The chemistry and microstructural arrangements of the aqueous morphologies of dissolved materials are usually sensitive to the aforementioned stimuli which subsequently results in rheological sensitivity as well. Herein, we overview different structures capable of viscosity modification as well as go over the rheological theory associated with classical systems studied in literature. A detailed analysis allows us to explore correlations between commonly discussed models such as molecular packing parameter, tube reptation and stress relaxation with structural and rheological changes. We then present five primary mechanisms corresponding to stimuli responsive viscosity modification: (i) packing parameter modification via functional group conditioning and (ii) via dynamic bond formation, (iii) mesh formation by interlinking of network nodes, (iv) viscosity modification by chain conformation changes and (v) viscosity modification by particle jamming. We also overview several recent examples from literature that employ the concepts discussed to create novel classes of intriguing stimuli responsive structures and their corresponding rheological properties. Furthermore, we also explore systems that are responsive to multiple stimuli which can provide enhanced functionality and versatility by providing multi-level and precise actuation. Such systems have been used for programmed site-specific drug delivery.

Colloidal Polymer-Templated Formation of Inorganic Nanocrystals and their Emerging Applications

Inorganic nanocrystals possess unique physicochemical properties compared to their bulk counterparts. Stabilizing agents are commonly used for the preparation of inorganic nanocrystals with controllable properties. Particularly, colloidal polymers have emerged as general and robust templates for in situ formation and confinement of inorganic nanocrystals. In addition to templating and stabilizing inorganic nanocrystals, colloidal polymers can tailor their physicochemical properties such as size, shape, structure, composition, surface chemistry, and so on. By incorporating functional groups into colloidal polymers, desired functions can be integrated with inorganic nanocrystals, advancing their potential applications. Here, recent advances in the colloidal polymer-templated formation of inorganic nanocrystals are reviewed. Seven types of colloidal polymers, including dendrimer, polymer micelle, stare-like block polymer, bottlebrush polymer, spherical polyelectrolyte brush, microgel, and single-chain nanoparticle, have been extensively applied for the synthesis of inorganic nanocrystals. Different strategies for the development of these colloidal polymer-templated inorganic nanocrystals are summarized. Then, their emerging applications in the fields of catalysis, biomedicine, solar cells, sensing, light-emitting diodes, and lithium-ion batteries are highlighted. Last, the remaining issues and future directions are discussed. This review will stimulate the development and application of colloidal polymer-templated inorganic nanocrystals.

Synthesis approaches of amphiphilic copolymers for spherical micelle preparation: application in drug delivery

The formation of polymeric micelles in aqueous environments through the self-assembly of amphiphilic polymers can provide a versatile platform to increase the solubility and permeability of hydrophobic drugs and pave the way for their administration. In comparison to various self-assembly-based vehicles, polymeric micelles commonly have a smaller size, spherical morphology, and simpler scale up process. The use of polymer-based micelles for the encapsulation and carrying of therapeutics to the site of action triggered a line of research on the synthesis of various amphiphilic polymers in the past few decades. The extended knowledge on polymers includes biocompatible smart amphiphilic copolymers for the formation of micelles, therapeutics loading and response to external stimuli, micelles with a tunable drug release pattern, etc. Different strategies such as ring-opening polymerization, atom transfer radical polymerization, reversible addition-fragmentation chain-transfer, nitroxide mediated polymerization, and a combination of these methods were employed to synthesize copolymers with diverse compositions and topologies with the proficiency of self-assembly into well-defined micellar structures. The current review provides a summary of the important polymerization techniques and recent achievements in the field of drug delivery using micellar systems. This review proposes new visions for the design and synthesis of innovative potent amphiphilic polymers in order to benefit from their application in drug delivery fields.

In Situ Monitoring of Block Copolymer Self-Assembly via Solvent Exchange through Controlled Dialysis with Light and Neutron Scattering Detection

Solution self-assembly of amphiphilic block copolymers (BCs) is typically performed by a solvent-to-water exchange. However, BC assemblies are often trapped in metastable states depending on the mixing conditions such as the magnitude and rate of water addition. BC self-assembly can be performed under near thermodynamic control by dialysis, which accounts for a slow and gradual water addition. In this Letter we report the use of a specifically designed dialysis cell to continuously monitor by dynamic light scattering and small-angle neutron scattering the morphological changes of PDMS-b-PEG BCs self-assemblies during THF-to-water exchange. The complete phase diagrams of near-equilibrium structures can then be established. Spherical micelles first form before evolving to rod-like micelles and vesicles, decreasing the total developed interfacial area of self-assembled structures in response to increasing interfacial energy as the water content increases. The dialysis kinetics can be tailored to the time scale of BC self-assembly by modifying the membrane pore size, which is of interest to study the interplay between thermodynamics and kinetics in self-assembly pathways.

Polymer Vesicles with Integrated Photothermal Responsiveness

Functionalized polymer vesicles have been proven to be highly promising in biomedical applications due to their good biocompatibility, easy processability, and multifunctional responsive capacities. However, photothermal-responsive polymer vesicles triggered by near-infrared (NIR) light have not been widely reported until now. Herein, we propose a new strategy for designing NIR light-mediated photothermal polymer vesicles. A small molecule (PTA) with NIR-triggered photothermal features was synthesized by combining a D-D'-A-D'-D configuration framework with a molecular rotor function (TPE). The feasibility of the design strategy was demonstrated through density functional theory calculations. PTA moieties were introduced in the hydrophobic segment of a poly(ethylene glycol)-poly(trimethylene carbonate) block copolymer, of which the carbonate monomers were modified in the side chain with an active ester group. The amphiphilic block copolymers (PEG44-PTA2) were then used as building blocks for the self-assembly of photothermal-responsive polymer vesicles. The new class of functionalized polymer vesicles inherited the NIR-mediated high photothermal performance of the photothermal agent (PTA). After NIR laser irradiation for 10 min, the temperature of the PTA-Ps aqueous solution was raised to 56 °C. The photothermal properties and bilayer structure of PTA-Ps after laser irradiation were still intact, which demonstrated that they could be applied as a robust platform in photothermal therapy. Besides their photothermal performance, the loading capacity of PTA-Ps was investigated as well. Hydrophobic cargo (Cy7) and hydrophilic cargo (Sulfo-Cy5) were successfully encapsulated in the PTA-Ps. These properties make this new class of functionalized polymer vesicles an interesting platform for synergistic therapy in anticancer treatment.

Self-Assembly of Poly(Amino Acid)s Mediated by Secondary Conformations

Self-assembly of block copolymers has recently drawn great attention due to its remarkable performance and wide variety of applications in biomedicine, biomaterials, microelectronics, photoelectric materials, catalysts, etc. Poly(amino acid)s (PAAs), formed by introducing synthetic amino acids into copolymer backbones, are able to fold into different secondary conformations when compared with traditional amphiphilic copolymers. Apart from changing the chemical composition and degree of polymerization of copolymers, the self-assembly behaviors of PAAs could be controlled by their secondary conformations, which are more flexible and adjustable for fine structure tailoring. In this article, we summarize the latest findings on the variables that influence secondary conformations, in particular the regulation of order-to-order conformational changes and the approaches used to manage the self-assembly behaviors of PAAs. These strategies include controlling pH, redox reactions, coordination, light, temperature, and so on. Hopefully, we can provide valuable perspectives that will be useful for the future development and use of synthetic PAAs.