Synthesis and Self-Assembly of CO2–Temperature Dual Stimuli-Responsive Triblock Copolymers

Cascade Mesophase Transitions of Multi-enzyme Responsive Polymeric Formulations

Studying how synthetic polymer assemblies respond to sequential enzymatic stimuli can uncover intricate interactions in biological systems. Using amidase- and esterase-responsive PEG-based diblock (DBA) and triblock amphiphiles (TBAs), we created two distinct formulations: amidase-responsive DBA with esterase-responsive TBA and vice versa. We studied their cascade responses to the two enzymes and the sequence of their introduction. These formulations underwent cascade mesophase transitions upon the addition of the DBA-degrading enzyme, transitioning from (i) coassembled micelles to (ii) triblock-based hydrogel, and ultimately to (iii) dissolved polymers when exposed to the TBA hydrolyzing enzyme. The specific pathway of the two mesophase transitions depended on the compositions of the formulations and the enzyme introduction sequence. The results highlight the potential for designing polymeric formulations with programmable multistep enzymatic responses, mimicking the complex behavior of biological macromolecules.

Stimuli-Responsive Pickering Emulsions Regulated via Polymerization-Induced Self-Assembly Nanoparticles

With the development of reversible deactivated radical polymerization techniques, polymerization-induced self-assembly (PISA) is emerging as a facile method to prepare block copolymer nanoparticles in situ with high concentrations, providing wide potential applications in different fields, including nanomedicine, coatings, nanomanufacture, and Pickering emulsions. Polymeric emulsifiers synthesized by PISA have many advantages comparing with conventional nanoparticle emulsifiers. The morphologies, size, and amphiphilicity can be readily regulated via the synthetic process, post-modification, and external stimuli. By introducing stimulus responsiveness into PISA nanoparticles, Pickering emulsions stabilized with these nanoparticles can be endowed with "smart" behaviors. The emulsions can be regulated in reversible emulsification and demulsification. In this review, the authors focus on recent progress on Pickering emulsions stabilized by PISA nanoparticles with stimuli-responsiveness. The factors affecting the stability of emulsions during emulsification and demulsification are discussed in details. Furthermore, some viewpoints for preparing stimuli-responsive emulsions and their applications in antibacterial agents, diphase reaction platforms, and multi-emulsions are discussed as well. Finally, the future developments and applications of stimuli-responsive Pickering emulsions stabilized by PISA nanoparticles are highlighted.

Asymmetric polymersomes, from the formation of asymmetric membranes to the application on drug delivery

Nano drug delivery systems have attracted researchers' growing attention and are gradually emerging into the public views. More and more nano-formulations are being approved for marketing or clinical use, representing the field's booming development. Copolymer self-assembly systems such as micelles, nanoparticles, polymersomes occupy a prominent position in the field of nano-drug delivery carriers. Among them, polymersomes, unlike micelles or nanoparticles, resemble liposomes' structure and possess large internal hollow hydrophilic reservoirs, allowing them to carry hydrophilic drugs. Nevertheless, their insufficient drug loading efficiency and unruly self-assembly morphology have somewhat constrained their applications. Especially for the delivery of biomacromolecule such as peptides, the encapsulation efficiency is always considered to be a formidable obstacle, even if the enormous hydrophilic core would render the polymersomes to have considerable potential in this regard. Reassuringly, the emergence of asymmetric polymersomes holds the prospect of solving this problem. With the development of synthetic technology and a deeper understanding of the self-assembly process, the asymmetric polymersomes which are with different inner and outer shell composition have been gradually recognized by researchers. It has made possible elevated drug loading, more controllable assembly processes and release performance. The internal hydrophilic blocks different from the outer shell could be engineered to have a more remarkable affinity to the cargos or could contain a non-watery aqueous phase to enable the thermodynamically preferred encapsulation of cargos, which would allow for a substantial improvement in drug encapsulation efficiency compared to the conventional approach. In this paper, we aim to deepen the understanding to asymmetric polymersomes and lay the foundation for the development of this field by describing four main elements: the mechanism of their preparation and asymmetric membrane formation process, the characterization of asymmetric membranes, the efficient drug loading, and the special stimulus-responsive release mechanism.

Thermoresponsive Polymers Based on Tertiary Amine Moieties

Thermoresponsive polymers exhibiting unique reversible phase transition properties in aqueous solution in response to temperature stimuli have been extensively investigated. In the past two decades, thermoresponsive polymers based on tertiary amine moieties have achieved considerable progress and become an important family of thermoresponsive polymers, including tertiary amine functionalized poly((meth)acrylamide)s, poly((meth)acrylate)s, poly(styrene)s, poly(vinyl alcohol)s, and poly(ethylene oxide)s, which exhibit lower critical solution temperature and/or upper critical solution temperature in water or aliphatic alcohols. Their phase transition behavior can be modulated by the solution pH and CO₂ due to the protonation of tertiary amine moieties in acidic condition and deprotonation in alkaline condition and the charged ammonium bicarbonate formed by the tertiary amine moieties and CO₂ . The aim of this review is to summarize the recent progress in the thermoresponsive polymers based on tertiary amine moieties.

Functionalized Particles Designed for Targeted Delivery

Pure bioactive compounds alone can only be exceptionally administered in medical treatment. Usually, drugs are produced as various forms of active compounds and auxiliary substances, combinations assuring the desired healing functions. One of the important drug forms is represented by a combination of active substances and particle-shaped polymer in the nano- or micrometer size range. The review describes recent progress in this field balanced with basic information. After a brief introduction, the paper presents a concise overview of polymers used as components of nano- and microparticle drug carriers. Thereafter, progress in direct synthesis of polymer particles with functional groups is discussed. A section is devoted to formation of particles by self-assembly of homo- and copolymer-bearing functional groups. Special attention is focused on modification of the primary functional groups introduced during particle preparation, including introduction of ligands promoting anchorage of particles onto the chosen living cell types by interactions with specific receptors present in cell membranes. Particular attention is focused on progress in methods suitable for preparation of particles loaded with bioactive substances. The review ends with a brief discussion of the still not answered questions and unsolved problems.

When polymerization meets coordination-driven self-assembly: metallo-supramolecular polymers based on supramolecular coordination complexes

Polymers have greatly changed and are still changing the way we live ever since, and the construction of novel polymers as functional materials remains an attractive topic in polymer science and related areas. During the past few years, the marriage of discrete supramolecular coordination complexes (SCCs), including two-dimensional (2D) metallacycles and three-dimensional (3D) metallacages, and polymers gave rise to two novel types of metallo-supramolecular polymers, i.e., metallacycle/metallacage-cored star polymers (MSPs) and metallacycle/metallacage-crosslinked polymer networks (MPNs), which has attracted increasing attention and emerged as an exciting new research direction in polymer chemistry. Attributed to their well-defined and diverse topological architectures as well as the unique dynamic features of metallacycles/metallacages as cores or crosslinks, these novel polymers have shown extensive applications. In this review, aiming at providing a practical guide to this emerging area, the introduction of synthetic strategies towards MSPs and MPNs will be presented. In addition, their wide applications in areas such as functional materials, molecular sieving, drug delivery, bacterial killing and bioimaging are also discussed.

Thermoresponsive Diblock Copolymer Films with a Linear Shrinkage Behavior and Its Potential Application in Temperature Sensors

The linear shrinkage behavior in thermoresponsive diblock copolymer films and its potential application in temperature sensors are investigated. The copolymer is composed of two thermoresponsive blocks with different transition temperatures (TTs): di(ethylene glycol) methyl ether methacrylate (MEO₂MA; TT₁ = 25 °C) and poly(ethylene glycol) methyl ether methacrylate (OEGMA₃₀₀; TT₂ = 60 °C) with a molar ratio of 1:1. Aqueous solutions of PMEO₂MA-b-POEGMA₃₀₀ show a three-stage transition upon heating as seen with optical transmittance and small-angle X-ray scattering: dissolution (T < TT₁), self-assembled micelles with core-shell structure (TT₁ < T < TT₂), and aggregation of collapsed micelles (T > TT₂). Due to the restrictions in the polymer chain arrangement introduced by the solid Si substrate, spin-coated PMEO₂MA-b-POEGMA₃₀₀ films exhibit an entirely different internal structure and transition behavior. Neutron reflectivity shows the absence of an ordered structure normal to the Si substrate in as-prepared PMEO₂MA-b-POEGMA₃₀₀ films. After exposure to D₂O vapor for 3 h and then increasing the temperature above its TT₁ and TT₂, the ordered structure is still not observed. Only a D₂O enrichment layer is formed close to the hydrophilic Si substrate. Such PMEO₂MA-b-POEGMA₃₀₀ films show a linear shrinkage between TT₁ and TT₂ in a D₂O vapor atmosphere. This special behavior can be attributed to the synergistic effect between the restrained collapse of the PMEO₂MA blocks by the still swollen POEGMA₃₀₀ blocks and the impedance of chain arrangement by the Si substrate. Based on this unique behavior, spin-coated PMEO₂MA-b-POEGMA₃₀₀ films are further prepared into a temperature sensor by implementing Ag electrodes. Its resistance decreases linearly with temperature between TT₁ and TT₂.

Natural cyclodextrins and their derivatives for polymer synthesis

A toolbox of cyclodextrin derivatives, synthetic strategies for the preparation of cyclodextrin-polymer conjugates using various polymerisation techniques and representative applications of such conjugates are discussed.

Morphology transformation of pillararene-based supramolecular nanostructures

In this feature article, the construction methods and the factors that influence the morphological transformation of pillararene-based supramolecular nanostructures are reviewed.

Multistimuli-Responsive Emulsifiers Based on Two-Way Amphiphilic Diblock Polymers

Diblock copolymers of poly(tert-butyl methacrylate) (PtBuMA) and poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) of four different block lengths were prepared by sequential two-step reversible addition-fragmentation chain transfer radical polymerization, followed by hydrolysis of the PtBuMA blocks to obtain poly(methacrylic acid)-b-PDMAEMA (PMAA-b-PDMAEMA). The effect of the PDMAEMA block length on the multistimuli-responsive amphiphilic features of both types of diblock copolymers was investigated as CO2-switchable emulsifiers for emulsification/demulsification of n-octane (an oil) in water in response to CO2/N2 bubbling. The amphiphilicity of PtBuMA-b-PDMAEMA was switched on, and the amphiphilicity of PMAA-b-PDMAEMA was switched off by CO2 bubbling at pH 12 and 25 °C to achieve emulsification/demulsification. A longer PDMAEMA block length in PMAA-b-PDMAEMA conferred more sensitive CO2-responsive amphiphilicity but reduced the extent of recovery of emulsification ability on N2 bubbling. This newly developed diblock copolymer system could potentially serve as a "multifunctional surfactant" for CO2-switchable emulsification/demulsification of oil-in-water and water-in-oil mixtures.

Hemozoin-catalyzed precipitation polymerization as an assay for malaria diagnosis

Methods to diagnose malaria are of paramount interest to eradicate the disease. Current methods have severe limitations, as they are either costly or not sensitive enough to detect low levels of parasitemia. Here we report an ultrasensitive, yet low-resource chemical assay for the detection and quantification of hemozoin, a biomarker of all Plasmodium species. Solubilized hemozoin catalyzes the atom transfer radical polymerization of N-isopropylacrylamide above the lower critical solution temperature of poly(N-isopropylacrylamide). The solution becomes turbid, which can be observed by naked eye and quantified by UV-visible spectroscopy. The rate of turbidity increase is proportional to the concentration of hemozoin, with a detection limit of 0.85 ng mL-1. Malaria parasites in human blood can be detected down to 10 infected red blood cells μL-1. The assay could potentially be applied as a point-of-care test. The signal-amplification of an analyte by biocatalytic precipitation polymerization represents a powerful approach in biosensing.

CO2-Responsive Cellulose Nanofibers Aerogels for Switchable Oil-Water Separation

Cellulose nanofibers (CNFs) aerogels with controllable surface wettability were prepared by grafting poly( N, N-dimethylamino-2-ethyl methacrylate) (PDMAEMA) polymer brushes via surface-initiated atom-transfer radical polymerization. After grafting PDMAEMA polymer, the surface of the aerogel was hydrophobic. However, in the presence of CO₂, the surface of the aerogel gradually changes from hydrophobic to hydrophilic. The porous structure and CO₂-responsiveness of PDMAEMA brushes within the CNFs aerogels allowed for the on-off switching of the oil-water mixture separation process. These CNFs aerogels were recyclable and displayed attractive separation efficiency for oil-water mixture and surfactant-stabilized emulsions. Furthermore, the switchable surface wettability holds an advantage of avoiding oil-fouling, which will greatly improve its recyclability.

The construction of thiol-functionalized DNAsomes with small molecules response and protein release

In this work, a poly(N-isopropylacrylamide) polymer (PNIPAAm) was prepared via the photoinduced reversible addition-fragmentation chain transfer (RAFT) polymerization using Ru(bpy)₃Cl₂·6H₂O as photoinitiator. The design and spontaneous assembly of thiol-functionalized DNA-Thiol/PNIPAAm polymeric capsule (DNAsomes) by water-in-oil Pickering emulsion method and effective response with small molecules (Sybr green and phenanthrene) were described. The intermediate product, DNA-Thiol/PNIPAAm conjugates and DNAsomes were characterized by using ¹H NMR, dynamic light scattering (DLS), SEM, TEM and UV-vis methods. The obtained results indicated that DNA-Thiol/PNIPAAm constructs assembled in a Pickering emulsion could produce DNA-based spherical DNAsomes with typically 3.3-267.7 μm in diameter. The DNAsomes showed a vesicle formation approximately 2 μm in diameter, resulting in phenanthrene molecule intercalating with DNAsomes. The phenomenon indicated that the DNA-Thiol/PNIPAAm conjugates may have potential applications in recognition polycyclic aromatic hydrocarbon molecules. The membrane of the DNAsomes could effective response toward small molecules such as Sybr green or phenanthrene, and DNAsomes has release capability of protein (BSA) under reductive agent glutathione (GSH). Our results highlight the potential of integrating aspects of supramolecular and polymer chemistry into the design and construction of DNA-polymeric capsule, guest molecule encapsulation, control delivery of drugs, recognition organic polycyclic aromatic hydrocarbon molecules and gene-directed capsule synthesis.

Dual CO2/temperature-responsive diblock copolymers confer controlled reversible emulsion behavior

Dual-stimuli responsive diblock copolymers possessing unique temperature-sensitive and CO₂/N₂-switching ability were successfully developed to promote efficient manipulation of reversible emulsification processes.

Functional materials generated by allying cyclodextrin-based supramolecular chemistry with living polymerization

Cyclodextrin molecules are cyclic oligosaccharides that display a unique structure including an inner side and two faces on their outer sides.

Molecular engineering of polymeric supra-amphiphiles

Polymeric supra-amphiphiles are amphiphiles that are fabricated by linking polymeric segments, or small molecules and polymeric segments, by noncovalent interactions or dynamic covalent bonds. Compared with conventional amphiphilic polymers, polymeric supra-amphiphiles are advantageous in that they possess dynamic features and their preparation may be to some extent more facile. Moreover, polymeric supra-amphiphiles are endowed with richer structure and higher stability compared with small-molecule supra-amphiphiles. Owing to these properties, polymeric supra-amphiphiles have so far shown great promise as surfactants, nanocarriers and in therapies. In this tutorial review, recent work on polymeric supra-amphiphiles, from molecular architectures to functional assemblies, is presented and summarized. Different polymeric supra-amphiphile topologies and related applications are highlighted. By combining polymer chemistry with supramolecular chemistry and colloid science, we anticipate that the study of polymeric supra-amphiphiles will promote the continued development of the molecular engineering of functional supramolecular systems, and lead to practical applications, especially in drug delivery.

Construction of Stimuli-Responsive Functional Materials via Hierarchical Self-Assembly Involving Coordination Interactions

Supramolecular self-assembly, which creates the ordered structures as a result of spontaneous organization of building blocks driven by noncovalent interactions (NCIs), is ubiquitous in nature. Recently, it has become increasingly clear that nature often builds up complex structures by employing a hierarchical self-assembly (HSA) strategy, in which the components are brought together in a stepwise process via multiple NCIs. Inspired by the dedicated biological structures in nature, HSA has been widely explored to construct well-defined assemblies with increasing complexity. The employment of direct metal-ligand bonds to drive the formation of discrete metallosupramolecular architectures has proven to be a highly efficient strategy to prepare structurally diverse architectures like two-dimensional (2-D) polygons and three-dimensional (3-D) polyhedra with well-defined shapes, sizes, and geometries. Such well-defined organometallic assemblies provide an ideal platform for designing novel artificial supramolecular systems with the increasing complexity though HSA. The presence of a well-defined organometallic scaffold brings an additional dimension to the final nanoscale structures. Moreover, the multilevel dynamic nature of hierarchical self-assemblies brings more structural and functional possibilities of resultant supramolecular systems. This Account will focus on our recent advance on construction of stimuli-responsive functional materials through HSA involving coordination interactions. In our study, a series of functionalized metallacycles were first constructed through coordination-driven self-assembly (CDSA). Then, the secondary noncovalent interaction sites were integrated within the functionalized metallacycle system via either preassembly or postassembly approach. Different segments, such as alkyl chains, dendrimers, cholesteryl moiety, covalent macrocycles, and even polymeric fragments, which could provide hydrophobic and hydrophilic interactions, van der Waals forces, hydrogen bonding, CH-π and π-π interactions, and host-guest interactions, have been utilized to provide the secondary NCIs. Further self-assembly of functionalized metallacycles gives rise to the formation of complex higher-order structures driven by other NCIs by taking advantages of orthogonal property of coordination bonds with other NCIs. By changing the type of additional NCIs embodied in building blocks, different supramolecular architectures, such as the ordered nanostructures, supramolecular polymers and gels, fluorescent materials and sensors, have been successfully prepared with the tailored chemical and physical properties. In particular, the dynamic nature of coordination bonds as well as other NCIs endows final assemblies with stimuli-responsive functions. Collectively, our studies suggest that combining coordination and other NCIs in a well-defined and precise manner is a highly efficient strategy to achieve the complex architectures and functional materials. Therefore, it is very promising to develop the desired functional materials with high precision and fidelity by employing HSA involving coordination interactions.

Controlled Formation of a Main Chain Supramolecular Polymer Based on Metal-Ligand Interactions and a Thiol-Ene Click Reaction

Supramolecular polymers with multiple functionalities and hierarchical structures have received considerable attention and become a hot research topic over the past years. Herein, a main-chain supramolecular polymer has been successfully fabricated by using metal-ligand interactions and a thiol-ene click reaction. ¹ H NMR, UV/Vis, DOSY, and viscosity measurements were carried out to investigate the molecular recognition and the process of supramolecular polymerization. From the study, the orthogonality between thiol-ene click reactions and the terpyridine-metal ions complexation behavior was testified, and supramolecular polymeric assemblies could be constructed by a one pot method. In the meantime, due to the incorporation of metal-ligand interactions, the supramolecular polymer shows stimuli-responsive properties toward chemical stimuli. Hence, this work could provide a methodology for developing supramolecular polymers as smart materials.

Polymersomes: Breaking the Glass Ceiling?

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

Self-Assembly and Applications of Amphiphilic Hybrid POSS Copolymers

Understanding the mechanism of molecular self-assembly to form well-organized nanostructures is essential in the field of supramolecular chemistry. Particularly, amphiphilic copolymers incorporated with polyhedral oligomeric silsesquioxanes (POSSs) have been one of the most promising materials in material science, engineering, and biomedical fields. In this review, new ideas and research works which have been carried out over the last several years in this relatively new area with a main focus on their mechanism in self-assembly and applications are discussed. In addition, insights into the unique role of POSSs in synthesis, microphase separation, and confined size were encompassed. Finally, perspectives and challenges related to the further advancement of POSS-based amphiphilics are discussed, followed by the proposed design considerations to address the challenges that we may face in the future.

Controlling CO2 -Responsive Behaviors of Polymersomes Self-Assembled by Coumarin-Containing Star Polymer via Regulating Its Crosslinking Pattern

An oligo(ethylene glycol)-based star polymer of N₂ -(OEG-C)₃ with fluorescent coumarin as hydrophobic end groups and dual tertiary amines as the star center is designed and synthesized. Owing to its amphiphilic nature of N₂ -(OEG-C)₃ , it will self-assemble into hollow vesicles with coumarin groups dispersed in the hydrophobic membrane and exhibits CO₂ -responsive behavior due to the protonation of amine centers with CO₂ . More importantly, coumarin moieties can either form non-crosslinking with γ-cyclodextrin via the 2/1 host-guest inclusion, or covalently photodimerized by 365 nm light, offering a tunable crosslinking pattern in the hydrophobic membrane and thus adjusting its CO₂ -stimulated reorganization and disassembly behaviors of these vesicles in aqueous solution.

Dual-Responsive Self-Propulsion Smart Device Steadily Driven by CO2 and H2O2

In this paper, we introduce a kind of tertiary amine-based CO₂-responsive material combining with the H₂O₂-responsive material to develop a dual-responsive self-propulsion smart device which can convert the chemical energy of H₂O₂ into mechanical energy steadily through diving-surfacing cycles. In this dual-responsive device, the CO₂-responsive material is designed as a wettability conversion species, which is wrapped with a strip of platinum to catalyze the decomposition of H₂O₂ to generate gaseous O₂ to realize surfacing. In deionized water, the device floats on the surface of the water initially and can perform a diving-surfacing cycle when CO₂ and H₂O₂ stimuli are alternately applied to the aqueous solution. The cyclic movement of the device can be realized by the generation and release of the inner gas through the hydrophobic cover, leading to a new controllable transition of different kinds of energy.

Controllable CO2-responsiveness of O/W emulsions by varying the alkane carbon number of a tertiary amine

A series of CO₂-responsive oil-in-water (O/W) emulsions were prepared by introducing a hydrophobic tertiary amine (TA) with a varying alkane carbon number (ACN) into the emulsion stabilized by sodium dodecyl benzene sulfonate (SDBS).

An eco-friendly approach for heavy metal adsorbent regeneration using CO2-responsive molecular octopus

Perennial problems of adsorption in wastewater treatment include adsorbent recycling, generation of waste sludge and secondary pollution because harmful concentrated acids, bases or strong chelators are often used for adsorbent regeneration and adsorbate recovery. We report, for the first time, an eco-friendly regeneration concept demonstrated with a CO₂-responsive octopus-like polymeric adsorbent. Various heavy metals can be scavenged at very high Q_e by such adsorbent through coordination. Most importantly, the rapid and complete regeneration of the adsorbent and recovery of the heavy metal ions can be readily achieved by CO₂ bubbling within a few minutes under mild conditions, i.e., room temperature and atmospheric pressure. The adsorbent can then be restored to its adsorptive state and reused upon removal of CO₂ by simply bubbling another gas. This eco-friendly, effective, ultra-fast and repeatable CO₂-triggered regeneration process using CO₂-responsive adsorbent with versatile structure, morphology or form can be incorporated into a sustainable closed-loop wastewater treatment process to solve the perennial problems.

NIR Light-, Temperature-, pH-, and Redox-Responsive Polymer-Modified Reduced Graphene Oxide/Mesoporous Silica Sandwich-Like Nanocomposites for Controlled Release

Here a novel quadruple-responsive nanocarrier based on reduced graphene oxide/mesoporous silica sandwich-like nanocomposites (rGO@MS) modified by pH- and temperature-responsive poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) with a linker of disulfide was constructed via surface-initiated atom transfer radical polymerization. The polymer chains would be used as gatekeepers to control the release of the loaded cargo molecules under pH, temperature, NIR light and redox stimuli. The cargo molecules (rhodamine B) were demonstrated to release from the polymer-modified nanocomposites triggered by the quadruple-stimuli. It is noted that the release of the loaded rhodamine B from the nanocarriers could be enhanced greatly under the synergistic effect of multiple stimuli. The prepared quadruple-responsive polymer-modified nanocomposites show a bright prospect in the field of smart nanocarriers for controlled release.

Polymersomes with Rapid K+-Triggered Drug-Release Behaviors

A novel type of smart polymersomes with rapid K⁺-triggered drug-release properties is developed in this work. Block copolymers with biocompatible poly(ethylene glycol) (PEG) as the hydrophilic block and poly(N-isopropylacrylamide-co-benzo-18-crown-6-acrylamide) (PNB) copolymer as the K⁺-responsive block are successfully synthesized. Because of the presence of 18-crown-6 units, the PEG-b-PNB block copolymers exhibit excellent K⁺-dependent phase-transition behaviors, which show a hydrophilic-hydrophobic state in simulated extracellular fluid and present a hydrophilic-hydrophilic state in simulated intracellular fluid. Polymersomes with regular spherical shape and good monodispersity are prepared by the self-assembly of the PEG-b-PNB block copolymers. Both hydrophilic fluorescein isothiocyanate-dextran and hydrophobic doxorubicin are selected as model drugs and are successfully encapsulated into the PEG-b-PNB polymersomes. After being placed in a simulated intracellular fluid with high K⁺ concentration, the PEG-b-PNB polymersomes immediately disassemble accompanied by the rapid and complete release of drugs. Such K⁺-responsive polymersomes with the desired drug-release properties provide a novel strategy for advanced intracellular drug delivery and release, which can enhance the safety and efficacy of cancer therapy.