Polymer Vesicles Research Articles

Membrane Manipulation of Giant Unilamellar Polymer Vesicles with a Temperature‐Responsive Polymer

AbstractUnderstanding the complex behavior and dynamics of cellular membranes is integral to gain insight into cellular division and fusion processes. Bottom‐up synthetic cells are as a platform for replicating and probing cellular behavior. Giant polymer vesicles are more robust than liposomal counterparts, as well as having a broad range of chemical functionalities. However, the stability of the membrane can prohibit dynamic processes such as membrane phase separation and division. Here, we present a method for manipulating the membrane of giant polymersomes using a temperature responsive polymer. Upon elevation of temperature deformation and phase separation of the membrane was observed. Upon cooling, the membrane relaxed and became homogeneous again, with infrequent division of the synthetic cells.

Probing Crowdedness of Artificial Organelles by Clustering Polymersomes for Spatially Controlled and pH-Triggered Enzymatic Reactions.

Most sophisticated biological functions and features of cells are based on self-organization, and the coordination and connection between their cell organelles determines their key functions. Therefore, spatially ordered and controllable self-assembly of polymersomes to construct clusters to simulate complex intracellular biological functions has attracted widespread attention. Here, we present a simple one-step copper-free click strategy to cross-link nanoscale pH-responsive and photo-cross-linked polymersomes (less than 100 nm) to micron-level clusters (more than 90% in 0.5-2 μm range). Various influencing factors in the clustering process and subsequent purification methods were studied to obtain optimal clustered polymeric vesicles. Even when polymeric vesicles separately loaded with different enzymes (glucose oxidase and myoglobin) are coclustered, the overall permeability of the clusters can still be regulated through tuning the pH values on demand. Compared with simple blending of those enzyme-loaded polymersomes, the rate of enzymatic cascade reaction increased significantly due to the interconnected complex microstructure established. The connection of catalytic nanocompartments into clusters confining different enzymes of a cascade reaction provides an excellent platform for the development of artificial systems mimicking natural organelles or cells.

Inside Cover Picture

This review describes our ongoing journey regarding the research of polymersomes from macromolecular self‐assembly to emerging particle assembly. To develop polymersomes that are more suitable for various biomedical applications, our group constructed three promising polymersomes with unique structures: polymersomes with inhomogeneous membranes, asymmetrical coronas, and membranes that are fused with the coronas. Additionally, N‐carboxyanhydrides‐induced self‐assembly (NCA‐PISA) as a convenient method for large‐scale production of biodegradable polymersomes has been first proposed by our group. Finally, we prosed a novel concept of fusion‐induced particle assembly (FIPA) for preparing higher‐order polymersomes including tetrapod polymersomes and giant polymer vesicles with a latticelike membrane. More details are given in the article by Du et al. on page 1842—1855.image

PH-stable polymersome as nanocarrier for post-loaded rose bengal in photodynamic therapy

Photodynamic therapy is one of the best alternatives to chemo-, radio- or surgical therapy, as it is noninvasive and causes no severe side effects. The mechanism of photodynamic therapy involves activation of the drug (photosensitizer) with light of appropriate wavelength, which combined with molecular oxygen, leads to production of reactive oxygen species. This starts a cascade of reactions leading to cell death. Thus, the efficiency of this therapy is based mainly on the properties of a photosensitizer, including singlet oxygen yield and accumulation in the tumor area. Current research is aimed at applying nanosystems for the improvement of availability and photodynamic properties of photosensitizers. In order to improve the activity and increase photodynamic potential of rose bengal, one of the most promising drugs in anticancer photodynamic therapy, several drug delivery systems were developed. Among them, polymersomes represent a group of innovative polymeric vesicles mimicking membranous cell structures. Polymersomes are nanosystems made of amphiphilic block copolymers, possessing a spherical, liposome-like architecture. Within this study we present biophysical and in vitro biological characterization of this novel pH-stable nanosystem, which due to the improvement of singlet oxygen and reactive oxygen species (ROS) production by rose bengal is a good candidate for nanocarrier in photodynamic therapy.

Polymer Vesicles in a Nanochannel under Flow Fields: A DPD Simulation Study

AbstractThe general lack of knowledge on the dynamics of polymer vesicles under flow field has confounded their applications in drug delivery and other fields. Therefore, dissipative particle dynamics (DPD) simulations on the dynamic behavior of diblock copolymer vesicles in a nanochannel under Poiseuille flow are conducted. The simulation results show that the block copolymer vesicles with hydrophobic blocks of different rigidities exhibit significantly different mechanical stabilities under the flow fields. With increasing the Reynolds number, the coil–coil block copolymer vesicles undergo a shape transition from spherical to bullet‐like to asymmetric and eventually split into two parts. In contrast, the rod–coil block copolymer vesicles deform from spherical to bullet‐like to parachute‐like structures and ultimately ruptured. The flow‐induced distortion and reorganization of copolymers mainly cause the deformation of vesicles. The distinguished motions of the block copolymers with different rigid blocks lead to the distinct performance of the vesicles. The findings could help understand the flow behavior of polymer vesicles in a nanochannel or a blood vessel and assist the design of bio‐functional polymersomes.

Twin-Engine Janus Supramolecular Nanomotors with Counterbalanced Motion.

Supramolecular nanomotors were created with two types of propelling forces that were able to counterbalance each other. The particles were based on bowl-shaped polymer vesicles, or stomatocytes, assembled from the amphiphilic block copolymer poly(ethylene glycol)-block-polystyrene. The first method of propulsion was installed by loading the nanocavity of the stomatocytes with the enzyme catalase, which enabled the decomposition of hydrogen peroxide into water and oxygen, leading to a chemically induced motion. The second method of propulsion was attained by applying a hemispherical gold coating on the stomatocytes, on the opposite side of the opening, making the particles susceptible to near-infrared laser light. By exposing these Janus-type twin engine nanomotors to both hydrogen peroxide (H2O2) and near-infrared light, two competing driving forces were synchronously generated, resulting in a counterbalanced, “seesaw effect” motion. By precisely manipulating the incident laser power and concentration of H2O2, the supramolecular nanomotors could be halted in a standby mode. Furthermore, the fact that these Janus stomatocytes were equipped with opposing motile forces also provided a proof of the direction of motion of the enzyme-activated stomatocytes. Finally, the modulation of the “seesaw effect”, by tuning the net outcome of the two coexisting driving forces, was used to attain switchable control of the motile behavior of the twin-engine nanomotors. Supramolecular nanomotors that can be steered by two orthogonal propulsion mechanisms hold considerable potential for being used in complex tasks, including active transportation and environmental remediation.

Intelligent design of polymersomes for antibacterial and anticancer applications.

Polymersomes (or polymer vesicles) have attracted much attention for biomedical applications in recent years because their lumen can be used for drug delivery and their coronas and membrane can be modified with a variety of functional groups. Thus, polymersomes are very suitable for improved antibacterial and anticancer therapy. This review mainly highlighted recent advances in the synthetic protocols and design principles of intelligent antibacterial and anticancer polymersomes. Antibacterial polymersomes are divided into three categories: polymersomes as antibiotic nanocarriers, intrinsically antibacterial polymersomes, and antibacterial polymersomes with supplementary means including photothermal and photodynamic therapy. Similarly, the anticancer polymersomes are divided into two categories: polymersomes-based delivery systems and anticancer polymersomes with supplementary means. In addition, the bilateral relationship between bacteria and cancer is addressed, since more and more evidences show that bacteria may cause cancer or promote cancer progression. Finally, prospective on next-generation antibacterial and anticancer polymersomes are discussed. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Biology-Inspired Nanomaterials > Lipid-Based Structures.

Polymersomes: From Macromolecular Self‐Assembly to Particle Assembly†

Comprehensive SummaryPolymersomes, or polymer vesicles, have attracted a tremendous amount of interest over the last decade. This led to the development of polymer vesicles that are suitable for various biomedical applications, including blood sugar regulation, cancer theranostics, and antibacterial agents. This review mainly describes the research from our group on macromolecular self‐assembly of polymersomes and emerging particle assembly methods. First, the building blocks and general principles for the design of functional polymersomes are introduced. Thereafter, we present three polymersomes with various membrane structures: polymersomes with inhomogeneous membranes, asymmetrical coronas, and membranes that are fused with the coronas. Furthermore, given that N‐carboxyanhydrides‐induced self‐assembly (NCA‐PISA) is a convenient method for the large‐scale production of biodegradable polymersomes, recent advances in self‐assembly methods based on ring‐opening polymerization of NCA‐PISA are discussed. Finally, the mechanism of particle assembly and recent advances in producing higher‐order polymer vesicles, including tetrapod polymersomes and giant polymer vesicles with a latticelike membrane (GVLM), are discussed. What is the most favorite and original chemistry developed in your research group?Ring‐opening polymerization‐induced self‐assembly of N‐carboxyanhydrides (NCA‐PISA), and fusion‐induced particle assembly (FIPA).How do you get into this specific field? Could you please share some experiences with our readers?NCA‐PISA was developed to solve the biodegradability problem of nanoparticles by traditional PISA, while FIPA was inspired by nature.What is the most important personality for scientific research?The spirit of putting forward scientific problems.What are your hobbies?Driving, badminton, jogging, and music.What are your favorite journals?J. Am. Chem. Soc. and Macromolecules.Who influences you mostly in your life?My family and my Ph.D. and postdoctoral supervisors.

Dually Responsive Poly(N-vinylcaprolactam)-b-poly(dimethylsiloxane)-b-poly(N-vinylcaprolactam) Polymersomes for Controlled Delivery.

Limited tissue selectivity and targeting of anticancer therapeutics in systemic administration can produce harmful side effects in the body. Various polymer nano-vehicles have been developed to encapsulate therapeutics and prevent premature drug release. Dually responsive polymeric vesicles (polymersomes) assembled from temperature-/pH-sensitive block copolymers are particularly interesting for the delivery of encapsulated therapeutics to targeted tumors and inflamed tissues. We have previously demonstrated that temperature-responsive poly(N-vinylcaprolactam) (PVCL)-b-poly(dimethylsiloxane) (PDMS)-b-PVCL polymersomes exhibit high loading efficiency of anticancer therapeutics in physiological conditions. However, the in-vivo toxicity of these polymersomes as biocompatible materials has not yet been explored. Nevertheless, developing an advanced therapeutic nanocarrier must provide the knowledge of possible risks from the material’s toxicity to support its future clinical research in humans. Herein, we studied pH-induced degradation of PVCL10-b-PDMS65-b-PVCL10 vesicles in-situ and their dually (pH- and temperature-) responsive release of the anticancer drug, doxorubicin, using NMR, DLS, TEM, and absorbance spectroscopy. The toxic potential of the polymersomes was evaluated in-vivo by intravenous injection (40 mg kg−1 single dose) of PVCL10-PDMS65-PVCL10 vesicles to mice. The sub-acute toxicity study (14 days) included gravimetric, histological, and hematological analyses and provided evidence for good biocompatibility and non-toxicity of the biomaterial. These results show the potential of these vesicles to be used in clinical research.

Intracellular transport of biomacromolecular drugs by a designed microgel capsule with pH/redox stimulus-responsiveness

Biological macromolecular drugs usually have good efficacy and recognition performance. However, due to their large molecular weight and easy degradation/inactivation, general carriers are difficult to transport them into cell stably and safely. Here, a pH/redox dual-responsive microgel capsule was prepared for constructing a double-locked drug delivery system. Firstly, the pH-sensitive poly(ethyleneimine)-block-poly(2-(diisopropylamino ethylmethacry-late)-block-poly(ethyleneimine) triblock copolymers (PEI-PDPA-PEI) were synthesized for preparing polymer vesicles. The PEI layer was crosslinked by disulfide groups to finally obtain pH/redox dual-responsive microgel capsule, marked as P-VesicleGEL. Then, the P-VesicleGEL was used to encapsulate different types of drugs (doxorubicin hydrochloride, rhodamine, proteins, aptamer), and had a higher loading capacity than the corresponding polymer micelles for macromolecules. Compared with small molecules, P-VesicleGEL had much better "double-locked" function for macromolecules. I.e., only when the two “locks” were opened simultaneously the release could be triggered. Furtherly, cell experiments had proved that the P-VesicleGEL had excellent biocompatibility and cell transfection ability. It could not only effectively identify normal and cancer cells, but also transport biological drugs that were difficult to enter into cells by themselves. The microgel capsule designed here is expected to be applied for the intracellular delivery/release of biological macromolecular drugs.

Polymersomes as virus-surrogate particles for evaluating the performance of air filter materials

The development of antivirus air filter materials has attracted considerable interests due to the pandemic of coronavirus disease 2019 (COVID-19). Filtration efficiency (FE) of these materials against virus is critical in the assessment of their use in disease prevention. Due to the high cost and biosafety laboratory required for conducting research using actual virus samples, surrogates for virus are commonly used in the filtration test. Here, we explore the employment of polymersomes (polymeric vesicles) as a new type of surrogate. The polymersomes are hollow shell nanoparticles with amphiphilic bilayer membranes, which can be fabricated in nanosized, and possess similar size and structural features to virus. The performance of commercial KN95 mask and surgical mask with micro-sized fibers, and electrospun polyvinylidene fluoride (PVDF) and polyacrylonitrile (PAN) nanofibers were chosen to be evaluated. The filtration tests against fluorescent-labeled virus-surrogate particles (VSPs), i.e. polymersomes, allowed the determination of the FE of the multilayered filter materials in a layer-specific manner. The results suggested the importance of hydrophobicity in designing the nanofibrous filter materials. The employment of VSPs in filtration performance evaluation allows a cost-effective way to estimate the FE against virus, providing guidance on future development of air filter materials.

Preparation of carboxymethyl cellulose/chitosan-CuO giant vesicles for the adsorption and catalytic degradation of dyes

To effectively remove the dyes from wastewater, novel carboxymethyl cellulose/chitosan-CuO giant vesicles with dual function of adsorption and catalytic degradation were prepared. The vesicles were facilely obtained via blending chitosan solution and carboxymethyl cellulose/CuO mixed solution with sequent fast and slow stirring. The removal ratios of methyl orange (MO) and acid black-172 (AB) can reach 86.3% and 88.6% with the catalytic oxidation system of ammonium persulfate and vesicles. Compared with the CuO catalysis without the vesicles, the degradation rates of MO and AB increased by 1.3 and 3.1 times, respectively. The enhanced dye removal is ascribed to the excellent dye adsorption capacity of giant vesicles. Furthermore, the giant vesicles worked well in wide ranges of environmental pH and temperature, and exhibited excellent stability and reusability. This study provides a facile method to load catalyst onto polymeric giant vesicle with outstanding performance for the adsorption and catalytic degradation of dyes.

Antibacterial and Biofilm-Eradicating Activities of pH-Responsive Vesicles against Pseudomonas aeruginosa.

The formation of biofilms by a microcolony of bacteria is a significant burden on the healthcare industry due to difficulty eradicating it. In this study, pH-responsive vesicles capable of releasing apramycin (APR), a model aminoglycoside antibiotic, in response to the low pH typical of establishedPseudomonas aeruginosa biofilms resulted in improved eradication of existing biofilms in comparison to the free drug. The amphiphilic polymeric vesicle (PV) comprised of block polymer poly (ethylene glycol)-block-poly 2-(dimethylamino) ethyl methacrylate (mPEG-b-pDEAEMA) averaged 128 nm. The drug encapsulation content of APR in PV/APR was confirmed to be 28.2%, and the drug encapsulation efficiency was confirmed to be 51.2%. At pH 5.5, PV/APR released >90% APR after 24 h compared to <20% at pH 7.4. At pH 5.5, protonation of the pDEAEMA block results in a zeta potential of +23 mV compared to a neutral zeta potential of +2.2 mV at pH 7.4. Confocal microscopy, flow cytometry, and scanning electron microscopy reveal that the positively charged vesicles can compromise the integrity of the planktonic bacterial membrane in a pH-dependent manner. In addition, PV/APR is able to diffuse into mature biofilms to release APR in the acidic milieu of biofilm bacteria, and PV/APR was more efficient at eliminating preexisting biofilms compared to free APR at 128 and 256 μg/mL. This study reveals that dynamic charge density in response to pH can lead to differential levels of interactions with the biofilm and bacterial membrane. This effectively results in enhanced antibacterial and antibiofilm properties against both planktonic and difficult-to-treat biofilm bacteria at concentrations significantly lower than those of the free drug. Overall, this pH-responsive vesicle could be especially promising for treating biofilm-associated infectious diseases.

Evaluation of PEG-b-polycarbonates self-assemblies containing azobenzene or coumarin moieties as nanocarriers using paclitaxel as a model hydrophobic drug

The work assesses the performance of nanocarriers from amphiphilic block copolymers with functional azobenzene or coumarin moieties for delivery of paclitaxel. Placlitaxel was encapsulated by the nanoprecipitation method. Characterisations were performed by DLS, TEM, Zeta potential and HPLC. Cell viability was investigated in HeLa and Huh-5-2-cell lines. Coumarin-containing polymeric micelles (Dh = 26 ± 2 nm, PDI = 0.28, ζ = ‒22.9 ± 3.6 mV) with 11.2 ± 0.5%w/w drug loading showed enhanced cytotoxicity in HeLa cells (IC50 < 0.02 nM) compared to free paclitaxel (IC50 = 0.17 ± 0.02 nM). Azobenzene-containing polymeric vesicles (Dh = 390 ± 20 nm, PDI = 0.24, ζ = ‒33.2 ± 5.0 mV) with a 6.8 ± 0.4%w/w drug loading showed increased cytotoxicity under 530 nm light (IC50 = 0.0114 ± 0.00033 nM) in HeLa cells due to a stimulated delivery of paclitaxel. Effectivity of these block copolymers as paclitaxel nanovectors and light stimulated release has been demonstrated.

Poly(N-vinylpyrrolidone)-block-Poly(dimethylsiloxane)-block-Poly(N-vinylpyrrolidone) Triblock Copolymer Polymersomes for Delivery of PARP1 siRNA to Breast Cancers.

Nearly 20% of HER2-positive breast cancers develop resistance to HER2-targeted therapies requiring the use of advanced therapies. Silencing RNA therapy may be a powerful modality for treating resistant HER2 cancers due to its high specificity and low toxicity. However, the systemic administration of siRNAs requires a safe and efficient delivery platform because of siRNA's low stability in physiological fluids, inefficient cellular uptake, immunoreactivity, and rapid clearance. We have developed theranostic polymeric vesicles to overcome these hurdles for encapsulation and delivery of small functional molecules and PARP1 siRNA for in vivo delivery to breast cancer tumors. The 100 nm polymer vesicles were assembled from biodegradable and non-ionic poly(N-vinylpyrrolidone)14-block-poly(dimethylsiloxane)47-block-poly(N-vinylpyrrolidone)14 triblock copolymer PVPON14-PDMS47-PVPON14 using nanoprecipitation and thin-film hydration. We demonstrated that the vesicles assembled from the copolymer covalently tagged with the Cy5.5 fluorescent dye for in vivo imaging could also encapsulate the model drug with high loading efficiency (40%). The dye-loaded vesicles were accumulated in tumors after 18 h circulation in 4TR breast tumor-bearing mice via passive targeting. We found that PARP1 siRNA encapsulated into the vesicles was released intact (13%) into solution by the therapeutic ultrasound treatment as quantified by gel electrophoresis. The PARP1 siRNA-loaded polymersomes inhibited the proliferation of MDA-MB-361TR cells by 34% after 6 days of treatment by suppressing the NF-kB signaling pathway, unlike their scrambled siRNA-loaded counterparts. Finally, the treatment by PARP1 siRNA-loaded vesicles prolonged the survival of the mice bearing 4T1 breast cancer xenografts, with the 4-fold survival increase, unlike the untreated mice after 3 weeks following the treatment. These biodegradable, non-ionic PVPON14-PDMS47-PVPON14 polymeric nanovesicles capable of the efficient encapsulation and delivery of PARP1 siRNA to successfully knock down PARP1 in vivo can provide an advanced platform for the development of precision-targeted therapeutic carriers, which could help develop highly effective drug delivery nanovehicles for breast cancer gene therapy.

Polymersomes: Soft Nanoparticles from Miktoarm Stars for Applications in Drug Delivery.

Self-assembly of amphiphilic macromolecules has provided an advantageous platform to address significant issues in a variety of areas, including biology. Such soft nanoparticles with a hydrophobic core and hydrophilic corona, referred to as micelles, have been extensively investigated for delivering lipophilic therapeutics by physical encapsulation. Polymeric vesicles or polymersomes with similarities in morphology to liposomes continue to play an essential role in understanding the behavior of cell membranes and, in addition, have offered opportunities in designing smart nanoformulations. With the evolution in synthetic methodologies to macromolecular precursors, the construction of such assemblies can now be modulated to tailor their properties to match desired needs. This review brings into focus the current state-of-the-art in the design of polymersomes using amphiphilic miktoarm star polymers through a detailed analysis of the synthesis of miktoarm star polymers with tuned lengths of varied polymeric arms, their self-assembly, and applications in drug delivery.

Research Progress and Prospects for Polymeric Nanovesicles in Anticancer Drug Delivery.

Polymeric vesicles served as the most promising candidates of drug delivery nanocarriers are attracting increasing attention in cancer therapy. Significant advantages have been reported, including hydrophilic molecules with high loading capacity, controllable drug release, rapid and smart responses to stimuli and versatile functionalities. In this study, we have made a systematic review of all aspects of nano-vesicles as drug delivery vectors for cancer treatment, mainly including the following aspect: characteristics of polymeric nanovesicles, polymeric nanovesicle synthesis, and recent progress in applying polymeric nanovesicles in antitumor drug delivery. Polymer nanovesicles have the advantages of synergistic photothermal and imaging in improving the anticancer effect. Therefore, we believe that drug carrier of polymer nanovesicles is a key direction for cancer treatment.

Inside Back Cover Picture

The inside back cover picture shows that polymer vesicles with low‐polydispersity (&lt; 0.1) and controllable size in the scope of sub‐100 nm are fabricated by polymerization‐induced self‐assembly (PISA) using ternary macro RAFT agents of different lengths. The ternary stabilizers play a crucial role in the formation of small and low‐polydispersity vesicles. More details are given in the article by Hong et al. on page 453—459. image

Stability and Deformation of Vesicles in a Cylindrical Flow.

In this work, we used dissipative particle dynamics to study the stability, deformation, and rupture of polymer vesicles confined in cylindrical channels under the flow field. The morphological evolution, elongation, and rupture of vesicles and the corresponding mechanisms were intensively investigated. Bullet-like vesicles, leaking vesicles, spherical micelles, hamburger-like micelles, and bilayers were observed by changing the degree of confinement and dimensionless shear rate. We found that increasing the dimensionless shear rate and the degree of confinement can cause the deformation or rupture of polymeric vesicles. The asphericity parameter was utilized to describe the degree of elongation of vesicles deviating from the sphere in the direction of the flow. The results show that the aggregates are more likely to be spherical when the confinement is weak, while they become elongated bullet-like shapes when the confinement is strong. The investigation of dynamics reveals that the degree of confinement and the dimensionless shear rate can affect the chain stretching and reorganization during the process of vesicle elongation. Furthermore, the rupture time of the vesicle shows a nonlinear decrease with an increase in the dimensionless shear rate, and the confinement also contributes to the rupture. The results are very useful for guiding the application of vesicles in a flow environment.

Formation Kinetics of Polymer Vesicles from Spherical and Cylindrical Micelles Bearing the Polyelectrolyte Complex Core Studied by Time-Resolved USAXS and SAXS

Formation Kinetics of Polymer Vesicles from Spherical and Cylindrical Micelles Bearing the Polyelectrolyte Complex Core Studied by Time-Resolved USAXS and SAXS