Amphiphilic gradient copolymers: Synthesis, self-assembly, and applications

Polymersomes as Innovative, Stimuli-Responsive Platforms for Cancer Therapy

This review addresses the urgent need for more targeted and less toxic cancer treatments by exploring the potential of multi-responsive polymersomes. These advanced nanocarriers are engineered to deliver drugs precisely to tumor sites by responding to specific stimuli such as pH, temperature, light, hypoxia, and redox conditions, thereby minimizing the side effects associated with traditional chemotherapy. We discuss the design, synthesis, and recent applications of polymersomes, emphasizing their ability to improve therapeutic outcomes through controlled drug release and targeted delivery. Moreover, we highlight the critical areas for future research, including the optimization of polymersome-biological interactions and biocompatibility, to facilitate their clinical adoption. Multi-responsive polymersomes emerge as a promising development in nanomedicine, offering a pathway to safer and more effective cancer treatments.

Polymeric surfactants at liquid-liquid interfaces: Dependence of structural and thermodynamic properties on copolymer architecture

Polymeric surfactants are amphiphilic molecules with two or more different types of monomers. If one type of monomer interacts favorably with a liquid, and another type of monomer interacts favorably with another, immiscible liquid, then polymeric surfactants adsorb at the interface between the two liquids and reduce the interfacial tension. The effects of polymer architecture on the structural and thermodynamic properties of the liquid-liquid interface are studied using molecular simulations. The interface is modeled with a non-additive binary Lennard-Jones fluid in the two-phase region of the phase diagram. Block and gradient copolymer surfactants are represented with coarse-grained, bead-spring models, where each component of the polymer favors one or the other liquid. Gradient copolymers have a greater concentration at the interface than do block copolymers because the gradient copolymers adopt conformations partially aligned with the interface. The interfacial tension is determined as a function of the surface excess of polymeric surfactant. Gradient copolymers are more potent surfactants than block copolymers because the gradient copolymers cross the dividing surface multiple times, effectively acting as multiple individual surfactants. For a given surface excess, the interfacial tension decreases monotonically when changing from a block to a gradient architecture. The coarse-grained simulations are complemented by all-atom simulations of acrylic-acid/styrene copolymers at the chloroform-water interface, which have been studied in experiments. The agreement between the simulations (both coarse-grained and atomistic) and experiments is shown to be excellent, and the molecular-scale structures identified in the simulations help explain the variation of surfactancy with copolymer architecture.

Preparation of reversible cross-linked amphiphilic polymeric micelles with pH-responsive behavior for smart drug delivery

A new type of reversible cross-linked and pH-responsive polymeric micelle (PM), poly[polyethylene glycol methacrylate-co-2-(acetoacetoxy)ethyl methacrylate]-b-poly [2-(dimethylamino)ethyl methacrylate] [P(PEGMA-co-AEMA)-b-PDMAEMA], was synthesized for targeted delivery of curcumin. After reversible cross-linking of the micellar shell, the PMs with a typical core-shell structure exhibited excellent stability against extensive dilution and good reversibility of pH-responsiveness in solutions with different pH values. P(PEGMA9-co-AEMA6)-b-PDMAEMA10 has the lowest critical micelle concentration (CMC) value (0.0041 mg mL-1), the highest loading capacity (13.86%) and entrapment efficiency (97.03%). A slow sustained drug release at pH 7.4 with 12.36% in 108 h, while a fast release (42.36%) was observed at pH 5.0. Furthermore, a dissipative particle dynamics (DPD) simulation method was employed to investigate the self-assembly process and pH-responsive behavior of PMs. The optimal drug-carrier ratio (2%) and fraction of water (92%) were confirmed by analyzing the drug distribution and morphology of micelles during the self-assembly process of the block copolymer. The simulation results were consistent with experimental results, indicating DPD simulation shows potential to study the structure properties of reversible cross-linked micelles. The present findings provide a new method for the development of SDDS with good structural stability and controlled drug release properties.

Process intensification of continuous-flow seATRP by a sonicated multi-reactor setup

Simplified electrochemically mediated atom transfer radical polymerization (seATRP) is a versatile technique for synthesizing polymers with precise control and complex architecture. Continuous-flow seATRP has recently been realized by using a sonicated microreactor but still faces limitations such as relatively low conversion and difficulties in synthesizing polymers with high molecular weight. Herein, a novel multi-reactor setup is demonstrated. By tuning the currents applied to different reaction stages in the setup, 90% conversion can be achieved while maintaining relatively low dispersity (<1.35). Meanwhile, the unique design enables a wider processing window for sonication due to greater viscous attenuation in the second reactor, thus largely addressing the problem associated with high viscosity during the synthesis of high molecular weight polymers. The developed setup also offers an alternative strategy for future scale-up of continuous-flow seATRP.

Unexpected toroidal micelles formed from St/MMA gradient copolymers

Toroidal micelles are of great interest and rarely observed in gradient copolymer systems. Herein, we report massive toroidal micelles formed from styrene (St)/methyl methacrylate (MMA) gradient copolymers using a common solvent mixing method followed by a cooling-heating procedure. Furthermore, we demonstrate that the obtained toroidal morphology is sensitively dependent on a heat treatment procedure. Solely spherical micelles are obtained by a common solvent mixing method. These spherical micelles could be transformed into toroidal micelles via vesicles during a cooling-heating process. When a reverse heating-cooling process is adopted, no toroidal micelles formed. Thus, these results add new members to the family of toroidal micelles and reveal pathway dominating morphologies in gradient copolymer micelles.

Influence of Chain Length of Gradient and Block Copoly(2-oxazoline)s on Self-Assembly and Drug Encapsulation

Amphiphilic gradient copolymers represent a promising alternative to extensively used block copolymers due to their facile one-step synthesis by statistical copolymerization of monomers of different reactivity. Herein, an in-depth analysis is provided of micelles based on amphiphilic gradient poly(2-oxazoline)s with different chain lengths to evaluate their potential for micellar drug delivery systems and compare them to the analogous diblock copolymer micelles. Size, morphology, and stability of self-assembled nanoparticles, loading of hydrophobic drug curcumin, as well as cytotoxicities of the prepared nanoformulations are examined using copoly(2-oxazoline)s with varying chain lengths and comonomer ratios. In addition to several interesting differences between the two copolymer architecture classes, such as more compact self-assembled structures with faster exchange dynamics for the gradient copolymers, it is concluded that gradient copolymers provide stable curcumin nanoformulations with comparable drug loadings to block copolymer systems and benefit from more straightforward copolymer synthesis. The study demonstrates the potential of amphiphilic gradient copolymers as a versatile platform for the synthesis of new polymer therapeutics.

Coarse-Grained Model of Thiol-Epoxy-Based Alternating Copolymers in Explicit Solvents

The cosolvent method has been widely used in the self-assembly of amphiphilic alternating copolymers (ACPs), but the role of good and selective solvents is rarely investigated. Here, we have developed a coarse-grained (CG) model for the widely studied thiol-epoxy-based amphiphilic ACPs and a three-bead CG model for tetrahydrofuran (THF) as the good solvent, which is compatible with the MARTINI water model. The accuracy of both the CG polymer and THF models was validated by reproducing the structural and thermodynamic properties obtained from experiments or atomistic simulation results. Density in bulk, the radius of gyration, and solvation free energy in water or THF showed a good agreement between CG and atomistic models. The CG models were further employed to explore the self-assembly of ACPs in THF/water mixtures with different compositions. Chain folding and liquid-liquid phase separation behaviors were found with increasing water fractions, which were the key steps of the self-assembly process. This work will provide a basic platform to explore the self-assembly of amphiphilic ACPs in solvent mixtures and to reveal the real role of different solvents in self-assembly.

MPEG-PCL Nanomicelles Platform for Synergistic Metformin and Chrysin Delivery to Breast Cancer in Mice

BACKGROUND

Metformin (MET) is a well-known anti-diabetic drug that also has anti-cancer effects. However, high therapeutic doses of MET on cancer cells and the low efficacy of combinatory therapeutic approaches limit its clinical application. Recent studies have shown that chrysin (CHR) can improve the pharmaceutical efficacy of MET by suppressing human telomerase reverse transcriptase (hTERT) and cyclin D1 gene expression.

OBJECTIVE

This study aimed to develop different ratios of methoxy poly(ethylene glycol)-b-poly(e-caprolactone) (MPEG-PCL) micelles for breast cancer to co-deliver a synergistic CHR/MET combination.

METHODS

CHR/MET drug-loaded micelles were prepared by modified thin-film hydration. Fourier infrared spectrum, gel permeation chromatography, transmission electron microscopy, and high-performance liquid chromatography were used to evaluate the physicochemical properties of nanostructures. Cell proliferation and cell apoptosis were assessed by MTT and Annexin V-FITC/PI double staining method. The gene expression of hTERT and cyclin D1 was measured by real-time PCR assay. A subcutaneous mouse T47D xenograft model was established to evaluate the in vivo efficiency.

RESULTS

When the ratio of MPEG-PCL was 1:1.7, the highest drug loading rate and encapsulation efficiency of CHR (11.31±0.37) and MET (12.22±0.44) were observed. Uniform MPEG-PCL micelles of 51.70±1.91 nm allowed MET to incorporate with CHR, which were co-delivered to breast cancer cells. We demonstrated that CHR/MET co-delivery micelles showed a good synergistic effect on inhibiting proliferation in T47D cells (combination index=0.87) by suppressing hTERT and cyclin D1 gene expression. Compared with the free CHR/MET group, the apoptosis rate on T47D cells by CHR/MET nano-micelles significantly improved from 71.33% to 79.25%. The tumour volume and tumour weight of the CHR/MET group increased more slowly than that of the single-drug treatment group (P<0.05). Compared with the CHR/MET group, the tumour volume and tumour weight of the CHR/MET nano-micelle group decreased by 42% and 59%, respectively.

CONCLUSIONS

We demonstrated that ratiometric CHR/MET micelles could provide an effective technique for the treatment of breast cancer.

Amphiphilic Zwitterionic Acrylate/Methacrylate Copolymers for Marine Fouling-Release Coatings

Methacrylate and acrylate monomers are popular building blocks for antifouling (AF) and fouling-release (FR) coatings to counteract marine biofouling. They are used in various combinations and often combined into amphiphilic materials. This study investigated the FR properties of amphiphilic ethylene glycol dicyclopentenyl ether acrylate (DCPEA) and the corresponding methacrylate (DCPEMA) blended with 5 wt % zwitterionic carboxybetaine acrylate (CBA) and the corresponding methacrylate (CBMA). A series of (co)polymers with different acrylate/methacrylate compositions were synthesized and tested against the attachment of the diatom Navicula perminuta and in short-term dynamic field exposure experiments. The more hydrophobic methacrylate DCPEMA homopolymer outperformed its acrylate counterpart DCPEA. Incorporated zwitterionic functionality of both CBMA and CBA imparted ultralow fouling capability in the amphiphilic polymers toward diatom attachment, whereas in the real ocean environment, only the employment of CBMA reduced marine biofouling. Moreover, it was observed that CBA-containing coatings showed different surface morphologies and roughnesses compared to the CBMA analogues. Particularly, a high impact was found when acrylic CBA was mixed with methacrylic DCPEMA. While the wettability of the coatings was comparable, investigated methacrylates in general exhibited superior fouling resistance compared to the acrylates.

Amphiphilic copolymers in biomedical applications: Synthesis routes and property control

The request of new materials, matching strict requirements to be applied in precision and patient-specific medicine, is pushing for the synthesis of more and more complex block copolymers. Amphiphilic block copolymers are emerging in the biomedical field due to their great potential in terms of stimuli responsiveness, drug loading capabilities and reversible thermal gelation. Amphiphilicity guarantees self-assembly and thermoreversibility, while grafting polymers offers the possibility of combining blocks with various properties in one single material. These features make amphiphilic block copolymers excellent candidates for fine tuning drug delivery, gene therapy and for designing injectable hydrogels for tissue engineering. This manuscript revises the main techniques developed in the last decade for the synthesis of amphiphilic block copolymers for biomedical application. Strategies for fine tuning the properties of these novel materials during synthesis are discussed. A deep knowledge of the synthesis techniques and their effect on the performance and the biocompatibility of these polymers is the first step to move them from the lab to the bench. Current results predict a bright future for these materials in paving the way towards a smarter, less invasive, while more effective, medicine.

Synthesis of CO2-responsive gradient copolymers by switchable RAFT polymerization and their controlled self-assembly

Switchable RAFT agents, so-called because they can be reversibly switched by an acid/base stimulus to offer very good control over polymerization of both MAMs and LAMs, provide a route to prepare well-defined polyMAM-block-polyLAM copolymers.

Gradient copolymer micelles: an introduction to structures as well as structural transitions

Exhibiting variation of the composition along a chain, gradient copolymers bring new blood to the old story of polymeric micelles. The gradient chain structure results in some special features in micellar structures and leads to unique structural transitions, potentially leading to new properties and applications. Henceforth, gradient copolymer micellar structures and their transitions from the viewpoint of soft matter physics will be reviewed. Concepts such as a diffuse interface, shrinkage-stretching of micelles, and intrinsic temperature responsiveness are summarized from current research, which highlight new characteristic structures, relaxation modes and novel properties of micelles, respectively.

The influence of gradient and statistical arrangements of guanidinium or primary amine groups in poly(methacrylate) copolymers on their DNA binding affinity

Herein, we report the first gradient guanidinium containing cationic copolymers and investigate their binding ability to plasmid DNA (pDNA).

Self-assembly of fluorinated gradient copolymer in three-dimensional co-flow focusing microfluidic

HYPOTHESIS

The microfluidic technology can drive molecules to organize into aggregates with nano-structures, and gives a possibility to control aggregate morphologies by adjusting hydrodynamic parameters of microfluidics. COMSOL Multiphysics is a useful software to simulate the mixing situation of solutions in microfluidic. Here, experiments and simulation are combined to study the self-assembly of gradient copolymers in the microfluidic device.

EXPERIMENTS

Fluorinated gradient copolymers self-assembled in a three-dimensional co-flow focusing microfluidic device (3D CFMD). Hydrodynamic parameters of 3D CFMD were adjusted to control morphologies and the sizes of copolymer aggregates. A simulation software, COMSOL Multiphysics, was used to simulate the mixing and diffusion of outer phase stream and inner phase stream to explore the mixing kinetics of two streams in the microchannels.

FINDINGS

3D CFMD offered a novel platform for the continuous and controllable self-assembly of fluorinated gradient copolymer. Various morphologies of copolymer aggregates were obtained in 3D CFMD, but just spherical micelles were formed by a traditional solvent-inducing method. The flow velocity, initial water content of outer-phase stream, and the copolymer concentration of inner-phase stream had great effects on the morphology and size of copolymer aggregates. The simulation results made us a better understanding on the microfluidic self-assembly.

Unravelling the Excellent Chemical Stability and Bioavailability of Solvent Responsive Curcumin-Loaded 2-Ethyl-2-oxazoline-grad-2-(4-dodecyloxyphenyl)-2-oxazoline Copolymer Nanoparticles for Drug Delivery

A new gradient copolymer has been synthesized by the living cationic ring-opening polymerization of hydrophilic 2-ethyl-2-oxazoline with lipophilic 2-(4-dodecyloxyphenyl)-2-oxazoline (EtOx-grad-DPOx). The prepared copolymer is capable of assembling in water to yield polymeric nanoparticles that are successfully loaded with an anticancer agent, curcumin. Self-assembly of the copolymer was found to be tuned by the polarity as well as the hydrogen bonding ability of solvents. Solvent took distinctive role in the preparation of unloaded and curcumin-loaded nanoparticles. The stability of the nanoparticles was increased by curcumin loading promoted by curcumin-polymer interactions. Further, the chemical stability of curcumin in water is largely enhanced inside the polymeric nanoparticles. Curcumin-loaded (EtOx-grad-DPOx) copolymer nanoparticles showed excellent stability in the biological medium, low cytotoxicity, and concentration dependent uptake by U87 MG and HeLa cells, which indicate the possibility of their efficient application in drug delivery.