A general orthogonal functionalization strategy for tailoring zwitterionic polymers with adjustable isoelectric points

Zwitterionic polymers, bearing a pair of oppositely charged groups in their repeat units, have demonstrated significant promise in both biomedical and engineering fields. Tunability of isoelectric points (IEPs) is of great value for bio-applications as it relates to key properties such as the surface charge reversal behavior, biocompatibility and the affinity to biomacromolecules. However, zwitterionic polymers with adjustable IEPs are difficult to obtain due to the fixed combination of ion pairs such as carboxybetaine-, sulfobetaine- and phosphorylcholine-based structures. To address this issue, we present a general approach to tailor zwitterionic polymers with adjustable IEPs. By developing an orthogonal functionalization strategy with sequence-controlled alternating polyesters, a series of zwitterionic polymers featuring customizable ion pairs were synthesized. This strategy, which involves aza-Michael addition and thiol-ene reaction, enables precise control over the alternating sequence of cations and anions, thereby allowing the generation of customizable ion pairs in each repeat unit. By forming block copolyesters with a hydrophobic polycaprolactone block, these polymers self-assemble into nanoparticles with tunable IEPs (e.g., 6.03, 6.37, and 6.54) and surface-charge-reversal properties, responding to physiological (pH 7.4) and tumor microenvironment (pH 6.5 ∼ 6.9) conditions. Notably, PCL54-b-P(MA-alt-AGE-g-Pip/NAC)9 (PPS3) nanoparticles, with the optimal IEP values, exhibited remarkable efficacy in inhibiting murine melanoma tumors in vivo when loaded with curcumin. This innovative approach holds promise for developing biocompatible and biodegradable drug delivery systems with tailored properties for potential clinical applications.

Facile synthesis of rapamycin‐loaded PEG‐b‐PLA nanoparticles and their application in immunotherapy

Poly(ethylene glycol)‐block‐poly(lactide) (PEG‐b‐PLA) micro‐ and nanoparticles (NPs) have been intensively investigated for applications in biomedicine, due to their inherent biocompatibility and biodegradability, which allows them to be used as sustained release systems. Current methods for preparing PEG‐b‐PLA NPs typically require two different steps that include polymer synthesis and NP assembly, with the necessary intermediate polymer purification and the use of a variety of organic solvents in the process. In order to facilitate the biomedical application of PEG‐b‐PLA NPs, it is of great interest to develop a strategy to formulate the NPs in a simplified manner. Here, we report a straightforward method to construct PEG‐b‐PLA NPs through a sequential two‐step process without intermediate work‐up, which involves synthesizing the polymer in a water‐miscible organic solvent that is, N,N‐dimethylformamide (DMF), followed by addition of water to the polymer solution. In this way, large NPs (~600 nm) were prepared. We comprehensively characterized the NPs using turbidity studies, dynamic light scattering (DLS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. We further demonstrated the ability of the NPs to encapsulate drugs, exemplified in the immunotherapeutic agent rapamycin, with relatively high encapsulation efficiency. In vitro drug release tests showed that rapamycin‐encapsulating NPs had comparable sustained‐release profiles at different pH conditions, highlighting the broad application window of our NP platform. Moreover, in vitro T cell suppression assays revealed that rapamycin‐loaded NPs exhibited similar inhibitory performance to free rapamycin on CD8+ cells at all rapamycin concentrations and on CD4+ cells at high and intermediate rapamycin concentrations, while the performance of the NPs was superior on CD4+ at low rapamycin concentration. Overall, this work provides a route for the scalable synthesis of biocompatible PEG‐b‐PLA NPs, which can be extended to other polymeric NPs, with potential in biomedical applications such as immunotherapy.

Co-assembly of Amphiphilic Triblock Copolymers with Nanodrugs and Drug Release Kinetics in Solution

Polymeric vesicles present great potential in disease treatment as they can be featured as a structurally stable and easily functionalized drug carrier that can simultaneously encapsulate multiple drugs and release them on-demand. Based on the dissipative particle dynamics (DPD) simulation, the drug-loaded vesicles were designed by the co-assembly process of linear amphiphilic triblock copolymers and hydrophobic nanodrugs in solvents, and most importantly, the drug release behavior of drug-loaded vesicles were intensively investigated. The drug-loaded aggregates, such as vesicles, spherical micelles, and disk-like micelles, were observed by varying the size and concentration of nanodrugs and the length of the hydrophobic block. The distribution of nanodrugs in the vesicles was intensively analyzed. As the size of the nanodrugs increases, the localization of nanodrugs change from being unable to fully wrap in the vesicle wall to the uniform distribution and finally to the aggregation in the vesicles at the fixed concentration of nanodrugs. The membrane thickness of the drug-loaded polymeric vesicle can be increased, and the nanodrugs localized closer to the center of the vesicle by increasing the length of the hydrophobic block. The nanodrugs will be released from vesicles by varying the interactions between the nanodrug and the solvent or the hydrophobic block and the solvent, respectively. We found that the release kinetics conforms to the first-order kinetic model, which can be used to fit the cumulative release rate of nanodrugs over time. The results showed that increasing the size of nanodrugs, the length of hydrophobic block, and the interaction parameters between the hydrophobic block and the solvent will slow down the release rate of the nanodrug and change the drug release process from monophasic to biphasic release model.

Physically and Chemically Compartmentalized Polymersomes for Programmed Delivery and Biological Applications

Multicompartment polymersomes (MCPs) refer to polymersomes that not only contain one single compartment, either in the membrane or in the internal cavity, but also mimic the compartmentalized structure of living cells, attracting much attention in programmed delivery and biological applications. The investigation of MCPs may promote the application of soft nanomaterials in biomedicine. This Review seeks to highlight the recent advances of the design principles, synthetic strategies, and biomedical applications of MCPs. The compartmentalization types including chemical, physical, and hybrid compartmentalization are discussed. Subsequently, the design and controlled synthesis of MCPs by the self-assembly of amphiphilic polymers, double emulsification, coprecipitation, microfluidics and particle assembly, etc. are summarized. Furthermore, the diverse applications of MCPs in programmed delivery of various cargoes and biological applications including cancer therapy, antimicrobials, and regulation of blood glucose levels are highlighted. Finally, future perspectives of MCPs from the aspects of controlled synthesis and applications are proposed.

Membrane and Lumen-Compartmentalized Polymersomes for Biocatalysis and Cell Mimics

Compartmentalization is a crucial feature of a natural cell, manifested in cell membrane and inner lumen. Inspired by the cellular structure, multicompartment polymersomes (MCPs), including membrane-compartmentalized polymersomes and lumen-compartmentalized polymersomes (polymersomes-in-polymersomes), have aroused great expectations for biological applications such as biocatalysis and cell mimics in the past decades. Compared with traditional polymersomes, MCPs have advantages in encapsulating multiple enzymes separately for multistep enzymatic cascade reactions. In this review, first, the design principles and preparation methods of membrane-compartmentalized and lumen-compartmentalized polymersomes are summarized. Next, recent advances of MCPs as nanoreactors and cell mimics to mimic subcellular organelles or artificial cells are discussed. Finally, the future research directions of MCPs are prospected.

Multicompartment colloid systems with lipid and polymer membranes for biomedical applications

Multicompartment structures have the potential for biomedical applications because they can act as multifunctional systems and provide simultaneous delivery of drugs and diagnostics agents of different types. Moreover, some of them mimic biological cells to some extent with organelles as separate sub-compartments. This article analyses multicompartment colloidal structures with smaller sub-units covered with lipid or polymer membranes that provide additional protection for the encapsulated substances. Vesosomes with small vesicles encapsulated in the inner pools of larger liposomes are the most studied systems to date. Dendrimer molecules are enclosed by a lipid bilayer shell in dendrosomes. Capsosomes, polymersomes-in-polymer capsules, and cubosomes-in-polymer capsules are composed of sub-compartments encapsulated within closed multilayer polymer membranes. Janus or Cerberus emulsions contain droplets composed of two or three phases: immiscible oils in O/W emulsions and aqueous polymer or salt solutions that are separated into two or three phases and form connected droplets in W/O emulsions. In more cases, the external surface of engulfed droplets in Janus or Cerberus emulsions is covered with a lipid or polymer monolayer. eLiposomes with emulsion droplets encapsulated into a bilayer shell have been given little attention so far, but they have very great prospects. In addition to nanoemulsion droplets, solid lipid nanoparticles, nanostructured lipid carriers and inorganic nanoparticles can be loaded into eLiposomes. Molecular engineering of the external membrane allows the creation of ligand-targeted and stimuli-responsive multifunctional systems. As a result, the efficacy of drug delivery can be significantly enhanced.

Structure-Controlled Preparation of Multicompartment Micelles with Tunable Emission through Hydrodynamics-Dependent Self-Assembly in Microfluidic Chips

Multicompartment micelles (MCMs) attracted much attention since they have subdivided domains that could be employed to encapsulate and transport diverse compounds simultaneously. Usually, preparation of MCMs relied on precise synthesis of block copolymers (BCPs) and elegant control of assembly kinetics, making it difficult to successively produce MCMs. Herein, we report a facile yet effective method for preparing MCMs by adjusting the hydrodynamics in microfluidic channels. It was found that well-defined MCMs were formed through hydrodynamics-dependent secondary assembly in microfluidic chips. By adjusting the flow diffusion process by varying the flow rate ratio and total flow rate, both the internal structure and size of MCMs could be effectively changed. A product diagram of micellar morphologies associated to the initial polymer concentration and flow rate ratio of water/BCPs solution was constructed. More interestingly, quantum dots (QDs) could be selectively loaded into different domains of the MCMs. Consequently, the Förster resonance energy transfer among QDs could be effectively suppressed. Thus, the emission spectrum of MCMs/QDs hybrid particles could be easily tuned by changing the ratio of QDs, showing great potential application in photonics and sensors.

Hyaluronan-fullerene/AIEgen nanogel as CD44-targeted delivery of tirapazamine for synergistic photodynamic-hypoxia activated therapy

The therapeutic effect of oxygen-concentration-dependent photodynamic therapy (PDT) can be diminished in the hypoxic environment of solid tumours, the effective solution to this problem is utilising hypoxic-activated bioreduction therapy (BRT). In this research, a biocompatible HA-C60/TPENH₂nanogel which can specifically bind to CD44 receptor was developed for highly efficient PDT-BRT synergistic therapy. The nanogel was degradable in acidic microenvironments of tumours and facilitated the release of biological reduction prodrug tirapazamine (TPZ). Importantly, HA-C60/TPENH₂nanogel produced reactive oxygen species and consumed oxygen content in the cell to activate TPZ, leading to higher cytotoxicity than the free TPZ did. The intracellular observation of nanogel indicated that the HA-C60/TPENH₂nanogel was self-fluorescence for cell imaging. This study applied PDT-BRT to design smart HA-based nanogel with targeted delivery, pH response, and AIEgen feature for efficient cancer therapy.