The rational design of theranostic nanoparticles exhibiting synergistic turn-on of therapeutic potency and enhanced diagnostic imaging in response to tumor milieu is critical for efficient ...personalized cancer chemotherapy. We herein fabricate self-reporting theranostic drug nanocarriers based on hyperbranched polyprodrug amphiphiles (hPAs) consisting of hyperbranched cores conjugated with reduction-activatable camptothecin prodrugs and magnetic resonance (MR) imaging contrast agent (Gd complex), and hydrophilic coronas functionalized with guanidine residues. Upon cellular internalization, reductive milieu-actuated release of anticancer drug in the active form, activation of therapeutic efficacy (>70-fold enhancement in cytotoxicity), and turn-on of MR imaging (∼9.6-fold increase in T 1 relaxivity) were simultaneously achieved in the simulated cytosol milieu. In addition, guanidine-decorated hPAs exhibited extended blood circulation with a half-life up to ∼9.8 h and excellent tumor cell penetration potency. The hyperbranched chain topology thus provides a novel theranostic polyprodrug platform for synergistic imaging/chemotherapy and enhanced tumor uptake.
Reactive oxygen species (ROS) and oxidative stress are implicated in various physiological and pathological processes, and this feature provides a vital biochemical basis for designing novel ...therapeutic and diagnostic nanomedicines. Among them, oxidation-responsive micelles and vesicles (polymersomes) of amphiphilic block copolymers have been extensively explored; however, in previous works, oxidation by ROS including H2O2 exclusively leads to microstructural destruction of polymeric assemblies. For oxidation-responsive polymersomes, fast release of encapsulated hydrophilic drugs and bioactive macromolecules will occur upon microstructural disintegration. Under certain application circumstances, this does not meet design requirements for sustained-release drug nanocarriers and long-acting in vivo nanoreactors. Also note that conventional polymersomes possess thick hydrophobic bilayers and compromised membrane permeability, rendering them as ineffective nanocarriers and nanoreactors. We herein report the fabrication of oxidation-responsive multifunctional polymersomes exhibiting intracellular milieu-triggered vesicle bilayer cross-linking, permeability switching, and enhanced imaging/drug release features. Mitochondria-targeted H2O2 reactive polymersomes were obtained through the self-assembly of amphiphilic block copolymers containing arylboronate ester-capped self-immolative side linkages in the hydrophobic block, followed by surface functionalization with targeting peptides. Upon cellular uptake, intracellular H2O2 triggers cascade decaging reactions and generates primary amine moieties; prominent amidation reaction then occurs within hydrophobic bilayer membranes, resulting in concurrent cross-linking and hydrophobic-to-hydrophilic transition of polymersome bilayers inside live cells. This process was further utilized to achieve integrated functions such as sustained drug release, (combination) chemotherapy monitored by fluorescence and magnetic resonance (MR) imaging turn-on, and to construct intracellular fluorogenic nanoreactors for cytosolic thiol-containing bioactive molecules.
Stimuli-triggered disassembly of block copolymer vesicles or polymersomes has been conventionally achieved via solubility switching of the bilayer-forming block, requiring cooperative changes of most ...of the repeating units. Herein we report an alternative approach by incorporating hydrophobic blocks exhibiting stimuli-triggered head-to-tail cascade depolymerization features. Amphiphilic block copolymers bearing this motif self-assemble into self-immolative polymersomes (SIPsomes). By modular design of terminal capping moieties, visible light, UV light, and reductive milieu can be utilized to actuate SIPsomes disintegration into water-soluble small molecules and hydrophilic blocks. The design of SIPsomes allows for triggered drug co-release and controllable access toward protons, oxygen, and enzymatic substrates. We also demonstrate programmed (OR-, AND-, and XOR-type logic) enzymatic reactions by integrating SIPsome encapsulation and trigger/capping moiety-selective cascade depolymerization events.
We report on the fabrication of photochromic polymersomes exhibiting photoswitchable and reversible bilayer permeability from newly designed poly(ethylene oxide)-b-PSPA (PEO-b-PSPA) diblock ...copolymers, where SPA is spiropyran (SP)-based monomer containing a unique carbamate linkage. Upon self-assembling into polymersomes, SP moieties within vesicle bilayers undergo reversible phototriggered isomerization between hydrophobic spiropyran (SP, λ2 > 450 nm irradiation) and zwitterionic merocyanine (MC, λ1 < 420 nm irradiation) states. For both SP and MC polymersomes, their microstructures are stabilized by multiple cooperative noncovalent interactions including hydrophobic, hydrogen bonding, π–π stacking, and paired electrostatic (zwitterionic) interactions, with the latter two types being exclusive for MC polymersomes. Control experiments using analogous block copolymers of hydrophobic SP monomer with a carbonate linkage (SPO) and conventional spiropyran methacrylate monomer (SPMA) containing a single ester functionality were then conducted, revealing that carbamate-incurred hydrogen bonding interactions in PEO-b-PSPA are crucial for polymersome stabilization in the zwitterionic MC state. Moreover, reversible phototriggered SP-to-MC polymersome transition is accompanied by membrane polarity and permeability switching from being nonimpermeable to selectively permeable toward noncharged, charged, and zwitterionic small molecule species below critical molar masses. Intriguingly, UV-actuated MC polymersomes possess two types of release modules: (1) sustained release upon short UV irradiation duration by taking advantage of the unexpectedly slow spontaneous MC-to-SP transition kinetics (t 1/2 > 20 h) under dark conditions; (2) on-demand and switchable release under alternated UV–vis light irradiation. We further demonstrate photoswitchable spatiotemporal release of 4′,6-diamidino-2-phenylindole (DAPI, cell nuclei-staining dye) within living HeLa cells.
The fabrication of block copolymer (BCP) vesicles (polymersomes) exhibiting synchronized covalent crosslinking and bilayer permeabilization remains a considerable challenge as crosslinking typically ...leads to compromised membrane permeability. Herein it is demonstrated how to solve this dilemma by employing a stimuli‐triggered crosslinking strategy with amphiphilic BCPs containing photolabile carbamate‐caged primary amines. Upon self‐assembling into polymersomes, light‐triggered self‐immolative decaging reactions release primary amine moieties and extensive amidation reactions then occur due to suppressed amine pKa within hydrophobic milieu. This leads to serendipitous vesicle crosslinking and the process is associated with bilayer hydrophobicity‐to‐hydrophilicity transition and membrane permeabilization.
Two processes in one: A stimuli‐triggered crosslinking strategy was developed to concurrently crosslink and permeabilize block copolymer assemblies. Upon self‐assembling into polymersomes (see picture), light‐triggered self‐immolative decaging reactions release primary amine moieties and lead to extensive amidation reactions.
Combination chemotherapy with both hydrophobic and hydrophilic therapeutic drugs is clinically vital toward the treatment of persistent cancers. Though conventional liposomes and polymeric vesicles ...possessing hydrophobic bilayers and aqueous interiors can serve as codelivery nanocarriers, it remains a considerable challenge to achieve synchronized release of both types of drugs due to distinct encapsulation mechanisms; premature release of water‐soluble cargos from unstable liposomes and ruptured vesicles is also a major concern. Herein, the fabrication of physiologically stable polyprodrug‐gated crosslinked vesicles (GCVs) via the self‐assembly of camptothecin (CPT) polyprodrug amphiphiles and in situ bilayer crosslinking through traceless sol–gel reaction is reported. Polyprodrug‐GCVs possess high CPT loading (>30 wt%) and minimized leakage of encapsulated hydrophilic doxorubicin (DOX) hydrochloride due to the suppressed permeability of crosslinked membrane, exhibiting extended blood circulation (t
1/2 > 13 h) with caged cytotoxicity in physiological circulation. Upon cellular uptake by cancer cells, cytosolic reductive milieu‐triggered CPT unplugging from vesicle bilayers is demonstrated to generate hydrophilic mesh channels and make the membrane highly permeable. Concurrently, it will promote DOX corelease from hydrophilic lumen (≈36‐fold increase). The reduction‐activated combination chemotherapeutic potency based on polyprodrug‐GCVs is confirmed by both in vitro and in vivo explorations.
Concurrent drug unplugging and permeabilization of polyprodrug‐gated crosslinked vesicles (GCVs) are activated by cytosolic glutathione (GSH) for cancer combination chemotherapy. The GCVs exhibit high camptothecin (CPT) loading content, minimized leakage of encapsulated hydrophilic doxorubicin (DOX), caged cytotoxicity, and extended blood circulation. In cancer cells, cytosolic GSH triggers CPT unplugging and concurrent formation of hydrophilic channels to promote DOX corelease.
The unique permselectivity of cellular membranes is of crucial importance to maintain intracellular homeostasis while adapting to microenvironmental changes. Although liposomes and polymersomes have ...been widely engineered to mimic microstructures and functions of cells, it still remains a considerable challenge to synergize the stability and permeability of artificial cells and to imitate local milieu fluctuations. Herein, we report concurrent crosslinking and permeabilizing of pH-responsive polymersomes containing Schiff base moieties within bilayer membranes via enzyme-catalyzed acid production. Notably, this synergistic crosslinking and permeabilizing strategy allows tuning of the mesh sizes of the crosslinked bilayers with subnanometer precision, showing discriminative permeability toward maltooligosaccharides with molecular sizes of ~1.4-2.6 nm. The permselectivity of bilayer membranes enables intravesicular pH oscillation, fueled by a single input of glucose. This intravesicular pH oscillation can further drive the dissipative self-assembly of pH-sensitive dipeptides. Moreover, the permeabilization of polymersomes can be regulated by intracellular pH gradient as well, enabling the controlled release of encapsulated payloads.
Homo‐ and hetero‐bifunctional linkers play vital roles in constructing a variety of functional systems, ranging from protein bioconjugates with drugs and functional agents, to surface modification of ...nanoparticles and living cells, and to the cyclization/dimerization of synthetic polymers and biomolecules. Conventional approaches for assaying conjugation extents typically rely on ex situ techniques, such as mass spectrometry, gel electrophoresis, and size‐exclusion chromatography. If the conjugation process involving bifunctional linkers was rendered fluorogenic, then in situ monitoring, quantification, and optical tracking/visualization of relevant processes would be achieved. In this review, conventional non‐fluorogenic linkers are first discussed. Then the focus is on the evolution and emerging applications of fluorogenic bifunctional linkers, which are categorized into hetero‐bifunctional single‐caging fluorogenic linkers, homo‐bifunctional double‐caging fluorogenic linkers, and hetero‐bifunctional double‐caging fluorogenic linkers. In addition, stimuli‐cleavable bifunctional linkers designed for both conjugation and subsequent site‐specific triggered release are also summarized.
Functional conjugation: Recent developments in non‐fluorogenic and fluorogenic bifunctional linkers are reviewed; the latter include hetero‐bifunctional single‐caging fluorogenic linkers, homo‐bifunctional double‐caging fluorogenic linkers, and hetero‐bifunctional double‐caging fluorogenic linkers. Cleavable bifunctional linkers designed for conjugation and subsequent site‐specific triggered release are also discussed.
Abstract To emulate the ordered arrangement of monomer units found in natural macromolecules, single-unit monomer insertion (SUMI) have emerged as a potent technique for synthesizing ...sequence-controlled vinyl polymers. Specifically, numerous applications necessitate vinyl polymers encompassing both radically and cationically polymerizable monomers, posing a formidable challenge due to the distinct thiocarbonylthio end-groups required for efficient control over radical and cationic SUMIs. Herein, we present a breakthrough in the form of interconvertible radical and cationic SUMIs achieved through the manipulation of thiocarbonylthio end-groups. The transition from a trithiocarbonate (for radical SUMI) to a dithiocarbamate (for cationic SUMI) is successfully accomplished via a radical-promoted reaction with bis(thiocarbonyl) disulfide. Conversely, the reverse transformation utilizes the reaction between dithiocarbamate and bistrithiocarbonate disulfide under a cationic mechanism. Employing this strategy, we demonstrate a series of synthetic examples featuring discrete oligomers containing acrylate, maleimide, vinyl ether, and styrene, compositions unattainable through the SUMI of a single mechanism alone.
Spatiotemporal switching of respective phototherapy modes at the cellular level with minimum side effects and high therapeutic efficacy is a major challenge for cancer phototherapy. Herein we ...demonstrate how to address this issue by employing photosensitizer-conjugated pH-responsive block copolymers in combination with intracellular endocytic pH gradients. At neutral pH corresponding to extracellular and cytosol milieu, the copolymers self-assemble into micelles with prominently quenched fluorescence emission and low 1O2 generation capability, favoring a highly efficient photothermal module. Under mildly acidic pH associated with endolysosomes, protonation-triggered micelle-to-unimer transition results in recovered emission and enhanced photodynamic 1O2 efficiency, which synergistically actuates release of encapsulated drugs, endosomal escape, and photochemical internalization processes.
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