Membrane protein channels equipped with a cleavable linker for inducing catalysis inside nanocompartments

Precisely timed initiation of reactions and stability of the catalysts are fundamental in catalysis. We introduce here an efficient closing-opening method for nanocompartments that contain sensitive catalysts and so achieve a controlled and extended catalytic activity. We developed a chemistry-oriented approach for modifying a pore-forming membrane protein which allows for a stimuli-responsive pore opening within the membrane of polymeric nanocompartments. We synthesized a diol-containing linker that selectively binds to the pores, blocking them completely. In the presence of an external stimulus (periodate), the linker is cleaved allowing the diffusion of substrate through the pores to the nanocompartment interior where it sets off the in situ enzymatic reaction. Besides the precise initiation of catalytic activity by opening of the pores, oxidation by periodate guarantees the cleavage of the linker under mild conditions. Accordingly, this kind of responsive nanocompartment lends itself to harboring a large variety of sensitive catalysts such as proteins and enzymes.

Dual-responsive polymersomes as anticancer drug carriers for the co-delivery of doxorubicin and paclitaxel

Multi stimuli-responsive polymersomes are in high demand as smart drug carriers, particularly for the treatment of complex cancers. However, most polymersomes have multi-responsiveness that does not affect each other and focus on single drug loading. Here, we have designed photo-crosslinked temperature and pH dual-responsive polymersomes by the self-assembly of a triblock polymer of methoxyl poly(ethylene glycol)-b-poly(N-isopropylacrylamide)-b-poly[2-(diethylamino)ethyl methacrylate-co-2-hydroxy-4-(methacryloyloxy)benzophenone] (mPEG-b-PNIPAM-b-P(DEAEMA-co-BMA)) synthesized via reversible addition-fragmentation chain transfer polymerization (RAFT). The dual-responsive polymersomes had a layered membrane, resulting in tunable permeability. Importantly, the polymersomes were proved to have a pH-controlled temperature-responsiveness. A hydrophilic-hydrophobic drug pair (doxorubicin hydrochloride, DOX, and paclitaxel, PTX) could be co-encapsulated in the fabricated polymersomes. The membrane permeability based on its layered structure was triggered by the change in temperature and pH to permit the separate control on the release of DOX and PTX. In a simulated tumor microenvironment, DOX and PTX encapsulated in the polymersomes could take effect for a relatively longer period and could work synergistically. Thus, the photo-crosslinked and dual-responsive polymersomes can be considered as promising drug carriers in the field of tumor combination chemotherapy.

The rise of bio-inspired polymer compartments responding to pathology-related signals

Self-organized nano- and microscale polymer compartments such as polymersomes, giant unilamellar vesicles (GUVs), polyion complex vesicles (PICsomes) and layer-by-layer (LbL) capsules have increasing potential in many sensing applications. Besides modifying the physicochemical properties of the corresponding polymer building blocks, the versatility of these compartments can be markedly expanded by biomolecules that endow the nanomaterials with specific molecular and cellular functions. In this review, we focus on polymer-based compartments that preserve their structure, and highlight the key role they play in the field of medical diagnostics: first, the self-assembling abilities that result in preferred architectures are presented for a broad range of polymers. In the following, we describe different strategies for sensing disease-related signals (pH-change, reductive conditions, and presence of ions or biomolecules) by polymer compartments that exhibit stimuli-responsiveness. In particular, we distinguish between the stimulus-sensitivity contributed by the polymer itself or by additional compounds embedded in the compartments in different sensing systems. We then address necessary properties of sensing polymeric compartments, such as the enhancement of their stability and biocompatibility, or the targeting ability, that open up new perspectives for diagnostic applications.

Giant "Breathing" Proteinosomes with Jellyfish-like Property

The design and construction of "breathing" self-assemblies has been a rather popular topic due to their potential in materials science and nanotechnology. Inspired by the "breathing" behavior of natural jellyfish, herein, we presented the construction of a giant "breathing" proteinosome through an interfacial self-assembly of proteins and surfactants at the oil/water interface of emulsions: The proteinosome displays "breathing" behavior and can swell and shrink for multiple cycles by protein folding and unfolding through the alternate addition and removal of denaturant; more importantly, when green fluorescent proteins were selected as alternative protein building blocks, the fluorescence of proteinosome can be reversibly switched on/off just like the behavior of jellyfish. Moreover, accompanied by reversible swelling and shrinking and on/off fluorescence, the expanded and shrunk membrane pore can be tuned for distinguishing quantum dots of different sizes. The folding-responsive breathing behavior of intelligent proteinosomes provides a platform for functional biomaterials.

Thermoresponse and self-assembly of an ABC star quarterpolymer with O2 and redox dual-responsive Y junctions

The stimuli-tunable LCST-type phase transition and self-assembly behaviors of a multi-responsive 3-miktoarm star bearing O₂/redox-sensitive and H-bond-switchable Y junctions were revealed.