Biotransporting Biocatalytic Reactors toward Therapeutic Nanofactories

Glycooligomer-Functionalized Catalytic Nanocompartments Co-Loaded with Enzymes Support Parallel Reactions and Promote Cell Internalization

A major shortcoming associated with the application of enzymes in drug synergism originates from the lack of site-specific, multifunctional nanomedicine. This study introduces catalytic nanocompartments (CNCs) made of a mixture of PDMS-b-PMOXA diblock copolymers, decorated with glycooligomer tethers comprising eight mannose-containing repeating units and coencapsulating two enzymes, providing multifunctionality by their in situ parallel reactions. Beta-glucuronidase (GUS) serves for local reactivation of the drug hymecromone, while glucose oxidase (GOx) induces cell starvation through glucose depletion and generation of the cytotoxic H2O2. The insertion of the pore-forming peptide, melittin, facilitates diffusion of substrates and products through the membranes. Increased cell-specific internalization of the CNCs results in a substantial decrease in HepG2 cell viability after 24 h, attributed to simultaneous production of hymecromone and H2O2. Such parallel enzymatic reactions taking place in nanocompartments pave the way to achieve efficient combinatorial cancer therapy by enabling localized drug production along with reactive oxygen species (ROS) elevation.

Synthetic Cells Revisited: Artificial Cells Construction Using Polymeric Building Blocks

The exponential growth of research on artificial cells and organelles underscores their potential as tools to advance the understanding of fundamental biological processes. The bottom-up construction from a variety of building blocks at the micro- and nanoscale, in combination with biomolecules is key to developing artificial cells. In this review, artificial cells are focused upon based on compartments where polymers are the main constituent of the assembly. Polymers are of particular interest due to their incredible chemical variety and the advantage of tuning the properties and functionality of their assemblies. First, the architectures of micro- and nanoscale polymer assemblies are introduced and then their usage as building blocks is elaborated upon. Different membrane-bound and membrane-less compartments and supramolecular structures and how they combine into advanced synthetic cells are presented. Then, the functional aspects are explored, addressing how artificial organelles in giant compartments mimic cellular processes. Finally, how artificial cells communicate with their surrounding and each other such as to adapt to an ever-changing environment and achieve collective behavior as a steppingstone toward artificial tissues, is taken a look at. Engineering artificial cells with highly controllable and programmable features open new avenues for the development of sophisticated multifunctional systems.

Nanoreactor-based catalytic systems for therapeutic applications: Principles, strategies, and challenges

Inspired by natural catalytic compartments, various synthetic compartments that seclude catalytic reactions have been developed to understand complex multistep biosynthetic pathways, bestow therapeutic effects, or extend biosynthetic pathways in living cells. These emerging nanoreactors possessed many advantages over conventional biomedicine, such as good catalytic activity, specificity, and sustainability. In the past decade, a great number of efficient catalytic systems based on diverse nanoreactors (polymer vesicles, liposome, polymer micelles, inorganic-organic hybrid materials, MOFs, etc.) have been designed and employed to initiate in situ catalyzed chemical reactions for therapy. This review aims to present the recent progress in the development of catalytic systems based on nanoreactors for therapeutic applications, with a special emphasis on the principles and design strategies. Besides, the key components of nanoreactor-based catalytic systems, including nanocarriers, triggers or energy inputs, and products, are respectively introduced and discussed in detail. Challenges and prospects in the fabrication of therapeutic catalytic nanoreactors are also discussed as a conclusion to this review. We believe that catalytic nanoreactors will play an increasingly important role in modern biomedicine, with improved therapeutic performance and minimal side effects.

Recent advances in permeable polymersomes: fabrication, responsiveness, and applications

Polymersomes are vesicular nanostructures enclosed by a bilayer-membrane self-assembled from amphiphilic block copolymers, which exhibit higher stability compared with their biological analogues (e.g. liposomes). Due to their versatility, polymersomes have found various applications in different research fields such as drug delivery, nanomedicine, biological nanoreactors, and artificial cells. However, polymersomes prepared with high molecular weight components typically display low permeability to molecules and ions. It hence remains a major challenge to balance the opposing features of robustness and permeability of polymersomes. In this review, we focus on the design and strategies for fabricating permeable polymersomes, including polymersomes with intrinsic permeability, the formation of nanopores in the membrane bilayers by protein insertion, and the construction of stimuli-responsive polymersomes. Then, we highlight the applications of permeable polymersomes in the fields of biomimetic nanoreactors, artificial cells and organelles, and nanomedicine, to underline the challenges in the development of polymersomes as soft matter with biomedical utilities.

Polymeric core-crosslinked particles prepared via a nanoemulsion-mediated process: from particle design and structural characterization to in vivo behavior in chemotherapy

Various polymeric nanoparticles have been used as drug carriers in drug delivery systems (DDSs). Most of them were constructed from dynamic self-assembly systems formed via hydrophobic interactions and from structures that are unstable in an in vivo environment owing to their relatively weak formation forces. As a solution to this issue, physically stabilized core-crosslinked particles (CP) with chemically crosslinked cores have received attention as alternatives to the dynamic nanoparticles. This focused review summarizes recent advances in the construction, structural characterization, and in vivo behavior of polymeric CPs. First, we introduce a nanoemulsion-mediated method to create polyethylene glycol (PEG)-bearing CPs and their structural characterization. The relationship between the PEG chain conformations in the particle shell and the in vivo fate of the CPs is also discussed. After that, the development and advantages of zwitterionic amino acid-based polymer (ZAP)-bearing CPs are presented to address the poor penetration and the internalization of PEG-based CPs into tumor tissues and cells, respectively. Finally, we conclude and discuss prospects for application of polymeric CPs in the DDS field.

Confining the Sol-Gel Reaction at the Water/Oil Interface: Creating Compartmentalized Enzymatic Nano-Organelles for Artificial Cells

Living organisms compartmentalize their catalytic reactions in membranes for increased efficiency and selectivity. To mimic the organelles of eukaryotic cells, we develop a mild approach for in situ encapsulating enzymes in aqueous-core silica nanocapsules. In order to confine the sol-gel reaction at the water/oil interface of miniemulsion, we introduce an aminosilane to the silica precursors, which serves as both catalyst and an amphiphilic anchor that electrostatically assembles with negatively charged hydrolyzed alkoxysilanes at the interface. The semi-permeable shell protects enzymes from proteolytic attack, and allows the transport of reactants and products. The enzyme-carrying nanocapsules, as synthetic nano-organelles, are able to perform cascade reactions when enveloped in a polymer vesicle, mimicking the hierarchically compartmentalized reactions in eukaryotic cells. This in situ encapsulation approach provides a versatile platform for the delivery of biomacromolecules.

Bridging the Gap between Nonliving Matter and Cellular Life

A cell, the fundamental unit of life, contains the requisite blueprint information necessary to survive and to build tissues, organs, and systems, eventually forming a fully functional living creature. A slight structural alteration can result in data misprinting, throwing the entire life process off balance. Advances in synthetic biology and cell engineering enable the predictable redesign of biological systems to perform novel functions. Individual functions and fundamental processes at the core of the biology of cells can be investigated by employing a synthetically constrained micro or nanoreactor. However, constructing a life-like structure from nonliving building blocks remains a considerable challenge. Chemical compartments, cascade signaling, energy generation, growth, replication, and adaptation within micro or nanoreactors must be comparable with their biological counterparts. Although these reactors currently lack the power and behavioral sophistication of their biological equivalents, their interface with biological systems enables the development of hybrid solutions for real-world applications, such as therapeutic agents, biosensors, innovative materials, and biochemical microreactors. This review discusses the latest advances in cell membrane-engineered micro or nanoreactors, as well as the limitations associated with high-throughput preparation methods and biological applications for the real-time modulation of complex pathological states.

Bacteriophage P22 Capsid as a Pluripotent Nanotechnology Tool

The Salmonella enterica bacteriophage P22 is one of the most promising models for the development of virus-like particle (VLP) nanocages. It possesses an icosahedral T = 7 capsid, assembled by the combination of two structural proteins: the coat protein (gp5) and the scaffold protein (gp8). The P22 capsid has the remarkable capability of undergoing structural transition into three morphologies with differing diameters and wall-pore sizes. These varied morphologies can be explored for the design of nanoplatforms, such as for the development of cargo internalization strategies. The capsid proteic nature allows for the extensive modification of its structure, enabling the addition of non-native structures to alter the VLP properties or confer them to diverse ends. Various molecules were added to the P22 VLP through genetic, chemical, and other means to both the capsid and the scaffold protein, permitting the encapsulation or the presentation of cargo. This allows the particle to be exploited for numerous purposes-for example, as a nanocarrier, nanoreactor, and vaccine model, among other applications. Therefore, the present review intends to give an overview of the literature on this amazing particle.

Peg-Grafted Liposomes for L-Asparaginase Encapsulation

L-asparaginase (ASNase) is an important biological drug used to treat Acute Lymphoblastic Leukemia (ALL). It catalyzes the hydrolysis of L-asparagine (Asn) in the bloodstream and, since ALL cells cannot synthesize Asn, protein synthesis is impaired leading to apoptosis. Despite its therapeutic importance, ASNase treatment is associated to side effects, mainly hypersensitivity and immunogenicity. Furthermore, degradation by plasma proteases and immunogenicity shortens the enzyme half-life. Encapsulation of ASNase in liposomes, nanostructures formed by the self-aggregation of phospholipids, is an attractive alternative to protect the enzyme from plasma proteases and enhance pharmacokinetics profile. In addition, PEGylation might prolong the in vivo circulation of liposomes owing to the spherical shielding conferred by the polyethylene (PEG) corona around the nanostructures. In this paper, ASNase was encapsulated in liposomal formulations composed by 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) or 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) containing or not different concentrations of 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N [methoxy (polyethylene glycol)-2000] (DSPE-PEG). Nanostructures of approximately 142-202 nm of diameter and polydispersity index (PDI) of 0.069 to 0.190 were obtained and the vesicular shape confirmed by Transmission Electron Microscopy (TEM and cryo-TEM). The encapsulation efficiency (%EE) varied from 10% to 16%. All formulations presented activity in contact with ASNase substrate, indicating the liposomes permeability to Asn and/or enzyme adsorption at the nanostructures' surface; the highest activity was observed for DMPC/DSPE-PEG 10%. Finally, we investigated the activity against the Molt 4 leukemic cell line and found a lower IC50 for the DMPC/DSPE-PEG 10% formulation in comparison to the free enzyme, indicating our system could provide in vivo activity while protecting the enzyme from immune system recognition and proteases degradation.

Bioorthogonal micellar nanoreactors for prodrug cancer therapy using an inverse-electron-demand Diels-Alder reaction

Block copolymer micelles functionalized with tetrazine groups can act as nanoreactors to activate a trans-cyclooctene-functionalized prodrug for releasing anticancer drugs via a bioorthogonal inverse-electron-demand Diels-Alder (IEDDA) reaction. In addition, the IEDDA reaction can be accelerated in the micellar nanoreactor system compared to the free tetrazine system. Moreover, In vivo prodrug activation in a mouse tumor model led to the inhibition of tumor growth without significant systemic toxicity. These results demonstrated their potential for applications as bioorthogonal micellar nanoreactors for cancer chemotherapy.

Supramolecular Shear-Thinning Glycopeptide Hydrogels for Injectable Enzyme Prodrug Therapy Applications

Transplantable catalytic reactors have attracted considerable attention as therapeutic biomedical materials. However, existing transplantable reactors such as biocatalytic films are limited by their invasiveness. Here, we report the fabrication of biocatalytic supramolecular hydrogels via self-assembly of amphiphilic glycopeptides. We show that the hydrogels have shear-thinning properties, demonstrating their potential to be administered using a syringe. Enzymes can be loaded into the hydrogels by simply adding enzyme solution, and the enzyme-loaded hydrogels can transform a prodrug into an anticancer drug that inhibits tumor cell growth. This study demonstrates the potential of these biocatalytic hydrogels as injectable therapeutic reactors for enzyme prodrug therapy.

Tumor-dilated polymersome nanofactories for enhanced enzyme prodrug chemo-immunotherapy

Combination chemo-immunotherapy of cancers has attracted great attention due to its significant synergistic antitumor effect. The response rates and therapeutic efficacy of immunotherapy can be enhanced significantly after proper combination with chemotherapy. However, chemo-immunotherapy is frequently limited by severe immune-related adverse events and systemic side toxicity. In this report, efficient nanofactory-directed enzyme prodrug chemo-immunotherapy is demonstrated based on enzyme-loaded tumor-dilatable polymersomes with optimized membrane cross-linking density. Upon intravenous injection of the nanofactories, they can passively accumulate at the tumor site. The tumor pH-responsive nanofactories can swell from ~100 nm to ~200 nm under the trigger of tumor acidity, leading to prolonged retention of up to one week inside tumor tissues. Simultaneously, the membrane permeability of the nanofactories has improved significantly, which allows hydrophilic small molecules to pass across the membranes while keeping the enzymes in the inner cavities. Subsequently, the non-toxic prodrug mixtures of chemo-immunotherapy are administrated three times within 6 days, which are in situ activated by the nanofactories selectively at tumor sites. Activated chemotherapeutic drugs kill cancer cells and generate tumor-associated antigens to promote the maturation of dendritic cells. Activated indoleamine 2, 3-dioxygenase 1 inhibitors reverse the immunosuppressive tumor microenvironment. Finally, primary tumors can be effectively suppressed while causing minimal systemic toxicity. The distant tumors that are established after treatment can also be inhibited completely via activation of antitumor immunity in mice. Thus, the tumor-dilatable polymersome nanofactories with long-term intratumoral retention offer a promising paradigm for enhanced enzyme prodrug chemo-immunotherapy.

Clustering of catalytic nanocompartments for enhancing an extracellular non-native cascade reaction

Compartmentalization is fundamental in nature, where the spatial segregation of biochemical reactions within and between cells ensures optimal conditions for the regulation of cascade reactions. While the distance between compartments or their interaction are essential parameters supporting the efficiency of bio-reactions, so far they have not been exploited to regulate cascade reactions between bioinspired catalytic nanocompartments. Here, we generate individual catalytic nanocompartments (CNCs) by encapsulating within polymersomes or attaching to their surface enzymes involved in a cascade reaction and then, tether the polymersomes together into clusters. By conjugating complementary DNA strands to the polymersomes' surface, DNA hybridization drove the clusterization process of enzyme-loaded polymersomes and controlled the distance between the respective catalytic nanocompartments. Owing to the close proximity of CNCs within clusters and the overall stability of the cluster architecture, the cascade reaction between spatially segregated enzymes was significantly more efficient than when the catalytic nanocompartments were not linked together by DNA duplexes. Additionally, residual DNA single strands that were not engaged in clustering, allowed for an interaction of the clusters with the cell surface as evidenced by A549 cells, where clusters decorating the surface endowed the cells with a non-native enzymatic cascade. The self-organization into clusters of catalytic nanocompartments confining different enzymes of a cascade reaction allows for a distance control of the reaction spaces which opens new avenues for highly efficient applications in domains such as catalysis or nanomedicine.

Ordered Conformation-Regulated Vesicular Membrane Permeability

In nature, the folding and conformation of proteins can control the cell or organelle membrane permeability and regulate the life activities. Here we report the first example of synthetic polypeptide vesicles that regulate their permeability via ordered transition of secondary conformations, in a manner similar to biological systems.  The polymersomes undergo a β-sheet to α-helix transition in response to reactive oxygen species (ROS), leading to wall thinning without loss of vesicular integrity. The change  of membrane structure increases the vesicular permeability and enables specific transport of payloads with different molecular weights.The change of membrane structure increases the vesicular permeability.  As a proof-of-concept, the polymersomes encapsulating enzymes could serve as nanoreactors and carries for glucose-stimulated insulin secretion in vivo inspired by human glucokinase, resulting in safe and effective treatment of type 1 diabetes mellitus in mouse models. This study will help understand the biology of biomembranes and facilitate the engineering of nanoplatforms for biomimicry, biosensing, and controlled delivery applications.

Thermoresponsive Carbohydrate-b-Polypeptoid Polymer Vesicles with Selective Solute Permeability and Permeable Factors for Solutes

Solute-permeable polymer vesicles are structural compartments for nanoreactors/nanofactories in the context of drug delivery and artificial cells. We previously proposed design guidelines for polymers that form solute-permeable vesicles, yet we did not provide enough experimental verification. In addition, the fact that there is no clear factor for identifying permeable solutes necessitates extensive trial and error. Herein, we report solute-permeable polymer vesicles based on an amphiphilic copolymer, thermoresponsive oligosaccharide-block-poly(N-n-propylglycine). The introduction of a thermoresponsive polymer as a hydrophobic segment into amphiphilic polymers is a viable approach to construct solute-permeable polymer vesicles. We also demonstrate that the polymer vesicles are preferentially permeable to cationic and neutral fluorophores and are hardly permeable to anionic fluorophores due to the electrostatic repulsion between the bilayer and anionic fluorophores. In addition, the permeability of neutral fluorophores increases with the increasing log P value of the fluorophores. Thus, the electrical charge and log P value are important factors for membrane permeability. These findings will help researchers develop advanced nanoreactors based on permeable vesicles for a broad range of fundamental and biomedical applications.

Polymeric Nanoreactors as Emerging Nanoplatforms for Cancer Precise Nanomedicine

How to precisely detect and effectively cure cancer which is defined as precise nanomedicine has drawn great attention worldwide. Polymeric nanoreactors which can in situ catalyze inert species into activated ones, can greatly increase imaging quality and enhance therapeutic effects along with decreased background interference and reduced serious side effects. After a brief introduction, the design and preparation of polymeric nanoreactors are discussed from the following aspects, that is, solvent-switch, pH-tuning, film rehydration, hard template, electrostatic interaction, and polymerization-induced self-assembly (PISA). Subsequently, the biomedical applications of these nanoreactors in the fields of cancer imaging, cancer therapy, and cancer theranostics are highlighted. The last but not least, conclusions and future perspectives about polymeric nanoreactors are given. It is believed that polymeric nanoreactors can bring a great opportunity for future fabrication and clinical translation of precise nanomedicine.

Fake It 'Till You Make It-The Pursuit of Suitable Membrane Mimetics for Membrane Protein Biophysics

Membrane proteins evolved to reside in the hydrophobic lipid bilayers of cellular membranes. Therefore, membrane proteins bridge the different aqueous compartments separated by the membrane, and furthermore, dynamically interact with their surrounding lipid environment. The latter not only stabilizes membrane proteins, but directly impacts their folding, structure and function. In order to be characterized with biophysical and structural biological methods, membrane proteins are typically extracted and subsequently purified from their native lipid environment. This approach requires that lipid membranes are replaced by suitable surrogates, which ideally closely mimic the native bilayer, in order to maintain the membrane proteins structural and functional integrity. In this review, we survey the currently available membrane mimetic environments ranging from detergent micelles to bicelles, nanodiscs, lipidic-cubic phase (LCP), liposomes, and polymersomes. We discuss their respective advantages and disadvantages as well as their suitability for downstream biophysical and structural characterization. Finally, we take a look at ongoing methodological developments, which aim for direct in-situ characterization of membrane proteins within native membranes instead of relying on membrane mimetics.

Biocatalytic Hybrid Films Self-Assembled from Carbohydrate Block Copolymers and Polysaccharides for Enzyme Prodrug Therapy

Biocatalytic films are attracting growing attention for their significant potential as scaffolds for therapeutic reactor devices. However, conventional film fabrication methods result either in enzyme denaturation or require cumbersome procedures. Here, we report the preparation of biocatalytic films via self-assembly of a carbohydrate block copolymer and a polysaccharide. Enzyme-loaded films can be prepared by simply drying the polymer solution, and the loaded enzymes retain their biocatalytic activities in the film for prolonged periods of time. We also demonstrate that the enzyme-loaded films can successfully transform a prodrug into an antitumor drug that inhibits tumor cell growth. Our work highlights the potential of these biocatalytic self-assembled films as therapeutic reactor devices for enzyme prodrug therapy. Given the simplicity of the preparation method, this approach could improve the versatility of biocatalytic films and consequently expand their applicability from exclusive use in therapeutic reactor devices to sensing and diagnosis.

Camouflaged, activatable and therapeutic tandem bionanoreactors for breast cancer theranosis

The one-pot cascade reaction of naturally occurring enzymes is exciting for highly selective complex reaction and biodegradable approaches. Tamoxifen is the main drug against breast cancer for decades and induces an anticancerous effect upon metabolic activation by cytochrome P450 (CYP450). Herein, bi-enzymatic nanoreactors (NRs) are developed as a multimodality platform for smart action against breast tumors. CYP_BM3 of Bacillus magaterium (CYP) is co-confined with glucose oxidase (GOx) where GOx produces H₂O₂ in the presence of glucose that elicits the CYP-mediated transformation of tamoxifen. The scintillating and mesoporous LaF₃:Tb as nanocarrier showed advantages like a wide range of pore size and positive surface charge for efficient loading of enzyme couple, while the smallest pores were available for substrate/product diffusion. The obtained NRs were camouflaged with human serum albumin (HSA) to overcome premature enzyme leaching and provide active stealth properties. The nanocomposite was characterized for physicochemical properties and glucose-mediated sequential catalysis. The in vitro studies demonstrated the cell internalization of NRs in both ER+ and triple-negative breast cancer cell lines and showed significant cytotoxicity. The developed NRs not only improve the outcomes of endocrine therapy in ER+ cells but also synergistically act with oxidation therapy for enhanced therapeutic effect. Importantly, inhibition of triple-negative cells was also achieved. Thus, the development of the new multimodal nanomedicine of the present work should afford new tools towards the theranosis of breast cancer with minimized adverse effects.

Cascade Reactions Catalyzed by Planar Metal-Organic Framework Hybrid Architecture for Combined Cancer Therapy

Chemical transformation in cellular environment is critical for regulating biological processes and metabolic pathways. Harnessing biocatalytic cascades to produce chemicals of interest has become a research focus to benefit industrial and pharmaceutic areas. Nanoreactors, which can act as artificial cell-like devices to organize cascade reactions, have been recently proposed for potential therapeutic applications for life-threatening illnesses. Among various types of nanomaterials, there is a growing interest in 2D metal-organic frameworks (MOFs). By virtue of the ultralarge specific surface area, high porosity, and structural diversity, 2D MOF nanosheets hold great promise for a broad spectrum of biomedical use. Herein, a unique planar MOF-based hybrid architecture (GMOF-LA) is introduced by incorporating ultrasmall gold nanoparticles (Au NPs) as nanozyme and l-Arginine (l-Arg) as nitric oxide (NO) donor. The prepared Au NPs enable oxidation of glucose into hydrogen peroxide, which drives biocatalytic cascades to covert l-Arg into NO. Interestingly, the well-designed nanosheets not only possess excellent catalytical activity for NO generation, resulting in gas therapeutic effect, but also serve as a desired photosensitizer for photodynamic therapy. This study establishes a good example of exploring bioinspired nanoreactors for cooperative anticancer effect, which may pave the path for future "bench-to-bedside" design of nanomedicine.

Bioactive Catalytic Nanocompartments Integrated into Cell Physiology and Their Amplification of a Native Signaling Cascade

Bioactive nanomaterials have the potential to overcome the limitations of classical pharmacological approaches by taking advantage of native pathways to influence cell behavior, interacting with them and eliciting responses. Herein, we propose a cascade system mediated by two catalytic nanocompartments (CNC) with biological activity. Activated by nitric oxide (NO) produced by inducible nitric oxidase synthase (iNOS), soluble guanylyl cyclase (sGC) produces cyclic guanosine monophosphate (cGMP), a second messenger that modulates a broad range of physiological functions. As alterations in cGMP signaling are implicated in a multitude of pathologies, its signaling cascade represents a viable target for therapeutic intervention. Following along this line, we encapsulated iNOS and sGC in two separate polymeric compartments that function in unison to produce NO and cGMP. Their action was tested in vitro by monitoring the derived changes in cytoplasmic calcium concentrations of HeLa and differentiated C2C12 myocytes, where the produced second messenger influenced the cellular homeostasis.

Polymer Capsules with Hydrophobic Liquid Cores as Functional Nanocarriers

Recent developments in the fabrication of core-shell polymer nanocapsules, as well as their current and future applications, are reported here. Special attention is paid to the newly introduced surfactant-free fabrication method of aqueous dispersions of nanocapsules with hydrophobic liquid cores stabilized by amphiphilic copolymers. Various approaches to the efficient stabilization of such vehicles, tailoring their cores and shells for the fabrication of multifunctional, navigable nanocarriers and/or nanoreactors useful in various fields, are discussed. The emphasis is placed on biomedical applications of polymer nanocapsules, including the delivery of poorly soluble active compounds and contrast agents, as well as their use as theranostic platforms. Other methods of fabrication of polymer-based nanocapsules are briefly presented and compared in the context of their biomedical applications.

Thermoresponsive Polysaccharide Graft Polymer Vesicles with Tunable Size and Structural Memory

Controlling polymer vesicle size is difficult and a major obstacle for their potential use in biomedical applications, such as drug-delivery carriers and nanoreactors. Herein, we report size-tunable polymer vesicles based on self-assembly of a thermoresponsive amphiphilic graft copolymer. Unilamellar polymer vesicles form upon heating chilled polymer solutions, and vesicle size can be tuned in the range of 40-70 nm by adjusting the initial polymer concentration. Notably, the polymer can reversibly switch between a monomer state and a vesicle state in accordance with a cooling/heating cycle, which changes neither the size nor the size distribution of the vesicles. This lack of change suggests that the polymer memorizes a particular vesicle conformation. Given our vesicles' size tunability and structural memory, our research considerably expands the fundamental and practical scope of thermoresponsive amphiphilic graft copolymers and renders amphiphilic graft copolymers useful tools for synthesizing functional self-assembled materials.

Polymersome-Based Modular Nanoreactors with Size-Selective Transmembrane Permeability

Polymersome nanoreactors encapsulating the enzymes or particulate catalysts attract interest because of their potential use as modular reactors to synthesize complex compounds via a cascade of chemical reactions in a single batch. To achieve these goals, a key requirement is the tunable permeability of the polymersome membrane, which allows the size-selective transportation of reagents and products while protecting the encapsulated catalysts during the chemical reaction. We report here a stimuli-responsive route for controlling the permeability of the polymersomes of the binary blend of poly(ethylene glycol)-b-polystyrene (PEG-b-PS) and poly(ethylene glycol)-b-poly(acrylbenzylborate) (PEG-b-PABB). The presence of H₂O₂ (1 mM) in the medium (0.1 M PBS, pH 7.4) triggers the oxidation of benzyl borate pendants of PABB to form poly(acrylic acid) (PAA). This transformation results in the perforation of the compartmentalizing membrane of polymersomes by the dissolution of PEG-b-PAA domains embedded in the inert PEG-b-PS matrix. By controlling the composition of the stimuli-responsive block copolymer, the polymersomes of the binary blend exhibit size-selective permeability without losing the structural integrity. Release of fluorescent guests with different sizes (fluorescein, PEG2k-Cm, PEG5k-Rho) can be controlled by tuning the composition (PEG-b-PS/PEG-b-PABB = 100/0-80/20) of blended polymersomes. Selective permeability of the membrane provides protection of the encapsulated enzymes from external proteases present in the medium, resulting in the one-pot synthesis of small molecules via cascades of chemical reactions. The nanoparticular catalysts are also encapsulated within the permeable polymersomes, serving as modular reactors for the conversion of organic compounds via a cascade of reactions.

Thermomagneto-Responsive Smart Biocatalysts for Malonyl-Coenzyme A Synthesis

Smart biocatalysts, in which enzymes are conjugated to stimuli-responsive polymers, have gained considerable attention because of their catalytic switchability and recyclability. Although many systems have been developed, they require separate laboratory techniques for their recovery, making them unsuitable for many practical applications. To address these issues, we designed a thermomagneto-responsive biocatalyst by immobilizing an enzyme on the terminal of thermo-responsive polymer brushes tethered on magnetic nanoparticle (NP) clusters. The concept is demonstrated by a system consisting of iron oxide NPs, poly(N-isopropyl-acrylamide), and a malonyl-Coenzyme A synthetase (MatB). By using free malonate and coenzyme A (CoA), the designed catalyst exhibits adequate activity for the production of malonyl-CoA. Thanks to the use of a magnetic NP cluster, whose magnetic moment is high, this system is fully recoverable under the magnetic field at above 32 °C because of the collapse of the thermo-responsive polymer shell in the clusters. In addition, the recycled catalyst maintains moderate activity even after three cycles, and it also shows excellent catalytic switchability, that is, negligible catalytic activity at 25 °C because of the blockage of the active sites of the enzyme by the extended hydrophilic polymer chains but great catalytic activity at a temperatures above the lower critical solution temperature at which the enzymes are exposed to the reaction medium because of the thermo-responsive contraction of polymer chains. Because the azide functionality in our system can be easily functionalized depending upon our need, such catalytically switchable, fully recoverable, and recyclable multiresponsive catalytic systems can be of high relevance for other cell-free biosynthetic approaches.

Self-assembled colloidal gold superparticles to enhance the sensitivity of lateral flow immunoassays with sandwich format

Background: Traditional lateral flow immunoassay (LFIA) based on 20-40 nm gold nanoparticles (AuNPs) as signal reporter always suffers from relatively low detection sensitivity due to its insufficient brightness, severely restricting its wide-ranging application in the detection of target analytes with trace concentration.

Methods: To address this problem, the self-assembled colloidal gold superparticles (GSPs) were synthesized as an improved absorption-dominated labeling probe for improving the sensitivity of sandwich LFIA. Five kinds of GSPs with the size ranging from 100 nm to 400 nm were synthesized by embedding hydrophobic AuNPs of size 12 nm as building blocks into the polymer nanobeads. The as-prepared GSPs were suggested as novel labeling probes of LFIA. The effects of the size of assembled GSPs on the sensitivity of sandwich LFIA was assessed, and the detection performance of GSPs-LFIA was further compared with traditional AuNPs-LFIA.

Results: The resultant GSPs showed extremely high light absorption but very low light scattering, which favor the absorption-dominated signal output in LFIA. Among them, the GSP₂₇₀-LFIA (size 270 nm) exhibits the highest sensitivity for human chorionic gonadotropin and hepatitis B surface antigen detection in real serum sample, which are approximate 39.79- and 13.8-fold higher than that of traditional AuNP₄₀-LFIA.

Conclusions: The proposed research demonstrated that the current GSPs can provide an ultrasensitive and quantitative detection for disease biomarkers in real serum samples as promising reporters of sandwich LFIA platform.

A unique polymersome covered by loop-cluster polyamine corona

The comb with teeth of amphiphilic block copolymer possessing hydrophilic polyethyleneimine (inside) and hydrophobic poly(2-phenyl-2-oxazoline) (outside) self-assembled into extremely stable loop-cluster covered polymersome with very thin vesicular wall (ca. 3 nm).

Mechanical Deformation Mediated Transmembrane Transport

Transmembrane transport is essential and plays critical roles for molecule exchange for cell survival. Methods capable of mimicking and regulating transmembrane transport have transformed the ability to create biosensors, separation membranes, and drug carriers. However, artificial channels have been largely restricted by their complicated chemical fabrication and inefficiency to dynamically manipulate the transport process. Here, a novel approach to regulate transmembrane transport is described by simply adjusting the mechanical deformation of liposomal bilayers which are covalently embedded in a crosslinked hydrogel network. This new approach is able to dynamically control transmembrane transport by stretching and loosening. The transmembrane diffusion of molecules can be switched on and off, and precisely tuned by varying strain. A potential of this method to programmably regulate cell growth is demonstrated by tuning external mechanical force. Given its unique characteristics, this method allows the development of innovative systems for controlled transmembrane transport of molecules.

Catalytically Selective Chemotherapy from Tumor-Metabolic Generated Lactic Acid

Lactic acid (LA) is a powerful molecule as the metabolic driver in tumor microenvironments (TMEs). Inspired by its high intratumoral level (5-20 µmol g^-1 ), a novel treatment paradigm via the cascade release of H₂ O₂ and ·OH from the LA generated by tumor metabolism is developed for catalytic and pH-dependent selective tumor chemotherapy. By utilizing the acidity and overexpression of LA within the TME, the constructed lactate oxidase (LOD)-immobilized Ce-benzenetricarboxylic acid (Ce-BTC) metal organic framework enables the intratumoral generation of ·OH via a cascade reaction: 1) the in situ catalytic release of H₂ O₂ from LA by LOD, and 2) the catalytic production of ·OH from H₂ O₂ by Ce-BTC with peroxidase-like activity. Highly toxic ·OH effectively induces tumor apoptosis/death. A new strategy for selective tumor chemotherapy is provided herein.

Therapeutic Polymersome Nanoreactors with Tumor-Specific Activable Cascade Reactions for Cooperative Cancer Therapy

Therapeutic nanoreactors are of increasing interest in precise cancer therapy, which have been explored to in situ produce therapeutic compounds from inert prodrugs or intrinsic molecules at the target sites. However, engineering a nanoreactor with tumor activable cascade reactions for efficient cooperative cancer therapy remains a great challenge. Herein, we demonstrate a polymersome nanoreactor with tumor acidity-responsive membrane permeability to activate cascade reactions for orchestrated cooperative cancer treatment. The nanoreactors are constructed from responsive polyprodrug polymersomes incorporating ultrasmall iron oxide nanoparticles and glucose oxidase in the membranes and inner aqueous cavities, respectively. The cascade reactions including glucose consumption to generate H₂O₂, accelerated iron ion release, Fenton reaction between H₂O₂ and iron ion to produce hydroxyl radicals (•OH), and •OH-triggered rapid release of parent drugs can be specifically activated by the tumor acidity-responsive membrane permeability. During this process, the orchestrated cooperative cancer therapy including starving therapy, chemodynamic therapy, and chemotherapy is realized for high-efficiency tumor suppression by the in situ consumed and produced compounds. The nanoreactor design with tumor-activable cascade reactions represents an insightful paradigm for precise cooperative cancer therapy.

Intrinsically permeable polymer vesicles based on carbohydrate-conjugated poly(2-oxazoline)s synthesized using a carbohydrate-based initiator system

A thermo-responsive poly(n-propyl oxazoline) block was employed as the hydrophobic segment in an amphiphilic glyco polymer. This approach affords intrinsically permeable polymer vesicles for water-soluble compounds.