Efficient Self-assembly Research Articles

Antibody-Directing Antibody Conjugates (ADACs) Enabled by Orthogonal Click Chemistry for Targeted Intracellular Delivery.

Using orthogonal click chemistries for efficient nanoscale self-assembly, a new antibody-directing antibody conjugate (ADAC) nanogel is generated. In this system, one of the antibodies is displayed on the nanogel surface to specifically recognize cell-surface epitopes while the other antibody is encapsulated inside the nanogel core. The system is programmed to release the latter antibody in its functional form in the cytosolic environment of a specific cell to engage intracellular targets. ADACs offer a potential solution to harness the advantages seen with antibody-drug conjugates (ADCs) to deliver therapeutic cargos to specific tissues, but with the added capability of carrying biologics as the cargo. In this manuscript, this potential is demonstrated through delivery of antibodies against intracellular targets in specific cells. This platform offers new avenues for precise therapeutic interventions and the potential to address previously "undruggable" cellular targets.

Highly Efficient Self-Assembly of Heterometallic [2]Catenanes and Cyclic Bis[2]catenanes via Orthogonal Metal-Coordination Interactions.

Although catenated cages have been widely constructed due to their unique and elegant topological structures, cyclic catenanes formed by the connection of multiple catenane units have been rarely reported. Herein, based on the orthogonal metal-coordination-driven self-assembly, we prepare a series of heterometallic [2]catenanes and cyclic bis[2]catenanes, whose structures are clearly evidenced by single-crystal X-ray analysis. Owing to the multiple positively charged nature, as well as the potential synergistic effect of the Cu(I) and Pt(II) metal ions, the cyclic bis[2]catenanes display broad-spectrum antibacterial activity. This work not only provides an efficient strategy for the construction of heterometallic [2]catenanes and cyclic bis[2]catenanes but also explores their applications as superior antibacterial agents, which will promote the construction of advanced supramolecular structures for biomedical applications.

Chain Architecture as an Orthogonal Parameter to Tune Morphologies of Polymer Assemblies: Efficient Synthesis and Self-Assembly of Linear-Branched Block Copolymers via RAFT Dispersion Polymerization

Chain Architecture as an Orthogonal Parameter to Tune Morphologies of Polymer Assemblies: Efficient Synthesis and Self-Assembly of Linear-Branched Block Copolymers via RAFT Dispersion Polymerization

Fabricating supramolecular lyotropic crystals at subzero temperatures: The pivotal role of antifreeze and nanostructures

The classical lyotropic liquid crystals (LLCs) prepared in pure water are not adapted to subzero temperatures. However, the fabrication of cryogenic LLCs is highly significant for gaining profound insights into self-assembly at extremely low temperatures. A proficient solution strategy, namely introducing alcohol antifreeze to water, faces a challenge in balancing frozen resistance and efficient self-assembly. Herein, we address this unmet challenge by selecting four alcohols with comparable structure to fabricate cryogenic LLCs system through the supramolecular self-assembly of a long-chain non-ionic surfactant. The freezing point, surfactant solubility, and self-assembly behavior at subzero temperatures were investigated. The alcohol antifreeze plays a significant role in depressing water freezing point and governing assembled microstructures. Both experimental and computational results revealed that alcohols bearing more hydroxyl groups are efficient to lower water freezing point while remain the capability to induce surfactant self-assembly. They can realize solvophobic balance and strong hydrogen-bond interactions. A simple approach based on Gordon parameter was established to evaluate the suitability as an anti-freezing medium for amphiphile self-assembly. Strikingly, a new LLCs system capable of withstanding the extremely low temperature of −80 °C was developed, which shows interestingly continuous phase transitions as temperature lowers to subzero. Overall, this study provides valuable insights into cryogenic supramolecular self-assembly, and offers a significant foundation and evaluation method for the selection of appropriate alcohol antifreeze for cryogenic self-assembly.

Integrating spin-dependent emission and dielectric switching in FeII catenated metal-organic frameworks

Mechanically interlocked molecules (MIMs) including famous catenanes show switchable physical properties and attract continuous research interest due to their potential application in molecular devices. The advantages of using spin crossover (SCO) materials here are enormous, allowing for control through diverse stimuli and highly specific functions, and enabling the transfer of the internal dynamics of MIMs from solution to solid state, leading to macroscopic applications. Herein, we report the efficient self-assembly of catenated metal-organic frameworks (termed catena-MOFs) induced by stacking interactions, through the combination of rationally selected flexible and conjugated naphthalene diimide-based bis-pyridyl ligand (BPND), [MI(CN)2]− (M = Ag or Au) and Fe2+ in a one-step strategy. The obtained bimetallic Hofmann-type SCO-MOFs [FeII(BPND){Ag(CN)2}2]·3CHCl3 (1Ag) and [FeII(BPND{Au(CN)2}2]·2CHCl3·2H2O (1Au) possess a unique three-dimensional (3D) catena-MOF constructed from the polycatenation of two-dimensional (2D) layers with hxl topology. Both complexes undergo thermal- and light-induced SCO. Significantly, abnormal increases in the maximum emission intensity and dielectric constant can be detected simultaneously with the switching of spin states. This research opens up SCO-actuated bistable MIMs that afford dual functionality of coupled fluorescence emission and dielectricity.

Interfacial Self-Assembly of Oriented Semiconductor Monolayer for Chemiresistive Sensing.

Semiconductor nanofilm fabrication with advanced technology is of great importance for next-generation electronics/optoelectronics. Fabrication of high-quality and perfectly oriented semiconductor thin films and integration into high-performance electronic devices with low cost and high efficiency are huge challenges. Here we exquisitely utilized the Marangoni effect to perfectly guide tin disulfide (SnS2) nanocoins into an ordered assembly in milliseconds, resulting in an uniaxial-oriented monolayer semiconductor film. Further exploration revealed that the formed "crumple zone" at the interface caused by the Marangoni force endows the nanofilm with a rapid healable capability, which can be easily transferred to arbitrary substrates. As a proof of concept, the nanocoin-monolayer was transferred onto a micro-interdigitated electrode substrate to form a high-performance chemiresistive sensor that can effectively monitor the trace amounts of toxic gases. In addition, the assembled monolayer nanofilms can be conformally printed on freeform surfaces: both flat and nonflat substrates. This efficient and low-cost Marangoni force-assisted surface self-assembly (MFA-SSA) strategy is promising for advanced microelectronics and real industrial applications.

Enhanced interfacial interactions and enriched active sites in self-assembly amino-functionalized bacterial cellulose/MXene composite for wastewater treatment

With rapid industrialization and economic growth, the serious environmental pollution caused by heavy metals and dyes is a pressing issue to be solved. The efficient construction of enriched active sites and porous structures is the key to obtain water purification material for pollution removal. In this study, an efficient electrostatic self-assembly strategy to achieve amino-functionalized bacterial cellulose/Ti3C2Tx MXene (ABC/MX) composite with a 3D cross-linked porous structure has been proposed. Experimental characterization and theoretical calculations reveal that the successful incorporation of amino groups not only enhances the interfacial interactions between BC nanofibers and Ti3C2Tx nanosheets, but also increases the active sites available for adsorption. The results highlight that the ABC/MX composite exhibits exceptional removal efficiency, with maximum adsorption capacities of 200.7 mg/g for Cr(VI) and 1103.7 mg/g for Congo red (CR). In particular, it reveals that the multifaceted adsorption processes of Cr(VI) and CR involve electrostatic interactions, reduction reactions, chelation, and hydrogen bonding effects. These findings highlight a versatile strategy for synthesizing BC-based adsorbents with remarkable adsorption properties and are suitable for practical wastewater treatment applications.

Naphthalene Diimide-Based Metallacage as an Artificial Ion Channel for Chloride Ion Transport.

Developing synthetic molecular devices for controlling ion transmembrane transport is a promising research field in supramolecular chemistry. These artificial ion channels provide models to study ion channel diseases and have huge potential for therapeutic applications. Compared with self-assembled ion channels constructed by intermolecular weak interactions between smaller molecules or cyclic compounds, metallacage-based ion channels have well-defined structures and can exist as single components in the phospholipid bilayer. A naphthalene diimide-based artificial chloride ion channel is constructed through efficient subcomponent self-assembly and its selective ion transport activity in large unilamellar vesicles and the planar lipid bilayer membrane by fluorescence and ion-current measurements is investigated. Molecular dynamics simulations and density functional theory calculations show that the metallacage spans the entire phospholipid bilayer as an unimolecular ion transport channel. This channel transports chloride ions across the cell membrane, which disturbs the ion balance of cancer cells and inhibits the growth of cancer cells at low concentrations.

Organelle-Mediated Dissipative Self-Assembly of Peptides in Living Cells.

Implementing dissipative assembly in living systems is meaningful for creation of living materials or even artificial life. However, intracellular dissipative assembly remains scarce and is significantly impeded by the challenges lying in precisely operating chemical reaction cycles under complex physiological conditions. Here, we develop organelle-mediated dissipative self-assembly of peptides in living cells fueled by GSH, via the design of a mitochondrion-targeting and redox-responsive hexapeptide. While the hexapeptide undergoes efficient redox-responsive self-assembly, the addition of GSH into the peptide solution in the presence of mitochondrion-biomimetic liposomes containing hydrogen peroxide allows for transient assembly of peptides. Internalization of the peptide by LPS-stimulated macrophages leads to the self-assembly of the peptide driven by GSH reduction and the association of the peptide assemblies with mitochondria. The association facilitates reversible oxidation of the reduced peptide by mitochondrion-residing ROS and thereby dissociates the peptide from mitochondria to re-enter the cytoplasm for GSH reduction. The metastable peptide-mitochondrion complexes prevent the thermodynamically equilibrated self-assembly, thus establishing dissipative assembly of peptides in stimulated macrophages. The entire dissipative self-assembling process allows for elimination of elevated ROS and decrease of pro-inflammatory cytokine expression. Creating dissipative self-assembling systems assisted by internal structures provides new avenues for the development of living materials or medical agents in the future.

Minimalist Design of Wireframe DNA Nanotubes: Tunable Geometry, Size, Chirality, and Dynamics.

DNA nanotubes (NTs) have attracted extensive interest as artificial cytoskeletons for biomedical, synthetic biology, and materials applications. Here, we report the modular design and assembly of a minimalist yet robust DNA wireframe nanotube with tunable cross-sectional geometry, cavity size, chirality, and length, while using only four DNA strands. We introduce an h-motif structure incorporating double-crossover (DX) tile-like DNA edges to achieve structural rigidity and provide efficient self-assembly of h-motif-based DNA nanotube (H-NT) units, thus producing programmable, micrometer-long nanotubes. We demonstrate control of the H-NT nanotube length via short DNA modulators. Finally, we use an enzyme, RNase H, to take these structures out of equilibrium and trigger nanotube assembly at a physiologically relevant temperature, underlining future cellular applications. The minimalist H-NTs can assemble at near-physiological salt conditions and will serve as an easily synthesized, DNA-economical modular template for biosensors, plasmonics, or other functional materials and as cost-efficient drug-delivery vehicles for biomedical applications.

Unique electromagnetic wave absorber for three-dimensional framework engineering with copious heterostructures

In order to obtain high-performance electromagnetic wave absorbers, the adjustment of structure and components is essential. Based on the above requirements, this system forms a three-dimensional frame structure consisting of MXene and transition metal oxides (TMOs) through efficient electrostatic self-assembly. This three-dimensional network structure has rich heterojunction structures, which can cause a large amount of interface polarization and conduction losses in incident electromagnetic waves. Hollow structures cause multiple reflections and scattering of electromagnetic waves, which is also an important reason for further increasing electromagnetic wave losses. When the doping ratio is 1:1, the system has the best impedance matching, the maximum effective absorption bandwidth (EABmax) can reach 5.12 GHz at 1.7 mm, and the minimum reflection loss (RLmin) is -50.30 dB at 1.8 mm. This provides a reference for the subsequent formation of 2D-MXene materials into 3D materials.

Fluorescent detection of tartrazine based on the supramolecular self-assembly of cationic perylene diimide.

A cationic perylene probe was designed and synthesized for sensitive determination of tartrazine. In the presence of tartrazine, the fluorescence of theperylene probe was quenched by efficient supramolecular self-assembly of theperylene derivate. The quenching iscaused by the synergistic effect of noncovalent interactions including static electricity, π-π stacking, and hydrophobic interaction. Benefiting from these advantages, the probe exhibited excellent sensing performance to tartrazine within 2 min. The detection and quantification limit of tartrazine are as low as 2.42 and 8.07 nmol L-1, respectively, with a wide linear operation range from 15 to 500 nmol L-1. Most importantly, due to the high binding affinity (3.22 × 107 mol L-1) between the perylene probe and tartrazine, the sensing system shows great anti-interference capacity. Subsequently, the visualization application of the approach was evaluated by portable device, and the limits of detection for visual detection for test strip, membrane, and hydrogel were 0.5, 0.5, and 5 μmol L-1, respectively. Theapproach has been applied to monitor tartrazine in various food condiments with recoveries in the range 91.29-108.83%. As far as we know, this is the first report of using perylene-based probe for tartrazine determination, offering a promising strategy for the construction of perylene-based detection system in the field of food safety.

Highly Efficient Self-Assembly of Metallacages and Their Supramolecular Catalysis Behaviors in Microdroplets.

Developing a new strategy to improve the self-assembly efficiency of functional assemblies in a confined space and construct hybrid functional materials is a significant and fascinating endeavor. Herein, we present a highly efficient strategy for achieving the supramolecular self-assembly of well-defined metallacages in microdroplets through continuous-flow microfluidic devices. The high efficiency and versatility of this approach are demonstrated by the generation of five representative metallacages in different solvents containing water, DMF, acetonitrile, and methanol in a few minutes with nearly quantitative yields, in contrast to the yields obtained with the hour-scale reaction time in a batch reactor. A ring-opening catalytic reaction of the metallacages was selected as a model reaction for exploring supramolecular catalysis in microdroplets, whereby the catalytic yield was enhanced by 2.22-fold compared to that of the same reaction in the batch reactor. This work illustrates a new promising approach for the self-assembly of supramolecular systems.

Grand canonical Brownian dynamics simulations of adsorption and self-assembly of SAS-6 rings on a surface.

The Spindle Assembly Abnormal Protein 6 (SAS-6) forms dimers, which then self-assemble into rings that are critical for the nine-fold symmetry of the centriole organelle. It has recently been shown experimentally that the self-assembly of SAS-6 rings is strongly facilitated on a surface, shifting the reaction equilibrium by four orders of magnitude compared to the bulk. Moreover, a fraction of non-canonical symmetries (i.e., different from nine) was observed. In order to understand which aspects of the system are relevant to ensure efficient self-assembly and selection of the nine-fold symmetry, we have performed Brownian dynamics computer simulation with patchy particles and then compared our results with the experimental ones. Adsorption onto the surface was simulated by a grand canonical Monte Carlo procedure and random sequential adsorption kinetics. Furthermore, self-assembly was described by Langevin equations with hydrodynamic mobility matrices. We find that as long as the interaction energies are weak, the assembly kinetics can be described well by coagulation-fragmentation equations in the reaction-limited approximation. By contrast, larger interaction energies lead to kinetic trapping and diffusion-limited assembly. We find that the selection of nine-fold symmetry requires a small value for the angular interaction range. These predictions are confirmed by the experimentally observed reaction constant and angle fluctuations. Overall, our simulations suggest that the SAS-6 system works at the crossover between a relatively weak binding energy that avoids kinetic trapping and a small angular range that favors the nine-fold symmetry.

Exploring the Extreme Acid Tolerance of a Dynamic Protein Nanocage.

Encapsulins are microbial protein nanocages capable of efficient self-assembly and cargo enzyme encapsulation. Due to their favorable properties, including high thermostability, protease resistance, and robust heterologous expression, encapsulins have become popular bioengineering tools for applications in medicine, catalysis, and nanotechnology. Resistance against physicochemical extremes like high temperature and low pH is a highly desirable feature for many biotechnological applications. However, no systematic search for acid-stable encapsulins has been carried out, while the influence of pH on encapsulin shells has so far not been thoroughly explored. Here, we report on a newly identified encapsulin nanocage from the acid-tolerant bacterium Acidipropionibacterium acidipropionici. Using transmission electron microscopy, dynamic light scattering, and proteolytic assays, we demonstrate its extreme acid tolerance and resilience against proteases. We structurally characterize the novel nanocage using cryo-electron microscopy, revealing a dynamic five-fold pore that displays distinct "closed" and "open" states at neutral pH but only a singular "closed" state under strongly acidic conditions. Further, the "open" state exhibits the largest pore in an encapsulin shell reported to date. Non-native protein encapsulation capabilities are demonstrated, and the influence of external pH on internalized cargo is explored. Our results expand the biotechnological application range of encapsulin nanocages toward potential uses under strongly acidic conditions and highlight pH-responsive encapsulin pore dynamics.

Azido azole-1,3,4-triazine fused energetic materials: A bioinspired strategy for tuning thermal stability and sensitivity of metal-free primary explosives via hierarchical hydrogen-bond self-assembly

Primary explosives are useful but they usually pose low thermal stability and underlying safety threat to manufacturers and users. It is highly desirable yet challenging to develop next-generation primary explosives with lead-free, environmentally friendly, high-dense, thermostable and safe organic energetic materials for replacement. Here, inspired by biosystem’s architecture, we report a simple and efficient hierarchical hydrogen-bond self-assembly strategy to synthesize high-performance primary explosives with enhanced thermal stability (Tonset > 200 °C) and decreased sensitivity (40 J). Owing to the above-efficient strategy, 7-azide-3-(1H-tetrazol-5-yl)-[1,2,4]triazolo[5,1-c] [1,2,4]triazin-4-amine-2- oxide (EM-4) and 7-azide-4-amino-3-nitro-[1,2,4]triazolo[5,1-c][1,2,4]triazine (EM-6) feature high densities of 1.825 and 1.816 g cm−3, much superior to their analogues 7-azide-3-(1H-tetrazol-5-yl)-[1,2,4]triazolo[5,1-c][1,2,4]triazin-4-amine (EM-3) and 8-azide-4-amino-3,7-dinitropyrazolo-[5,1-c][1,2,4]triazine (EM-9), comparable to that of 6-azido-8-nitrotetrazolo[1,5-b]-pyridazine-7-amine (ANTP). Meanwhile, EM-3 (Td = 225 °C), EM-4 (Td = 290 °C) and EM-6 (Td = 210 °C) exhibit better thermal stability and lower sensitivities (IS = 40 J) than those representative metal-free primary explosives (Td = 114–193 °C, IS = 0.25–17 J). The as-synthesized materials all feature superior performance to those of commercially scale-up and industrial applicable primary explosive 2-diazo-4,6-dinitrophenol (DDNP). Moreover, the calculated detonation velocity of EM-6 reaches up to 9029 m s−1, which is comparable to that of 6-nitro-7-azido-pyazol[3,4-d][1,2,3]triazine-2-oxide (ICM-103) but EM-6 features better thermal stability and safety performance. Bioinspired organic primary explosive may open a new gate for the design and development of more thermostable, higher dense and safer initiating substances towards future advanced applications.

Highly efficient light-induced self-assembly of gold nanoparticles promoted by photoexcitation-induced aggregatable ligands.

There are numerous ways to achieve light-induced self-assembly of gold nanoparticles, but most of them are through chemical reaction and slow. Ligands that can perform photoexcitation-induced aggregation were synthesized and modified onto gold nanoparticles. The leading functionalized nanoparticles exhibit highly efficient light-induced self-assembly properties and show high-contrast color fading in tens of seconds.

Precision nanoengineering for functional self-assemblies across length scales.

As nanotechnology continues to push the boundaries across disciplines, there is an increasing need for engineering nanomaterials with atomic-level precision for self-assembly across length scales, i.e., from the nanoscale to the macroscale. Although molecular self-assembly allows atomic precision, extending it beyond certain length scales presents a challenge. Therefore, the attention has turned to size and shape-controlled metal nanoparticles as building blocks for multifunctional colloidal self-assemblies. However, traditionally, metal nanoparticles suffer from polydispersity, uncontrolled aggregation, and inhomogeneous ligand distribution, resulting in heterogeneous end products. In this feature article, I will discuss how virus capsids provide clues for designing subunit-based, precise, efficient, and error-free self-assembly of colloidal molecules. The atomically precise nanoscale proteinic subunits of capsids display rigidity (conformational and structural) and patchy distribution of interacting sites. Recent experimental evidence suggests that atomically precise noble metal nanoclusters display an anisotropic distribution of ligands and patchy ligand bundles. This enables symmetry breaking, consequently offering a facile route for two-dimensional colloidal crystals, bilayers, and elastic monolayer membranes. Furthermore, inter-nanocluster interactions mediated via the ligand functional groups are versatile, offering routes for discrete supracolloidal capsids, composite cages, toroids, and macroscopic hierarchically porous frameworks. Therefore, engineered nanoparticles with atomically precise structures have the potential to overcome the limitations of molecular self-assembly and large colloidal particles. Self-assembly allows the emergence of new optical properties, mechanical strength, photothermal stability, catalytic efficiency, quantum yield, and biological properties. The self-assembled structures allow reproducible optoelectronic properties, mechanical performance, and accurate sensing. More importantly, the intrinsic properties of individual nanoclusters are retained across length scales. The atomically precise nanoparticles offer enormous potential for next-generation functional materials, optoelectronics, precision sensors, and photonic devices.

Hydrogen bonding and phase separation cooperatively guide the self-assembly of U60 and the polymer to fabricate multiscale nanostructures.

U60 (Li44K16[UO2(O2)(OH)]60, U60) and polymers are directionally enriched on the polymer surface by hydrogen bonding. In this study, we used several different polymers and U60 for self-assembly. The morphology and non-covalent interaction between core-shell nanocomplexes were studied by electron microscopy and vibration spectroscopy. Under the synergistic action of hydrogen bonding and nanometer phase separation, block copolymers and U60 formed different structures of core-shell nanocomposites. At a low concentration of U60, spherical nanocomposites with frozen structures were formed, at a high concentration of U60, stable worm-like structures, and micelles were formed. We used block copolymers to absorb U60, and after one month, about 96% of U60 could be removed from the solution. Because of uranium toxicity and long half-life, storage and transportation are important for the environment and public health. This study may open the door for further development of novel and efficient polymer self-assembly materials to adsorb and remove nuclear pollution in the environment.

Steering bi-directional charge transfer via non-conjugated insulating polymer

Exquisite tuning of spatial charge transfer and separation has been an enduringly core issue in heterogeneous photocatalysis. Nevertheless, precise modulation of directional charge transfer to the ideal catalytically active sites remains challenging owing to rapid recombination rate of photoinduced charge carriers and sluggish charge transfer kinetics. Herein, bi-directional spatially separated electron and hole transport channels were simultaneously constructed over transition metal chalcogenides (TMCs)-based heterostructures via an efficient and facile electrostatic self-assembly strategy. Tailor-made positively charged non-conjugated polymer of branched polyethyleneimine (BPEI) and negatively charged metal nanocrystals (NCs) building blocks were controllably anchored on the TMCs substrate. We found that electrons photoexcited over TMCs substrate can migrate spontaneously, smoothly and unidirectionally to the tightly integrated neighboring metal NCs, wherein metal NCs function as Schottky-type electron-trapping reservoirs and the ultra-thin intermediate BPEI layer serves as a directional hole transport mediator, thus synergistically contributing to the significantly enhanced charge separation and prolonged charge lifetime. Benefiting from these merits, such self-assembled TMC@BPEI/metal heterostructure exhibits the markedly enhanced photoreduction catalysis toward photocatalytic hydrogen generation and anaerobic selective reduction of nitroaromatics to amino derivatives under visible light irradiation. Our work would provide inspiring idea for fine modulation of charge separation and transfer toward solar-to-chemical energy conversion.