Engineering Globular Protein Vesicles through Tunable Self‐Assembly of Recombinant Fusion Proteins

Vesicles assembled from folded, globular proteins have potential for functions different from traditional lipid or polymeric vesicles. However, they also present challenges in understanding the assembly process and controlling vesicle properties. From detailed investigation of the assembly behavior of recombinant fusion proteins, this work reports a simple strategy to engineer protein vesicles containing functional, globular domains. This is achieved through tunable self‐assembly of recombinant globular fusion proteins containing leucine zippers and elastin‐like polypeptides. The fusion proteins form complexes in solution via high affinity binding of the zippers, and transition through dynamic coacervates to stable hollow vesicles upon warming. The thermal driving force, which can be tuned by protein concentration or temperature, controls both vesicle size and whether vesicles are single or bi‐layered. These results provide critical information to engineer globular protein vesicles via self‐assembly with desired size and membrane structure.     

Self‐Assembled Metal–Phenolic Networks on Emulsions as Low‐Fouling and pH‐Responsive Particles

Interfacial self‐assembly is a powerful organizational force for fabricating functional nanomaterials, including nanocarriers, for imaging and drug delivery. Herein, the interfacial self‐assembly of pH‐responsive metal–phenolic networks (MPNs) on the liquid–liquid interface of oil‐in‐water emulsions is reported. Oleic acid emulsions of 100–250 nm in diameter are generated by ultrasonication, to which poly(ethylene glycol) (PEG)‐based polyphenolic ligands are assembled with simultaneous crosslinking by metal ions, thus forming an interfacial MPN. PEG provides a protective barrier on the emulsion phase and renders the emulsion low fouling. The MPN‐coated emulsions have a similar size and dispersity, but an enhanced stability when compared with the uncoated emulsions, and exhibit a low cell association in vitro, a blood circulation half‐life of ≈50 min in vivo, and are nontoxic to healthy mice. Furthermore, a model anticancer drug, doxorubicin, can be encapsulated within the emulsion phase at a high loading capacity (≈5 fg of doxorubicin per emulsion particle). The MPN coating imparts pH‐responsiveness to the drug‐loaded emulsions, leading to drug release at cell internalization pH and a potent cell cytotoxicity. The results highlight a straightforward strategy for the interfacial nanofabrication of pH‐responsive emulsion–MPN systems with potential use in biomedical applications.     

Multitriggered Tumor‐Responsive Drug Delivery Vehicles Based on Protein and Polypeptide Coassembly for Enhanced Photodynamic Tumor Ablation

Tumor‐responsive nanocarriers are highly valuable and demanded for smart drug delivery particularly in the field of photodynamic therapy (PDT), where a quick release of photosensitizers in tumors is preferred. Herein, it is demonstrated that protein‐based nanospheres, prepared by the electrostatic assembly of proteins and polypeptides with intermolecular disulfide cross‐linking and surface polyethylene glycol coupling, can be used as versatile tumor‐responsive drug delivery vehicles for effective PDT. These nanospheres are capable of encapsulation of various photosensitizers including Chlorin e6 (Ce6), protoporphyrin IX, and verteporfin. The Chlorin e6‐encapsulated nanospheres (Ce6‐Ns) are responsive to changes in pH, redox potential, and proteinase concentration, resulting in multitriggered rapid release of Ce6 in an environment mimicking tumor tissues. In vivo fluorescence imaging results indicate that Ce6‐Ns selectively accumulate near tumors and the quick release of Ce6 from Ce6‐Ns can be triggered by tumors. In tumors the fluorescence of released Ce6 from Ce6‐Ns is observed at 0.5 h postinjection, while in normal tissues the fluorescence appeared at 12 h postinjection. Tumor ablation is demonstrated by in vivo PDT using Ce6‐Ns and the biocompatibility of Ce6‐Ns is evident from the histopathology imaging, confirming the enhanced in vivo PDT efficacy and the biocompatibility of the assembled drug delivery vehicles.     

Photo‐Crosslinkable Unnatural Amino Acids Enable Facile Synthesis of Thermoresponsive Nano‐ to Microgels of Intrinsically Disordered Polypeptides

Hydrogel particles are versatile materials that provide exquisite, tunable control over the sequestration and delivery of materials in pharmaceutics, tissue engineering, and photonics. The favorable properties of hydrogel particles depend largely on their size, and particles ranging from nanometers to micrometers are used in different applications. Previous studies have only successfully fabricated these particles in one specific size regime and required a variety of materials and fabrication methods. A simple yet powerful system is developed to easily tune the size of polypeptide‐based, thermoresponsive hydrogel particles, from the nano‐ to microscale, using a single starting material. Particle size is controlled by the self‐assembly and unique phase transition behavior of elastin‐like polypeptides in bulk and within microfluidic‐generated droplets. These particles are then stabilized through ultraviolet irradiation of a photo‐crosslinkable unnatural amino acid (UAA) cotranslationally incorporated into the parent polypeptide. The thermoresponsive property of these particles provides an active mechanism for actuation and a dynamic responsive to the environment. This work represents a fundamental advance in the generation of crosslinked biomaterials, especially in the form of soft matter colloids, and is one of the first demonstrations of successful use of UAAs in generating a novel material.     

Precisely Size‐Tunable Monodisperse Hairy Plasmonic Nanoparticles via Amphiphilic Star‐Like Block Copolymers

In situ precision synthesis of monodisperse hairy plasmonic nanoparticles with tailored dimensions and compositions by capitalizing on amphiphilic star‐like diblock copolymers as nanoreactors are reported. Such hairy plasmonic nanoparticles comprise uniform noble metal nanoparticles intimately and perpetually capped by hydrophobic polymer chains (i.e., “hairs”) with even length. Interestingly, amphiphilic star‐like diblock copolymer nanoreactors retain the spherical shape under reaction conditions, and the diameter of the resulting plasmonic nanoparticles and the thickness of polymer chains situated on the surface of the nanoparticle can be readily and precisely tailored. These hairy nanoparticles can be regarded as hard/soft core/shell nanoparticles. Notably, the polymer “hairs” are directly and permanently tethered to the noble metal nanoparticle surface, thereby preventing the aggregation of nanoparticles and rendering their dissolution in nonpolar solvents and the homogeneous distribution in polymer matrices with long‐term stability. This amphiphilic star‐like block copolymer nanoreactor‐based strategy is viable and robust and conceptually enables the design and synthesis of a rich variety of hairy functional nanoparticles with new horizons for fundamental research on self‐assembly and technological applications in plasmonics, catalysis, energy conversion and storage, bioimaging, and biosensors.     

Hierarchically Nanoporous 3D Assembly Composed of Functionalized Onion‐Like Graphitic Carbon Nanospheres for Anode‐Minimized Li Metal Batteries

Despite the recent attention for Li metal anode (LMA) with high theoretical specific capacity of ≈ 3860 mA h g^?1, it suffers from not enough practical energy densities and safety concerns originating from the excessive metal load, which is essential to compensate for the loss of Li sources resulting from their poor coulombic efficiencies (CEs). Therefore, the development of high‐performance LMA is needed to realize anode‐minimized Li metal batteries (LMBs). In this study, high‐performance LMAs are produced by introducing a hierarchically nanoporous assembly (HNA) composed of functionalized onion‐like graphitic carbon building blocks, several nanometers in diameter, as a catalytic scaffold for Li‐metal storage. The HNA‐based electrodes lead to a high Li ion concentration in the nanoporous structure, showing a high CE of ≈ 99.1%, high rate capability of 12 mA cm^?2, and a stable cycling behavior of more than 750 cycles. In addition, anode‐minimized LMBs are achieved using a HNA that has limited Li content ( ≈ 0.13 mg cm^?2), corresponding to 6.5% of the cathode material (commercial NCM622 ( ≈ 2 mg cm^?2)). The LMBs demonstrate a feasible electrochemical performance with high energy and power densities of ≈ 510 Wh kg_electrode^?1 and ≈ 2760 W kg_electrode^?1, respectively, for more than 100 cycles.     

Multistimuli Sensing Adhesion Unit for the Self‐Positioning of Minimal Synthetic Cells

Cells have the ability to sense different environmental signals and position themselves accordingly in order to support their survival. Introducing analogous capabilities to the bottom‐up assembled minimal synthetic cells is an important step for their autonomy. Here, a minimal synthetic cell which combines a multistimuli sensitive adhesion unit with an energy conversion module is reported, such that it can adhere to places that have the right environmental parameters for ATP production. The multistimuli sensitive adhesion unit senses light, pH, oxidative stress, and the presence of metal ions and can regulate the adhesion of synthetic cells to substrates in response to these stimuli following a chemically coded logic. The adhesion unit is composed of the light and redox responsive protein interaction of iLID and Nano and the pH sensitive and metal ion mediated binding of protein His‐tags to Ni²⁺‐NTA complexes. Integration of the adhesion unit with a light to ATP conversion module into one synthetic cell allows it to adhere to places under blue light illumination, non‐oxidative conditions, at neutral pH and in the presence of metal ions, which are the right conditions to synthesize ATP. Thus, the multistimuli responsive adhesion unit allows synthetic cells to self‐position and execute their functions.     

Thermoreversible Morphology and Conductivity of a Conjugated Polymer Network Embedded in Block Copolymer Self‐Assemblies

Self‐assembly of block copolymers provides numerous opportunities to create functional materials, utilizing self‐assembled microdomains with a variety of morphology and periodic architectures as templates for functional nanofillers. Here new progress is reported toward the fabrication of thermally responsive and electrically conductive polymeric self‐assemblies made from a water‐soluble poly(thiophene) derivative with short poly(ethylene oxide) side chains and Pluronic L62 block copolymer solution in water. The structural and electrical properties of conjugated polymer‐embedded self‐assembled architectures are investigated by combining small‐angle neutron and X‐ray scattering, coarse‐grained molecular dynamics simulations, and impedance spectroscopy. The L62 solution template organizes the conjugated polymers by stably incorporating them into the hydrophilic domains thus inhibiting aggregation. The changing morphology of L62 during the micellar‐to‐lamellar phase transition defines the embedded conjugated polymer network. As a result, the conductivity is strongly coupled to the structural change of the templating L62 phase and exhibits thermally reversible behavior with no signs of quenching of the conductivity at high temperature. This study shows promise for enabling more flexibility in processing and utilizing water‐soluble conjugated polymers in aqueous solutions for self‐assembly based fabrication of stimuli‐responsive nanostructures and sensory materials.     

Molecular Targeting‐Mediated Mild‐Temperature Photothermal Therapy with a Smart Albumin‐Based Nanodrug

Photothermal therapy (PTT) usually requires hyperthermia >50 °C for effective tumor ablation, which inevitably induces heating damage to the surrounding normal tissues/organs. Moreover, low tumor retention and high liver accumulation are the two main obstacles that significantly limit the efficacy and safety of many nanomedicines. To solve these problems, a smart albumin‐based tumor microenvironment‐responsive nanoagent is designed via the self‐assembly of human serum albumin (HSA), dc‐IR825 (a cyanine dye and a photothermal agent), and gambogic acid (GA, a heat shock protein 90 (HSP90) inhibitor and an anticancer agent) to realize molecular targeting‐mediated mild‐temperature PTT. The formed HSA/dc‐IR825/GA nanoparticles (NPs) can escape from mitochondria to the cytosol through mitochondrial disruption under near‐infrared (NIR) laser irradiation. Moreover, the GA molecules block the hyperthermia‐induced overexpression of HSP90, achieving the reduced thermoresistance of tumor cells and effective PTT at a mild temperature (<45 °C). Furthermore, HSA/dc‐IR825/GA NPs show pH‐responsive charge reversal, effective tumor accumulation, and negligible liver deposition, ultimately facilitating synergistic mild‐temperature PTT and chemotherapy. Taken together, the NIR‐activated NPs allow the release of molecular drugs more precisely, ablate tumors more effectively, and inhibit cancer metastasis more persistently, which will advance the development of novel mild‐temperature PTT‐based combination strategies.     

Metallo‐Supramolecular Block Copolymers

Supramolecular copolymers have become of increasing interest in recent years for the search of new materials with tunable properties. In particular, metallo‐supramolecular block copolymers—copolymers in which the blocks are linked together by a metal–ligand complex—have seen important progresses, allowing better control over the synthetic strategies for various architectures, and providing a better understanding of the parameters governing their self‐assembly. We review here recent developments on the synthesis and self‐assembly of such materials achieved in this field.     

Influence of the Thermodynamic and Kinetic Control of Self‐Assembly on the Microstructure Evolution of Silk‐Elastin‐Like Recombinamer Hydrogels

Complex recombinant biomaterials that merge the self‐assembling properties of different (poly)peptides provide a powerful tool for the achievement of specific structures, such as hydrogel networks, by tuning the thermodynamics and kinetics of the system through a tailored molecular design. In this work, elastin‐like (EL) and silk‐like (SL) polypeptides are combined to obtain a silk‐elastin‐like recombinamer (SELR) with dual self‐assembly. First, EL domains force the molecule to undergo a phase transition above a precise temperature, which is driven by entropy and occurs very fast. Then, SL motifs interact through the slow formation of β‐sheets, stabilized by H‐bonds, creating an energy barrier that opposes phase separation. Both events lead to the development of a dynamic microstructure that evolves over time (until a pore size of 49.9 ± 12.7 µm) and to a delayed hydrogel formation (obtained after 2.6 h). Eventually, the network is arrested due to an increase in β‐sheet secondary structures (up to 71.8 ± 0.8%) within SL motifs. This gives a high bond strength that prevents the complete segregation of the SELR from water, which results in a fixed metastable microarchitecture. These porous hydrogels are preliminarily tested as biomimetic niches for the isolation of cells in 3D cultures.     

Interfacial Capillary‐Force‐Driven Self‐Assembly of Monolayer Colloidal Crystals for Supersensitive Plasmonic Sensors

Colloidal lithography technology based on monolayer colloidal crystals (MCCs) is considered as an outstanding candidate for fabricating large‐area patterned functional nanostructures and devices. Although many efforts have been devoted to achieve various novel applicatons, the quality of MCCs, a key factor for the controllability and reproducibility of the patterned nanostructures, is often overlooked. In this work, an interfacial capillary‐force‐driven self‐assembly strategy (ICFDS) is designed to realize a high‐quality and highly‐ordered hexagonal monolayer MCCs array by resorting the capillary effect of the interfacial water film at substrate surface as well as controlling the zeta potential of the polystyrene particles. Compared with the conventional self‐assembly method, this approach can realize the reself‐assembly process on the substrate surface with few colloidal aggregates, vacancy, and crystal boundary defects. Furthermore, various typical large‐scale nanostructure arrays are achieved by combining reactive ion etching, metal‐assisted chemical etching, and so forth. Specifically, benefiting from the as‐fabricated high‐quality 2D hexagonal colloidal crystals, the surface plasmon resonance (SPR) sensors achieve an excellent refractive index sensitivity value of 3497 nm RIU^?1, which is competent for detecting bovine serum albumin with an ultralow concentration of 10^?8 m . This work opens a window to prepare high‐quality MCCs for more potential applications.     

Gadolinium Metallofullerene‐Based Activatable Contrast Agent for Tumor Signal Amplification and Monitoring of Drug Release

Activatable imaging probes are promising to achieve increased signal‐to‐noise ratio for accurate tumor diagnosis and treatment monitoring. Magnetic resonance imaging (MRI) is a noninvasive imaging technique with excellent anatomic spatial resolution and unlimited tissue penetration depth. However, most of the activatable MRI contrast agents suffer from metal ion‐associated potential long‐term toxicity, which may limit their bioapplications and clinical translation. Herein, an activatable MRI agent with efficient MRI performance and high safety is developed for drug (doxorubicin) loading and tumor signal amplification. The agent is based on pH‐responsive polymer and gadolinium metallofullerene (GMF). This GMF‐based contrast agent shows high relaxivity and low risk of gadolinium ion release. At physiological pH, both GMF and drug molecules are encapsulated into the hydrophobic core of nanoparticles formed by the pH‐responsive polymer and shielded from the aqueous environment, resulting in relatively low longitudinal relativity and slow drug release. However, in acidic tumor microenvironment, the hydrophobic‐to‐hydrophilic conversion of the pH‐responsive polymer leads to amplified MR signal and rapid drug release simultaneously. These results suggest that the prepared activatable MRI contrast agent holds great promise for tumor detection and monitoring of drug release.     

Higher Order Assembly of Virus‐like Particles (VLPs) Mediated by Multi‐valent Protein Linkers

Two‐ and three‐dimensional assembly of nanoparticles has generated significant interest because these higher order structures could exhibit collective behaviors/properties beyond those of the individual nanoparticles. Highly specific interactions between molecules, which biology exploits to regulate molecular assemblies such as DNA hybridization, often provide inspiration for the construction of higher order materials using bottom‐up approaches. In this study, higher order assembly of virus‐like particles (VLPs) derived from the bacteriophage P22 is demonstrated by using a small adaptor protein, Dec, which binds to symmetry specific sites on the P22 capsid. Two types of connector proteins, which have different number of P22 binding sites and different geometries (ditopic linker with liner geometry and tetratopic linker with tetrahedral geometry) have been engineered through either a point mutation of Dec or genetic fusion with another protein, respectively. Bulk assembly and layer‐by‐layer deposition of P22 VLPs from solution was successfully achieved using both of the engineered multi‐topic linker molecules, while Dec with only a single binding site does not mediate P22 assembly. Beyond the two types of linkers developed in this study, a wide range of different connector geometries could be envisioned using a similar engineering approach. This is a powerful strategy to construct higher order assemblies of VLP based nanomaterials.     

One‐Step Construction of N,P‐Codoped Porous Carbon Sheets/CoP Hybrids with Enhanced Lithium and Potassium Storage

Despite the desirable advancement in synthesizing transition‐metal phosphides (TMPs)‐based hybrid structures, most methods depend on foreign‐template‐based multistep procedures for tailoring the specific structure. Herein, a self‐template and recrystallization–self‐assembly strategy for the one‐step synthesis of core–shell‐like cobalt phosphide (CoP) nanoparticles embedded into nitrogen and phosphorus codoped porous carbon sheets (CoP?NPPCS), is first proposed. Relying on the unusual coordination ability of melamine with metal ions and the cooperative hydrogen bonding of melamine and phytic acid to form a 2D network, a self‐synthesized single precursor can be attained. Importantly, this approach can be easily expanded to synthesize other TMPs?NPPCS. Due to the unique compositional and structural characteristics, these CoP?NPPCSs manifest outstanding electrochemical performances as anode materials for both lithium‐ and potassium‐ion batteries. The unusual hybrid architecture, the high specific surface area, and porous features make the CoP?NPPCS attractive for other potential applications, such as supercapacitors and electrocatalysis.     

Structure‐Guided Design and Synthesis of a Mitochondria‐Targeting Near‐Infrared Fluorophore with Multimodal Therapeutic Activities

An urgent challenge for imaging‐guided disease‐targeted multimodal therapy is to develop the appropriate multifunctional agents to meet the requirements for potential applications. Here, a rigid cyclohexenyl substitution in the middle of a polymethine linker and two asymmetrical amphipathic N‐alkyl side chains to indocyanine green (ICG) (the only FDA‐approved NIR contrast agent) are introduced, and a new analog, IR‐DBI, is developed with simultaneous cancer‐cell mitochondrial targeting, NIR imaging, and chemo‐/PDT/PTT/multimodal therapeutic activities. The asymmetrical and amphipathic structural modification renders IR‐DBI a close binding to albumin protein site II to form a drug–protein complex and primarily facilitates its preferential accumulation at tumor sites via the enhanced permeability and retention (EPR) effect. The released IR‐DBI dye is further actively taken up by cancer cells through organic‐anion‐transporting polypeptide transporters, and the lipophilic cationic property leads to its selective accumulation in the mitochondria of cancer cells. Finally, based on the high albumin‐binding affinity, IR‐DBI is modified into human serum albumin (HSA) via self‐assembly to produce a nanosized complex, which exhibits significant improvement in the cancer targeting and multimodal cancer treatment with better biocompatibility. This finding may present a practicable strategy to develop small‐molecule‐based cancer theranostic agents for simultaneous cancer diagnostics and therapeutics.     

Inkjet‐Printed High‐Performance Flexible Micro‐Supercapacitors with Porous Nanofiber‐Like Electrode Structures

Flexible planar micro‐supercapacitors (MSCs) with unique loose and porous nanofiber‐like electrode structures are fabricated by combining electrochemical deposition with inkjet printing. Benefiting from the resulting porous nanofiber‐like structures, the areal capacitance of the inkjet‐printed flexible planar MSCs is obviously enhanced to 46.6 mF cm^?2, which is among the highest values ever reported for MSCs. The complicated fabrication process is successfully averted as compared with previously reported best‐performing planar MSCs. Besides excellent electrochemical performance, the resultant MSCs also show superior mechanical flexibility. The as‐fabricated MSCs can be highly bent to 180° 1000 times with the capacitance retention still up to 86.8%. Intriguingly, because of the remarkable patterning capability of inkjet printing, various modular MSCs in serial and in parallel can be directly and facilely inkjet‐printed without using external metal interconnects and tedious procedures. As a consequence, the electrochemical performance can be largely enhanced to better meet the demands of practical applications. Additionally, flexible serial MSCs with exquisite and aesthetic patterns are also inkjet‐printed, showing great potential in fashionable wearable electronics. The results suggest a feasible strategy for the facile and cost‐effective fabrication of high‐performance flexible MSCs via inkjet printing.     

Photopatterning of Cross‐Linkable Epoxide‐Functionalized Block Copolymers and Dual‐Tone Nanostructure Development for Fabrication Across the Nano‐ and Microscales

The self‐assembly of block copolymers in thin films provides an attractive approach to patterning 5–100 nm structures. Cross‐linking and photopatterning of the self‐assembled block copolymer morphologies provide further opportunities to structure such materials for lithographic applications, and to also enhance the thermal, chemical, or mechanical stability of such nanostructures to achieve robust templates for subsequent fabrication processes. Here, model lamellar‐forming diblock copolymers of polystyrene and poly(methyl methacrylate) with an epoxide functionality are synthesized by atom transfer radical polymerization. We demonstrate that self‐assembly and cross‐linking of the reactive block copolymer materials in thin films can be decoupled into distinct, controlled process steps using solvent annealing and thermal treatment/ultraviolet exposure, respectively. Conventional optical lithography approaches can also be applied to the cross‐linkable block copolymer materials in thin films and enable simultaneous structure formation across scales—micrometer scale patterns achieved by photolithography and nanostructures via self‐assembly of the block copolymer. Such materials and processes are thus shown to be capable of self‐assembling distinct block copolymers (e.g., lamellae of significantly different periodicity) in adjacent regions of a continuous thin film.     

Layer‐by‐Layer Hydrogen‐Bonded Polymer Films: From Fundamentals to Applications

Recent years have seen increasing interest in the construction of nanoscopically layered materials involving aqueous‐based sequential assembly of polymers on solid substrates. In the booming research area of layer‐by‐layer (LbL) assembly of oppositely charged polymers, self‐assembly driven by hydrogen bond formation emerges as a powerful technique. Hydrogen‐bonded (HB) LbL materials open new opportunities for LbL films, which are more difficult to produce than their electrostatically assembled counterparts. Specifically, the new properties associated with HB assembly include: 1) the ease of producing films responsive to environmental pH at mild pH values, 2) numerous possibilities for converting HB films into single‐ or two‐component ultrathin hydrogel materials, and 3) the inclusion of polymers with low glass transition temperatures (e.g., poly(ethylene oxide)) within ultrathin films. These properties can lead to new applications for HB LbL films, such as pH‐ and/or temperature‐responsive drug delivery systems, materials with tunable mechanical properties, release films dissolvable under physiological conditions, and proton‐exchange membranes for fuel cells. In this report, we discuss the recent developments in the synthesis of LbL materials based on HB assembly, the study of their structure–property relationships, and the prospective applications of HB LbL constructs in biotechnology and biomedicine.     

CeO2‐Encapsulated Hollow Ag–Au Nanocage Hybrid Nanostructures as High‐Performance Catalysts for Cascade Reactions

Inspired by bio‐enzymes, multistep cascade reactions are highly attractive in catalysis. Despite extensive research in recent years, it remains a challenge to promote the stability and activity of catalysts. Here, well‐defined core–shell structured Ag–Au nanocage@CeO₂ (Ag–Au NC@CeO₂) are designed by a simple and facile self‐assembly method. The results indicate that the Ag–Au NC@CeO₂ has glucose oxidase‐like activity and intrinsic peroxidase‐like activity at the same time. As expected, Ag–Au NC@CeO₂ hybrid nanomaterials exhibit cascade reactions activity. Moreover, the hybrid materials are promising to detect glucose without bio‐enzymes. This research has potential applications in biomedicine and biomimetic catalysis.