Bacteriorhodopsin-Inspired Light-Driven Artificial Molecule Motors for Transmembrane Mass Transportation

Azobenzene-based liposomes with nanomechanical action for cytosolic chemotherapeutic drug delivery

The stimuli-responsive nano-carriers are at the forefront of research in nanotechnology and materials science. These advanced systems are designed to alter their physicochemical properties upon exposure to specific stimuli, enabling controllable and targeted delivery of therapeutic agents. Nevertheless, limited endosomal escape reduces the drug bioavailability in clinical use. We herein report azobenzene (Azo)-based liposomes, prepared by co-assembling the photoisomerizable cationic Azo lipids and helper lipids, which achieve controllable doxorubicin (Dox) release and enhanced cytosolic transport upon light irradiation. Azo lipids undergo reversible isomerization between cis-isomers and trans-isomer when received UV and visible (Vis) light irradiation, causing liposomal membrane permeability changes for controlled drug release. Moreover, the nanomechanical action created by the isomerization of Azo lipids promotes the endosomal escape of the liposomes. DSPC-Azo liposomes, with minimal Dox leakage, showed significant tumor cell killing upon irradiation. For in vivo study, we co-encapsulated the upconverting nanoparticles (UCNPs), which can convert the near-infrared (NIR) light into UV/Vis emissions, facilitating Azo units activation. UCNP/Dox-loaded DSPC-Azo liposomes inhibited tumor growth under NIR irradiation in a 4T1 tumor-bearing mouse model.

Bionic Potassium Ion Channel in Live Cells Repairs Cardiomyocyte Function

The disturbance of potassium current in cardiac myocytes caused by potassium channel dysfunction can lead to cardiac electrophysiological disorders, resulting in associated cardiovascular diseases. The emergence of artificial potassium ion channels opens up a way to replace dysfunctional natural ion channels and cure related diseases. However, bionic potassium ion channels have not been introduced into living cells to regulate cell function. One of the biggest challenges is that when the bionic channel fuses with the cell, it is difficult to control the inserting angle of the bionic potassium channel to ensure its penetration of the entire cell membrane. In nature, the extracellular vesicles can fuse with living cells with a completely preserved structure of vesicle protein. Inspired by this, we developed a vesicle fusion-based bionic porin (VFBP), which integrates bionic potassium ion channels into cardiomyocytes to replace damaged potassium ion channels. Theoretical and experimental results show that the inserted bionic ion channels have a potassium ion transport rate comparable to that of natural ion channels, which can restore the potassium ion outflow in cardiomyocytes and repair the abnormal action potential and excitation-contraction coupling of cardiomyocytes. Therefore, the bionic potassium ion channel system based on membrane fusion is expected to become the research object in many fields such as ultrafast ion transport, transmembrane delivery, and channelopathies treatment.

Collective Molecular Machines: Multidimensionality and Reconfigurability

Molecular machines are key to cellular activity where they are involved in converting chemical and light energy into efficient mechanical work. During the last 60 years, designing molecular structures capable of generating unidirectional mechanical motion at the nanoscale has been the topic of intense research. Effective progress has been made, attributed to advances in various fields such as supramolecular chemistry, biology and nanotechnology, and informatics. However, individual molecular machines are only capable of producing nanometer work and generally have only a single functionality. In order to address these problems, collective behaviors realized by integrating several or more of these individual mechanical units in space and time have become a new paradigm. In this review, we comprehensively discuss recent developments in the collective behaviors of molecular machines. In particular, collective behavior is divided into two paradigms. One is the appropriate integration of molecular machines to efficiently amplify molecular motions and deformations to construct novel functional materials. The other is the construction of swarming modes at the supramolecular level to perform nanoscale or microscale operations. We discuss design strategies for both modes and focus on the modulation of features and properties. Subsequently, in order to address existing challenges, the idea of transferring experience gained in the field of micro/nano robotics is presented, offering prospects for future developments in the collective behavior of molecular machines.

Nanomechanical action opens endo-lysosomal compartments

Endo-lysosomal escape is a highly inefficient process, which is a bottleneck for intracellular delivery of biologics, including proteins and nucleic acids. Herein, we demonstrate the design of a lipid-based nanoscale molecular machine, which achieves efficient cytosolic transport of biologics by destabilizing endo-lysosomal compartments through nanomechanical action upon light irradiation. We fabricate lipid-based nanoscale molecular machines, which are designed to perform mechanical movement by consuming photons, by co-assembling azobenzene lipidoids with helper lipids. We show that lipid-based nanoscale molecular machines adhere onto the endo-lysosomal membrane after entering cells. We demonstrate that continuous rotation-inversion movement of Azo lipidoids triggered by ultraviolet/visible irradiation results in the destabilization of the membranes, thereby transporting cargoes, such as mRNAs and Cre proteins, to the cytoplasm. We find that the efficiency of cytosolic transport is improved about 2.1-fold, compared to conventional intracellular delivery systems. Finally, we show that lipid-based nanoscale molecular machines are competent for cytosolic transport of tumour antigens into dendritic cells, which induce robust antitumour activity in a melanoma mouse model.

Rocket-Inspired Effervescent Motors for Oral Macromolecule Delivery

Oral administration is among the most convenient ways with good patient compliance for drug delivery; while it remains a challenge to achieve desirable bioavailability of most macromolecules due to the complex gastrointestinal barriers. Here, inspired by the structure and function of rocket, a novel micromotor delivery system is presented with scaled-down rocket-like architecture and effervescent-tablets-derived fuel for efficient oral macromolecule delivery by penetrating intestinal barrier. These rocket-inspired effervescent motors (RIEMs) are composed of sharp needle tips for both loading cargoes and efficient penetrating, and tail wings for loading effervescent powders and avoiding perforation. When exposed to a water environment, the effervescent fuel generates intensive CO2 bubbles to propel the RIEMs to move at high speed. Thus, the RIEMs with their sharp tip can inject into the surrounding mucosa for effective drug release. Furthermore, benefiting from their tail-wing design, perforation can be effectively avoided during the injection process, ensuring the safety of the RIEMs in gastrointestinal active delivery. Based on these advantages, it is demonstrated that the RIEMs can efficiently move and stab into the intestinal mucosa for insulin delivery, exhibiting efficacy in regulating blood sugar glucose in a diabetic rabbit model. These features indicate that these RIEMs are versatile and valuable for clinical oral delivery of macromolecules.

Dual-Functional Super-Assembled Mesoporous Carbon-Titania/AAO Hetero-Channels for Bidirectionally Photo-Regulated Ion Transport

Photo-regulated nanofluidic devices have attracted great attention in recent years due to their adjustable ion transport in real time. However, most of the photo-responsive nanofluidic devices can only adjust the ionic current unidirectionally, and cannot simultaneously increase or decrease the current signal intelligently by one device. Herein, a mesoporous carbon-titania/ anodized aluminum hetero-channels (MCT/AAO) is constructed by super-assembly strategy, which exhibits dual-function of cation selectivity and photo response. The polymer and TiO2 nanocrystals jointly build the MCT framework. Polymer framework with abundant negatively charged sites endows MCT/AAO with excellent cation selectivity, and TiO2 nanocrystals are responsible for the photo-regulated ion transport. High photo current densities of 1.8 mA m-2 (increase) and 1.2 mA m-2 (decrease) are realized by MCT/AAO benefiting from the ordered hetero-channels. Significantly, MCT/AAO can also achieve the bidirectionally adjustable osmotic energy by alternating the configurations of concentration gradient. Theoretical and experimental results reveal that the superior photo-generated potential is responsible for the bidirectionally adjustable ion transport. Consequently, MCT/AAO performs the function of harvesting ionic energy from the equilibrium electrolyte solution, which greatly expands its practical application field. This work provides a new strategy in constructing dual-functional hetero-channels toward bidirectionally photo-regulated ionic transport and energy harvesting.

Superassembly of 4-Aminothiophenol-Modified Mesoporous Titania-Alumina Oxide Heterochannels for Smart Ion Transport Based on the Photo-Induced Electron-Transfer Process

Light-responsive nanochannels have attracted extensive attention due to their noninvasive external field control and intelligent ion regulation. However, the limited photoresponsive current and the low photoelectric conversion efficiency still restrict their development. Here, a light-controlled nanochannel composed of 4-aminothiophenol and gold nanoparticles-modified mesoporous titania nanopillar arrays and alumina oxide (4-ATP-Au-MTI/AAO) is fabricated by the interfacial super-assembly strategy. Inspired by the process of electron transfer between photosystem I and photosystem II, the efficient electron transfer between TiO₂, AuNPs, and 4-ATP under light is achieved by coupling the photoresponsive materials and functional molecules. Under illumination, 4-ATP is oxidized to p-nitrothiophenol (PNTP), which brings about changes in the wettability of the nanochannel, resulting in significant improvement (252.8%) of photoresponsive current. In addition, under the action of the reductant, the nanochannels can be restored to the initial dark state, enabling multiple reversible cycles. This work opens a new route for the fabrication of high-performance light-controlled nanochannels by coupling light-responsive materials and light-responsive molecules, which may guide the development of photoelectric conversion nanochannel systems.

Accounts of applied molecular rotors and rotary motors: recent advances

Molecular machines are nanoscale devices capable of performing mechanical works at molecular level. These systems could be a single molecule or a collection of component molecules that interrelate with one another to produce nanomechanical movements and resulting performances. The design of the components of molecular machine with bioinspired traits results in various nanomechanical motions. Some known molecular machines are rotors, motors, nanocars, gears, elevators, and so on based on their nanomechanical motion. The conversion of these individual nanomechanical motions to collective motions via integration into suitable platforms yields impressive macroscopic output at varied sizes. Instead of limited experimental acquaintances, the researchers demonstrated several applications of molecular machines in chemical transformation, energy conversion, gas/liquid separation, biomedical use, and soft material fabrication. As a result, the development of new molecular machines and their applications has accelerated over the previous two decades. This review highlights the design principles and application scopes of several rotors and rotary motor systems because these machines are used in real applications. This review also offers a systematic and thorough overview of current advancements in rotary motors, providing in-depth knowledge and predicting future problems and goals in this area.

Engineering solid nanochannels with macrocyclic host-guest chemistry for stimuli responses and molecular separations

Biological channels in the cell membrane play a critical role in the regulation of signal transduction and transmembrane transport. Researchers have been committed to building biomimetic nanochannels to imitate the above significant biological processes. Unlike the fragile feature of biological channels, numerous solid nanochannels have aroused extensive interests for their controllable chemical properties on the surface and superior mechanical properties. Surface functionalization has been confirmed to be vital to determine the properties of solid nanochannels. Macrocyclic hosts (e.g., the crown ethers, cyclodextrins, calix[n]arenes, cucurbit[n]urils, pillar[n]arenes, and trianglamine) can be tailored to the interior surface of the nanochannels with the performance of stimuli response and separation. Macrocycles have good reversibility and high selectivity toward specific ions or molecules, promoting functionalies of solid nanochannels. Hence, the combination of macrocyclic hosts and solid nanochannels is conducive to taking both advantages and achieving applications in functional nanochannels (e.g., membranes separations, biosensors, and smart devices). In this review, the most recent advances in nanochannel membranes decorated by macrocyclic host-guest chemistry are briefed. A variety of macrocyclic hosts-based responsive nanochannels are organized (e.g., the physical stimuli and specific molecules or ions stimuli) and nanochannels are separated (e.g., water purifications, enantimerseparations, and organic solvent nanofiltration), respectively. Hopefully, this review can enlighten on how to effectively build functional nanochannels and facilitate their practical applications in membrane separations.

Highly Altered State of Proton Transport in Acid Pools in Charged Reverse Micelles

Transport mechanisms of solvated protons of 1 M HCl acid pools, confined within reverse micelles (RMs) containing the negatively charged surfactant sodium bis(2-ethylhexyl) sulfosuccinate (NaAOT) or the positively charged cetyltrimethylammonium bromide (CTABr), are analyzed with reactive force field simulations to interpret dynamical signatures from TeraHertz absorption and dielectric relaxation spectroscopy. We find that the forward proton hopping events for NaAOT are further suppressed compared to a nonionic RM, while the Grotthuss mechanism ceases altogether for CTABr. We attribute the sluggish proton dynamics for both charged RMs as due to headgroup and counterion charges that expel hydronium and chloride ions from the interface and into the bulk interior, thereby increasing the pH of the acid pools relative to the nonionic RM. For charged NaAOT and CTABr RMs, the localization of hydronium near a counterion or conjugate base reduces the Eigen and Zundel configurations that enable forward hopping. Thus, localized oscillatory hopping dominates, an effect that is most extreme for CTABr in which the proton residence time increases dramatically such that even oscillatory hopping is slow.

Lipidoid Artificial Compartments for Bidirectional Regulation of Enzyme Activity through Nanomechanical Action

Photoresponsive inhibitor and noninhibitor systems have been developed to achieve on-demand enzyme activity control. However, inhibitors are only effective for a specific and narrow range of enzymes. Noninhibitor systems usually require mutation and modification of the enzymes, leading to irreversible loss of enzymatic activities. Inspired by biological membranes, we herein report a lipidoid-based artificial compartment composed of azobenzene (Azo) lipidoids and helper lipids, which can bidirectionally regulate the activity of the encapsulated enzymes by light. In this system, the reversible photoisomerization of Azo lipidoids triggered by UV/vis light creates a continuous rotation-inversion movement, thereby enhancing the permeability of the compartment membrane and allowing substrates to pass through. Moreover, the membrane can revert to its impermeable state when light is removed. Thus, enzyme activity can be switched on and off when encapsulating enzymes in the compartments. Importantly, since neither mutation nor modification is required, negligible loss of activity is observed for the encapsulated enzymes after repeated activation and inhibition. Furthermore, this approach provides a generic strategy for controlling multiple enzymes by forgoing the use of inhibitors and may broaden the applications of enzymes in biological mechanism research and precision medicine.

Photoinduced movement: how photoirradiation induced the movements of matter

Pioneered by the success on active transport of ions across membranes in 1980 using the regulation of the binding properties of crown ethers with covalently linked photoisomerizable units, extensive studies on the movements by using varied interactions between moving objects and environments have been reported. Photoinduced movements of various objects ranging from molecules, polymers to microscopic particles were discussed from the aspects of the driving for the movements, materials design to achieve the movements and systems design to see and to utilize the movements are summarized in this review.

Bioinspired Artificial Ion Pumps

Ion pumps are important membrane-spanning transporters that pump ions against the electrochemical gradient across the cell membrane. In biological systems, ion pumping is essential to maintain intracellular osmotic pressure, to respond to external stimuli, and to regulate physiological activities by consuming adenosine triphosphate. In recent decades, artificial ion pumping systems with diverse geometric structures and functions have been developing rapidly with the progress of advanced materials and nanotechnology. In this Review, bioinspired artificial ion pumps, including four categories: asymmetric structure-driven ion pumps, pH gradient-driven ion pumps, light-driven ion pumps, and electron-driven ion pumps, are summarized. The working mechanisms, functions, and applications of those artificial ion pumping systems are discussed. Finally, a brief conclusion of underpinning challenges and outlook for future research are tentatively discussed.

Light-responsive nanochannels based on the supramolecular host–guest system

The light-responsive nanochannel of rhodopsin gained wider research interest from its crucial roles in light-induced biological functions, such as visual signal transduction and energy conversion, though its poor stability and susceptibility to inactivation in vitro have limited its exploration. However, the fabrication of artificial nanochannels with the properties of physical stability, controllable structure, and easy functional modification becomes a biomimetic system to study the stimulus-responsive gating properties. Typically, light-responsive molecules of azobenzene (Azo), retinal, and spiropyran were introduced into nanochannels as photo-switches, which can change the inner surface wettability of nanochannels under the influence of light; this ultimately results in the photoresponsive nature of biomimetic nanochannels. Furthermore, the fine-tuning of their stimulus-responsive properties can be achieved through the introduction of host–guest systems generally combined with a non-covalent bond, and the assembling process is reversible. These host–guest systems have been introduced into the nanochannels to form different functions. Based on the host–guest system of light-responsive reversible interaction, it can not only change the internal surface properties of the nanochannel and control the recognition and transmission behaviors but also realize the controlled release of a specific host or guest molecules in the nanochannel. At present, macrocyclic host molecules have been introduced into nanochannels including pillararenes, cyclodextrin (CD), and metal–organic frameworks (MOFs). They are introduced into the nanochannel through chemical modification or host–guest assemble methods. Based on the changes in the light-responsive structure of azobenzene, spiropyran, retinal, and others with macrocycle host molecules, the surface charge and hydrophilic and hydrophobic properties of the nanochannel were changed to regulate the ionic and molecular transport. In this study, the development of photoresponsive host and guest-assembled nanochannel systems from design to application is reviewed, and the research prospects and problems of this photo-responsive nanochannel membrane are presented.

Fabrication of Redox-Controllable Bioinspired Nanochannels for Precisely Regulating Protein Transport

Redox regulation is an inherent feature of nature and plays a crucial role in the transport of ions/small molecules. However, whether redox status affects the biomolecule transport remains largely unknown. To explore the effects of redox status on biomolecule transport, herein, we constructed a glutathione/glutathione disulfide (GSH/GSSG)-driven and pillar[5]arene (P5)-modified artificial nanochannel for protein transport. The results indicate that hemoglobin (Hb) protein is selectively and effectively transported across the GSH-driven P5-modified nanochannel, which suggests that the redox status of the nanochannel could affect the process of protein transport. Therefore, this redox-driven nanochannel could provide a potential application for biomolecule detection and redox-controllable biomolecular drug release.

An Ultraviolet/Visible Light Regulated Protein Transport Gate Constructed by Pillar[6]arene-based Host-Guest System

Protein transport is an interesting and intrinsic life feature that is highly relevant to physiology and disease in living beings. Herein, inspired by nature, based on the supramolecular host-guest interaction, we have introduced the classical azobenzene light switches and L-phenylalanine derived pillar[6]arene (L-Phe-P6) into the artificial nanochannel to construct light-responsive nanochannels that could regulate protein transport effectively under the control of ultraviolet (UV) and visible (Vis) light. The light-controlled distribution of L-Phe-P6 in the channel led to the difference in surface charges in the nanochannel, which eventually brought the difference in protein transport. This research may not only provide a convenient theoretical model for biological research, but also a flexible light-responsive protein transport model, which will play a crucial role in light-controlled release of protein drugs and so on.

Light-Controlled Ionic/Molecular Transport through Solid-State Nanopores and Nanochannels

Biological nanochannels perfectly operate in organisms and exquisitely control mass transmembrane transport for complex life process. Inspired by biological nanochannels, plenty of intelligent artificial solid-state nanopores and nanochannels are constructed based on various materials and methods with the development of nanotechnology. Specially, the light-controlled nanopores/nanochannels have attracted much attention due to the unique advantages in terms of that ion and molecular transport can be regulated remotely, spatially and temporally. According to the structure and function of biological ion channels, light-controlled solid-state nanopores/nanochannels can be divided into light-regulated ion channels with ion gating and ion rectification functions, and light-driven ion pumps with active ion transport property. In this review, we present a systematic overview of light-controlled ion channels and ion pumps according to the photo-responsive components in the system. Then, the related applications of solid-state nanopores/nanochannels for molecular sensing, water purification and energy conversion are discussed. Finally, a brief conclusion and short outlook are offered for future development of the nanopore/nanochannel field.

Photoresponsive Solid Nanochannels Membranes: Design and Applications

Light stimuli have notable advantages over other environmental stimuli, such as more precise spatial and temporal regulation, and the ability to serve as an energy source to power the system. In nature, photoresponsive nanochannels are important components of organisms, with examples including the rhodopsin channels in optic nerve cells and photoresponsive protein channels in the photosynthesis system of plants. Inspired by biological channels, scientists have constructed various photoresponsive, smart solid-state nanochannels membranes for a range of applications. In this review, the methods and applications of photosensitive nanochannels membranes are summarized. The authors believe that this review will inspire researchers to further develop multifunctional artificial nanochannels for applications in the fields of biosensors, stimuli-responsive smart devices, and nanofluidic devices, among others.

Engineering the Redox-Driven Channel for Precisely Regulating Nanoconfined Glutathione Identification and Transport

Bioinspired artificial nanochannels for molecular and ionic transport have extensive applications. However, it is still a huge challenge to achieve an intelligent transport system with high selectivity/efficiency and controllability. Inspired by glutathione transport across the plasma membrane via redox regulation, we herein designed and fabricated a redox-reactive artificial nanochannel based on the host-guest chemical strategy. The nanochannel platform achieved high selectivity/efficiency for the identification and transmission of glutathione in the confined space. In addition, this nanochannel can switch between the ON and OFF states through the redox reaction. This redox-regulated system can provide a potential application for detection/binding of biological analytes and redox-controlled drug release.

Tailoring CO2-Activated Ion Nanochannels Using Macrocyclic Pillararenes

Gas-responsive nanochannels have great relevance for applications in many fields. Inspired by CO₂-sensitive ion channels, herein we present an approach for designing solid-state nanochannels that allow controlled regulation of ion transport in response to alternate CO₂/N₂ stimuli. The pillar[5]arene (P5N) bearing diethylamine groups can convert into the water-soluble host P5C, containing cationic tertiary ammonium salt groups after absorbing CO₂. Subsequently, the nanochannel walls are tailored using P5N-based host-guest chemistry. The ion transport rate of K⁺ in the P5N nanochannels under CO₂ was 1.66 × 10^-4 mol h^-1 m^-2, whereas that under N₂ was 7.98 × 10^-4 mol h^-1 m^-2. Notably, there was no significant change to the ion current after eight cycles, which may indicate the stability and repeatability of CO₂-activated ion nanochannels. It is speculated that the difference in ion conductance resulted from the change in wettability and surface charge within the nanochannels in response to the gas stimuli. Achieving CO₂-activated ion transport in solid-state nanochannels opens new avenues for biomimetic nanopore systems and advanced separation processes.

Electrochemical Trans-Channel Assay for Efficient Evaluation of Tumor Cell Invasiveness

Efficiently assessing the invasive capability of tumor cells is critical both for the research and treatment of cancer. Here, we report a novel method called the electrochemical trans-channel assay for efficient evaluation of tumor cell invasiveness. A bioinspired extracellular matrix degradation model (EDM) has been first fabricated on a porous anodic alumina (PAA) membrane to construct the electrochemical apparatus. Upon contacting the invasive tumor cells, invasive capability can be sensitively evaluated by the degree of EDM impairment, which is recorded by the electrochemical trans-channel ionic currents in a label-free manner. Compared to the most commonly used trans-well migration method, this assay can be accomplished in an efficient way that is significantly faster (20 min) and more convenient. Besides, quantitation can also be realized for monitoring the invasion process, which cannot be achieved by other currently used methods. Our proposed electrochemical trans-channel assay method has shown a synergistic effect for the evaluation of tumor cell invasiveness, providing a promising method for clinical assessment or prognostic applications of tumor metastasis.

A Visible-Light-Regulated Chloride Transport Channel Inspired by Rhodopsin

Inspired by the light-regulating capabilities of naturally occurring rhodopsin, we have constructed a visible-light-regulated Cl^- -transport membrane channel based on a supramolecular host-guest interaction. A natural retinal chromophore, capable of a visible-light response, is used as the guest and grafted into the artificial channel. Upon introduction of an ethyl-urea-derived pillar[6]arene (Urea-P6) host, threading or de-threading of the retinal and selective bonding of Cl^- can be utilized to regulate ion transport. Based on the visible-light responsiveness of the host-guest interaction, Cl^- transport can be regulated by visible light between ON and OFF states. Visible-light-regulated Cl^- transport as a chemical model permits to understand comparable biological ion-selective transport behaviors. Furthermore, this result also supplies a smart visible-light-responsive Cl^- transporter, which may have applications in natural photoelectric conversion and photo-controlled delivery systems.

Bioinspired hydrogel-based nanofluidic ionic diodes: nano-confined network tuning and ion transport regulation

Biological ion channel-based mass transport and signal transduction play a crucial role in physiological activities, and biomimetic nanochannels in aqueous solutions for ion transport regulation have been extensively studied. Few studies on non-aqueous systems, gel-based nanochannels, mainly focus on the charged gel network or embedded electrolytes. However, the basic issue of how a nanoscale gel network affects the ion transport in nanochannels has been neglected. Here, we demonstrate a non-aqueous biomimetic nanochannel system by employing the agarose hydrogel in conical nanochannels. To tune the hydrogel network by adjusting the gel concentration, the ion transport behavior in gel-based nanochannels is systemically investigated. The experimental results show that the ion transport behaviors in gel-nanochannels with 2% gel present similar ion selectivity and rectification performance to the aqueous system, indicating fast investigation of gel-based systems with the knowledge of the extensively studied aqueous systems. Furthermore, a gel-based solid-state diode and logic circuits were fabricated.

The evolution of molecular machines through interfacial nanoarchitectonics: from toys to tools

Molecular machines are often regarded as molecular artworks and sometimes as fancy molecular toys. However, many researchers strive to operate molecular machines as useful tools for realistic practical applications. In this perspective article, shifting the working environment of molecular machines from solution to interfacial media is discussed from the viewpoint of their evolution from scientific toys to useful tools. Following a short description of traditional research into molecular machines in solution and their nanotechnological manipulation on clean solid surfaces, pioneering research into molecular machine operation at dynamic interfaces, such as liquid surfaces, is discussed, along with cutting-edge research into molecular machine functions in living cells and their models. Biomolecular machines within organisms are the products of evolution over billions of years. We may nanoarchitect such sophisticated functional systems with artificial molecular machines within much shorter periods.

Optoelectronic modulation of ionic conductance and rectification through a heterogeneous 1D/2D nanofluidic membrane

A smart mixed-dimensional heterogeneous membrane is fabricated, through which the ionic conductance and rectification can be precisely and robustly modulated by visible light of 420 nm wavelength with different power intensities simultaneously.

Engineering Smart Nanofluidic Systems for Artificial Ion Channels and Ion Pumps: From Single-Pore to Multichannel Membranes

Biological ion channels and ion pumps with intricate ion transport functions widely exist in living organisms and play irreplaceable roles in almost all physiological functions. Nanofluidics provides exciting opportunities to mimic these working processes, which not only helps understand ion transport in biological systems but also paves the way for the applications of artificial devices in many valuable areas. Recent progress in the engineering of smart nanofluidic systems for artificial ion channels and ion pumps is summarized. The artificial systems range from chemically and structurally diverse lipid-membrane-based nanopores to robust and scalable solid-state nanopores. A generic strategy of gate location design is proposed. The single-pore-based platform concept can be rationally extended into multichannel membrane systems and shows unprecedented potential in many application areas, such as single-molecule analysis, smart mass delivery, and energy conversion. Finally, some present underpinning issues that need to be addressed are discussed.

Photo- and Redox-Driven Artificial Molecular Motors

Directed motion at the nanoscale is a central attribute of life, and chemically driven motor proteins are nature's choice to accomplish it. Motivated and inspired by such bionanodevices, in the past few decades chemists have developed artificial prototypes of molecular motors, namely, multicomponent synthetic species that exhibit directionally controlled, stimuli-induced movements of their parts. In this context, photonic and redox stimuli represent highly appealing modes of activation, particularly from a technological viewpoint. Here we describe the evolution of the field of photo- and redox-driven artificial molecular motors, and we provide a comprehensive review of the work published in the past 5 years. After an analysis of the general principles that govern controlled and directed movement at the molecular scale, we describe the fundamental photochemical and redox processes that can enable its realization. The main classes of light- and redox-driven molecular motors are illustrated, with a particular focus on recent designs, and a thorough description of the functions performed by these kinds of devices according to literature reports is presented. Limitations, challenges, and future perspectives of the field are critically discussed.