Real-Time Detection of Multiple Intracellular MicroRNAs using an Ultrasound-Propelled Nanomotor-Based Dynamic Fluorescent Probe.

Multiple intracellular microRNA (miRNA) detection is essential for disease diagnosis and management. Nonetheless, the real-time detection of multiple intracellular miRNAs has remained challenging. Herein, we have developed an ultrasound (US)-powered nanomotor-based dynamic fluorescent probe for the real-time OFF-ON fluorescent determination of multiple intracellular miRNAs. The new probe relies on the utilization of multicolored quantum dot (QD)-labeled single-stranded DNA (ssDNA)/graphene oxide (GO)-coated US-powered gold nanowire (AuNW) nanomotors. The fluorescence of QDs is quenched due to π-π interactions with the GO. Upon binding to target miRNAs, the QDs-ssDNA is now distant from the AuNWs, resulting in effective OFF-ON QD fluorescence switching. Compared with conventional passive probes, the dynamic fluorescent probe enhances probe-target interactions by using the US-propelled nanomotor, resulting in exceptionally efficient and prompt hybridization. Simultaneous quantitative analysis of miR-10b and miR-21 in vitro can be achieved within 15 min with high sensitivity and specificity. Additionally, multicolor QDs provide strong signal intensity and multiplexed detection, enabling one-step real-time discrimination between cancer cells (A549) and normal cells (L02). The obtained results are in good agreement with those from qRT-PCR. This dynamic fluorescent probe based on a nanomotor and QDs enables rapid "on the move" specific detection of multiple intracellular miRNAs in intact cells, facilitating real-time monitoring of diverse intracellular miRNA expression, and it could pave the way for novel applications of nanomotors in biodetection.

Correction: Intelligent micro/nanorobots based on biotemplates.

Correction for 'Intelligent micro/nanorobots based on biotemplates' by Ting Chen et al., Mater. Horiz., 2024, https://doi.org/10.1039/d4mh00114a.

Intelligent micro/nanorobots based on biotemplates.

Intelligent micro/nanorobots based on natural materials as biotemplates are considered to be some of the most promising robots in the future in the microscopic field. Due to the advantages of biotemplates such as unique structure, abundant resources, environmental friendliness, easy removal, low price, easy access, and renewability, intelligent micro/nanorobots based on biotemplates can be endowed with both excellent biomaterial activity and unique structural morphology through biotemplates themselves and specific functions through artificial micro/nanotechnology. Thus, intelligent micro/nanorobots show excellent application potential in various fields from biomedical applications to environmental remediation. In this review, we introduce the advantages of using natural biological materials as biotemplates to build intelligent micro/nanorobots, and then, classify the micro/nanorobots according to different types of biotemplates, systematically detail their preparation strategies and summarize their application prospects. Finally, in order to further advance the development of intelligent micro/nanorobots, we discuss the current challenges and future prospects of biotemplates. Intelligent micro/nanorobots based on biotemplates are a perfect combination of natural biotemplates and micro/nanotechnology, which is an important trend for the future development of micro/nanorobots. We hope this review can provide useful references for developing more intelligent, efficient and safe micro/nanorobots in the future.

Ultrasound-propelled nanomotors for efficient cancer cell ferroptosis.

Ferroptosis is a non-apoptotic form of cell death that is dependent on the accumulation of intracellular iron that causes elevation of toxic lipid peroxides. Therefore, it is crucial to improve the levels of intracellular iron and reactive oxygen species (ROS) in a short time. Here, we first propose ultrasound (US)-propelled Janus nanomotors (Au-FeOx/PEI/ICG, AFPI NMs) to accelerate cellular internalization and induce cancer cell ferroptosis. This nanomotor consists of a gold-iron oxide rod-like Janus nanomotor (Au-FeOx, AF NMs) and a photoactive indocyanine green (ICG) dye on the surface. It not only exhibits accelerating cellular internalization (∼4-fold) caused by its attractive US-driven propulsion but also shows good intracellular motion behavior. In addition, this Janus nanomotor shows excellent intracellular ROS generation performance due to the synergistic effect of the "Fenton or Fenton-like reaction" and the "photochemical reaction". As a result, the killing efficiency of actively moving nanomotors on cancer cells is 88% higher than that of stationary nanomotors. Unlike previous passive strategies, this work is a significant step toward accelerating cellular internalization and inducing cancer-cell ferroptosis in an active way. These novel US-propelled Janus nanomotors with strong propulsion, efficient cellular internalization and excellent ROS generation are suitable as a novel cell biology research tool.

Five in One: Multi-Engine Highly Integrated Microrobot.

A multi-engine highly integrated microrobot, which is a Janus hemispherical shell structure composed of Pt and α-Fe2 O3 , is successfully developed. The microrobot can be efficiently driven and flexibly regulated by five stimuli, including an optical field, an acoustic field, magnetic field, an electric field, and chemical fuel. In addition, no matter which way it is driven by, the direction can be effectively controlled through the magnetic field regulation. Furthermore, this microrobot can also utilize magnetic or acoustic fields to achieve excellent aggregation control and swarm movement. Finally, this study demonstrates that the microrobots' propulsion can be effectively synergistically enhanced through the simultaneous action of two driving mechanisms, which can greatly improve the performance of the motor in applications, such as pollutant degradation. This multi-engine, highly integrated microrobot not only can adapt to more complex environments and has a wider application range, better application prospects, but also provides important ideas for designing future advanced micro/nanorobots.

Catalytic micromotors as self-stirring microreactors for efficient dual-mode colorimetric detection.

A catalytic micromotor-based (MIL-88B@Fe3O4) colorimetric detection system which exhibit rapid color reaction for quantitative colorimetry and high-throughput testing for qualitative colorimetry have been successfully developed. Taking the advantages of the micromotor with dual roles (micro-rotor and micro-catalyst), under rotating magnetic field, each micromotor represents a microreactor which have micro-rotor for microenvironment stirring and micro-catalyst for the color reaction. Numerous self-string micro-reactions rapidly catalyze the substance and show the corresponding color for the spectroscopy testing and analysis. Additionally, owing to the tiny motor can rotate and catalyze within microdroplet, a high-throughput visual colorimetric detection system with 48 micro-wells has been innovatively conducted. The system enables up to 48 microdroplet reactions based on micromotors run simultaneously under the rotating magnetic field. Multi-substance, including their species difference and concentration strength, can be easily and efficiently identified by observing the color difference of the droplet with naked eye after just one test. This novel catalytic MOF-based micromotor with attractive rotational motion and excellent catalytic performance not only endowed a new nanotechnology to colorimetry, but also shows hold great potentials in other fields, such as refined production, biomedical analysis, environmental governance etc., since such micromotor-based microreactor can be easily applied to other chemical microreactions.

Recent Advances in One-Dimensional Micro/Nanomotors: Fabrication, Propulsion and Application.

Due to their tiny size, autonomous motion and functionalize modifications, micro/nanomotors have shown great potential for environmental remediation, biomedicine and micro/nano-engineering. One-dimensional (1D) micro/nanomotors combine the characteristics of anisotropy and large aspect ratio of 1D materials with the advantages of functionalization and autonomous motion of micro/nanomotors for revolutionary applications. In this review, we discuss current research progress on 1D micro/nanomotors, including the fabrication methods, driving mechanisms, and recent advances in environmental remediation and biomedical applications, as well as discuss current challenges and possible solutions. With continuous attention and innovation, the advancement of 1D micro/nanomotors will pave the way for the continued development of the micro/nanomotor field.

Quantum Dot-Based Micromotors with NIR-I Light Photocatalytic Propulsion and NIR-II Fluorescence.

Here, we report the first PbS quantum dot (QD)-based micromotors with NIR-I light-driven photocatalytic propulsion and NIR-II fluorescence. Under the irradiation of NIR-I light (808 nm), PbS QD-doped cuprous oxide (Cu2O@PbS) micromotors can display efficient propulsion in a variety of biocompatible fuels such as malic acid, glucose, and urea. Among them, the Cu2O@PbS micromotors exhibit the best propulsion performance in a very low concentration of malic acid, with an average speed as high as 11.86 µm/s. The enhanced NIR-I photocatalytic activity of Cu2O@PbS micromotors benefits from the doping of NIR-I PbS QDs that can be excited by NIR-I light and exhibit high electron transport efficiency. The doped PbS QDs can effectively increase the absorption efficiency of the micromotors in the NIR-I region while also inhibiting the recombination of photogenerated electron-hole pairs. Interestingly, due to the presence of NIR PbS QDs, the Cu2O@PbS micromotors demonstrate prominent and stable NIR-II fluorescence (emission wavelength: 1100 nm), which offer promising potential for visualization of their position in vivo. In comparison to other photocatalytic micromotors, the simple fabrication strategy, excellent NIR-II fluorescence, together with the NIR-I light-dependent propulsion behavior of the current Cu2O@PbS micromotors, thus pave the way for further development of advanced smart "robots" for intelligent biomedical applications.

Editorial: Enzymatic Catalysis and Applications.

This Special Collection highlights the latest developments in the field of enzymatic catalysis and applications. In this Editorial, guest editors Lei Wang, Binju Wang and Renfeng Dong briefly introduced the research in this special collection.

Single-Metal Hybrid Micromotor.

Multimode stimuli-regulated propulsions are extremely useful for artificial micro-/nanomotors in performing specialized tasks in different microscopic environments. However, it is still a great challenge to develop a simple and efficient micro/nanosystem which can operate in complicated environments, either with fuel or without fuel. Here, we report a novel hybrid micromotor which only needs one metal with a special structure: micro-spherical shell with a hole. Since we attractively combine the inherently catalytic properties of Pt for chemical propulsion with a designed concave structure for acoustic propulsion, the micromotors can not only move rapidly in H2O2 fueled environment due to the chemical reaction between Pt and H2O2 but also can exhibit excellent acoustic propulsion in a fuel-free environment due to the non-uniform stress caused by ultrasound. In addition, the attractive group motion behavior of the motors, including aggregation, group migration, and dispersion, is easily realized by acoustic field regulation. The brand-new single-metal hybrid micromotors with a dual driving mode, flexible propulsion regulation, and efficient group motion regulation, which are essential for making micro-/nanomotors compatible with different surrounding environments, are expected to advance the field of artificial nanomachines.

Bioinspired micro/nanomotor with visible light energy-dependent forward, reverse, reciprocating, and spinning schooling motion.

In nature, microorganisms could sense the intensity of the incident visible light and exhibit bidirectional (positive or negative) phototaxis. However, it is still challenging to achieve the similar biomimetic phototaxis for the artificial micro/nanomotor (MNM) counterparts with the size from a few nanometers to a few micrometers. In this work, we report a fuel-free carbon nitride (C3N4)/polypyrrole nanoparticle (PPyNP)-based smart MNM operating in water, whose behavior resembles that of the phototactic microorganism. The MNM moves toward the visible light source under low illumination and away from it under high irradiation, which relies on the competitive interplay between the light-induced self-diffusiophoresis and self-thermophoresis mechanisms concurrently integrated into the MNM. Interestingly, the competition between these two mechanisms leads to a collective bidirectional phototaxis of an ensemble of MNMs under uniform illuminations and a spinning schooling behavior under a nonuniform light, both of which can be finely controllable by visible light energy. Our results provide important insights into the design of the artificial counterpart of the phototactic microorganism with sophisticated motion behaviors for diverse applications.

One body, two hands: photocatalytic function- and Fenton effect-integrated light-driven micromotors for pollutant degradation.

The threat of water pollution represents a serious global concern and requires rapid and efficient neutralization methods. Herein, we report novel two-in-one light-driven micromotors, i.e., light-driven TiO2-Fe Janus micromotors with both photocatalysis and photo-Fenton processes, for efficiently degrading organic pollutants in contaminated water. The TiO2-Fe micromotors moved rapidly by utilizing the photocatalytic H2O2 decomposition over TiO2 under UV irradiation, as well as generating highly reactive oxygen species responsible for the in situ degradation of the organic pollutants into non-harmful products. Notably, such coupling of photocatalysis generated on the TiO2 sides and the photo-Fenton process generated on the Fe sides, along with the rapid movement of these catalytic Janus micromotors, results in a synergetic effect that can greatly enhance the degradation of organic pollutants. The degradation efficiency of the TiO2-Fe micromotors is 52-fold that of only Fenton effects, and it is further improved by 40% compared to photocatalytic degradation alone. Considering the excellent advantages of the high efficiency, simple structure, reusability and the bubble-driven property, the new "on-the-fly" TiO2-Fe micromotor-based method has a promising potential for future water cleaning and waste-water treatments.

One Modification, Two Functions: Single Ni-modified Light-Driven ZnO Microrockets with Both Efficient Propulsion and Steerable Motion.

Efficient propulsion and effective direction control are essential for self-propelled micro/nanomotors. Here, a new "two-in-one" strategy for making attractive light-driven micro/nanomotors is demonstrated. We make use of the metallic and magnetic properties of low-cost Ni and incorporate just a single Ni layer into ZnO-based microrockets, so that the resulting ZnO-Ni microrockets can be both efficiently propelled by low energy (low light intensities and fuel concentrations) and effectively steered by a magnetic field. This successful demonstration of ZnO-Ni microrockets is significant for the development of highly efficient synthetic micro/nanomotors, which have strong delivery ability and efficient direction control for future applications across the micro/nanoscale field.

Glucose-Fueled Micromotors with Highly Efficient Visible-Light Photocatalytic Propulsion.

Synthetic micro/nanomotors fueled by glucose are highly desired for numerous practical applications because of the biocompatibility of their required fuel. However, currently all of the glucose-fueled micro/nanomotors are based on enzyme-catalytic-driven mechanisms, which usually suffer from strict operation conditions and weak propulsion characteristics that greatly limit their applications. Here, we report a highly efficient glucose-fueled cuprous oxide@N-doped carbon nanotube (Cu2O@N-CNT) micromotor, which can be activated by environment-friendly visible-light photocatalysis. The speeds of such Cu2O@N-CNT micromotors can reach up to 18.71 µm/s, which is comparable to conventional Pt-based catalytic Janus micromotors usually fueled by toxic H2O2 fuel. In addition, the velocities of such motors can be efficiently regulated by multiple approaches, such as adjusting the N-CNT content within the micromotors, glucose concentrations, or light intensities. Furthermore, the Cu2O@N-CNT micromotors exhibit a highly controllable negative phototaxis behavior (moving away from light sources). Such motors with outstanding propulsion in biological environments and wireless, repeatable, and light-modulated three-dimensional motion control are extremely attractive for future practical applications.

A Review on Artificial Micro/Nanomotors for Cancer-Targeted Delivery, Diagnosis, and Therapy.

Micro/nanomotors have been extensively explored for efficient cancer diagnosis and therapy, as evidenced by significant breakthroughs in the design of micro/nanomotors-based intelligent and comprehensive biomedical platforms. Here, we demonstrate the recent advances of micro/nanomotors in the field of cancer-targeted delivery, diagnosis, and imaging-guided therapy, as well as the challenges and problems faced by micro/nanomotors in clinical applications. The outlook for the future development of micro/nanomotors toward clinical applications is also discussed. We hope to highlight these new advances in micro/nanomotors in the field of cancer diagnosis and therapy, with the ultimate goal of stimulating the successful exploration of intelligent micro/nanomotors for future clinical applications.

Photocatalytic Micro/Nanomotors: From Construction to Applications.

Synthetic micro/nanomotors (MNMs) are a particular class of micrometer or nanometer scale devices with controllable motion behavior in solutions by transferring various energies (chemical, optical, acoustic, magnetic, electric, etc.) into mechanical energy. These tiny devices can be functionalized either chemically or physically to accomplish complex tasks in a microcosm. Up to now, MNMs have exhibited great potential in various fields, ranging from environmental remediation, nanofabrication, to biomedical applications. Recently, light-driven MNMs as classic artificial MNMs have attracted much attention. Under wireless remote control, they can perform reversible and repeatable motion behavior with immediate photoresponse. Photocatalytic micro/nanomotors (PMNMs) based on photocatalysts, one of the most important light-driven MNMs, can utilize energy from both the external light source and surrounding chemicals to achieve efficient propulsion. Unlike other kinds of MNMs, the PMNMs have a unique characteristic: photocatalytic property. On one hand, since photocatalysts can convert both optical and chemical energy inputs into mechanical propulsion of PMNMs via photocatalytic reactions, the propulsion generated can be modulated in many ways, such as through chemical concentration or light intensity. In addition, these PMNMs can be operated at low levels of optical and chemical energy input which is highly desired for more practical scenarios. Furthermore, PMNMs can be operated with custom features, including go/stop motion control through regulating an on/off switch, speed modulation through varying light intensities, direction control through adjusting light source position, and so forth. On the other hand, as superoxide radicals can be generated by photocatalytic reactions of activated photocatalysts, the PMNMs show great potential in environment remediation, especially in organic pollutant degradation. In order to construct more practical PMNMs for future applications and further extend their application fields, the ideal PMNMs should be operated in a fully environmentally friendly system with strong propulsion. In the past decade, great progress in the construction, motion regulation, and application of PMNMs has been achieved, but there are still some challenges to realize the perfect system. In this Account, we will summarize our recent efforts and those of other groups in the development toward attractive PMNM systems. First, we will illustrate basic principles about the photocatalytic reactions of photocatalysts and demonstrate how the photocatalytic reactions affect the propulsion of PMNMs. Then, we will illustrate the construction strategies for highly efficient and biocompatible PMNMs from two key aspects: (1) Improvement of energy conversion efficiency to achieve strong propulsion of PMNMs. (2) Expansion of the usable wavelengths of light to operate PMNMs in environment-friendly conditions. Next, potential applications of PMNMs have been described. In particular, environment remediation has taken major attention for the applications of PMNMs due to their photocatalytic properties. Finally, in order to promote the development of PMNMs which can be operated in fully green environments for more practical applications, an outlook of key challenges and opportunities in construction of ideal PMNMs is presented.

Controlled Self-Assembly of Multiple-Responsive Superamphiphilc Polymers Based on Host-Guest Inclusions of a Modified PEG with ß-Cyclodextrin.

Superamphiphilic polymers (SAPs) constructed by host-guest inclusion can self-assemble into various nanostructures in solution, which can find applications in many fields such as nanodevices, drug delivery, and template synthesis. Herein, we report the controlled self-assembly of multiple-responsive SAP based on a selective host-guest inclusion of ß-cyclodextrin (ß-CD) with a modified poly(ethylene glycol) (PEG) (FcC11AzoPEG) consisting of a ferrocene (Fc) end group, a C11 alkyl chain, an azobenzene (Azo) block, and a poly(ethylene glycol)methyl ether (PEG) chain. These SAPs can self-assemble into interesting nanostructures in water upon exposure to different stimuli because ß-CD can be selectively included with different guests, such as Fc, Azo, and C11 alkyl chain, under different stimuli. The inclusion complex of Fc with ß-CD (Fc@ß-CD SAP) can form nanowire micelles in aqueous solution. The nanowire micelles can be transformed into spindle micelles with the addition of oxidant because the majority of ß-CDs dissociated from the complex Fc@ß-CD SAP due to a conversion of Fc to Fc+ and will preferentially include with Azo group to form another dominant inclusion complex (Azo@ß-CD SAP). After UV irradiation, the spindle micelles can be further transformed into spherical micelles because most of ß-CDs are excluded from the complex Azo@ß-CD SAP due to a trans- to cis-Azo conversion and then form a dominant inclusion complex with C11 alkyl chains (C11@ß-CD SAP). This work not only demonstrates the selective host-guest inclusion of stimuli-responsive groups modified PEG with ß-CD but also provides a useful approach for construction of diverse morphologies.

Efficient Encapsulation of Small S2-4 Molecules in MOF-Derived Flowerlike Nitrogen-Doped Microporous Carbon Nanosheets for High-Performance Li-S Batteries.

Lithium-sulfur (Li-S) battery is regarded as one of the most promising next-generation efficient energy storage systems because of its ultrahigh theoretical capacity of 1675 mAh/g and energy density of 2600 Wh/kg accompanied by the environmental benignity and abundance from natural sulfur. However, the insulating nature of sulfur and the dissolution of the polysulfides Li2S n (4 ≤ n ≤ 8) seriously restrict its practical application. The metastable small sulfur molecules (S2-4) stored in microporous carbon (pore size of <0.6 nm) as the active materials can avoid the production of the soluble polysulfide and solve the shuttle effect thoroughly. In addition, the conductivity of sulfur can be also improved. However, the preparation of microporous carbon materials with reasonable pore size and unique morphology for efficiently encapsulating S2-4 is still challenging. Herein, three flowerlike microporous nitrogen-doped carbon nanosheets with the pore size of <0.6 nm (namely, FMNCN-800, -900, and -1000) as the cathode materials in Li-S batteries were obtained from temperature-dependent carbonization of the metal-organic framework (MOF), Zn-TDPAT, which was from the simply reflux reaction of N-rich ligand H6TDPAT with Zn(II) salt. Our study showed that the FMNCN-900 from carbonization of Zn-TDPAT at 900 °C has suitable pore volume and nitrogen content, accommodating small S2-4 molecules in its micropores with the mass uptake of about 45%. Meanwhile, the appropriate amount of the nitrogen doping and the unique nanostructure of the flowerlike carbon nanosheet in the FMNCN-900 can effectively support its fast electronic transmission and lithium-ion conduction. The resulting S@FMNCN-900 composite cathode material presents the excellent electrochemical property in the Li-S battery (here the carbonate as electrolytes) with a reversible capacity of about 1220 mAh/g at 0.1C after 200 cycles and even 727 mAh/g at 2C after the long-term cycle of 1000 with only around 0.02% capacity loss per cycle. Obviously, the results indicate that the delicate construction of MOF-derived nitrogen-doped microporous carbon nanosheet is a promising strategy to develop novel electrode material for high-performing Li-S batteries.

Emulsion Hydrogel Soft Motor Actuated by Thermal Stimulation.

An emulsion hydrogel motor (E-H motor), constituted by low-boiling-point oil fuel and a hydrogel matrix, is prepared through a simple yet versatile oil-in-water (O/W) emulsion template method. The E-H motor can be efficiently propelled by the bubbles generated under a thermal stimulus. As thermally induced explosion occurs inside the E-H motor (diameter ∼4.0 mm and length ∼6.0 mm), the gas bubbles resulting from thermotropic phase transition are violently ejected from one side, leading to a fast speed of 14.78 ± 4.82 mm s-1 in a 60 °C aqueous solution. Additionally, multiple water-insoluble organic solvents can serve as the fuel for self-propulsion, which demonstrates the favorable universality of the E-H motor. The magnetic navigation and near-infrared propulsion can be realized through incorporating hydrophilic iron oxide (Fe3O4) nanoparticles and graphene oxide (GO) into the aqueous phase. Moreover, the synchronous integration of GO and enrofloxacin bactericide can enable intelligent targeted cargo transportation and delivery. The attractive self-propulsion performance, precise locomotion control, and formidable integration ability of the emulsion hydrogel-based miniaturized soft motor hold great promise for numerous practical applications.