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Multi-Stimuli-Responsive Tadpole-like Polymer/Lipid Janus Microrobots for Advanced Smart Material Applications
Abstract
Microrobots are of significant interest due to their smart transport capabilities, especially for precisely targeted delivery in dynamic environments (blood, cell membranes, tumor interstitial matrixes, blood–brain barrier, mucosa, and other body fluids). To perform a more complex micromanipulation in biological applications, it is highly desirable for microrobots to be stimulated with multiple stimuli rather than a single stimulus. Herein, the biodegradable and biocompatible smart micromotors with a Janus architecture consisting of PrecirolATO 5 and polycaprolactone compartments inspired by the anisotropic geometry of tadpoles and sperms are newly designed. These bioinspired micromotors combine the advantageous properties of polypyrrole nanoparticles (NPs), a high near-infrared light-absorbing agent with high photothermal conversion efficiency, and magnetic NPs, which respond to the magnetic field and exhibit multistimulus-responsive behavior. By combining both fields, we achieved an “on/off” propulsion mechanism that can enable us to overcome complex tasks and limitations in liquid environments and overcome the limitations encountered by single actuation applications. Moreover, the magnetic particles offer other functions such as removing organic pollutants via the Fenton reaction. Janus-structured motors provide a broad perspective not only for biosensing, optical detection, and on-chip separation applications but also for environmental water treatment due to the catalytic activities of multistimulus-responsive micromotors.
... In the natural world, organisms frequently exhibit remarkable adaptability to environmental changes, exemplified by phenomena such as mimosa leaves instantly closing upon contact [1], chameleons altering their hues to blend with their surroundings, and squids evading predators by releasing ink [2]. To harness this intelligence in modern materials, synthetic stimuli-responsive smart materials, which mimic natural biological deformation, have garnered significant attention and importance [3]. Among these, shape memory polymers (SMPs) stand out as stimuliresponsive materials that can undergo mechanical activation in response to external stimuli. ...
In the field of smart materials, an increasing demand is being observed for shape memory materials that exhibit advanced stimuli‐sensing and responsive capabilities. Two‐way shape memory polymers (2 W‐SMPs), as a novel type of smart shape memory material, offer numerous advantages over traditional one‐way shape memory polymers (1 W‐SMPs), particularly the fully reversible shape memory effect (SME), where the two‐way process (low‐temperature shape fixation and high‐temperature recovery to the original shape) occurs without the need for external energy input. These polymers are lightweight and exhibit remarkable deformation abilities, reversible changes in modulus, and multiple actuation modes. Additionally, they feature a high elastic modulus and increased response stress, making them particularly suitable and indispensable in fields ranging from medical devices and robotics to aerospace engineering and smart textiles. This review focuses on 2 W‐SMPs, detailing the underlying mechanisms of both 1 W‐SMPs and 2 W‐SMPs, as well as the various driving modes. We further discuss quasi‐2 W‐SMPs (with applied load force σ ≠ 0) and 2 W‐SMPs (with applied load force σ = 0) across different cross‐linking strategies. It also covers the broad applications of SMP materials and outlines the current challenges and potential avenues for future research.
Time-sequenced drug release, or sequential drug release, represents a pivotal strategy in the synergistic treatment of diseases using nanocomposites. Achieving this requires the rational integration of multiple therapeutic agents within a single nanocomposite, coupled with precise time-controlled release mechanisms. These nanocomposites offer many advantages, including enhanced therapeutic synergy, reduced side effects, attenuated adverse interactions, improved stability and optimized drug utilization. Consequently, research in the field of drug delivery and synergistic therapy has become increasingly important. Currently, sequential drug release research is still in the data collection and basic research stages, and its potential has not yet been fully explored. Although prior studies have explored the sequential drug release strategy in various contexts, a comprehensive review of the underlying mechanisms and their applications in nanocomposites remains scarce. This review categorizes different types of sequential drug release strategies and summarizes diverse nanocomposites, focusing on both physical approaches driven by structural variations and chemical methods based on stimulus-responsive mechanisms. Furthermore, we highlight the major applications of sequential drug release strategies in the treatment of various diseases and detail their therapeutic efficacy. Finally, emerging trends and challenges in advancing sequential drug release strategies based on nanocomposites for disease treatment are also discussed.
Although numerous technical advances have been made in cancer treatment, chemotherapy is still a viable treatment option. However, it is more effective when used in combination with photothermal therapy for resistant breast cancer cells. This study introduces a smart drug delivery system, (DOX-OA+VERA+AuNRs)@NLC, which is designed for dual chemo/photothermal therapy of multiple-drug-resistant breast cancer. Type-III nanostructured lipid carriers (NLCs) were used as drug delivery systems, where nano-in-nano structures offer several advantages. Doxorubicin (DOX) was used as the antitumor agent by ion-pairing it with oleic acid (OA) to increase the DOX loading capacity, as well as to reduce the burst release of the drug. Verapamil (VERA), which was used as a chemosensitizer to overcome the multiple-drug resistance, was co-loaded with DOX-OA. Gold nanorods (AuNRs) were exploited as the photothermal therapy agent in photothermal therapy (PTT) application, which would have a synergistic relation with chemotherapy. The release of DOX-OA and VERA from NLCs was studied in vitro by triggering with NIR laser irradiation. Thus, an all-in-one drug delivery system was designed to release the active pharmaceutical ingredients (APIs) at higher concentrations in the desired region and provide both chemo/PTT. Besides, the application of a folic acid-chitosan (FA-CS) coating to NLCs has facilitated the development of systems capable of targeting and specifically releasing their cargo within cancerous tissues while preserving their surrounding environment.
Nano-/microrobots have been demonstrated as an efficient solution for environmental remediation. Their strength lies in their propulsion abilities that allow active “on-the-fly” operation, such as pollutant detection, capture, transport, degradation, and disruption. Another advantage is their versatility, which allows the engineering of highly functional solutions for a specific application. However, the latter advantage can bring complexity to applications; versatility in dimensionality, morphology, materials, surface decorations, and other modifications has a crucial effect on the resulting propulsion abilities, compatibility with the environment, and overall functionality. Synergy between morphology, materials, and surface decorations and its projection to the overall functionality is the object of nanoarchitectonics. Here, we scrutinize the engineering of nano-/microrobots with the eyes of nanoarchitectonics: we list general concepts that help to assess the synergy and limitations of individual procedures in the fabrication processes and their projection to the operation at the macroscale. The nanoarchitectonics of nano-/microrobots is approached from microscopic level, focusing on the dimensionality and morphology, through the nanoscopic level, evaluating the influence of the decoration with nanoparticles and quantum dots, and moving to the decorations on molecular and single-atomic level to allow very fine tuning of the resulting functionality. The presented review aims to lay general concepts and provide an overview of the engineering of functional advanced nano-/microrobot for environmental remediation procedures and beyond.
Janus particles (JPs), initially introduced as soft matter, have evolved into a distinctive class of materials that set them apart from traditional surfactants, dispersants, and block copolymers. This mini-review examines the similarities and differences between JPs and their molecular counterparts to elucidate the unique properties of JPs. Key studies on the assembly behavior of JPs in bulk phases and at interfaces are reviewed, highlighting their unique ability to form diverse, complex structures. The superior interfacial stability and tunable amphiphilicity of JPs make them highly effective emulsifiers and dispersants, particularly in emulsion polymerization systems. Beyond these applications, JPs demonstrate immense potential as coating materials, facilitating the development of eco-friendly, anti-icing, and antifouling coatings. A comparative discussion with zwitterionic polymers also highlights the distinctive advantages of each system. This review emphasizes that while JPs mimic some of the behaviors of small molecular surfactants, they also open doors to entirely new applications, making them indispensable as next-generation functional materials.
Cooperative wrapping of nanoparticles (NPs) with small sizes is an important pathway for the uptake of NPs by cell membranes. However, the cooperative wrapping efficiency and the effects of the...
Today, smart materials are commonly used in various fields of science and technology, such as medicine, electronics, soft robotics, the chemical industry, the automotive field, and many others. Smart polymeric materials hold good promise for the future due to their endless possibilities. This group of advanced materials can be sensitive to changes or the presence of various chemical, physical, and biological stimuli, e.g., light, temperature, pH, magnetic/electric field, pressure, microorganisms, bacteria, viruses, toxic substances, and many others. This review concerns the newest achievements in the area of smart polymeric materials. The recent advances in the designing of stimuli-responsive polymers are described in this paper.
Magnetic motors are a class of out-of-equilibrium particles that exhibit controlled and fast motion overcoming Brownian fluctuations by harnessing external magnetic fields. The advances in this field resulted in motors that have been used for different applications, such as biomedicine or environmental remediation. In this Perspective, an overview of the recent advancements of magnetic motors is provided, with a special focus on controlled motion. This aspect extends from trapping, steering, and guidance to organized motor grouping and degrouping, which is known as swarm control. Further, the integration of magnetic motors in soft robots to actuate their motion is also discussed. Finally, some remarks and perspectives of the field are outlined.
One of the most important issues in the design and preparation of drug delivery systems in the recent years is versatility which includes providing synergistic therapeutic effects and sustainability. This study uses a redox‐active ferrocenyl surfactant (FcN⁺(CH2CH3)3(CH2)10CH3, Fc(C11) where Fc is ferrocene) and pH responsive Zeolitic Imidazolate Framework‐8 (ZIF‐8) structures to form multifunctional assemblies (Fc(C11)‐AOT/Rhb@ZIF‐8/PDA) that can be used in several application including the drug delivery. The vesicles prepared using AOT‐FC(C11) constitute the core of the structure. Since the location of the ferrocene group in the molecule structure, which is next to head group, the surface of the vesicles is decorated with the ferrocene group which can act as a Fenton reaction catalyst. The polydopamine (PDA) covered ZIF‐8 are used to decorate the surface of the vesicles, creating a truly remarkable structure. The porous structure of ZIF‐8 as well as the core of the vesicles can accommodate drug molecules. With the added NIR‐responsive character upon PDA coating, this assembled structure can be used for phototermal therapy applications. The properties of this designed multifunctional and multi‐responsive system are studied at different pH and under NIR‐laser irradiation and show that it has potential to display a triple chemodynamic/ photothermal/ chemotherapeutic effect.
Janus‐micromotors, as efficient self‐propelled materials, have garnered considerable attention for their potential applications in non‐agitated liquids. However, the design of micromotors is still challenging and with limited approaches, especially concerning speed and mobility in complex environments. Herein, a two‐step spray‐drying approach encompassing symmetrical assembly and asymmetrical assembly is introduced to fabricate the metal‐organic framework (MOF) Janus‐micromotors with hierarchical pores. Using a spray‐dryer, a symmetrical assembly is first employed to prepare macro‐meso‐microporous UiO‐66 with intrinsic micropores (<0.5 nm) alongside mesopores (≈24 nm) and macropores (≈400 nm). Subsequent asymmetrical assembly yielded the UiO‐66‐Janus loaded with the reducible nanoparticles, which underwent oxidation by KMnO4 to form MnO2 micromotors. The micromotors efficiently generated O2 for self‐propulsion in H2O2, exhibiting ultrahigh speeds (1135 µm s⁻¹, in a 5% H2O2 solution) and unique anti‐gravity diffusion effects. In a specially designed simulated sand‐water system, the micromotors traversed from the lower water to the upper water through the sand layer. In particular, the as‐prepared micromotors demonstrated optimal efficiency in pollutant removal, with an adsorption kinetic coefficient exceeding five times that of the micromotors only possessing micropores and mesopores. This novel strategy fabricating Janus‐micromotors shows great potential for efficient treatment in complex environments.
Polycaprolactone (PCL) is polymer of 21st centuries. PCL is a biodegradable and biocompatible polymer used for various healthcare applications. This review explores the properties, synthesis, and processing of PCL. The use of PCL polymer for nanoparticles (NPs), microparticles, films, and fibers offers several advantages for biomedical applications. The review highlights the potential of PCL‐based materials for tissue engineering, drug delivery, wound healing, and implantable medical devices. We also critically analyzed challenges in PCL‐based materials and the strategies used to overcome for successful translation into clinical applications. Overall, this review provides a comprehensive overview of PCL as a valuable biomaterial for healthcare applications.
Here, the study presents a thermally activated cell‐signal imaging (TACSI) microrobot, capable of photothermal actuation, sensing, and light‐driven locomotion. The plasmonic soft microrobot is specifically designed for thermal stimulation of mammalian cells to investigate cell behavior under heat active conditions. Due to the integrated thermosensitive fluorescence probe, Rhodamine B, the system allows dynamic measurement of induced temperature changes. TACSI microrobots show excellent biocompatibility over 72 h in vitro, and they are capable of thermally activating single cells to cell clusters. Locomotion in a 3D workspace is achieved by relying on thermophoretic convection, and the microrobot speed is controlled within a range of 5–65 µm s⁻¹. In addition, light‐driven actuation enables spatiotemporal control of the microrobot temperature up to a maximum of 60 °C. Using TACSI microrobots, this study targets single cells within a large population, and demonstrates thermal cell stimulation using calcium signaling as a biological output. Initial studies with human embryonic kidney 293 cells indicate a dose dependent change in intracellular calcium content within the photothermally controlled temperature range of 37–57 °C.
The present study aimed to prepare solid lipid-based nanoparticles (SLNs) using Precirol® ATO 5 as solid lipid and Poloxamer 188 and Tween 80 as surfactant and co-surfactant respectively, and SLNs-derived gel for sustained delivery, enhanced in-vitro cytotoxicity, enhanced cellular uptake of 5-FU and enhanced permeation of 5-FU across the skin. The 5-FU-loaded SLNs were prepared by the hot melt encapsulation method and converted into SLN-derived gel using a gelling agent (Carbopol 940). The 5-FU-loaded SLNs had a particle size in the range of 76.82±1.48 to 327±4.46 nm, zeta potential between -11.3±2.11 and -28.4±2.40 mV, and entrapment efficiency (%) in range of 63.46±1.13 and 76.08±2.42. The FTIR analysis depicted that there was no chemical interaction between 5-FU and formulation components. Differential scanning calorimetric analysis showed thermal stability of 5-FU in the nanoparticles and powdered X-ray diffraction analysis revealed successful incorporation of 5-FU in nanoparticles. The in-vitro release study of 5-FU-loaded SLNs showed biphasic release behavior with initial burst release followed by sustained release over 48 hr. The 5-FU-loaded SLNs showed a greater cytotoxic effect on skin melanoma (B16F10 cells) and squamous cell carcinoma (A-431 cells) as compared to free 5-FU drug solution after 48 hr. Flow cytometry and fluorescence microscopy displayed enhanced quantitative and qualitative cellular uptake of SLNs. The SLNs formulation showed acceptable safety and biocompatible profile after an acute toxicity study in Wistar rats. Moreover, ex-vivo permeation studies depicted 2.13±0.076 folds enhanced flux of 5-FU-loaded SLN derived gel compared to 5-FU plain gel, and skin retention studies revealed target efficiency (%) 2.54±0.03 of 5-FU-loaded SLN derived gel compared to 5-FU plain gel.
Owing to the omnipresent noise and crash hazards, multifunctional sound‐absorbing, and deformation‐tolerant materials are highly sought‐after for practical engineering design. However, challenges lie with designing such a material. Herein, leveraging the inherent mechanical robustness of the biological cuttlebone, by introducing dissipative pores, a high‐strength microlattice is presented which is also sound‐absorbing. Its absorption bandwidth and deformation tolerance are further enhanced by introducing another level of bioinspiration, based on geometrical heterogeneities amongst the building cells. A high‐fidelity microstructure‐based model is developed to predict and optimize properties. Across a broad range of frequencies from 1000 to 6300 Hz, at a low thickness of 21 mm, the optimized microlattice displays a high experimentally measured average absorption coefficient of 0.735 with 68% of the points higher than 0.7. The absorption mechanism attributes to the resonating air frictional loss whilst its broadband characteristics attribute to the multiple resonance modes working in tandem. The heterogeneous architecture also enables the microlattice to deform with a deformation‐tolerant plateau behavior not observed in its uniform counterpart, which thereby leads to a 30% improvement in the specific energy absorption. Overall, this work presents an effective approach to the design of sound and energy‐absorbing materials by modifying state‐of‐the‐art bioinspired structures.
Recently, robots have assisted and contributed to the biomedical field. Scaling down the size of robots to micro/nanoscale can increase the accuracy of targeted medications and decrease the danger of invasive operations in human surgery. Inspired by the motion pattern and collective behaviors of the tiny biological motors in nature, various kinds of sophisticated and programmable microrobots are fabricated with the ability for cargo delivery, bio-imaging, precise operation, etc. In this review, four types of propulsion—magnetically, acoustically, chemically/optically and hybrid driven—and their corresponding features have been outlined and categorized. In particular, the locomotion of these micro/nanorobots, as well as the requirement of biocompatibility, transportation efficiency, and controllable motion for applications in the complex human body environment should be considered. We discuss applications of different propulsion mechanisms in the biomedical field, list their individual benefits, and suggest their potential growth paths.
The present study deals with the preparation of nanomagnetite (NM), potassium carrageenan (KC), and nanomag-netite/potassium carrageenan bio-composite beads (NC). Characterization of the prepared solid materials using different physicochemical techniques such as X-ray diffraction analysis (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscope (TEM), energy-disperse X-ray spectroscopy (EDX), diffuse reflectance spectrophotometer (DRS), swelling ratio (SR%), N 2 adsorption, pH of point of zero charges (pH PZC), and Fourier transform infrared spectroscopy (FTIR). Comparing between adsorption and photo-Fenton degradation process for methylene blue (MB) on the surface of the prepared solid materials. Nanomagnetite/potassium carrageenan bio-composite (NC) exhibited high specific surface area (406 m 2 /g), mesoporosity (pore radius, 3.64 nm), point of zero charge around pH6.0, and the occurrence of abundant oxygen-containing functional groups. Comparison between adsorption and photo-Fenton oxidation process for methylene blue (MB) was carried out under different application conditions. NC exhibited the maximum adsorp-tion capacity with 374.50 mg/g at 40°C after 24 h of shaking time while 96.9% of MB was completely degraded after 20 min of photo-Fenton process. Langmuir's adsorption model for MB onto the investigated solid materials is the best-fitted adsorption model based on the higher correlation coefficient values (0.9771-0.9999). Kinetic and thermodynamic measurements prove that adsorption follows PSO, endothermic, and spontaneous process, while photo-Fenton degradation of MB achieves PFO, nonspontaneous, and endothermic process. Photo-Fenton degradation is a fast and simple technique at a lower concentration of dye (< 40 mg/L) while at higher dye concentration, the adsorption process is preferred in the removal of that dye.
Untethered microrobots offer a great promise for localized targeted therapy in hard-to-access spaces in our body. Despite recent advancements, most microrobot propulsion capabilities have been limited to homogenous Newtonian fluids. However, the biological fluids present in our body are heterogeneous and have shear rate–dependent rheological properties, which limit the propulsion of microrobots using conventional designs and actuation methods. We propose an acoustically powered microrobotic system, consisting of a three-dimensionally printed 30-micrometer-diameter hollow body with an oscillatory microbubble, to generate high shear rate fluidic flow for propulsion in complex biofluids. The acoustically induced microstreaming flow leads to distinct surface-slipping and puller-type propulsion modes in Newtonian and non-Newtonian fluids, respectively. We demonstrate efficient propulsion of the microrobots in diverse biological fluids, including in vitro navigation through mucus layers on biologically relevant three-dimensional surfaces. The microrobot design and high shear rate propulsion mechanism discussed herein could open new possibilities to deploy microrobots in complex biofluids toward minimally invasive targeted therapy.
Chemodynamic therapy (CDT) catalyzed by transition metal and starvation therapy catalyzed by intracellular metabolite oxidases are both classic tumor treatments based on nanocatalysts. CDT monotherapy has limitations including low catalytic efficiency of metal ions and insufficient endogenous hydrogen peroxide (H 2 O 2 ). Also, single starvation therapy shows limited ability on resisting tumors. The “metal-oxidase” cascade catalytic system is to introduce intracellular metabolite oxidases into the metal-based nanoplatform, which perfectly solves the shortcomings of the above-mentioned monotherapiesIn this system, oxidases can not only consume tumor nutrients to produce a “starvation effect”, but also provide CDT with sufficient H 2 O 2 and a suitable acidic environment, which further promote synergy between CDT and starvation therapy, leading to enhanced antitumor effects. More importantly, the “metal-oxidase” system can be combined with other antitumor therapies (such as photothermal therapy, hypoxia-activated drug therapy, chemotherapy, and immunotherapy) to maximize their antitumor effects. In addition, both metal-based nanoparticles and oxidases can activate tumor immunity through multiple pathways, so the combination of the “metal-oxidase” system with immunotherapy has a powerful synergistic effect. This article firstly introduced the metals which induce CDT and the oxidases which induce starvation therapy and then described the “metal-oxidase” cascade catalytic system in detail. Moreover, we highlight the application of the “metal-oxidase” system in combination with numerous antitumor therapies, especially in combination with immunotherapy, expecting to provide new ideas for tumor treatment.
Different iron oxides were evaluated for the discoloration of methylene blue (MB) at neutral pH by heterogeneous photo-Fenton-like reactions with a UV-LED lamp. Fe3O4, α-Fe2O3, and a-FeOOH catalysts were synthesized and characterized by X-ray diffraction, scanning electron microscopy (SEM), Raman spectroscopy, Fourier transform infrared spectroscopy, and adsorption isotherms of N2. The results show high crystallinity and relatively low surface areas for Fe3O4 and α-Fe2O3, and amorphous structure with high surface area for the case of a-FeOOH. The discoloration of MB by iron oxides as catalysts was studied using UV-Vis spectroscopy. Despite the relative high adsorption of MB for magnetite (12%) compared to the other oxides, it shows a slow discoloration kinetics. Besides, amorphous oxide (named a-FeOOH) shows a higher discoloration kinetics with negligible adsorption capacity. The pseudo first-order kinetic constant values for Fe3O4, α-Fe2O3, and a-FeOOH are 5.31 × 10−3, 6.89 × 10−3, and 13.01 × 10−3 min−1; and the discoloration efficiencies at 120 min were 56, 60, and 82%, respectively. It was testified that low crystallinity iron oxide can be used in the efficient discoloration of MB by photo-Fenton process with a hand UV-A lamp.
We report a new facile light-induced strategy to disperse micron-sized aggregated bulk covalent organic frameworks (COFs) into isolated COFs nanoparticles. This was achieved by a series of metal-coordinated COFs, namely COF-909-Cu, -Co or -Fe, where for the first time the diffusio-phoretic propulsion was utilized to design COF-based micro/nanomotors. The mechanism studies revealed that the metal ions decorated in the COF-909 backbone could promote the separation of electron and holes and trigger the production of sufficient ionic and reactive oxygen species under visible light irradiation. In this way, strong light-induced self-diffusiophoretic effect is achieved, resulting in good dispersion of COFs. Among them, COF-909-Fe showed the highest dispersion performance, along with a drastic decrease in particle size from 5 μm to 500 nm, within only 30 min light irradiation, which is inaccessible by using traditional magnetic stirring or ultrasonication methods. More importantly, benefiting from the outstanding dispersion efficiency, COF-909-Fe micro/nanomotors were demonstrated to be efficient in photocatalytic degradation of tetracycline, about 8 times faster than using traditional magnetic stirring method. This work opens up a new avenue to prepare isolated nanosized COFs in a high-fast, simple, and green manner.
Based on the phase separation phenomenon in micro-droplets, polymer-lipid Janus particles were prepared on a microfluidic flow focusing chip. Phase separation of droplets was caused by solvent volatilization and Janus morphology was formed under the action of interfacial tension. Because phase change from solid to liquid of the lipid hemisphere could be triggered by physiological temperature, the lipid hemisphere could be used for rapid release of drugs. While the polymer we selected was pH sensitive that the polymer hemisphere could degrade under acidic conditions, making it possible to release drugs in a specific pH environment, such as tumor tissues. Janus particles with different structures were obtained by changing the experimental conditions. To widen the application range of the particles, fatty alcohol and fatty acid-based phase change materials were also employed to prepare the particles, such as 1-tetradecanol, 1-hexadecanol and lauric acid. The melting points of these substances are higher than the physiological temperature, which can be applied in fever triggered drug release or in thermotherapy. The introduction of poly (lactic-co-glycolic acid) enabled the formation of multicompartment particles with three distinct materials. With different degradation properties of each compartment, the particles generated in this work may find applications in programmed and sequential drug release triggered by multiple stimuli.
Self-propelling micro- and nano-motors (MNMs) have been extensively investigated as an emerging oral drug delivery carrier for gastrointestinal (GI) tract diseases. However, the propulsion of current MNMs reported so far is mostly based on the redox reaction of metals (such as Zn and Mg) with severe propulsion gas generation, remaining non-degradable residue in the GI tract. Here, we develop a bioinspired enzyme-powered biopolymer micromotor mimicking the mucin penetrating behavior of Helicobacter pylori in the stomach. It converts urea to ammonia and the subsequent increase of pH induces local gel-sol transition of the mucin layer facilitating the penetration into the stomach tissue layer. The successful fabrication of micromotors is confirmed by high-resolution transmission electron microscopy, electron energy loss spectroscopy, dynamic light scattering analysis, zeta-potential analysis. In acidic condition, the immobilized urease can efficiently converted urea to ammonia, comparable with that of neutral condition because of the increase of surrounding pH during propulsion. After administration into the stomach, the micromotors show enhanced penetration and prolonged retention in the stomach for 24 h. Furthermore, histological analysis shows that the micromotors are cleared within 3 days without causing any toxicity in the GI tract. The enhanced penetration and retention of the micromotors as an active oral delivery carrier in the stomach would be successfully harnessed for the treatment of various GI tract diseases.
The remediation of methylene blue from wastewater using chitosan-sunflower-nano-iron (CSN) beds was examined in this study with the Fenton process. Nano-iron is synthesized using the green synthesis process. Then, biopolymer beds obtained nano-iron, sunflower tray waste, and chitosan. These beds used the Fenton process for removing Methylene blue (MB) from water. Beds synthesis and dye removing are characterized using SEM, TEM, FTIR, and XRD techniques. For the method optimization, the effects of dye concentration, temperature, pH, H 2 O 2 , and amount of biocatalyst were studied. The result of the wavelength scan was found 660 nm for methylene blue dye. Using CSN, catalyst was very effective in color removal for MB under optimal conditions. The highest removal rate 98% was obtained at pH 6 for 270 min. The optimum conditions for the MB dye are as follows; dye concentration: 25 mg/L, amount of absorbent: 2.5 mg/mL, temperature: 60 °C, H 2 O 2 amount: 20 mg/L (600 µL, 30%). When the experiment is studied in optimum conditions, max. dye removal was calculated to be 98%. From SEM, TEM, XRD, and FTIR results, the change in the surface of the biocatalyst could be clearly observed. It is understood that the biocatalyst synthesized from the results we obtained easily removed a large amount of dye (MB).
Most cancer treatments can cause vital side effects on healthy tissues. Ascorbic acid (AA) is a water-soluble antioxidant molecule and possesses a variety of functions such as prevention of tumor proliferation and treatment of cancer. However, AA, is very sensitive to air, heat and light. Its high hydrophilicity also makes the controlled delivery difficult. To overcome these problems, AA can be chemically-modified and made more hydrophobic by the esterification. Palmitic acid is one of the most common long-chain fatty acids that can be used for this purpose. It is known that Ascorbyl palmitate (AP) which is a lipopihilic derivative of AA, can inhibit cell proliferation and DNA synthesis in many types of cancer. Although AP has higher stability, its bioavailability and therapeutic effect is low due to its lipophilicity and low release capacity.
•In this study, nanostructured lipid carriers (NLC) which are colloidal nanoparticles with high biocompatibility, low crystallinity and high hydrophobic-drug encapsulation capacity was prepared to increase the bioavailability of AP.
•To provide triggered drug release via hyperthermia, magnetic nanoparticles (MNps) were integrated into the NLCs besides AP.
•The synthesis of biocompatible NLCs with controlled and triggered release ability, is successfully completed and controlled release of AP as an antitumor agent is achieved.
Heterogeneous Fenton catalysts are emerging as excellent materials for applications related to water purification. In this review, recent trends in the synthesis and application of heterogeneous Fenton catalysts for the abatement of organic pollutants and disinfection of microorganisms are discussed. It is noted that as the complexity of cell wall increases, the resistance level towards various disinfectants increases and it requires either harsh conditions or longer exposure time for the complete disinfection. In case of viruses, enveloped viruses (e.g. SARS-CoV-2) are found to be more susceptible to disinfectants than the non-enveloped viruses. The introduction of plasmonic materials with the Fenton catalysts broadens the visible light absorption efficiency of the hybrid material, and incorporation of semiconductor material improves the rate of regeneration of Fe(II) from Fe(III). A special emphasis is given to the use of Fenton catalysts for antibacterial applications. Composite materials of magnetite and ferrites remain a champion in this area because of their easy separation and reuse, owing to their magnetic properties. Iron minerals supported on clay materials, perovskites, carbon materials, zeolites and metal-organic frameworks (MOFs) dramatically increase the catalytic degradation rate of contaminants by providing high surface area, good mechanical stability, and improved electron transfer. Moreover, insights to the zero-valent iron and its capacity to remove a wide range of organic pollutants, heavy metals and bacterial contamination are also discussed. Real world applications and the role of natural organic matter are summarised. Parameter optimisation (e.g. light source, dosage of catalyst, concentration of H2O2 etc.), sustainable models for the reusability or recyclability of the catalyst and the theoretical understanding and mechanistic aspects of the photo-Fenton process are also explained. Additionally, this review summarises the opportunities and future directions of research in the heterogeneous Fenton catalysis.
Reactive oxygen species (ROS) play an important role in various physiological processes of living organisms. However, their increased concentration is usually considered as a threat for our health. Plants, invertebrates, and vertebrates including humans have various enzymatic and non-enzymatic defence systems against reactive oxygen species. Unfortunately, both bad condition of surrounding environment and unhealthy lifestyle can interfere with an activity of enzymes responsible for a regulation of ROS levels. Therefore, it is important to look for alternative ROS scavengers, which could be administrated to chosen tissues to prevent pathological processes such as distortion of DNA or RNA structures and oxidation of proteins and lipids. One of the most recently proposed solutions is the application of nanozymes, which could mimic the activity of essential enzymes and prevent excessive activity of ROS. In this work, nanoparticles of Au, Pt, Pd, Ru and Rh were synthesized and studied in this regard. Peroxidase-, catalase- and superoxide dismutase-like activity of obtained nanoparticles were tested and compared using different methods. The influence of bovine and human albumins on catalase- and peroxidase-like activity was examined. Moreover, in the case of catalase-like activity, an influence of pH and temperature was examined and compared. Determination of superoxide dismutase-like activity using the methods described for the examination of the activity of native enzyme was not fully successful. Moreover, cytotoxicity of chosen nanoparticles was studied on both regular and tumor cells.
Micro/nanomachines have attracted extensive attention in the biomedical and environmental fields for realizing functionalities at small scales. However, they have been rarely investigated as active nanocatalysts. Heterogeneous nanocatalysts have exceptional reusability and recyclability, and integration with magnetic materials enables their recovery with minimum loss. Herein, we propose a model active nanocatalyst using magnetic nanomotor ensembles (MNEs) that can degrade contaminants in an aqueous solution with high catalytic performance. MNEs composed of a magnetite core coated with gold nanoparticles as the nanocatalyst can rotate under the action of a programmable external field and carry out rapid reduction of 4-nitrophenol (4-NP). The hydrogen bubbles generated in the catalytic reaction provide random perturbations for the MNEs to travel in the reaction solution, resulting in uniform processing. The reduction can be further boosted by irradiation with near-infrared (NIR) light. Magnetic field induces the rotation of the MNEs and provides microstirring in the catalysis. Light enhances the catalytic activity via the photothermal effect. These MNEs are also capable of moving to the targeted region through the application of a programmable magnetic field and then process the contaminant in the targeted region. We expect that such magnetic MNEs may help better in applying active heterogeneous nanocatalysts with magnetic field and light-enhanced performance in industrial applications due to their advantages of low material cost and short reaction time.
Self‐propelled micro‐ and nanomotors (MNMs) have shown great potential for applications in the biomedical field, such as active targeted delivery, detoxification, minimally invasive diagnostics, and nanosurgery, owing to their tiny size, autonomous motion, and navigation capacities. To enter the clinic, biomedical MNMs request the biodegradability of their manufacturing materials, the biocompatibility of chemical fuels or externally physical fields, the capability of overcoming various biological barriers (e.g., biofouling, blood flow, blood–brain barrier, cell membrane), and the in vivo visual positioning for autonomous navigation. Herein, the recent advances of synthetic MNMs in overcoming biological barriers and in vivo motion‐tracking imaging techniques are highlighted. The challenges and future research priorities are also addressed. With continued attention and innovation, it is believed that, in the future, biomedical MNMs will pave the way to improve the targeted drug delivery efficiency. Synthetic micro‐/nanomotors (MNMs) with efficient autonomous motion and drug‐transport capabilities are recognized as the next generation of diagnostic and therapeutic systems. Recent progress of MNMs in overcoming biological barriers and in vivo motion‐tracking imaging technologies are summarized. The challenges and perspectives for developing biomedical MNMs are presented.
With the advent of small-scale robotics, several exciting new applications like Targeted Drug Delivery, single cell manipulation and so forth, are being discussed. However, some challenges remain to be overcome before any such technology becomes medically usable; among which propulsion and biocompatibility are the main challenges. Propulsion at micro-scale where the Reynolds number is very low is difficult. To overcome this, nature has developed flagella which have evolved over millions of years to work as a micromotor. Among the microscopic cells that exhibit this mode of propulsion, sperm cells are considered to be fast paced. Here, we give a brief review of the state-of-the-art of Spermbots—a new class of microrobots created by coupling sperm cells to mechanical loads. Spermbots utilize the flagellar movement of the sperm cells for propulsion and as such do not require any toxic fuel in their environment. They are also naturally biocompatible and show considerable speed of motion thereby giving us an option to overcome the two challenges of propulsion and biocompatibility. The coupling mechanisms of physical load to the sperm cells are discussed along with the advantages and challenges associated with the spermbot. A few most promising applications of spermbots are also discussed in detail. A brief discussion of the future outlook of this extremely promising category of microrobots is given at the end.
Janus particles represent a unique group of patchy particles combining two or more different physical or chemical functionalities at their opposite sides. Especially, individual Janus particles (JPs) with both chemical and geometrical anisotropy as well as their assembled layers provide considerable advantages over the conventional monofunctional particles or surfactant molecules offering (a) a high surface-to-volume ratio; (b) high interfacial activity; (c) target controlling and manipulation of their interfacial activity by external signals such as temperature, light, pH, or ionic strength and achieving switching between stable emulsions and macro-phase separation; (d) recovery and recycling; (e) controlling the mass transport across the interface between the two phases; and finally (f) tunable several functionalities in one particle allowing their use either as carrier materials for immobilized catalytically active substances or, alternatively, their site-selective attachment to substrates keeping another functionality active for further reactions. All these advantages of JPs make them exclusive materials for application in (bio-)catalysis and (bio-)sensing. Considering “green chemistry” aspects covering biogenic materials based on either natural or fully synthetic biocompatible and biodegradable polymers for the design of JPs may solve the problem of toxicity of some existing materials and open new paths for the development of more environmentally friendly and sustainable materials in the very near future. Considering the number of contributions published each year on the topic of Janus particles in general, the number of contributions regarding their environmentally friendly and sustainable applications is by far smaller. This certainly pinpoints an important challenge and is addressed in this review article. The first part of the review focuses on the synthesis of sustainable biogenic or biocompatible Janus particles, as well as strategies for their recovery, recycling, and reusability. The second part addresses recent advances in applications of biogenic/biocompatible and non-biocompatible JPs in environmental and biotechnological fields such as sensing of hazardous pollutants, water decontamination, and hydrogen production. Finally, we provide implications for the rational design of environmentally friendly and sustainable materials based on Janus particles.
Graphical abstract
Nano‐ and micromotors are fascinating objects that can navigate in complex fluidic environments. Their active motion can be triggered by external power sources or they can exhibit self‐propulsion using fuel extracted from their surroundings. The research field is rapidly evolving and has produced nano/micromotors of different geometrical designs, exploiting a variety of mechanisms of locomotion, being capable of achieving remarkable speeds in diverse environments ranging from simple aqueous solutions to complex media including cell cultures or animal tissue. This review aims to provide an overview of the recent developments with focus on predominantly experimental demonstrations of the various motor designs developed in the past 24 months. First, externally driven motors are discussed followed by considering fuel‐driven approaches. Finally, a short future perspective is provided. This review outlines the recent developments of nano‐ and micromotors, focusing on examples from the past 24 months. These motors employ external power sources such as magnetic fields, ultrasound, and light. Alternately, they can self‐propel using catalytic surfaces and environmental fuel or self‐disintegration. In both cases, fast locomotion in complex environments is illustrated.
Bicompartmental Janus particles have many advantages in drug delivery, including co-delivery of two compounds with varying solubilities, differential release kinetics, and two surfaces available for targeting ligands. We present a novel strategy using the double emulsion method for the coencapsulation and staggered release of a hydrophobic and hydrophilic drug from anisotropic PLGA/PCL Janus particles, as well as a UV detection method to measure the release of two different compounds from Janus particles. Curcumin and quercetin were chosen as the model hydrophobic compounds for drug loading studies, while acetaminophen (APAP) and naproxen were chosen as the model hydrophilic–hydrophobic drug pair for encapsulation methods and drug loading. Also, a similar double emulsion method was also applied for PLGA/Preicrol® Janus particles containing Doxorubicin and Curcumin. Hydrophobic drugs were encapsulated by the single O/W emulsion technique. Hydrophilic compounds required special modifications due to their poor oil solubility and tendency to escape to the outer aqueous phase during the emulsification and solvent evaporation steps. In total, three different strategies for incorporating hydrophilic drugs were employed: (1) O/W emulsion with partially water miscible solvent, (2) O/W emulsion with co-solvent (i.e. acetone, methanol, ethanol), or (3) W/O/W double emulsion. The encapsulation efficiencies and drug loading percentages were measured using UV/Vis spectroscopy and compared for the different synthesis methods. It was found that the double emulsion method resulted in the highest encapsulation efficiency and drug loading of the hydrophilic drug.
Electromagnetic interference (EMI) is the phenomenon occurring in remotely piloted aircraft systems, especially in the radio-frequency band emitted by motors and power supplies, that needs to be shielded in order to avoid disturbances in communication signals. This paper presents a solution to this problem in the form of EMI shielding housing based on electrically conducting epoxy resins filled with polyaniline (PANI) and polypyrrole (PPy). For this purpose, PANI and PPy were synthesized and characterized to achieve effective EMI shielding of the resulting composite materials and reinforced with carbon fabric. Optimized materials were then used as EMI shielding housing for a remotely piloted aircraft system. The obtained results of electromagnetic compatibility tests showed the ability of damping of both manufactured composites, especially in the range of 30–35 MHz, where damping was the highest, with the average difference between conducting and non-conducting composites of ca. 20 dBµV/m.
This paper presents the key role of Cu2O in Fenton catalysis using Cu2O–CuFe2O4 magnetic microparticles, which were prepared using Fenton sludge as an iron source. The catalytic activity of the as-prepared Cu2O–CuFe2O4 and CuFe2O4 microparticles was evaluated in a heterogeneous Fenton system for the degradation of recalcitrant phenol. The Cu2O–CuFe2O4 microparticles demonstrated relatively superior catalytic performance as compared to CuFe2O4 microparticles when used as a Fenton catalyst. The relatively higher catalytic activity of Cu2O–CuFe2O4 for phenol degradation during the Fenton process could be attributed to the availability of both monovalent [Cu(I)] and divalent [Cu(II)] as well as Fe(II)/Fe(III) redox pairs, which could react quickly with H2O2 to generate hydroxyl radicals (HO˙). An electron bridge was formed between Cu(I) and Fe(III), which accelerates the formation of Fe(II) species in order to boost the reaction rate. Highly reactive and excessively available Cu(I) species for as prepared Cu2O–CuFe2O4 microparticles could be considered to be rather crucial for the generation of highly reactive HO˙ radical species. In addition, the as-prepared Cu2O–CuFe2O4 magnetic microparticles exhibited sound stability and reusability.
Systems capable of precise motion in the vasculature can offer exciting possibilities for
applications in targeted therapeutics and non-invasive surgery. So far, the majority of the
work analysed propulsion in a two-dimensional setting with limited controllability near
boundaries. Here we show bio-inspired rolling motion by introducing superparamagnetic
particles in magnetic and acoustic fields, inspired by a neutrophil rolling on a wall. The
particles self-assemble due to dipole–dipole interaction in the presence of a rotating magnetic
field. The aggregate migrates towards the wall of the channel due to the radiation force of an
acoustic field. By combining both fields, we achieved a rolling-type motion along
the boundaries. The use of both acoustic and magnetic fields has matured in clinical settings.
The combination of both fields is capable of overcoming the limitations encountered by single
actuation techniques. We believe our method will have far-reaching implications in targeted
therapeutics.
Breast cancer is one of the fatal diseases renowned worldwide. Chemotherapy is not sufficient for the treatment of breast cancer in a significant number of cases. In this study, we present the doxorubicin (DOX) and gold nanoparticles (AuNPs) loaded nanostructured lipid carriers (DOX+AuNPs)@NLCs, designed for dual chemo/photothermal therapy. Different geometries of AuNPs (gold nanospheres (AuNSs), gold nanorods (AuNRs), and gold nanocubes (AuNCs)) were also loaded in NLCs to exploit their photothermal heating capacity and to conceptualize the most efficient combination of drug delivery system for combined therapy. The light-triggered on-demand release of DOX from NLCs was examined before and after NIR irradiation (808 nm). The highest heating potential was obtained via AuNRs with ∆T=22 o C in 5 min with µg Au/mg lipid. The cytotoxic effect of these formulations was evaluated on MDA-MB-231 breast cancer cells and the highest growth inhibition (81%) is achieved with (DOX+AuNRs)@NLC under 5 min NIR application. It is found that the geometry directly effects the photothermal capability of AuNPs, a synergistic interaction between cytotoxic action of DOX and local hyperthermia provided by AuNPs can significantly enhance the skills on the irreversible cellular damage and developed state-of-art formulations hold a great potential as a combined-cancer-therapy agent. Thus, this study offers promise for the development of a lipid-based nano-platform that is biocompatible, multifunctional, and can be utilized for combined therapy, with tunable properties.
A hetero-Fenton zeolite-supported Fe3O4 catalyst was synthesized using a simple impregnation–precipitation method. The structure, morphology, and components of the catalyst were characterized using various analytical methods (XRD, SEM, and ICP-MS). Subsequently, the catalyst was used to degrade the azo dye methylene blue (MB), via a heterogeneous photo-Fenton process under UV irradiation in an aqueous solution. This study investigated the influence of different parameters on MB decolorization efficiency, such as the initial concentration of hydrogen peroxide, amount of catalyst, initial dye concentration, and reusability of the catalyst. The removal efficiency was nearly 100% within only 5 min with an initial concentration of methylene blue of 50 mg L⁻¹ under the following experimental conditions: a pH solution of 3, a catalyst of 0.6 g L⁻¹, an H2O2 concentration of 66 mg L⁻¹, and a UV lamp power of 6 W. Moreover, the Fe3O4/zeolite A catalyst (Fe/ZA) showed good stability in the photo-Fenton degradation of methylene blue after four consecutive cycles, implying that the Fe/ZA catalyst could be a potential wastewater treatment option. Furthermore, the findings of the reaction kinetics study demonstrate that the kinetics of the dye removal reaction can be fitted using the Langmuir–Hinshelwood model for heterogeneous catalytic reactions.
In nature, all creatures have their unique characteristics that allow them to adapt to the complex and changeable living environments. In recent years, bionic fish has received increased attention from the research community, and many fish-like microrobots driven by the Marangoni effect have been developed. They are generally characterized by easy operation and rapid driving. However, traditional fish-like microrobots can only be driven by a single stimulus and move on two-dimensional (2D) gas-liquid interfaces, which greatly limits their ability in obstacle avoidance and transportation. In this article, we propose a multi-stimulus-responsive bionic fish microrobot, which is made of temperature-responsive hydrogel poly(N-isopropylacrylamide) (pNIPAM). This microrobot is impregnated with carbon nanotubes (CNTs) and Fe3O4 and therefore has magnetic and photothermal conversion properties. Under the action of optical, magnetic or ethanol molecules, the microrobot can perform complex programmable translational motion on 2D surfaces and controllable rising and sinking, while realizing motion simulation and obstacle avoidance. The microrobot is expected to be used for a wide range of applications in intelligent control systems.
Micro/nanomotors have emerged as a vibrant research topic in biomedical and environmental fields due to their attractive self-propulsion as well as small-scale functionalities. However, single actuated micro/nanomotors are not adaptive in facing intricate natural and industrial environments. Herein, we propose a new dual-mode-driven micromotor based on foam-like carbon nitride (f-C3N4) with precipitated Fe3O4 nanoparticles, namely, Fe3O4/f-C3N4, powered by chemical/magnetic stimuli for rapid reduction of organic pollutants. The Fe3O4/f-C3N4 motor composed of a three-dimensional (3D) porous "foam-like" structure and precipitated Fe3O4 nanoparticles (ca. 50 nm) not only exhibits efficient photocatalytic performance under visible light but also shows versatile and programmable motion behavior under the control of external magnetic fields. The aggregation of the micromotor under an external rotating magnetic field further enhances the catalytic activity by the increased local catalyst concentration. Furthermore, the magnetic property endows the micromotor with easy recyclability. This study provides a novel dual-mode-driven micromotor for antibiotics removal with magnetic field and light-enhanced performance in industrial wastewater treatment at a low cost.
The light harvesting capacity and thermal conductivity properties of photothermal materials play a vital role in the photothermal conversion. However, most materials do not possess both of these characteristics simultaneously or efficiently. Here, we design a composite material with both light harvesting capacity and thermal conductivity properties, which polypyrrole is loaded on the surface of boron nitride to form h-BN/PPy composites. The photothermal conversion efficiency can reach 82.84% when the concentration is 0.05 wt%. While combining this composite with PVA-1799 can form a hybrid membrane, which can still exhibits high photothermal conversion performance.
A general approach is proposed to large scale synthesize multi-stimuli responsive bottlebrush-colloid Janus nanoparticles (JNPs) by preferentially tuning the composition of a single chain nanoparticle (SCNP). The starting SCNP is...
Metal-containing covalent organic frameworks (MCOFs), as a class of crystalline organic polymers with abundant single-atom metal sites, can respond effectively to various vital reactions, including hydrogen evolution reaction (HER), CO2 reduction reaction (CO2RR), oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The advent of MCOFs provides a platform for the establishment of model catalysts with highly repetitive structure to facilitate theoretical calculations and high-throughput screening while designing flexibility in monomer construction to lay the foundation for the development of highly selective and active photo/electrocatalysts. In this review, we summarize the recent progress in this field and highlight several important MCOFs photo/electrocatalysts for OER, ORR, HER, and CO2RR. Moreover, various approaches are also mentioned to improve or optimize the catalysts and indicate the future research direction on enhancing the performance of MCOFs catalysts based on the current existing challenges.Graphical abstract
In the past decade, the field of micromotor has undergone tremendous progresses. The autonomous and controlled motion of the micromotors inside a liquid environment makes them potentially attractive for various fields including environmental remediation, the biomedical application, etc. In addition to the micromotors based on non-responsive materials, those based on stimuli-responsive polymers have recently attracted more and more attentions due to their functional versatility and stimuli responsiveness. In this review, we summarize the recent advances in the field of stimuli-responsive polymer based micromotor. Based on the stimuli responsiveness originating from the stimuli-responsive polymer components inside the micromotors, we highlight the unprecedented properties of the stimuli-responsive polymer based micromotors and elaborate the potential applications in various fields ranging from sensing to logic gate and the biomedical field, etc.
The ability to tune shapes of micromotors is challenging yet crucial for creating intelligent and functional micromachines with shape-dependent dynamics. Here, we demonstrate a facile strategy to synthesize Janus micromotors in large quantity whose shapes can be precisely tuned by a surfactant-induced dewetting strategy. The Janus micromotor is composed of a TiO2 microparticle partially encapsulated within a polysiloxane microsphere. A range of particle shapes, from approximately spherical to snowman, is achieved, and the shape-tunable dynamics of the micromotors are quantified. Our strategy is versatile and can be applicable to other photoactive materials, such as ZnO and Fe2O3 nanoparticles, demonstrating a general approach to synthesize Janus micromotors with controllable shapes. Such shape-tunable micromotors provide colloidal model systems for fundamental research on active matter, as well as building blocks for the fabrication of micromachines.
Synthetic soft matter systems, when driven beyond equilibrium by active processes, offer the potential to achieve dynamical states and functions of a complexity found in living matter. Emulsions offer the basis of a simple yet versatile system for identification of the physicochemical principles underlying active soft matter, but how multiple internal phases within emulsion droplets (e.g., Janus morphologies) organize to impact emergent dynamics is not understood. Here, we create multiphase oil droplets with ultralow interfacial tensions but distinct viscosities, and drive them into motion in aqueous micellar solutions. Preferential solubilization of select components of the oil both drives the droplet motion and yields a progression of internal phase morphological states with distinct symmetries. We find the active droplets to exhibit five dynamical states during morphogenesis. By quantifying microscopic flow fields, we show that it is possible to map the diverse droplet behaviors to squirmer models of spherical microswimmers in Stokes flow, thus showing that multiphase droplets offer the basis of a versatile platform with which to study and engineer the hydrodynamics of microswimmers.
Because of micro/nanoscale manipulation and task-performing capability, micro/nanomotors (MNMs) have attracted lots of research interests for potential applications in biomedical and environmental applications. Owing to the low-cost, good motion behavior, and environmental friendliness, various low-cost metal oxides based MNMs become promising alternatives to the precious metal based MNMs, in particular for environmental remediation applications. Hereby, we demonstrate the facile and scalable fabrication of two types of bubble-propelled iron oxides-MnO2 core-shell micromotors (Fe3O4-MnO2 and Fe2O3-MnO2) for pollutant removal. The Fe2O3-MnO2 micromotor exhibits efficient removals of both aqueous organics and suspended microplastics via the synergy of catalytic degradation, surface adsorption, and adsorptive bubbles separations mechanisms. The adsorptive bubbles separation achieved more than 10% removal of the suspended microplastics from the polluted water in 2 h. We clarified the major contributions of different remediation mechanisms in pollutants removals, and the findings may be beneficial to a wide range of environmental applications of MNMs.
Rod-shaped nanoparticles have been reported to exhibit improved cellular uptake, intracellular processing and transport through tissues and organs, as compared to spherical nanoparticles. We use C-S-B triblock polypeptides composed of a collagen-like block (C), a silk-like block (S) and an oligolysine domain (B) for one-dimensional co-assembly with siRNA into rod-shaped nanoparticles. Here we investigate these siRNA encapsulating rod-shaped nanoparticles as a gene delivery system. Uptake experiments for C-S-B and C-S-B/siPlk1 particles indicate that these rod-shaped nanoparticles can efficiently deliver siPlk1 into HeLa cells. Moreover, C-S-B/siPlk1 complexes display significant mPlk1 gene knockdown in a dose-dependent manner, causing apoptosis as intended. The lower effectiveness of C-S-B/siPlk1 in inducing cell death as compared to cationic lipid-based formulations is explained by the high lysosome-C-S-B/siPlk1 co-localization ratio, which will need to be addressed in a future redesign of polypeptide sequence. Overall, the non-toxic and unique rod-shaped C-S-B nanoparticles deserve further optimization as a new siRNA delivery system for cancer therapy.
Polymer Janus particles (PJPs) have been extensively investigated due to their intriguing features which cannot be achieved in traditional counterparts. Chiral polymer particles also have constituted a unique research area in polymer science. However, how to construct PJPs derived from chiral polymers, especially chiral helical polymers, still remains as a significant academic challenge. This contribution reports the first success in preparing optically active PJPs constructed by chiral helical substituted polyacetylene via emulsion polymerization combined with solvent evaporation to induce phase separation. In the emulsion polymerization systems, polymethyl methacrylate worked as template and separated from polyacetylene domains in the course of acetylenic monomers’ polymerization and evaporation of solvent, by which optically active PJPs were formed. Major affecting factors were explored to elucidate their effects on the formation and morphology of PJPs. Mushroom- and bowl-like PJPs were obtained. Scanning electron microscopic images ascertain non-spherical morphologies of the obtained PJPs. Circular dichroism and UV-vis absorption spectra demonstrate their optical activity, which is originated in the predominantly one-handed helical polyacetylene chains constructing the PJPs. A formation mechanism was then proposed for understanding this unprecedented type of PJPs.
Mucus is a viscoelastic biological hydrogel that protects the epithelial surface from penetrating by most nanoparticles, which limits the efficiency of oral drug delivery. Pursuing highly efficient, biocompatible and biodegradable oral drug vehicles is of central importance to the development of promising nanomedicine. Here, we prepared five peptosomes (PSs) with various sizes, shapes and rigidities based on self-assembly of amphiphilic α-lactalbumin (α-lac) peptides from partial enzymolysis and cross-linking. The mucus permeation of α-lac PSs and release of curcumin (Cur) encapsulated in these PSs were evaluated. Compared with long nanotube (LNT), big nanosphere (BNS), small nanosphere (SNS) and crosslinked short nanotube (CSNT), we demonstrated that short nanotube (SNT) exhibits excellent permeability in mucus, which enables it to arrive at epithelial cells quickly. Besides, SNT exhibits the highest cellular uptake and transmembrane permeability on Caco-2/HT29-MTX (E12) 3D model. In vivo pharmacokinetic evaluation revealed that the SNT shows the highest curcumin bioavailability, which is 6.85-folds higher than free Cur. Most importantly, Cur-loaded SNT exhibits the optimum therapeutic efficacy for in vivo treatment of DSS-induced ulcerative colitis (UC). In the end, the mechanism of the high permeability of SNT through mucus was explained by coarse-grained molecular dynamics simulations, which indicated that short timescale jiggling and flying across pores of mucus network played key roles. These findings revealed the tubular α-lac PSs could be a promising oral drug delivery system targeted to mucosal for improving absorption and bioavailability of hydrophobic bioactive ingredients.
Controlling the complex dynamics of active colloids—the autonomous locomotion of colloidal particles and their spontaneous assembly—is challenging yet crucial for creating functional, out-of-equilibrium colloidal systems potentially useful for nano- and micro-machines. Herein, by introducing the synthesis of active “patchy” colloids of various low-symmetry shapes, we demonstrate that the dynamics of such systems can be precisely tuned. The low-symmetry patchy colloids are made in bulk via a cluster-encapsulation-dewetting method. They carry essential information encoded in their shapes (particle geometry, number, size, and configurations of surface patches, etc.) that programs their locomotive and assembling behaviors. Under AC electric field, we show that the velocity of particle propulsion and the ability to brake and steer can be modulated by having two asymmetrical patches with various bending angles. The assembly of mono-patch particles leads to the formation of dynamic and reconfigurable structures such as spinners and “cooperative swimmers” depending on the particle’s aspect ratios. Particle with two patches of different sizes allows “directional bonding”, a concept popular in static assemblies but rare in dynamic ones. With the capability to make tunable and complex shapes, we anticipate the discovery of a diverse range of new dynamics and structures when other external stimuli (e.g., magnetic, optical, chemical, etc.) are employed and spark synergy with shapes.
This work demonstrated a microfluidic preparation process for novel Janus microparticles with individual drug release properties in each compartment. A flow-focusing microfluidic chip was designed to produce oil-in-water droplets from a mixed solution of poly(lactic-co-glycolic acid) and a triglyceride type lipid. Based on solvent evaporation-induced phase separation, droplets evolved and were solidified into Janus particles, each of which had a polymer compartment and a lipid compartment. The ratio of the two compartments in a particle can be discretionarily regulated, and the particle structure can also be flexibly altered to Janus-patchy, triple, quadruple or core-shell type. Phase transition of the chosen lipid from solid to liquid would occur under physiological temperature, which was applied for rapid release of the loaded drug. The polymer compartment would undergo a slow degradation process in physiological environment, facilitating sustained drug release. Paclitaxel was loaded into Janus particles during preparation, and staged release was achieved, leading to a combination of rapid and sustained release, which is highly desired in target drug delivery. This study would start the application of hybrid Janus particles of polymer-lipid type with novel release kinetics in drug delivery systems.
Complete tumor regression is a great challenge faced by single therapy of near infrared (NIR)-triggered hyperthermia or vascular disrupting agents. An injectable nanocomposite (NC) hydrogel is rationally designed for combined anti-cancer therapy based on NIR-triggered hyperthermia and vascular disruption. The NC hydrogel, co-delivered with Prussian blue (PB) nanoparticles and combretastatin A4 (CA4), has good shear-thinning, self-recovery and excellent photothermal property. Due to the remarkable tumor-site retention and sustained release of CA4 (about 10% over 12 days), the NC hydrogel has a tumor suppression rate of 99.6%. The programmed combinational therapy conveys a concept of “attack + guard”, where PB-based NIR irradiation impose intensive attack on most of cancer cells, and CA4 serves as guard against the tumor growth by cutting off the energy supply. Moreover, the biosafety and eco-friendliness of the hydrogel platform pave the way towards clinical application.
The catalytic activity of non-spherical shaped Fe3O4 nanoparticles synthesized by low cost co-precipitation method was tested. It was presented, that magnetite nanoparticles can be used to degrade not only Rhodamine B and Methylene Blue, but above all cancerogenic azo dye – Sudan I. It was confirmed, that the degradation of Rhodamine B can be described by pseudo-zero-order kinetic model, whereas degradation of Methylene Blue by pseudo-first-order kinetic model. The degradation mechanism of Sudan I by photo-Fenton reaction was proposed. It was noted, that this double-stage process can be associated with hydroxylation of Sudan I and degradation of derivates, such as 4′‑OH‑Sudan I and 6‑OH‑Sudan I. Therefore, it cannot be simple describe by one kinetic model. The introduction of hydroxyl group results in an increase of the absorbance, which in turn is associated with hyperchromic effect.
Micro/nanomotors that could convert chemical energy into autonomous motion to perform various tasks are the most active research areas in chemical engineering. Up to now, the majority of micromotors require complex procedures and expensive Pt as catalyst for propulsion, which hinder seriously their practical application. Herein, we demonstrate a facile biotemplate route to synthesize a novel Pt-free temperature-responsive micromachine with fascinating recognition, capture and release capacities for erythromycin in water based on the integration of surface imprinted technology, the temperature-response of poly (N-isopropylacrylamide) (PNIPAM) hydrogels, and the autonomous motion ability of micromotor. The resulting Janus micromotor not only exhibited high temperature-controlled recognition and adsorption capacities than most reported erythromycin-imprinted materials, but also revealed high trajectory control ability and easy recovery by an external magnetic field, showing great potential for biomedical and water purification applications.
Engines and motors are everywhere in the modern world, but it is a challenge to make them work if they are very small. On the micron length scale, inertial forces are weak and conventional motor designs involving, e.g., pistons, jets, or flywheels cease to function. Biological motors work by a different principle, using catalysis to convert chemical to mechanical energy on the nanometer length scale. To do this, they must apply force continuously against their viscous surroundings, and because of their small size, their movement is “jittery” because of the random shoves and turns they experience from molecules in their surroundings.
It is known that rod-like nanoparticles (NPs) can achieve higher diffusivity than their spherical counterparts in biological porous media such as mucus and tumor interstitial matrix, but the underlying mechanisms still remain elusive. Here, we present a joint experimental and theoretical study to show that the aspect ratio (AR) of NPs and their adhesive interactions with the host medium play key roles in such anomalous diffusion behaviors of nanorods. In an adhesive polymer solution/gel (e.g., mucus), hopping diffusion enables nanorods to achieve higher diffusivity than spherical NPs with diameters equal to the minor axis of the rods, and there exists an optimal AR that leads to maximum diffusivity. In contrast, the diffusivity of nanorods decreases monotonically with increasing AR in a non-adhesive polymer solution/gel (e.g., hydroxyethyl cellulose, HEC). Our theoretical model, which captures all the experimental observations, generalizes the so-called obstruction-scaling model by incorporating the effects of the NPs/matrix interaction via the mean first passage time (MFPT) theory. This work reveals the physical origin of the anomalous diffusion behaviors of rod-like NPs in biological gels and may provide guidelines for a range of applications that involve NPs diffusion in complex porous media.