Polyoxometalate-Nanozyme-Integrated Nanomotors (POMotors) for Self-Propulsion-Promoted Synergistic Photothermal-Catalytic Tumor Therapy

Enzyme-powered nanomotors have demonstrated promising potential in biomedical applications, especially for catalytic tumor therapy, owing to their ability of self-propulsion and bio-catalysis. However, the fragility of natural enzymes limits their environmental adaptability and also therapeutic efficacy in catalysis-enabled tumor therapy. Herein, polyoxometalate-nanozyme-based light-driven nanomotors were designed and synthesized for targeted synergistic photothermal-catalytic tumor therapy. In this construct, the peroxidase-like activity of the P2 W18 Fe4 polyoxometalates-based nanomotors can provide self-propulsion and facilitate their production of reactive oxygen species thus killing tumor cells, even in the weakly acidic tumor microenvironment. Conjugated polydopamine endows the nanomotors with the capability of light-driven self-propulsion behavior. After 10 min of NIR (808 nm) irradiation, along with the help of epidermal growth factor receptor antibody, the targeted accumulation and penetration of nanomotors in the tumor enabled highly efficient synergistic photothermal-catalytic therapy. This approach overcomes the disadvantages of the intrinsically fragile nature of enzyme-powered nanomotors in physiological environments and, more importantly, provides a motility-behavior promoted synergistic anti-tumor strategy.

Light-Switchable Biocatalytic Covalent-Organic Framework Nanomotors for Aqueous Contaminants Removal

Self-propelled nanomotors represent a promising class of adaptable and versatile technologies with broad applications in the realms of biomedicine and environmental remediation. Herein, we report a biocatalytic nanomotor based on a covalent-organic framework (COF) that demonstrates intelligent and switchable motion triggered by a blue-to-red light switch. Consequently, when exposed to blue light, the nanomotor significantly enhances the removal of contaminants in aqueous solutions due to its elevated mobility. Conversely, it effectively deactivates its motion and contaminant removal upon exposure to red light. This study explores the heterogeneous assembly strategy of the COF-based nanomotor and its light-controlled propulsion performance and provides a novel strategy for the regulation of movement, offering valuable insights for the design and practical applications of nanomotors.

Dual-source powered nanomotors coupled with dual-targeting ligands for efficient capture and detection of CTCs in whole blood and in vivo tumor imaging

Circulating tumor cells (CTCs) are important biomarkers in cancer diagnosis. However, the specific labeling of CTCs with high capture efficiency in whole blood remains a problem. Herein, a dual-source-driven nanomotor coupled with dual-targeting ligands (CD@NM) was designed for efficient capture, specific imaging and quantitative detection of CTCs. In both water and biological fluid, CD@NMs moved autonomously under the propulsion of a magnetic field and H2O2 solution, which improved the capture efficiency of CTCs to 97.50 ± 2.38%. More importantly, specific labeling of CTCs was achieved by fluorescence quenching and recovery of fluorescent carbon dots modified on the CD@NMs. As a result, the CD@NMs exhibited efficient CTC capture, specific CTC imaging and recognition in whole blood. CD@NMs were also successfully deployed in the specific imaging of tumor tissues in vivo. On this basis, CD@NMs are expected to provide a new platform for tumor diagnosis both in vitro and in vivo.

Effective myocardial infarction treatment by targeted accumulation of Sulforaphane using porous magnetic silica nanoparticles

Myocardial infarction (MI) is a common cardiovascular pathology that induces extensive sterile inflammation during its early stages, posing a severe threat to human health. Effectively modulating cardiac inflammation may improve post-MI outcomes. Unfortunately, owing to the side effects of therapeutic drugs and cardiac coronary artery occlusion, current MI drugs are sub-optimal for the clinical management of ischemic myocardia. Sulforaphane (SFN) has been adopted for MI treatment due to its myocardial protective effects and low toxicity. However, the targeted accumulation of SFN in infarcted areas remains challenging. Herein, porous magnetic silica nanoparticles (PMSNs) were synthesized and loaded with SFN to improve the specificity of targeted SFN delivery to infarcted areas in mouse models of MI. PMSNs loaded with SFN (PMSNs + SFN) decreased the levels of pro-inflammatory cytokines, thus leading to the improvement of cardiac function and cell survival without adverse effects. To further explore SFN's mechanisms of action in MI, a cellular (in vitro) model was established via oxygen and glucose deprivation (OGD). HSF1 and Nrf2 knockdown resulted in a decrease of SFN-induced HSP70 expression in OGD cells. Moreover, as a result of HSP70 knockdown, the pro-survival and anti-inflammatory effects of SFN were blocked in OGD cells. The level of pro-inflammatory cytokines decreased upon HSP70 overexpression, and cell survival rate increased under OGD conditions. In summary, the results confirm that PMSNs are capable of transporting SFN to infarcted areas in the myocardium, where the drug exerts cardioprotective effects against myocardial injury by up-regulating HSP70 through Nrf2/HSF1.

Nanomotors-loaded microneedle patches for the treatment of bacterial biofilm-related infections of wound

The biofilms formed by bacteria at the wound site can effectively protect the bacteria, which greatly weakens the effect of antibiotics. Herein, a microneedle patch for wound treatment is designed, which can effectively penetrate the biofilms in a physical way because of the penetration ability of the microneedles and the motion behavior of the nanomotors, and deliver bacterial quorum sensing inhibitor luteolin (Le) and nanomotors with multiple antibacterial properties within biofilms. Firstly, the nanomotors-loaded microneedle patches are prepared and characterized. The results of in vitro and in vivo experiments show that the microneedle patches have good biosafety and antibacterial properties. Among them, Le can inhibit the growth of biofilms. Further, under near-infrared (NIR) irradiation, the nanomotors loaded with photosensitizer ICG and nitric oxide (NO) donor L-arginine (L-Arg) can move in the biofilms under the double driving effect of photothermal and NO, and can give full play to the multiple anti-biological infection effects of photothermal therapy (PTT), photodynamic therapy (PDT) and NO, and finally realize the effective removal of biofilms and promote wound healing. The intervention of nanomotor technology has brought about a new therapeutic strategy for bacterial biofilm-related infection of wound.

Polydopamine nanomotors loaded indocyanine green and ferric ion for photothermal and photodynamic synergistic therapy of tumor

The limited penetration depth of nanodrugs in the tumor and the severe hypoxia inside the tumor significantly reduce the efficacy of photothermal-photodynamic synergistic therapy (PTT-PDT). Here, we synthesized a methoxypolyethylene glycol amine (mPEG-NH₂)-modified walnut-shaped polydopamine nanomotor (PDA-PEG) driven by near-infrared light (NIR). At the same time, it also loaded the photosensitizer indocyanine green (ICG) via electrostatic/hydrophobicinteractions and chelated with ferric ion (Fe³⁺). Under the irradiation of NIR, the asymmetry of PDA-PEG morphology led to the asymmetry of local photothermal effects and the formation of thermal gradient, which can make the nanomotor move autonomously. This ability of autonomous movement was proved to be used to improve the permeability of the nanomotor in three-dimensional (3D) tumor sphere. Fe³⁺ can catalyze endogenous hydrogen peroxide to produce oxygen, so as to overcome the hypoxia of tumor microenvironment and thereby generate more singlet oxygen to kill tumor cells. Animal experiments in vivo confirmed that the nanomotors had a good PTT-PDT synergistic treatment effect. The introduction of nanomotor technology has brought new ideas for cancer optical therapy.

Nanoengineering of biohybrid micro/nanobots for programmed biomedical applications

Biohybrid micro/nanobots have emerged as an innovative resource to be employed in the biomedical field due to their biocompatible and biodegradable properties. These are tiny nanomaterial-based integrated structures engineered in a way that they can move autonomously and perform the programmed tasks efficiently even at hard-to-reach organ/tissues/cellular sites. The biohybrid micro/nanobots can either be cell/bacterial/enzyme-based or may mimic the properties of an active molecule. It holds the potential to change the landscape in various areas of biomedical including early diagnosis of disease, therapeutics, imaging, or precision surgery. The propulsion mechanism of the biohybrid micro/nanobots can be both fuel-based and fuel-free, but the most effective and easiest way to propel these micro/nanobots is via enzymes. Micro/nanobots possess the feature to adsorb/functionalize chemicals or drugs at their surfaces thus offering the scope of delivering drugs at the targeted locations. They also have shown immense potential in intracellular sensing of biomolecules and molecular events. Moreover, with recent progress in the material development and processing is required for enhanced activity and robustness the fabrication is done via various advanced techniques to avoid self-degradation and cause cellular toxicity during autonomous movement in biological medium. In this review, various approaches of design, architecture, and performance of such micro/nanobots have been illustrated along with their potential applications in controlled cargo release, therapeutics, intracellular sensing, and bioimaging. Furthermore, it is also foregrounding their advancement offering an insight into their future scopes, opportunities, and challenges involved in advanced biomedical applications.

NIR-II Light Powered Asymmetric Hydrogel Nanomotors for Enhanced Immunochemotherapy

Nanomotors are appealing drug carriers, and the strength of the propelling force is important for their motion capability. Though high motion efficiency has been achieved with 808 nm light driven Janus-structured noble metal nanomotors, the NIR-I light penetration depth and material biocompatibility limit their broad application. Herein, we develop a 1064 nm NIR-II light driven asymmetric hydrogel nanomotor (AHNM) with high motion capability and load it with doxorubicin for enhanced immunochemotherapy. Magnetic field assisted photopolymerization generates an asymmetric distribution of Fe₃ O₄ @Cu₉ S₈ nanoparticles in the AHNM, producing self-thermophoresis as driving force under NIR-II irradiation. The AHNM is also functionalized with dopamine for the capture and retention of tumor-associated antigens to boost immune activation. The as-obtained NIR-II light driven AHNM has a high tumor tissue penetration capability and enhances immunochemotherapy, providing a promising strategy for cancer therapy.

How safe are magnetic nanomotors: From cells to animals

Helical magnetic nanomotors can be actuated using an external magnetic field and have potential applications in drug delivery, colloidal manipulation, and bio-microrheology. Recently, they have been maneuvered in biological environments such as vitreous humour, dentinal tubules, peritoneal fluid, stromal matrix, and blood, which are promising developments for clinical applications. However, their biocompatibility and biodistribution are vital parameters that must be assessed before further use. An extensive quantitative evaluation has been performed for these parameters for the first time through in vitro and in vivo experiments. Investigations of cell death, proliferation, and DNA damage ascertain that the motors are non-toxic. Also, an unbiased transcriptomic analysis affirms that the motors are not genotoxic till 20 motors/ cell. Toxicity studies in mice reveal that the motors show no signs of toxicity up to a dose of 55 mg/ kg body weight. Further, the biodistribution studies show that they remain in the blood circulation after injection and at later stages possibly adhere to the walls of the blood vessel because of adsorption. However, perfusion with physiological saline decreases this adsorption/adhesion. Overall, we demonstrate the biocompatibility of nanomotors in live cellular and organismal systems, and a systemic biodistribution analysis reveals organ-specific retention of motors.

Self-propelled nanomotors based on hierarchical metal-organic framework composites for the removal of heavy metal ions

The outstanding performance efficiency for the removal of heavy metal ions in solution is governed by various factors: (a) sufficient contact probability between heavy metal ions and the adsorbent, (b) convenient diffusion/accessibility of heavy metal ions to the surface and the interior of the adsorbent, and (c) abundant binding sites for heavy metal ions on the adsorbent. We designed an efficient MnFe₂O₄ @MIL-53 @UiO-66 @MnO₂ adsorbent for Pb(II) and Cd(II) removal. The adsorbents were fabricated by merging self-propelled nanomotors, exploiting hierarchical structure, and using a metal-organic framework (MOF) composite to simultaneously meet the three requirements. The sufficient contact probability between Pb(II)/Cd(II) and MnFe₂O₄ @MIL-53 @UiO-66 @MnO₂ was achieved via the self-propelled movement of MnFe₂O₄ @MIL-53 @UiO-66 @MnO₂ which was induced by the catalytic decomposition of H₂O₂ by MnO₂. The convenient diffusion/accessibility of Pb(II)/Cd(II) on the surface and interior of MnFe₂O₄ @MIL-53 @UiO-66 @MnO₂ was achieved by exploiting the properties of the hierarchical structure of MnFe₂O₄ @MIL-53 @UiO-66 @MnO₂. Abundant binding sites (-COOH) on MIL-53 and UiO-66 composites were present for the binding of the Pb(II)/Cd(II) ions to the adsorbent. The adsorption capacities of the nanomotor adsorbent for Pb(II) and Cd(II) were 1018 and 440.8 mg g^-1 at 25 °C, respectively. Additionally, the complex formed of MnFe₂O₄ and MIL-53 endowed the adsorbent with easy-recyclable properties under the influence of an external magnet. The nanomotors exhibit satisfactory removal performances for Pb(II) and Cd(II).

Fast approximative methods for study of ligand transport and rational design of improved enzymes for biotechnologies

Acceleration of chemical reactions by the enzymes optimized using protein engineering represents one of the key pillars of the contribution of biotechnology towards sustainability. Tunnels and channels of enzymes with buried active sites enable the exchange of ligands, ions, and water molecules between the outer environment and active site pockets. The efficient exchange of ligands is a fundamental process of biocatalysis. Therefore, enzymes have evolved a wide range of mechanisms for repetitive conformational changes that enable periodic opening and closing. Protein-ligand interactions are traditionally studied by molecular docking, whereas molecular dynamics is the method of choice for studying conformational changes and ligand transport. However, computational demands make molecular dynamics impractical for screening purposes. Thus, several approximative methods have been recently developed to study interactions between a protein and ligand during the ligand transport process. Apart from identifying the best binding modes, these methods also provide information on the energetics of the transport and identify problematic regions limiting the ligand passage. These methods use approximations to simulate binding or unbinding events rapidly (calculation times from minutes to hours) and provide energy profiles that can be used to rank ligands or pathways. Here we provide a critical comparison of available methods, showcase their results on sample systems, discuss their practical applications in molecular biotechnologies and outline possible future developments.

Photothermal interference urease-powered polydopamine nanomotor for enhanced propulsion and synergistic therapy

Enzyme-powered nanomotors with active motion have opened a new door in design of biocompatible drug delivery systems for cancer treatment. However, the movement of them still faces huge challenges due to the viscous physiological environment. To address this issue, we developed a photothermal interference (PTI) urease-modified polydopamine (PDA) nanomotor (PDA@HSA@Ur) for deeper-penetration of doxorubicin (DOX) through improved motion. The urease-powered nanomotors can generate self-propulsion via catalyzing decomposition of biocompatible urea into carbon dioxide and ammonia through a self-diffusiophoretic. Meanwhile, when exposed to near-infrared (NIR) laser, the increased temperature of tumors microenvironment from nanomotors can not only induce tumor cell apoptosis but also enhance the biocatalytic activity of urease to improve the motion of nanomotors. Compared to the nanomotors propelled only by urea, PTI nanomotors realize highly effective self-propulsion with improved cellular uptake in vitro. Furthermore, PTI nanomotors display an enhanced anticancer efficiency owing to synergistic photothermal and chemotherapy effect. The PTI reported in this manuscript is the first to provide a thermally assisted method for highly efficient cancer treatment with urease-powered nanomotors in a complex physiological environment through enhanced motion and synergistic therapy.

Torque-Driven Orientation Motion of Chemotactic Colloidal Motors

We report a direct experimental observation of the torque-driven active reorientation of glucose-fueled flasklike colloidal motors to a glucose gradient exhibiting a positive chemotaxis. These streamlined flasklike colloidal motors are prepared by combining a hydrothermal synthesis and a vacuum infusion and can be propelled by an enzymatic cascade reaction in the glucose fuel. Their flasklike architecture can be used to recognize their moving posture, and thus the dynamic glucose-gradient-induced alignment and orientation-dependent motility during positive chemotaxis can be examined experimentally. The chemotactic mechanism is that the enzymatic reactions inside lead to the glucose acid gradient and the glucose gradient which generate two phoretic torques at the bottom and the opening respectively, and thus continuously steer it to the glucose gradient. Such glucose-fueled flasklike colloidal motors resembling the chemotactic capability of living organisms hold considerable potential for engineering active delivery vehicles in response to specific chemical signals.

Nitric oxide-driven nanomotors with bowl-shaped mesoporous silica for targeted thrombolysis

Vein thrombosis is one of the most serious types of cardiovascular disease. During the traditional treatment, due to the excessive blood flow rate, the drug utilization rate at the thrombus site is low and the thrombolysis efficiency is poor. In this study, bowl-shaped silica nanomotors driven by nitric oxide (NO) are designed to target the thrombus surface by modifying arginine-glycine-aspartic acid (RGD) polypeptide, and simultaneously loading l-arginine (LA) and thrombolytic drug urokinase (UK) in its mesopore structure. LA can react with excessive reactive oxygen species (ROS) in the thrombus microenvironment to produce NO, thus promoting the movement of nanomotors to improve the retention efficiency and utilization rate of drugs in the thrombus site, and at the same time achieve the effect of eliminating ROS and reducing the oxidative stress of inflammatory endothelial cells. The loaded UK can dissolve thrombus quickly. It is worth mentioning that NO can not only be used as a power source of nanomotors, but also can be used as a therapeutic agent to stimulate the growth of endothelial cells and reduce vascular injury. This therapeutic agent based on nanomotor technology is expected to provide support for future research on thrombus treatment.

Recent development of autonomously driven micro/nanobots for efficient treatment of polluted water

Autonomously propelled micro/nanobots are one of the most advanced and integrated structures which have been fascinated researchers owing to its exceptional property that enables them to be carried out user-defined tasks more precisely even on an atomic scale. The unique architecture and engineering aspects of these manmade tiny devices make them viable options for widespread biomedical applications. Moreover, recent development in this line of interest demonstrated that micro/nanobots would be very promising for the water treatment as these can efficiently absorb or degrade the toxic chemicals from the polluted water based on their tunable surface chemistry. These auto propelled micro/nanobots catalytically degrade toxic pollutants into non-hazardous compounds more rapidly and effectively. Thus, for the last few decades, nanobots mediated water treatment gaining huge popularity due to its ease of operation and scope of guided motion that could be monitored by various external fields and stimuli. Also, these are economical, energy-saving, and suitable for large scale water treatment, particularly required for industrial effluents. However, the efficacy of these bots hugely relies on its design, characteristic of materials, properties of the medium, types of fuel, and surface functional groups. Minute variation for one of these things may lead to a change in its performance and hinders its dynamics of propulsion. It is deemed that nanobots might be a smart choice for using these as the new generation devices for treating industrial effluents before discharging it in the water bodies, which is a major concern for human health and the environment.

Self-propelling micro-/nano-motors: Mechanisms, applications, and challenges in drug delivery

In recent times, numerous efforts have been put forward to fabricating the self-propelling micro-/nano-motors (MNMs) for various applications, such as drug delivery, environmental remediation, biosensing, and precision surgery at the micro-/nanoscale, among others. Owing to their potential advantages, the application of such innovative architectures has been increasingly recognized towards addressing various challenges in the related fields. Specifically, these MNMs offer enormous potential in nanomedicine in overcoming the significant challenge of low permeation of the biological barriers. Herein, we emphasize the powered mechanism of MNMs, including artificial and natural-based MNMs, and discuss the characteristics, as well as the challenges being faced by MNMs in drug delivery. Further, the research progress of MNMs as drug carriers in different environments (gastrointestinal tract, saliva, urinary bladder, blood, and extracellular matrix, ECM) of the body in recent years is summarized, highlighting the representative works on MNMs towards in vivo applications. Together, we firmly believe that these innovative MNMs-based designs may play a crucial role in the clinical practice in the future.

Light-driven nanomotors and micromotors: envisioning new analytical possibilities for bio-sensing

The aim of this conceptual review is to cover recent developments of light-propelled micromotors for analytical (bio)-sensing. Challenges of self-propelled light-driven micromotors in complex (biological) media and potential solutions from material aspects and propulsion mechanism to achieve final analytical detection for in vivo and in vitro applications will be comprehensively covered. Graphical abstract.

Self-propelled cellulose nanocrystal based catalytic nanomotors for targeted hyperthermia and pollutant remediation applications

Inspired from biological motors, cellulose nanocrystals (CNCs) are strategically modified to induce self-propulsion behavior with the capabilities to catalytically degrade pollutants along with magnetic hyperthermia to clean arterial plaques during its course of propulsion. CNCs derived from renewable biomass, are decorated with catalytically active, magneto-responsive nanomaterials (Fe2O3/Pd nanoparticles) through sustainable routes. CNC nanomotors show improved propulsion at lowered peroxide concentrations with remotely controlled trajectory through chemo-magnetic field gradients and ideal surface-wettability characteristics, overcoming the requirement of surfactants, as with traditional nanomotors. We observed that nanomotors undergo motion through heterogeneous bubble propulsion mechanism, with capability to in situ degrade pollutants and generate local heat through hyperthermia, enhancing the rate of degradation process in real time. As proof of concept, we demonstrate that the dynamics of nanomotors can be controlled in a microfluidic channel through site-directed magnetic field and induction of pH gradient, mimicking the chemotaxis in cell-like environment and as swarm of nano-surgeons removes plaques from clogged arteries. Our study shows that strategic modification of CNCs results in fabrication of nanomotors with efficient propulsion system infused with multi-functional characteristics of high catalytic activity and magnetic hyperthermia which opens up new avenues for utilization of bio-based nanomotors derived from lignocellulose for myriad applications.

Micro and nanomotors in diagnostics

Synthetic micro/nanomotors are tiny devices than can be self-propelled or externally powered in the liquid phase by different types of energy source including but not limited to: catalytic, magnetic or acoustic. Showing a myriad of mechanical movements, building block materials, sizes, shapes and propulsion mechanisms micro/nanomotors are amenable to diagnostics and therapeutics. Herein we describe the most relevant micro/nanomotors, their fabrication pathways, propulsion strategies as well as in vivo and in vitro applications related with oligonucleotides, proteins, cells and tissues. We also discuss the main challenges in these applications such as the influence of complex media and toxicity issues as well as future perspectives.

Self-propelled affinity biosensors: Moving the receptor around the sample

Self-propelled nanomotors offer considerable promise for developing novel biosensing protocols involving 'on-the-fly' recognition events. This article reviews recent advances in using catalytic nanomotors for bioaffinity sensing and for isolating target biomolecules and cells from complex biological samples. A variety of receptors, attached to self-propelled nanoscale motors, can thus move around the sample and, along with the generated microbubbles, lead to greatly enhanced fluid transport and accelerated recognition process. Such operation addresses the challenges imposed by the slow analyte transport in designing sensitive bioaffinity assays. The recognition element can be attached onto the motor surface or embedded in the motor material itself. Receptor-functionalized nanomotors based on different biomolecular interactions have thus been shown extremely useful for rapid target isolation from complex biological samples without preparatory and washing steps. Tubular microengine microtransporters, functionalized with antibody, ss-DNA, aptamer or lectin receptors, are particularly useful for direct detection and isolation of proteins, nucleic acids, proteins or cancer cells. Micromotors with 'built-in' recognition, exploiting the selective binding properties of the outer layer of such micronegines, can also be used. Greatly enhanced analyte-receptor interactions can also be achieved through the increased fluid transport associated with the movement of unmodified micromotors. The attractive features of the new motion-based bioaffinity sensing and separation protocols open up new opportunities for diverse biomedical, environmental and security applications.