Magnetically Actuated Wormlike Nanomotors for Controlled Cargo Release

Micro/Nanomotor-Driven Intelligent Targeted Delivery Systems: Dynamics Sources and Frontier Applications

Micro/nanomotors represent a promising class of drug delivery carriers capable of converting surrounding chemical or external energy into mechanical power, enabling autonomous movement. Their distinct autonomous propulsive force distinguishes them from other carriers, offering significant potential for enhancing drug penetration across cellular and tissue barriers. A comprehensive understanding of micro/nanomotor dynamics with various power sources is crucial to facilitate their transition from proof-of-concept to clinical application. In this review, micro/nanomotors are categorized into three classes based on their energy sources: endogenously stimulated, exogenously stimulated, and live cell-driven. The review summarizes the mechanisms governing micro/nanomotor movements under these energy sources and explores factors influencing autonomous motion. Furthermore, it discusses methods for controlling micro/nanomotor movement, encompassing aspects related to their structure, composition, and environmental factors. The remarkable propulsive force exhibited by micro/nanomotors makes them valuable for significant biomedical applications, including tumor therapy, bio-detection, bacterial infection therapy, inflammation therapy, gastrointestinal disease therapy, and environmental remediation. Finally, the review addresses the challenges and prospects for the application of micro/nanomotors. Overall, this review emphasizes the transformative potential of micro/nanomotors in overcoming biological barriers and enhancing therapeutic efficacy, highlighting their promising clinical applications across various biomedical fields.

Progress on Physical Field-Regulated Micro/Nanomotors for Cardiovascular and Cerebrovascular Disease Treatment

Cardiovascular and cerebrovascular diseases (CCVDs) are two major vasculature-related diseases that seriously affect public health worldwide, which can cause serious death and disability. Lack of targeting effect of the traditional CCVD treatment drugs may damage other tissues and organs, thus more specific methods are needed to solve this dilemma. Micro/nanomotors are new materials that can convert external energy into driving force for autonomous movement, which can not only enhance the penetration depth and retention rates, but also increase the contact areas with the lesion sites (such as thrombus and inflammation sites of blood vessels). Physical field-regulated micro/nanomotors using the physical energy sources with deep tissue penetration and controllable performance, such as magnetic field, light, and ultrasound, etc. are considered as the emerging patient-friendly and effective therapeutic tools to overcome the limitations of conventional CCVD treatments. Recent efforts have suggested that physical field-regulated micro/nanomotors on CCVD treatments could simultaneously provide efficient therapeutic effect and intelligent control. In this review, various physical field-driven micro/nanomotors are mainly introduced and their latest advances for CCVDs are highlighted. Last, the remaining challenges and future perspectives regarding the physical field-regulated micro/nanomotors for CCVD treatments are discussed and outlined.

Synthesis of Candida Antarctica Lipase B (CALB) enzyme-powered magnetite nanomotor based on PCL/Chitosan Janus nanostructure

In this work, we report the design and synthesis of internal energy-driven Janus nanomotors (JNMs), which are composed of certain reactive materials that are capable of converting chemical energy in the backbone of nanomotors into kinetic energy. For this purpose, superparamagnetic iron oxide nanoparticles (SPIONs) with the anisotropic surface were obtained via a Pickering emulsion. Modified chitosan (as hydrophilic polymer) and functionalized polycaprolactone (as hydrophobic domain) were covalently linked to the surface of bi-functional SPIONs to produce Janus nanoparticles (JNPs). Then, the CALB enzyme was loaded in the PCL hemisphere of JNPs to form the Janus nanomotor. When nanomotors are placed in the phosphate-buffered saline solution, the driving force for motion is provided by the decomposition of polyester into monomers and oligomers on one side of the JNMs. The trajectories of the nanomotors were recorded under different circumstances by a video microscope and analyzed by the mean squared displacement. The results show that the velocity of JNMs increases with an increasing percentage of the loaded enzyme. In addition, the diffusion coefficient enhances up to 87.67% in compared with nanoparticles without enzyme. Controlling the motion direction of JNMs by an external magnetic field is also possible, due to the presence of SPIONs.

Core-Shell Structured Micro-Nanomotors: Construction, Shell Functionalization, Applications, and Perspectives

The successful integration of well-designed micro-nanomotors (MNMs) with diverse functional systems, such as, living systems, remote actuation systems, intelligent sensors, and sensing systems, offers many opportunities to not only endow them with diverse functionalization interfaces but also bring augmented or new properties in a wide variety of applications. Core-shell structured MNM systems have been considered to play an important role in a wide range of applications as they provide a platform to integrate multiple complementary components via decoration, encapsulation, or functionalization into a single functional system, being able to protect the active species from harsh environments, and bring improved propulsion performance, stability, non-toxicity, multi-functionality, and dispersibility, etc., which are not easily available from the isolated components. More importantly, the hetero-interfaces between individual components within a core-shell structure might give rise to boosted or new physiochemical properties. This review will bring together these key aspects of the core-shell structured MNMs, ranging from advanced protocols, enhanced/novel functionalities arising from diverse functional shells, to integrated core-shell structured MNMs for diverse applications. Finally, current challenges and future perspectives for the development of core-shell structured MNMs are discussed in term of synthesis, functions, propulsions, and applications.

Magnetomechanical force: an emerging paradigm for therapeutic applications

Mechanical forces, which play an profound role in cell fate regulation, have prompted the rapid development and popularization of mechanobiology. More recently, magnetic fields in combination with intelligent materials featuring...

Highly Efficient Magnetic Propulsion of NiFe Nanorod-Based Miniature Swimmers in Three Dimensions

Magnetically actuated miniature robots have attracted the attention of the scientific community over the past two decades, but the confined workspace of their manipulation system (typically a tri-axial coil or eight electromagnetic coils) and the low efficiency of propulsion have limited their utility. Here, we describe a highly efficient NiFe nanorod-based magnetic miniature swimmer that can be manipulated in 3D spaces using two pairs of coils placed in the x-y horizontal plane. In the new swimmer, the shape symmetry is broken along its body, and the asymmetry in magnetizations is introduced perpendicular to the long axis of its body simultaneously. Such a combined asymmetry design offers favorable controllability in planar magnetic fields, which relaxes the multi-axial coil requirement of the commonly used manipulation system and thus reduces the restriction on the shape and size of the workspaces. The new swimmers display efficient 3D propulsion, with a speed of over 5000 μm s^-1 (∼3 body length s^-1) and powerful locomotion in biological media such as raw human blood. The fuel utilization efficiency of the swimmer, defined as the ratio of the distance to the net input work in one period, was estimated to be approximately from 10^-2 to 10^-3 m/J, which is significantly higher than that of magnetic motors with a slender body. Moreover, to provide practical support for further potential use, we demonstrated that the swimmer is able to perform incision operations as a minimally invasive microsurgical tool. Such a swimmer actuation strategy provides a simple and efficient way for 3D manipulation of magnetic miniature robots, offering great potential for future biomedical and other applications.

Engineering Nanorobots for Tumor-Targeting Drug Delivery: From Dynamic Control to Stimuli-Responsive Strategy

Nanotechnology has been widely applied to the fabrication of drug delivery systems in the past decades. Recently, with the progress made in microfabrication approaches, nanorobots are steadily becoming a promising means for tumor-targeting drug delivery. In general, nanorobots can be divided into two categories: nanomotors and stimuli-responsive nanorobots. Nanomotors are nanoscale systems with the ability to convert surrounding energies into mechanical motion, whereas stimuli-responsive nanorobots are featured with activatable capacity in response to various endogenous and exogenous stimulations. In this minireview, the dynamic control of nanomotors and the rational design of stimuli-responsive nanorobots are overviewed, with particular emphasis on their contribution to tumor-targeting therapy. Moreover, challenges and perspectives associated with the future development of nanorobots are presented.

Biosafety, Functionalities, and Applications of Biomedical Micro/nanomotors

Due to their unique ability to actively move, micro/nanomotors offer the possibility of breaking through the limitations of traditional passive drug delivery systems for the treatment of many diseases, and have attracted the increasing attention of researchers. However, at present, the realization of many advantages of micro/nanomotors in disease treatment in vivo is still in its infancy, because of the complexity and particularity of diseases in different parts of human body. In this Minireview, we first focus on the biosafety and functionality of micro/nanomotors as a biomedical treatment system. Then, we address the treatment difficulties of various diseases in vivo (such as ophthalmic disease, orthopedic disease, gastrointestinal disease, cardiovascular disease, and cancer), and then review the research progress of biomedical micro/nanomotors in the past 20 years, Finally, we propose the challenges in this field and possible future development directions.

Recent Progress in Magnetically Actuated Microrobots for Targeted Delivery of Therapeutic Agents

Therapeutic agents, such as drugs and cells, play an essential role in virtually every treatment of injury, illness, or disease. However, the conventional practices of drug delivery often result in undesirable side effects caused by drug overdose and off-target delivery. In the case of cell delivery, the survival rate of the transplanted cells is extremely low and difficulties with the administration route of cells remain a problem. Recently, magnetically actuated microrobots have started offering unique opportunities in targeted therapeutic delivery due to their tiny size and ability to access hard-to-reach lesions in a minimally invasive manner; considerable advances in this regard have been made over the past decade. Here, recent progress in magnetically actuated microrobots, developed for targeted drug/cell delivery, is presented, with a focus on their design features and mechanisms for controlled therapeutic release. Additionally, the practical challenges faced by the microrobots, and future research directions toward the swift bench-to-bedside translation of the microrobots are addressed.

Polymer Nanoparticles and Nanomotors Modified by DNA/RNA Aptamers and Antibodies in Targeted Therapy of Cancer

Polymer nanoparticles and nano/micromotors are novel nanostructures that are of increased interest especially in the diagnosis and therapy of cancer. These structures are modified by antibodies or nucleic acid aptamers and can recognize the cancer markers at the membrane of the cancer cells or in the intracellular side. They can serve as a cargo for targeted transport of drugs or nucleic acids in chemo- immuno- or gene therapy. The various mechanisms, such as enzyme, ultrasound, magnetic, electrical, or light, served as a driving force for nano/micromotors, allowing their transport into the cells. This review is focused on the recent achievements in the development of polymer nanoparticles and nano/micromotors modified by antibodies and nucleic acid aptamers. The methods of preparation of polymer nanoparticles, their structure and properties are provided together with those for synthesis and the application of nano/micromotors. The various mechanisms of the driving of nano/micromotors such as chemical, light, ultrasound, electric and magnetic fields are explained. The targeting drug delivery is based on the modification of nanostructures by receptors such as nucleic acid aptamers and antibodies. Special focus is therefore on the method of selection aptamers for recognition cancer markers as well as on the comparison of the properties of nucleic acid aptamers and antibodies. The methods of immobilization of aptamers at the nanoparticles and nano/micromotors are provided. Examples of applications of polymer nanoparticles and nano/micromotors in targeted delivery and in controlled drug release are presented. The future perspectives of biomimetic nanostructures in personalized nanomedicine are also discussed.

Medical Micro/Nanorobots in Precision Medicine

Advances in medical robots promise to improve modern medicine and the quality of life. Miniaturization of these robotic platforms has led to numerous applications that leverages precision medicine. In this review, the current trends of medical micro and nanorobotics for therapy, surgery, diagnosis, and medical imaging are discussed. The use of micro and nanorobots in precision medicine still faces technical, regulatory, and market challenges for their widespread use in clinical settings. Nevertheless, recent translations from proof of concept to in vivo studies demonstrate their potential toward precision medicine.

Fantastic Voyage of Nanomotors into the Cell

Richard Feynman's 1959 vision of controlling devices at small scales and swallowing the surgeon has inspired the science-fiction Fantastic Voyage film and has played a crucial role in the rapid development of the microrobotics field. Sixty years later, we are currently witnessing a dramatic progress in this field, with artificial micro- and nanoscale robots moving within confined spaces, down to the cellular level, and performing a wide range of biomedical applications within the cellular interior while addressing the limitations of common passive nanosystems. In this review article, we discuss key recent advances in the field of micro/nanomotors toward important cellular applications. Specifically, we outline the distinct capabilities of nanoscale motors for such cellular applications and illustrate how the active movement of nanomotors leads to distinct advantages of rapid cell penetration, accelerated intracellular sensing, and effective intracellular delivery toward enhanced therapeutic efficiencies. We finalize by discussing the future prospects and key challenges that such micromotor technology face toward implementing practical intracellular applications. By increasing our knowledge of nanomotors' cell entry and of their behavior within the intracellular space, and by successfully addressing key challenges, we expect that next-generation nanomotors will lead to exciting advances toward cell-based diagnostics and therapy.

Micro/Nanorobot: A Promising Targeted Drug Delivery System

Micro/nanorobot, as a research field, has attracted interest in recent years. It has great potential in medical treatment, as it can be applied in targeted drug delivery, surgical operation, disease diagnosis, etc. Differently from traditional drug delivery, which relies on blood circulation to reach the target, the designed micro/nanorobots can move autonomously, which makes it possible to deliver drugs to the hard-to-reach areas. Micro/nanorobots were driven by exogenous power (magnetic fields, light energy, acoustic fields, electric fields, etc.) or endogenous power (chemical reaction energy). Cell-based micro/nanorobots and DNA origami without autonomous movement ability were also introduced in this article. Although micro/nanorobots have excellent prospects, the current research is mainly based on in vitro experiments; in vivo research is still in its infancy. Further biological experiments are required to verify in vivo drug delivery effects of micro/nanorobots. This paper mainly discusses the research status, challenges, and future development of micro/nanorobots.

Near-Infrared Light-Powered Janus Nanomotor Significantly Facilitates Inhibition of Amyloid-β Fibrillogenesis

Inspired by the natural motors, artificial nanomotors (NMs) have emerged as intelligent, advanced, and multifunctional nanoplatforms that can perform complex tasks in living environments. However, the functionalization of these fantastic materials is in its infancy, hindering the success of this booming field. Herein, an inhibitor-conjugated near-infrared (NIR) laser-propelled Janus nanomotor (JNM-I) was constructed and first applied in the modulation of amyloid-β protein (Aβ) aggregation which is highly associated with Alzheimer's disease (AD). Under NIR light illumination, JNM-I exhibited efficient propulsion through the "self-thermophoresis" effect, and the active motion of JNM-I increased the opportunity of the contacts between the immobilized inhibitors and Aβ species, leading to an intensification of JNM-I on modulating the on-pathway Aβ aggregation, as evidenced by the distinct changes of the amyloid morphology, conformation, and cytotoxicity. For example, with a NIR irradiation, 200 μg/mL of JNM-I increased the cultured SH-SY5Y cell viability from 68% to nearly 100%, but it only protected the cells to 89% viability without an NIR irradiation. Meanwhile, the NIR irradiation effectively improved the blood-brain barrier (BBB) penetration of JNM-I. Such a JNM-I has connected artificial nanomotors with protein aggregation and provided new insight into the potential applications of various nanomotors in the prevention and treatment of AD.

Magnetically Powered Shape-Transformable Liquid Metal Micromotors

Shape-transformable liquid metal (LM) micromachines have attracted the attention of the scientific community over the past 5 years, but the inconvenience of transfer routes and the use of corrosive fuels have limited their potential applications. In this work, a shape-transformable LM micromotor that is fabricated by a simple, versatile ice-assisted transfer printing method is demonstrated, in which an ice layer is employed as a "sacrificial" substrate that can enable the direct transfer of LM micromotors to arbitrary target substrates conveniently. The resulting LM microswimmers display efficient propulsion of over 60 µm s^-1 (≈3 bodylength s^-1 ) under elliptically polarized magnetic fields, comparable to that of the common magnetic micro/nanomotors with rigid bodies. Moreover, these LM micromotors can undergo dramatic morphological transformation in an aqueous environment under the irradiation of an alternating magnetic field. The ability to transform the shape and efficiently propel LM microswimmers holds great promise for chemical sensing, controlled cargo transport, materials science, and even artificial intelligence in ways that are not possible with rigid-bodies microrobots.

A Contactless and Biocompatible Approach for 3D Active Microrobotic Targeted Drug Delivery

As robotic tools are becoming a fundamental part of present day surgical interventions, microrobotic surgery is steadily approaching clinically-relevant scenarios. In particular, minimally invasive microrobotic targeted drug deliveries are reaching the grasp of the current state-of-the-art technology. However, clinically-relevant issues, such as lack of biocompatibility and dexterity, complicate the clinical application of the results obtained in controlled environments. Consequently, in this work we present a proof-of-concept fully contactless and biocompatible approach for active targeted delivery of a drug-model. In order to achieve full biocompatiblity and contacless actuation, magnetic fields are used for motion control, ultrasound is used for imaging, and induction heating is used for active drug-model release. The presented system is validated in a three-dimensional phantom of human vessels, performing ten trials that mimic targeted drug delivery using a drug-coated microrobot. The system is capable of closed-loop motion control with average velocity and positioning error of 0.3 mm/s and 0.4 mm, respectively. Overall, our findings suggest that the presented approach could augment the current capabilities of microrobotic tools, helping the development of clinically-relevant approaches for active in-vivo targeted drug delivery.

Encoding canonical DNA quadruplex structure

The main challenge in DNA quadruplex design is to encode a three-dimensional structure into the primary sequence, despite its multiple, repetitive guanine segments. We identify and detail structural elements describing all 14 feasible canonical quadruplex scaffolds and demonstrate their use in control of design. This work outlines a new roadmap for implementation of targeted design of quadruplexes for material, biotechnological, and therapeutic applications.

Applications of cobalt ferrite nanoparticles in biomedical nanotechnology

Magnetic nanoparticles (MNPs) are very attractive especially for biomedical applications, among which, iron oxide nanoparticles have received substantial attention in the past decade due to the elemental composition that makes them biocompatible and degradable. However recently, other magnetic nanomaterials such as spinel ferrites that can provide improved magnetic properties such as coercivity and anisotropy without compromising on inherent advantages of iron oxide nanoparticles are being researched for better applicability of MNPs. Among various spinel ferrites, cobalt ferrite (CoFe₂O₄) nanoparticles (NPs) are one of the most explored MNPs. Therefore, the intention of this article is to provide a comprehensive review of CoFe₂O₄ NPs and their inherent properties that make them exceptional candidates, different synthesis methods that influence their properties, and applications of CoFe₂O₄ NPs and their relevant applications that have been considered in biotechnology and bioengineering.

Magnetically Powered Annelid-Worm-Like Microswimmers

A bioinspired magnetically powered microswimmer is designed and experimentally demonstrated by mimicking the morphology of annelid worms. The structural parameters of the microswimmer, such as the surface wrinkling, can be controlled by applying prestrain on substrate for the precise fabrication and consistent performance of the microswimmers. The resulting annelid-worm-like microswimmers display efficient propulsion under an oscillating magnetic field, reaching a peak speed of ≈100 µm s^-1 . The speed and directionality of the microswimmer can be readily controlled by changing the parameters of the field inputs. Additionally, it is demonstrated that the microswimmers are able to transport microparticles toward a predefined destination, although the translation velocity is inevitably reduced due to the additional hydrodynamic resistance of the microparticles. These annelid-worm-like microswimmers have excellent mobility, good maneuverability, and strong transport capacity, and they hold considerable promise for diverse biomedical, chemical sensing, and environmental applications.

Micro/nanomotors towards in vivo application: cell, tissue and biofluid

Inspired by highly efficient natural motors, synthetic micro/nanomotors are self-propelled machines capable of converting the supplied fuel into mechanical motion. A significant advance has been made in the construction of diverse motors over the last decade. These synthetic motor systems, with rapid transporting and efficient cargo towing abilities, are expected to open up new horizons for various applications. Utilizing emergent motor platforms for in vivo applications is one important aspect receiving growing interest as conventional therapeutic methodology still remains limited for cancer, heart, or vasculature diseases. In this review we will highlight the recent efforts towards realistic in vivo application of various motor systems. With ever booming research enthusiasm in this field and increasing multidisciplinary cooperation, micro/nanomotors with integrated multifunctionality and selectivity are on their way to revolutionize clinical practice.

Conformational control of human transferrin covalently anchored to carbon-coated iron nanoparticles in presence of a magnetic field

The control of the interactions of proteins with the support matrix plays a key role in medicine, drug delivery systems and diagnostics. Herein, we report that covalent anchoring of human transferrin to carbon-coated iron magnetic nanoparticles functionalized with carboxylic groups (Fe@C-COOH Nps) in the presence of magnetic field results in its conformational integrity and electroactivity. We have found that, the direct contact of human transferrin with Fe@C-COOH Nps does not lead to release of iron and in consequence to the irreversible conformational changes of the protein. Moreover, the examination of the direct electron transfer between Tf molecules from the conjugate and the electrode surface was possible. The quartz crystal microbalance with dissipation (QCM-D)- and thermogravimetric data (TGA) showed that under such conditions, in addition to a monolayer, an adlayer of the protein can be formed on Fe@C-COOH Nps at constant pH.

STATEMENT OF SIGNIFICANCE

To our best knowledge this is the first paper that reports on covalent anchoring of human transferrin (Tf) to carbon-coated iron magnetic nanoparticles functionalized with carboxylic groups (Fe@C-COOH Nps) in the presence of magnetic field, which results in its conformational integrity and electroactivity. We showed that it is possible to attach, without changing pH, more than one single layer of transferrin to the Fe@C-COOH Nps. This is a very rare phenomenon in the case of proteins. We proved, using various experimental techniques, that the proposed methodology does not lead to release of iron from Tf molecules, what was the major problem so far. We believe that this finding opens new possibilities in targeting drug delivery systems and medical diagnostics.