Magnetic Field Guided Chemotaxis of iMushbots for Targeted Anticancer Therapeutics

Living material-derived intelligent micro/nanorobots

Living materials, which include various types of cells, organelles, and biological components from animals, plants, and microorganisms, have become central to recent investigations in micro and nanorobotics. Living material-derived intelligent micro/nanorobots (LMNRs) are self-propelled devices that combine living materials with synthetic materials. By harnessing energy from external physical fields or biological sources, LMNRs can move autonomously and perform various biomedical functions, such as drug delivery, crossing biological barriers, medical imaging, and disease treatment. This review, from a biomimetic strategy perspective, summarized the latest advances in the design and biomedical applications of LMNRs. It provided a comprehensive overview of the living materials used to construct LMNRs, including mammalian cells, plants, and microorganisms while highlighting their biological properties and functions. Lastly, the review discussed the major challenges in this field and offered suggestions for future research that may help facilitate the clinical application of LMNRs in the near future.

Recirculatory Solvotaxis of a Nematic Droplet on Water Surface Enabling Miniaturization

Self-organized contact line instabilities (CLI) of a macroscopic liquid crystal (LC) droplet can be an ingenious pathway to generate a large collection of miniaturized LC drops. For example, when a larger drop of volatile solvent (e.g., hexane) is dispensed near a smaller LC drop resting on a soft and slippery surface of a nonsolvent (e.g., water), unique self-organized locomotion in the form of a twin vortex has been observed within the droplets. This phenomenon is driven by the rapid counter diffusion of hexane and LC between the two droplets, resulting in the formation of a pair of vortices within the droplets before instigating a CLI at the three-phase contact line (TPCL) of the LC droplet. Initially, the higher Laplace pressure inside the LC droplet (PL,5CB) due to a net pressure gradient, PL,5CB > PL,Hex, drives the LC toward hexane. However, as the volatile solvent droplet shrinks due to rapid evaporation, a flow reversal happens owing to PL,5CB < PL,Hex. Subsequently, the diffusion of hexane into the LC droplet and its subsequent evaporation manifest a periodic oscillatory CLI expansion and retraction at the TPCL, which in turn form periodic finger-like structures. Following this, the fingers with a higher aspect ratio break into an array of miniaturized satellite LC droplets undergoing Rayleigh-Plateau instability (RPI). The observed deviation in the normalized satellite droplet spacingλ / R 5 CB ∼ 3.15 2 π compared to theoretical value ∼ 2 2 π affirm the stabilizing influence of LC elasticity in such fingers, where λ and R5CB are experimentally calculated droplet spacing and 5CB droplet radius. Control experiments elucidate the specific contributions of capillary, drag, solutal Marangoni, and osmotic forces to the 5CB droplet locomotion phenomena. The experimentally and analytically consistent demonstration also supports and predicts pressure drop-induced droplet velocities as v ∼ t1.16.

Recent Advances in Micro/Nanomotor for the Therapy and Diagnosis of Atherosclerosis

Atherosclerotic cardiovascular disease poses a significant global public health threat with a high incidence that can result in severe mortality and disability. The lack of targeted effects from traditional therapeutic drugs on atherosclerosis may cause damage to other organs and tissues, necessitating the need for a more focused approach to address this dilemma. Micro/nanomotors are self-propelled micro/nanoscale devices capable of converting external energy into autonomous movement, which offers advantages in enhancing penetration depth and retention while increasing contact area with abnormal sites, such as atherosclerotic plaque, inflammation, and thrombosis, within blood vessel walls. Recent studies have demonstrated the crucial role micro/nanomotors play in treating atherosclerotic cardiovascular disease. Hence, this review highlights the recent progress of micro/nanomotor technology in atherosclerotic cardiovascular disease, including the effective promotion of micro/nanomotors in the circulatory system, overcoming hemorheological barriers, targeting the atherosclerotic plaque microenvironment, and targeting intracellular drug delivery, to facilitate atherosclerotic plaque localization and therapy. Furthermore, we also describe the potential application of micro/nanomotors in the imaging of vulnerable plaque. Finally, we discuss key challenges and prospects for treating atherosclerotic cardiovascular disease while emphasizing the importance of designing individualized management strategies specific to its causes and microenvironmental factors.

Biosynthesis of pH-Responsive Mesoporous Silica Nanoparticles from Cucumber Peels for Targeting 3D Lung Tumor Spheroids

Lung adenocarcinoma is considered to be one of the primary causes of cancer-related deaths globally. Conventional treatments, such as chemotherapy and radiation therapy taken together, have not significantly lowered mortality rates. Repositioning of authorized anticancer medications supported by nanotechnology has therefore emerged as an effective strategy to close such gaps. In this context, mesoporous silica nanoparticles (MSNs) were biosynthesized from cucumber peels and were loaded with doxorubicin, a common anticancer drug to form doxorubicin-bound mesoporous silica nanoparticles (DMSNs). The study addresses a sustainable method for turning waste materials into MSNs, which can be used to create multifunctional nanosystems. The therapeutic module (DMSNs) was designed specifically to target 2D monolayer cells and 3D tumor spheroids of lung adenocarcinoma cancer. The DMSNs demonstrated notable antiproliferative activity and effective intracellular localization in addition to being biocompatible and innately fluorescent. Subsequent investigations revealed significant antibacterial activity against Staphylococcal infection, which is primarily prevalent in lung cancer patients. Thus, the developed MSNs held promising potential for anticancer drug delivery systems and have antibacterial potential to treat bacterial infections in patients with lung cancer. Furthermore, the cucumber peel-mediated synthesis of MSNs could also aid in the management of food waste and promote the adoption of the waste-to-health paradigm for sustainable solutions.

Magnetic motors in interphases: Motion control and integration in soft robots

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.

Collective Molecular Machines: Multidimensionality and Reconfigurability

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

Hydrodynamic Synchronization of Chiral Microswimmers

We study synchronization in bulk suspensions of spherical microswimmers with chiral trajectories using large scale numerics. The model is generic. It corresponds to the lowest order solution of a general model for self-propulsion at low Reynolds numbers, consisting of a nonaxisymmetric rotating source dipole. We show that both purely circular and helical swimmers can spontaneously synchronize their rotation. The synchronized state corresponds to velocity alignment with high orientational order in both the polar and azimuthal directions. Finally, we consider a racemic mixture of helical swimmers where intraspecies synchronization is observed while the system remains as a spatially uniform fluid. Our results demonstrate hydrodynamic synchronization as a natural collective phenomenon for microswimmers with chiral trajectories.

A Universal Chemotactic Targeted Delivery Strategy for Inflammatory Diseases

Above 50% of deaths can be attributed to chronic inflammatory diseases; thus, the construction of drug delivery systems based on effective interaction of inflammatory factors with chemotactic nanoparticles is meaningful. Herein, a zwitterion-based artificial chemotactic nanomotor is proposed for universal precise targeting strategy in vivo, where the high level of reactive oxygen species (ROS) and inducible nitric oxide synthase (iNOS) in inflammatory sites are used as a chemoattractant. Multidimensional static models, dynamic models, and in vivo models are established to evaluate chemotactic performance. The results show that the upregulated ROS and iNOS can induce the chemotaxis of nanomotors to diseased tissues in inflammation-related disease models. Further, mesoscale hydrodynamics simulations are performed to explain the chemotactic behavior of the nanomotors. Such a chemotactic delivery strategy is expected to improve delivery efficiency and may be applicable to a variety of inflammatory diseases.

Recent Process in Microrobots: From Propulsion to Swarming for Biomedical Applications

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.

Plant-Actuated Micro-Nanorobotics Platforms: Structural Designs, Functional Prospects, and Biomedical Applications

Plants are anatomically and physiologically different from humans and animals; however, there are several possibilities to utilize the unique structures and physiological systems of plants and adapt them to new emerging technologies through a strategic biomimetic approach. Moreover, plants provide safe and sustainable results that can potentially solve the problem of mass-producing practical materials with hazardous and toxic side effects, particularly in the biomedical field, which requires high biocompatibility. In this review, it is investigated how micro-nanostructures available in plants (e.g., nanoparticles, nanofibers and their composites, nanoporous materials, and natural micromotors) are adapted and utilized in the design of suitable materials for a micro-nanorobot platform. How plants' work on micro- and nanoscale systems (e.g., surface roughness, osmotically induced movements such as nastic and tropic, and energy conversion and harvesting) that are unique to plants, can provide functionality on the platform and become further prospective resources are examined. Furthermore, implementation across organisms and fields, which is promising for future practical applications of the plant-actuated micro-nanorobot platform, especially on biomedical applications, is discussed. Finally, the challenges following its implementation in the micro-nanorobot platform are also presented to provide advanced adaptation in the future.

Self-Adaptive Flask-like Nanomotors Based on Fe3O4 Nanoparticles to a Physiological pH

In living bodies, pH values, which are precisely regulated and closely associated with diseased cells, can act as an efficient biologically intrinsic indicator for future intelligent biomedicine microsystems. In this work, we have developed flask-like carbonaceous nanomotors (FCNMs), via loading Fe3O4 nanoparticles (NPs) into a cavity, which exhibit a self-adaptive feature to a specific physiological pH by virtue of the pH-dependent dual enzyme-like activities of Fe3O4 NPs. Specifically, the peroxidase-like activity of Fe3O4 NPs in an acidic pH range, and the catalase-like activity in a near neutral and alkaline pH range, determine the products in the motion system (•OH, ions and O2), whose diffusions from the inner to the outside of the flask result in fluid movement providing the driving force for the movement of the FCNMs. Correspondingly, changes of the product concentrations and species in the physiological pH range (4.4-7.4) result, firstly, in velocity decrease and, then, with increase in pH, increase of the FCNMs occurs. Thanks to the non-linear velocity responsiveness, the FCNMs show intriguing pH taxis towards 6.8 (generally corresponding to the physiological pH in tumor microenvironments), where a maximum velocity appears. Furthermore, the superparamagnetic feature of the Fe3O4 NPs simultaneously endows the FCNMs with the abilities to be magnetic-oriented and easily separated. This work could significantly increase the possibility of nanomotors for targeted therapy of tumors and next-generation biotechnological applications.

Micro/Nanosystems for Magnetic Targeted Delivery of Bioagents

Targeted delivery of pharmaceuticals is promising for efficient disease treatment and reduction in adverse effects. Nano or microstructured magnetic materials with strong magnetic momentum can be noninvasively controlled via magnetic forces within living beings. These magnetic carriers open perspectives in controlling the delivery of different types of bioagents in humans, including small molecules, nucleic acids, and cells. In the present review, we describe different types of magnetic carriers that can serve as drug delivery platforms, and we show different ways to apply them to magnetic targeted delivery of bioagents. We discuss the magnetic guidance of nano/microsystems or labeled cells upon injection into the systemic circulation or in the tissue; we then highlight emergent applications in tissue engineering, and finally, we show how magnetic targeting can integrate with imaging technologies that serve to assist drug delivery.

A Brief Review on Challenges in Design and Development of Nanorobots for Medical Applications

Robotics is a rapidly growing field, and the innovative idea to scale down the size of robots to the nanometer level has paved a new way of treating human health. Nanorobots have become the focus of many researchers aiming to explore their many potential applications in medicine. This paper focuses on manufacturing techniques involved in the fabrication of nanorobots and their associated challenges in terms of design architecture, sensors, actuators, powering, navigation, data transmission, followed by challenges in applications. In addition, an overview of various nanorobotic systems addresses different architectures of a nanorobot. Moreover, multiple medical applications, such as oncology, drug delivery, and surgery, are reviewed and summarized.

Multifunctional micro/nanomotors as an emerging platform for smart healthcare applications

Self-propelling micro- and nano-motors (MNMs) are emerging as a multifunctional platform for smart healthcare applications such as biosensing, bioimaging, and targeted drug delivery with high tissue penetration, stirring effect, and rapid drug transport. MNMs can be propelled and/or guided by chemical substances or external stimuli including ultrasound, magnetic field, and light. In addition, enzymatically powered MNMs and biohybrid micromotors have been developed using the biological components in the body. In this review, we describe emerging MNMs focusing on their smart propulsion systems, and diagnostic and therapeutic applications. Finally, we highlight several MNMs for in vivo applications and discuss the future perspectives of MNMs on their current limitations and possibilities toward further clinical applications.

Real-time transport kinetics of drug encapsulated nanoparticles into apoptotic cancer cells inside microchannels

Development of nanocomposites as drug delivery vectors is a burgeoning field of research. However, the usage of such newly invented nanomatrices are often limited by the shortcomings associated with the testing of their real-life efficacy. Many drugs fail because a monolayer framework ofin vitrocell line screening method does not adequately mimic thein vivothree-dimensional microenvironments. In this direction, the study unveils the development of a continuous flow microreactor wherein the cellulose acetate nanoparticles (CANPs) with varying sizes are prepared before encapsulating them with an anticancer drug-doxorubicin (DOX). Subsequently, anin vitromicrofluidic drug delivery model has been introduced in which the HeLa cells specific to cervical cancer is treated with the DOX encapsulated CANPs-DOX@CANPs. Thereafter, the transport of the drugs from the fluidic to cellular environment, their transport inside the cell, and the real-time kinetics of the cancer cell apoptosis have been analyzed systematically to uncover the real-time efficacy and cytotoxic effects of the nanocomposite. Interestingly, experiments reveal, (i) ∼89.4% DOX loading on the nanocomposite owing to a facile electrostatic interaction, (ii) a pH-dependent controlled release of drug during the transport with the cancer cells, and (iii) cell apoptosis after the diffused inoculation of the drug. A mathematical model has been developed to emulate the drug transport from the surrounding fluid to the cancer cells. Experiments together with the mathematical model uncover that the kinetics of cancer cell death is limited by the reaction at the cell-nucleus. The microfluidic model has shown significant potential to be translated as a useful tool for the real-time and on-demandin vitroscreening of the cancer drugs.

Multifunctional liquid marbles to stabilize and transport reactive fluids

The self-organized transport and delivery of reactive liquids without spillage or loss of activity have been among the most daunting challenges for a long time. In this direction, we employ the concept of forming "liquid marbles" (LMs) to encapsulate and transport reactive hydrogen peroxide (H2O2) coated with functional microparticles. For example, peroxide marbles coated with a toner ink display remote-controlled magnetotactic movement inside a fluidic medium, thus overcoming the weaknesses associated with use of the bare droplets. Interestingly, in such a scenario, the coating of the marbles could also be removed or reformed by bringing the magnet towards or away from the marble. In this way, this process could ensure an on-demand remotely guided coating on the peroxide droplet or its removal. The liquid marbles carrying peroxide solutions are found to preserve the activity of the peroxide and exhibit a low evaporation rate compared with the uncoated peroxide fuel. Interestingly, oil droplets floating on the water could be recovered by introducing the armoured LMs into water under magnetic guidance. Further, the functionalized marbles could be employed as suicide bags for the on-demand delivery of reactive materials in targeted locations. Preliminary research on the antibacterial activity of such liquid marbles has proven to be effective in bacterial killing, which may create new avenues for emerging antibacterial and antibiofilm applications. Finally, such functionalized LMs have been employed to investigate the effects of surface charge on attachment of recombinant Escherichia coli bacteria expressing green fluorescent protein and monitoring the real-time imaging of bacterial death attached to the marble surface.

Recent Advances in Microswimmers for Biomedical Applications

Microswimmers are a rapidly developing research area attracting enormous attention because of their many potential applications with high societal value. A particularly promising target for cleverly engineered microswimmers is the field of biomedical applications, where many interesting examples have already been reported for e.g., cargo transport and drug delivery, artificial insemination, sensing, indirect manipulation of cells and other microscopic objects, imaging, and microsurgery. Pioneered only two decades ago, research studies on the use of microswimmers in biomedical applications are currently progressing at an incredibly fast pace. Given the recent nature of the research, there are currently no clinically approved microswimmer uses, and it is likely that several years will yet pass before any clinical uses can become a reality. Nevertheless, current research is laying the foundation for clinical translation, as more and more studies explore various strategies for developing biocompatible and biodegradable microswimmers fueled by in vivo-friendly means. The aim of this review is to provide a summary of the reported biomedical applications of microswimmers, with focus on the most recent advances. Finally, the main considerations and challenges for clinical translation and commercialization are discussed.

Research Progress of Micro/Nanomotors for Cancer Treatment

Nanomaterials have been widely used in cancer treatment and have achieved remarkable results. However, the specificity of the tumor microenvironment and a series of biological barriers (such as blood flow, cell membrane, dense tissue, etc.) have caused many obstacles faced by nanomaterials after entering the human body, which makes traditional drug delivery vehicles have insurmountable difficulties, such as low delivery efficiency, poor permeability, etc. The micro/nanomotors with autonomous movement capabilities provide the possibility to solve the above problems. Therefore, this review summarizes the current researches of micro/nanomotors strategies to overcome the different biological barriers of nanomaterials in cancer treatment. The advantages and disadvantages of three typical micro/nanomotors (biological, physical and chemical micro/nanomotors) in cancer treatment are summarized separately, and the future design of micro/nanomotors more suitable for tumor environment was discussed.

Magnetotactic T-Budbots to Kill-n-Clean Biofilms

Treatment of persistent biofilm infections has turned out to be a formidable challenge even with broad-spectrum antibiotic therapies. In this direction, intelligent micromachines may serve as active mechanical means to dislodge such deleterious bacterial communities. Herein, we have designed biocompatible micromotors from tea buds, namely, T-Budbots, which shows the capacity to be magnetically driven on a biofilm matrix and remove or fragment biofilms with precision, as a part of the proposed non-invasive "Kill-n-Clean" strategy. In a way, we present a bactericidal robotic platform decorated with magnetite nanoparticles aimed at clearing in vitro biofilms present on the surfaces. We have also shown that the smart porous T-Budbots can integrate antibiotic ciprofloxacin due to electrostatic interaction on their surface to increase their antibacterial efficacy against dreadful pathogenic bacterial communities of Pseudomonas aeruginosa and Staphylococcus aureus. It is noteworthy that the release of this drug can be controlled by tuning the surrounding pH of the T-Budbots. For example, while the acidic environment of the biofilm facilitates the release of antibiotics from the porous T-Budbots, the drug release was rather minimal at higher pH. The work represents a first step in the involvement of a plant-based microbot exhibiting magneto-robotic therapeutic properties, providing a non-invasive and safe approach to dismantle harmful biofilm infections.

Unfolding the future: Self-controlled catalytic nanomotor in healthcare system

Nanomotors, multimetallic systems are biologically inspired self-propelled tiny engines able to perform difficult tasks of transporting cargos from one end to another in presence of hydrogen peroxide fuel. Nanomotors can revolutionize the drug delivery system at the desired target by converting chemical energy into mechanical energy. Nanomotors exhibit unique properties like moving at higher speed, self-propulsion and drilling into the complex cellular environment. The review focuses on fuel dependent and fuel-free nanomotors with their propulsion mechanism. Further, the review highlights the method of fabrication, biohybrid nanomotors, toxicities along with their application in the field of active drug delivery, diabetes, precise surgery, ischemic stroke therapy, diagnosis and treatment of coronavirus, microwave hyperthermia, zika virus detection, anti-bacterial activity, water treatment and sensing and challenges lying at the forefront in the development of these tiny nanomachines. Hydrogen peroxide is toxic to mankind; biohybrid motors give an extra edge of eliminating hydrogen peroxide as fuel for self-propulsion, this can be used for smart drug delivery by reducing toxicities as compared to artificial nanomotors. Cost-effective fabrication of nanomotors will extend their applications in commercial sector overcoming limitations like scale-up and regulatory approval. In near future, nanomotors will diversify in fields of restoring conductivity of electronic medical devices, 3D printing and theranostics.

Micro-/Nanomotors toward Biomedical Applications: The Recent Progress in Biocompatibility

Inspired by the highly versatile natural motors, artificial micro-/nanomotors that can convert surrounding energies into mechanical motion and accomplish multiple tasks are devised. In the past few years, micro-/nanomotors have demonstrated significant potential in biomedicine. However, the practical biomedical applications of these small-scale devices are still at an infant stage. For successful bench-to-bed translation, biocompatibility of micro-/nanomotor systems is the central issue to be considered. Herein, the recent progress in micro-/nanomotors in biocompatibility is reviewed, with a special focus on their biomedical applications. Through close collaboration between researches in the nanoengineering, material chemistry, and biomedical fields, it is expected that a promising real-world application platform based on micro-/nanomotors will emerge in the near future.

Coordinated behaviors of artificial micro/nanomachines: from mutual interactions to interactions with the environment

The interactions leading to coordinated behaviors of artificial micro/nanomachines are reviewed.

Nano/Micromotors for Diagnosis and Therapy of Cancer and Infectious Diseases

Micromotors are man-made nano/microscale devices capable of transforming energy into mechanical motion. The accessibility and force offered by micromotors hold great promise to solve complex biomedical challenges. This Review highlights current progress and prospects in the use of nano and micromotors for diagnosis and treatment of infectious diseases and cancer. Motion-based sensing and fluorescence switching detection strategies along with therapeutic approaches based on direct cell capture; killing by direct contact or specific drug delivery to the affected site, will be comprehensively covered. Future challenges to translate the potential of nano/micromotors into practical applications will be described in the conclusions.

Graphene oxide nanohybrids for electron transfer-mediated antimicrobial activity

The rapid increase in the prevalence of antibiotic-resistant bacterial strains poses a global health risk. In this scenario, alternative strategies are needed to combat the alarming rise in multidrug-resistant bacterial populations. For example, metal-incorporated graphene derivatives have emerged as model nanomaterials owing to their intrinsic antibacterial activity together with their biocompatibility. Interestingly, photon-activated phthalocyanine sensitizers have also shown promising physiochemical biocidal effects against pathogenic bacteria populations when conjugated with diverse nanomaterials. Herein, we report the facile synthesis of graphene oxide incorporated zinc phthalocyanine (ZnPc-GO) nanohybrids showing bactericidal activity against Gram-negative Escherichia coli (E. coli) cells, in the absence of any photo-excitation. The ZnPc-GO hybrid nanomaterials were synthesized by the in situ deposition of GO flakes on ZnPc-coated indium tin oxide (ITO) substrates. Two types of morphologically different ZnPc molecules, potato-chip-like α-phase ZnPc, namely ZnPc(A), and nanorod-like β-phase ZnPc(B), were used for the synthesis of the ZnPc(A/B)-GO nanocomposites. The interactions of GO with the underlying ZnPc(A/B) entities in the ZnPc-GO systems were investigated using multiple characterization techniques. It was observed that the GO flakes in the ZnPc(B)-GO nanocomposite possess stronger π-π interactions and thus show a more efficient electron transfer mechanism when compared with the ZnPc(A) counterpart. Furthermore, the E. coli bacterial cells with an electronegative surface demonstrated a profound adherence to the electron-withdrawing ZnPc(B)-GO surface. The death kinetics of bacteria with ZnPc(B)-GO were further investigated using surface potential mapping and Kelvin probe force microscopy (KPFM) analysis. Upon direct contact with ZnPc(B)-GO, the adhered bacterial cells showed outer cell deformation and membrane protein leakage, induced by a proposed charge-transfer mechanism between negatively charged cells and the electron-withdrawing ZnPc(B)-GO surface. These new findings may provide insights into the design of potential ZnPc-GO-based novel antimicrobial nanomaterials or surface coatings.

Magnetic Drug Delivery: Where the Field Is Going

Targeted delivery of anticancer drugs is considered to be one of the pillars of cancer treatment as it could allow for a better treatment efficiency and less adverse effects. A promising drug delivery approach is magnetic drug targeting which can be realized if a drug delivery vehicle possesses a strong magnetic moment. Here, we discuss different types of magnetic nanomaterials which can be used as magnetic drug delivery vehicles, approaches to magnetic targeted delivery as well as promising strategies for the enhancement of the imaging-guided delivery and the therapeutic action.

Self-Propelled Micro/Nanomotors for Sensing and Environmental Remediation

Self-propelled micro/nanomotors have gained attention for successful application in cargo delivery, therapeutic treatments, sensing, and environmental remediation. Unique characteristics such as high speed, motion control, selectivity, and functionability promote the application of micro/nanomotors in analytical sciences. Here, the recent advancements and main challenges regarding the application of self-propelled micro/nanomotors in sensing and environmental remediation are discussed. The current state of micro/nanomotors is reviewed, emphasizing the period of the last five years, then their developments into the future applications for enhanced sensing and efficient purification of water resources are extrapolated.

Boolean-chemotaxis of logibots deciphering the motions of self-propelling microorganisms

We demonstrate the feasibility of a self-propelling mushroom motor, namely a 'logibot', as a functional unit for the construction of a host of optimized binary logic gates. Emulating the chemokinesis of unicellular prokaryotes or eukaryotes, the logibots made stimuli responsive conditional movements at varied speeds towards a pair of acid-alkali triggers. A series of integrative logic operations and cascaded logic circuits, namely, AND, NAND, NOT, OR, NOR, and NIMPLY, have been constructed employing the decisive chemotactic migrations of the logibot in the presence of the pH gradient established by the sole or coupled effects of acid (HCl-catalase) and alkali (NaOH) drips inside a peroxide bath. The imposed acid and/or alkali triggers across the logibots were realized as inputs while the logic gates were functionally reconfigured to several operational modes by varying the pH of the acid-alkali inputs. The self-propelling logibot could rapidly sense the external stimuli, decide, and act on the basis of intensities of the pH triggers. The impulsive responses of the logibots towards and away from the external acid-alkali stimuli were interpreted as the potential outputs of the logic gates. The external stimuli responsive self-propulsion of the logibots following different logic gates and circuits can not only be an eco-friendly alternative to the silicon-based computing operations but also be a promising strategy for the development of intelligent pH-responsive drug delivery devices.

Geometry Design, Principles and Assembly of Micromotors

Discovery of bio-inspired, self-propelled and externally-powered nano-/micro-motors, rotors and engines (micromachines) is considered a potentially revolutionary paradigm in nanoscience. Nature knows how to combine different elements together in a fluidic state for intelligent design of nano-/micro-machines, which operate by pumping, stirring, and diffusion of their internal components. Taking inspirations from nature, scientists endeavor to develop the best materials, geometries, and conditions for self-propelled motion, and to better understand their mechanisms of motion and interactions. Today, microfluidic technology offers considerable advantages for the next generation of biomimetic particles, droplets and capsules. This review summarizes recent achievements in the field of nano-/micromotors, and methods of their external control and collective behaviors, which may stimulate new ideas for a broad range of applications.