Antioxidant properties of inorganic nanoparticles in aqueous media are attracting growing interest due to their high surface reactivity. Materials such as cerium oxide, iron oxide, silver, and gold exhibit distinct radical-scavenging behaviors at the nanoscale, but reliable quantification remains challenging. Conventional assays developed for molecular antioxidants cannot be directly applied because probes such as 2,2-diphenyl-1-picrylhydrazyl (DPPH) require methanol–water mixtures and are unstable in aqueous nanoparticle suspensions, while other assays are affected by nanoparticle-induced absorption or fluorescence changes. Here we demonstrate strategies to correct these interferences by independently measuring nanoparticle optical properties after oxidation and customizing assay conditions to account for the dilute, per-particle concentrations of nanomaterials. Using a high-throughput 96-well format, four adapted assays revealed that silver, ceria, and iron oxide nanoparticles possess substantially higher antioxidant capacities than Trolox, while gold showed negligible activity. This optimized approach enables reproducible comparison of nanoparticle antioxidants and provides a platform for tailoring nanostructures with enhanced radical-scavenging properties.

Over the past two decades Biomedical Engineering has emerged as a major discipline that bridges societal needs of human health care with the development of novel technologies. Every medical institution is now equipped at varying degrees of sophistication with the ability to monitor human health in both non-invasive and invasive modes. The multiple scales at which human physiology can be interrogated provide a profound perspective on health and disease. We are at the nexus of creating “avatars” (herein defined as an extension of “digital twins”) of human patho/physiology to serve as paradigms for interrogation and potential intervention. Motivated by the emergence of these new capabilities, the IEEE Engineering in Medicine and Biology Society, the Departments of Biomedical Engineering at Johns Hopkins University and Bioengineering at University of California at San Diego sponsored an interdisciplinary workshop to define the grand challenges that face biomedical engineering and the mechanisms to address these challenges. The Workshop identified five grand challenges with cross-cutting themes and provided a roadmap for new technologies, identified new training needs, and defined the types of interdisciplinary teams needed for addressing these challenges. The themes presented in this paper include: 1) accumedicine through creation of avatars of cells, tissues, organs and whole human; 2) development of smart and responsive devices for human function augmentation; 3) exocortical technologies to understand brain function and treat neuropathologies; 4) the development of approaches to harness the human immune system for health and wellness; and 5) new strategies to engineer genomes and cells.

Liquid robotics with arbitrary deformability and rich functionality can adapt to various environmental constraints and perform many significant tasks. To turn this vision into reality, an intelligent liquid system, ferrofluid, which possesses excellent macroscopic and microscopic responsiveness to external magnetic fields, is explored as the rudiment of liquid robotics. Focus is given not only to its improved fabrication and cooperative programming control, but also its underexplored object manipulation and signal transmission. The prepared ferrofluid consists of sterically stabilized ultra-small magnetic nanoparticles suspended in carrier liquids, showing strong stability, flexible mobility, and substantial magnetization. Intelligent locomotion and complex morphology control are successfully achieved by a programmable platform that generates sequential predesigned magnetic fields through the timing activation of specific electromagnets. Meanwhile, by utilizing the magneto-Archimedes effect, this ferrofluid system can perform multi-dimensional manipulation of objects with densities ranging from 1.1 to 8.9 g/cm3 in cooperation with varying magnetic fields. Furthermore, this system can sense vibrations due to its intrinsic liquid feature and send corresponding signals through detecting the changes in magnetic flux by external coils. Similarly, the flow, concentration, and speed of ferrofluids can also be detected. These advancements in fabrication, control, operation, and sensing are crucial for the development of liquid robotics.

Iron oxide nanoparticles are an FDA-approved and gadolinium-free alternative to conventional magnetic resonance imaging (MRI) contrast agents. While their magnetic cores are responsible for T2 contrast, the nonmagnetic polymers at the particle interfaces can affect the diffusion of bulk water near the particles. We show here how this interaction can alter the relaxation dynamics of water protons and, consequently, the nanoparticle's contrast performance. Libraries of iron oxide nanocrystals of different core diameters and surface coatings can form biocompatible, non-cytotoxic, and colloidally stable suspen-sions with excellent MRI properties. Both the grafting density and thickness of polymer coatings influence the amount of time water protons spend around a nanoparticle and thus their contrast agent performance. Characterization of the diameter-dependent contrast performance of these materials revealed that nanoparticles with dense, hydrophilic polymer coatings reached the static dephasing regime, and optimal T2 relaxivity, at smaller dimensions than other systems. We rationalized that such coatings offered a slow compartment for water diffusion near the magnetic particle, resulting in an effective diffusion constant lower than bulk water. By manipulating the surface coating and core diameter together, we could generate a material with one of the largest T2 relaxivities ever reported (510 mM-1 s-1) for an isolated nanocrystal. This conceptual framework can explain the complex structure-performance trends of this class of T2 contrast agents and those already reported in the existing literature. Water diffusion at iron oxide nanocrystals (IONCs) interfaces is an essential consideration in designing sensitive and possibly responsive T2 MRI contrast agents.

The ability to communicate scientific concepts to expert and nonexpert audiences is an essential skill for chemistry and STEM students. Current chemistry curricula mainly focus on developing skills to communicate technical information to expert audiences, while relaying the same information to general audiences receives much less attention. Although numerous initiatives work to close this gap, many have logistical or financial barriers that make them difficult to integrate in a large classroom setting. Herein, we present an assignment focused on improving advanced students' (i.e., graduate and advanced undergraduate students) ability to communicate current organometallic chemistry research (i.e., technical information) to a general audience using infographics. Our assignment features a unique, iterative feedback model incorporating instructor, peer, and near-peer (general audience) groups to provide students with multiple opportunities to refine their communication skills. Anonymous student self-assessments of advanced undergraduate/ graduate students (infographic creators and peer reviewers) and first year, non-major undergraduate students (near-peer reviewers and general audience) indicate that the assignment led to (i) increased confidence in communication skills (advanced undergraduate/graduate students), (ii) a broadened understanding of advanced chemistry in everyday life (both), and (iii) increased recognition for the importance of scientific communication to different audiences (both). Reflections on student outcomes as well as recommendations and considerations for instructors are discussed.

Objective.The recording instability of neural implants due to neuroinflammation at the device-tissue interface is a primary roadblock to broad adoption of brain-machine interfaces. While a multiphasic immune response, marked by glial scaring, oxidative stress (OS), and neurodegeneration, is well-characterized, the independent contributions of systemic and local 'innate' immune responses are not well-understood. We aimed to understand and mitigate the isolated the innate neuroinflammatory response to devices.Approach.Three-dimensional primary neural cultures provide a unique environment for studying the drivers of neuroinflammation by decoupling the innate and systemic immune systems, while conserving an endogenous extracellular matrix and structural and functional network complexity. We created a three-dimensionalin vitromodel of the device-tissue interface by seeding primary cortical cells around microwires. Live imaging of both dye and Adeno-Associated Virus (AAV) - mediated functional, structural, and lipid peroxidation fluorescence was employed to characterize the neuroinflammatory response.Main results.Live imaging of microtissues over time revealed independent innate neuroinflammation, marked by increased OS, decreased neuronal density, and increased functional connectivity. We demonstrated the use of this model for therapeutic screening by directly applying drugs to neural tissue, bypassing low bioavailability through thein vivoblood brain barrier. As there is growing interest in long-acting antioxidant therapies, we tested efficacy of 'perpetual' antioxidant ceria nanoparticles, which reduced OS, increased neuronal density, and protected functional connectivity.Significance.Our three-dimensionalin vitromodel of the device-tissue interface exhibited symptoms of OS-mediated innate neuroinflammation, indicating a significant local immune response to devices. The dysregulation of functional connectivity of microcircuits surround implants suggests the presence of an observer effect, in which the process of recording neural activity may fundamentally change the neural signal. Finally, the demonstration of antioxidant ceria nanoparticle treatment exhibited substantial promise as a neuroprotective and anti-inflammatory treatment strategy.

Manganese ferrite clusters (MFCs) are spherical assemblies of tens to hundreds of primary nanocrystals whose magnetic properties are valuable in diverse applications. Here we describe how to form these materials in a hydrothermal process that permits the independent control of product cluster size (from 30 to 120 nm) and manganese content of the resulting material. Parameters such as the total amount of water added to the alcoholic reaction media and the ratio of manganese to iron precursor are important factors in achieving multiple types of MFC nanoscale products. A fast purification method uses magnetic separation to recover the materials making production of grams of magnetic nanomaterials quite efficient. We overcome the challenge of magnetic nanomaterial aggregation by applying highly charged sulfonate polymers to the surface of these nanomaterials yielding colloidally stable MFCs that remain non-aggregating even in highly saline environments. These non-aggregating, uniform, and tunable materials are excellent prospective materials for biomedical and environmental applications.

Ceria nanoparticles are remarkable antioxidants due to their large cerium(III) content and the possibility of recovering cerium(III) from cerium(IV) after reaction. Here we increase the cerium(III) content of colloidally stable nanoparticles (e.g., nanocrystals) using a reactive polymeric surface coating. Catechol-grafted poly(ethylene glycols) (PEG) polymers of varying lengths and architectures yield materials that are non-aggregating in a variety of aqueous media. Cerium(IV) on the ceria surface both binds and oxidizes the catechol functionality, generating a dark-red colour emblematic of surface-oxidized catechols with a concomitant increase in cerium(III) revealed by X-ray photoemission spectroscopy (XPS). The extent of ceria reduction depends sensitively on the architecture of the coating polymer; small and compact polymer chains pack with high density at the nanoparticle surface yielding the most cerium(III). Nanoparticles with increased surface reduction, quantified by the intensity of their optical absorption and thermogravimetric measures of polymer grafting densities, were more potent antioxidants as measured by a standard TEAC antioxidant assay. For the same core composition nanoparticle antioxidant capacities could be increased over an order of magnitude by tailoring the length and architecture of the reactive surface coatings.

Silver nanomaterials have potent antibacterial properties that are the foundation for their wide commercial use as well as for concerns about their unintended environmental impact. The nanoparticles themselves are relatively biologically inert but they can undergo oxidative dissolution yielding toxic silver ions. A quantitative relationship between silver material structure and dissolution, and thus antimicrobial activity, has yet to be established. Here, this dissolution process and associated biological activity is characterized using uniform nanoparticles with variable dimension, shape, and surface chemistry. From this, a phenomenological model emerges that quantitatively relates material structure to both silver dissolution and microbial toxicity. Shape has the most profound influence on antibacterial activity, and surprisingly, surface coatings the least. These results illustrate how material structure may be optimized for antimicrobial properties and suggest strategies for minimizing silver nanoparticle effects on microbes.

The presence of arsenic in groundwater and other drinking water sources presents a notable public health concern. Although the utilization of iron oxide nanomaterials as arsenic adsorbents has shown promising results in batch experiments, few have succeeded in using nanomaterials in filter setups. In this study, the performance of nanomaterials, supported on sand, was first compared for arsenic adsorption by conducting continuous flow experiments. Iron oxide nanoparticles (IONPs) were prepared with different synthetic methodologies to control the degree of agglomeration. IONPs were prepared by thermal decomposition or coprecipitation and compared with commercially available IONPs. Electron microscopy was used to characterize the degree of agglomeration of the pristine materials after deposition onto the sand. The column experiments showed that IONPs that presented less agglomeration and were well dispersed over the sand had a tendency to be released during water treatment. To overcome this implementation challenge, we proposed the use of clusters of iron oxide nanoparticles (cIONPs), synthesized by a solvothermal methodology, which was explored. An isotherm experiment was also conducted to determine the arsenic adsorption capacities of the iron oxide nanomaterials. cIONPs showed higher adsorption capacities (121.4 mg/g) than the other IONPs (11.1, 6.6, and 0.6 mg/g for thermal decomposition, coprecipitation, and commercially available IONPs, respectively), without the implementation issues presented by IONPs. Our results show that the use of clusters of nanoparticles of other compositions opens up the possibilities for multiple water remediation applications.

Metastasis is the predominant cause of cancer deaths due to solid organ malignancies; however, anticancer drugs are not effective in treating metastatic cancer. Here we report a nanotherapeutic approach that combines magnetic nanocluster-based hyperthermia and free radical generation with an immune checkpoint blockade (ICB) for effective suppression of both primary and secondary tumors. We attached 2,2'-azobis(2-midinopropane) dihydrochloride (AAPH) molecules to magnetic iron oxide nanoclusters (IONCs) to form an IONC-AAPH nanoplatform. The IONC can generate a high level of localized heat under an alternating magnetic field (AMF), which decomposes the AAPH on the cluster surface and produces a large number of carbon-centered free radicals. A combination of localized heating and free radicals can effectively kill tumor cells under both normoxic and hypoxic conditions. The tumor cell death caused by the combination of magnetic heating and free radicals led to the release or exposure of various damage-associated molecule patterns, which promoted the maturation of dendritic cells. Treating the tumor-bearing mice with IONC-AAPH under AMF not only eradicated the tumors but also generated systemic antitumor immune responses. The combination of IONC-AAPH under AMF with anti-PD-1 ICB dramatically suppressed the growth of untreated distant tumors and induced long-term immune memory. This IONC-AAPH based magneto-immunotherapy has the potential to effectively combat metastasis and control cancer recurrence.

Precisely timed activation of genetically targeted cells is a powerful tool for the study of neural circuits and control of cell-based therapies. Magnetic control of cell activity, or ‘magnetogenetics’, using magnetic nanoparticle heating of temperature-sensitive ion channels enables remote, non-invasive activation of neurons for deep-tissue applications and freely behaving animal studies. However, the in vivo response time of thermal magnetogenetics is currently tens of seconds, which prevents precise temporal modulation of neural activity. Moreover, magnetogenetics has yet to achieve in vivo multiplexed stimulation of different groups of neurons. Here we produce subsecond behavioural responses in Drosophila melanogaster by combining magnetic nanoparticles with a rate-sensitive thermoreceptor (TRPA1-A). Furthermore, by tuning magnetic nanoparticles to respond to different magnetic field strengths and frequencies, we achieve subsecond, multichannel stimulation. These results bring magnetogenetics closer to the temporal resolution and multiplexed stimulation possible with optogenetics while maintaining the minimal invasiveness and deep-tissue stimulation possible only by magnetic control.

BACKGROUND Arsenic is one of the most serious drinking water contaminants around the world. The development of iron oxide materials, including nanoparticles, as sorbents for arsenic remediation has shown promising results in recent years. Some of these materials are already used as commercial-grade arsenic sorbents. However, the use of iron-oxide nanoparticles (IONPs) has barely been used in real-world conditions. This work compares commercial IONPs with three proven arsenic sorbents. RESULTS The full chemical characterization includes electron microscopy, X-ray diffraction and X-ray photon spectroscopy to determine morphology, crystalline structure and elemental analysis, respectively. Arsenic remediation studies also were conducted in both batch and column set-ups with real water samples from Salamanca, Mexico. The conditions (pH 8, high concentration of silica and presence of other interferences) found in this site are outside the recommended parameters of operations for most of the arsenic sorbents. All of the materials observed a negative effect because of silica presence. However, the effects observed in batch did not correlate directly to the column tests. This is important when evaluating the viability of using sorbents in specific conditions. CONCLUSIONS A feasibility analysis revealed that some commercial sorbents can treat water with the conditions presented in the selected site, but the cost of treatment is not viable for developing countries. In addition, the generated waste by using these sorbents would be substantial. These challenges could be diminished by using nanoparticles, yet the commercially-available IONPs do not fill this gap. Better designed nanomaterials are still needed for arsenic removal. (c) 2022 Society of Chemical Industry (SCI).

Magnetic nanocrystal clusters exhibit unique properties that differ from the constituent nanocrystals due to the intracluster interactions. This Review summarizes the recent advances in the synthesis and application of magnetic nanocrystal clusters. Specifically, we describe the formation mechanism of the clusters, discuss the strategies to control the dimensions of the clusters and primary nanocrystals, and showcase the applications of clusters in magnetic hyperthermia cancer therapy, magnetic resonance imaging, drug delivery, wastewater treatment, and the formation of photonic crystals. The opportunities and challenges in improving magnetic nanocrystal clusters for different applications are also discussed.

Flexible perovskite light‐emitting diodes (FPLEDs) that combine the superior optoelectronic properties of perovskites with the potential of highly flexible, stretchable, and portable electronics have emerged as a new class of revolutionary LED devices for various applications. This article focuses on the recent FPLED research and development. The flexible substrate and electrode are summarized, and the relationship between structure optimization and device performance is established. In order to improve the flexibility and optoelectronic characteristics of FPLEDs, some strategies are put forward, such as the optimization of flexible electrode and emissive layer, the interface engineering, the energy level adjustment, the improvement of light extraction, as well as the improvement of flexibility and stretchability. Furthermore, the future development of FPLEDs is prospected.

Lead-based halide perovskites have received great attention in light-emitting applications due to their excellent properties, including high photoluminescence quantum yield (PLQY), tunable emission wavelength, and facile solution preparation. In spite of excellent characteristics, the presence of toxic element lead directly obstructs their further commercial development. Hence, exploiting lead-free halide perovskite materials with superior properties is urgent and necessary. In this review, the deep-seated reasons that benefit light emission for halide perovskites, which help to develop lead-free halide perovskites with excellent performance, are first emphasized. Recent advances in lead-free halide perovskite materials (single crystals, thin films, and nanocrystals with different dimensionalities) from synthesis, crystal structures, optical and optoelectronic properties to applications are then systematically summarized. In particular, phosphor-converted LEDs and electroluminescent LEDs using lead-free halide perovskites are fully examined. Ultimately, based on current development of lead-free halide perovskites, the future directions of lead-free halide perovskites in terms of materials and light-emitting devices are discussed.

The recording instability of neural implants due to neuroinflammation at the device-tissue interface (DTI) is a primary roadblock to broad adoption of brain-machine interfaces. While a multiphasic immune response, marked by glial scaring, oxidative stress (OS), and neurodegeneration, is well-characterized, the independent contributions of systemic and local “innate” immune responses are not well-understood. Three-dimensional primary neural cultures provide a unique environment for studying the drivers of neuroinflammation by decoupling the innate and systemic immune systems, while conserving an endogenous extracellular matrix and structural and functional network complexity. We created a three-dimensional in vitro model of the DTI by seeding primary cortical cells around microwires. Live imaging of microtissues over time revealed independent innate neuroinflammation, marked by increased OS, decreased neuronal density, and increased functional connectivity. We demonstrated the use of this model for therapeutic screening by directly applying drugs to neural tissue, bypassing low bioavailability through the in vivo blood brain barrier. As there is growing interest in long-acting antioxidant therapies, we tested efficacy of “perpetual” antioxidant ceria nanoparticles, which reduced OS, increased neuronal density, and protected functional connectivity. Overall, our avascular in vitro model of the DTI exhibited symptoms of OS-mediated innate neuroinflammation which were mitigated by antioxidant intervention.

Millions of people a year receive magnetic resonance imaging (MRI) contrast agents for the diagnosis of conditions as diverse as fatty liver disease and cancer. Gadolinium chelates, which provide preferred T 1 contrast, are the current standard but face an uncertain future due to increasing concerns about their nephrogenic toxicity as well as poor performance in high‐field MRI scanners. Gadolinium‐containing nanocrystals are interesting alternatives as they bypass the kidneys and can offer the possibility of both intracellular accumulation and active targeting. Nanocrystal contrast performance is notably limited, however, as their organic coatings block water from close interactions with surface Gadoliniums. Here, these steric barriers to water exchange are minimized through shape engineering of plate‐like nanocrystals that possess accessible Gadoliniums at their edges. Sulfonated surface polymers promote second‐sphere relaxation processes that contribute remarkable contrast even at the highest fields ( r 1 = 32.6 × 10 −3 m Gd −1 s −1 at 9.4 T). These noncytotoxic materials release no detectable free Gadolinium even under mild acidic conditions. They preferentially accumulate in the liver of mice with a circulation half‐life 50% longer than commercial agents. These features allow these T 1 MRI contrast agents to be applied for the first time to the ex vivo detection of nonalcoholic fatty liver disease in mice.

The use of magnetism in medicine has changed dramatically since its first application by the ancient Greeks in 624 BC. Now, by leveraging magnetic nanoparticles, investigators have developed a range of modern applications that use external magnetic fields to manipulate biological systems. Drug delivery systems that incorporate these particles can target therapeutics to specific tissues without the need for biological or chemical cues. Once precisely located within an organism, magnetic nanoparticles can be heated by oscillating magnetic fields, which results in localized inductive heating that can be used for thermal ablation or more subtle cellular manipulation. Biological imaging can also be improved using magnetic nanoparticles as contrast agents; several types of iron oxide nanoparticles are US Food and Drug Administration (FDA)-approved for use in magnetic resonance imaging (MRI) as contrast agents that can improve image resolution and information content. New imaging modalities, such as magnetic particle imaging (MPI), directly detect magnetic nanoparticles within organisms, allowing for background-free imaging of magnetic particle transport and collection. "Lab-on-a-chip" technology benefits from the increased control that magnetic nanoparticles provide over separation, leading to improved cellular separation. Magnetic separation is also becoming important in next-generation immunoassays, in which particles are used to both increase sensitivity and enable multiple analyte detection. More recently, the ability to manipulate material motion with external fields has been applied in magnetically actuated soft robotics that are designed for biomedical interventions. In this review article, the origins of these various areas are introduced, followed by a discussion of current clinical applications, as well as emerging trends in the study and application of these materials.