In situ electrochemical generation of nitric oxide for neuronal modulation

The emerging role of nitric oxide in the synaptic dysfunction of vascular dementia

With an increase in global aging, the number of people affected by cerebrovascular diseases is also increasing, and the incidence of vascular dementia-closely related to cerebrovascular risk-is increasing at an epidemic rate. However, few therapeutic options exist that can markedly improve the cognitive impairment and prognosis of vascular dementia patients. Similarly in Alzheimer's disease and other neurological disorders, synaptic dysfunction is recognized as the main reason for cognitive decline. Nitric oxide is one of the ubiquitous gaseous cellular messengers involved in multiple physiological and pathological processes of the central nervous system. Recently, nitric oxide has been implicated in regulating synaptic plasticity and plays an important role in the pathogenesis of vascular dementia. This review introduces in detail the emerging role of nitric oxide in physiological and pathological states of vascular dementia and summarizes the diverse effects of nitric oxide on different aspects of synaptic dysfunction, neuroinflammation, oxidative stress, and blood-brain barrier dysfunction that underlie the progress of vascular dementia. Additionally, we propose that targeting the nitric oxide-sGC-cGMP pathway using certain specific approaches may provide a novel therapeutic strategy for vascular dementia.

Multifunctional Nanomaterials for Advancing Neural Interfaces: Recording, Stimulation, and Beyond

ConspectusNeurotechnology has seen dramatic improvements in the last three decades. The major focus in the field has been to design electrical communication platforms with high spatial resolution, stability, and translatability for understanding and affecting neural pathways. The deployment of nanomaterials in bioelectronics has enhanced the capabilities of conventional approaches employing microelectrode arrays (MEAs) for electrical interfaces, allowing the construction of miniaturized, high-performance neuroelectronics (Garg, R.; et al. ACS Appl. Nano Mater. 2023, 6, 8495). While these advancements in the electrical neuronal interface have revolutionized neurotechnology both in scale and breadth, an in-depth understanding of neurons' interactions is challenging due to the complexity of the environments where the cells and tissues are laid. The activity of large, three-dimensional neuronal systems has proven difficult to accurately monitor and modulate, and chemical cell-cell communication is often completely neglected. Recent breakthroughs in nanotechnology have provided opportunities to use new nonelectric modes of communication with neurons and to significantly enhance electrical signal interface capabilities. The enhanced electrochemical activity and optical activity of nanomaterials owing to their nonbulk electronic properties and surface nanostructuring have seen extensive utilization. Nanomaterials' enhanced optical activity enables remote neural state modulation, whereas the defect-rich surfaces provide an enormous number of available electrocatalytic sites for neurochemical detection and electrochemical modulation of cell microenvironments through Faradaic processes. Such unique properties can allow multimodal neural interrogation toward generating closed-loop interfaces with access to more complete neural state descriptors. In this Account, we will review recent advances and our efforts spearheaded toward utilizing nanostructured electrodes for enhanced bidirectional interfaces with neurons, the application of unique hybrid nanomaterials for remote nongenetic optical stimulation of neurons, tunable nanomaterials for highly sensitive and selective neurotransmitter detection, and the utilization of nanomaterials as electrocatalysts toward electrochemically modulating cellular activity. We highlight applications of these technologies across cell types through nanomaterial engineering with a focus on multifunctional graphene nanostructures applied though several modes of neural modulation but also an exploration of broad material classes for maximizing the potency of closed-loop bioelectronics.

Single-atom nanozymes for antibacterial applications

Bacteria have always been a thorny problem that threatens human health and food safety. Conventional antibiotic treatment often leads to the emergence of drug resistance. Therefore, the development of more effective antibacterial agents is urgently needed. Single-atom nanozymes (SAzymes) can efficiently eliminate bacteria due to their high atomic utilization, abundant active centers, and good natural enzyme mimicry, providing a potential alternative choice for antibiotics in antibacterial applications. Here, the antibacterial applications of SAzymes are reviewed and their catalytic properties are discussed from the aspects of active sites, coordination environment regulation and carrier selection. Then, the antibacterial effect of SAzymes is elaborated in combination with photothermal therapy (PTT) and sonodynamic therapy (SDT). Finally, the problems faced by SAzymes in antibacterial applications and their future development potential are proposed.

Active biointegrated living electronics for managing inflammation

Seamless interfaces between electronic devices and biological tissues stand to revolutionize disease diagnosis and treatment. However, biological and biomechanical disparities between synthetic materials and living tissues present challenges at bioelectrical signal transduction interfaces. We introduce the active biointegrated living electronics (ABLE) platform, encompassing capabilities across the biogenic, biomechanical, and bioelectrical properties simultaneously. The living biointerface, comprising a bioelectronics layout and a Staphylococcus epidermidis-laden hydrogel composite, enables multimodal signal transduction at the microbial-mammalian nexus. The extracellular components of the living hydrogels, prepared through thermal release of naturally occurring amylose polymer chains, are viscoelastic, capable of sustaining the bacteria with high viability. Through electrophysiological recordings and wireless probing of skin electrical impedance, body temperature, and humidity, ABLE monitors microbial-driven intervention in psoriasis.

Materials and Structural Designs toward Motion Artifact-Free Bioelectronics

Bioelectronics encompassing electronic components and circuits for accessing human information play a vital role in real-time and continuous monitoring of biophysiological signals of electrophysiology, mechanical physiology, and electrochemical physiology. However, mechanical noise, particularly motion artifacts, poses a significant challenge in accurately detecting and analyzing target signals. While software-based "postprocessing" methods and signal filtering techniques have been widely employed, challenges such as signal distortion, major requirement of accurate models for classification, power consumption, and data delay inevitably persist. This review presents an overview of noise reduction strategies in bioelectronics, focusing on reducing motion artifacts and improving the signal-to-noise ratio through hardware-based approaches such as "preprocessing". One of the main stress-avoiding strategies is reducing elastic mechanical energies applied to bioelectronics to prevent stress-induced motion artifacts. Various approaches including strain-compliance, strain-resistance, and stress-damping techniques using unique materials and structures have been explored. Future research should optimize materials and structure designs, establish stable processes and measurement methods, and develop techniques for selectively separating and processing overlapping noises. Ultimately, these advancements will contribute to the development of more reliable and effective bioelectronics for healthcare monitoring and diagnostics.

Application of magnetism in tissue regeneration: recent progress and future prospects

Tissue regeneration is a hot topic in the field of biomedical research in this century. Material composition, surface topology, light, ultrasonic, electric field and magnetic fields (MFs) all have important effects on the regeneration process. Among them, MFs can provide nearly non-invasive signal transmission within biological tissues, and magnetic materials can convert MFs into a series of signals related to biological processes, such as mechanical force, magnetic heat, drug release, etc. By adjusting the MFs and magnetic materials, desired cellular or molecular-level responses can be achieved to promote better tissue regeneration. This review summarizes the definition, classification and latest progress of MFs and magnetic materials in tissue engineering. It also explores the differences and potential applications of MFs in different tissue cells, aiming to connect the applications of magnetism in various subfields of tissue engineering and provide new insights for the use of magnetism in tissue regeneration.

Ratiometric fluorescent biosensor for detection and real-time imaging of nitric oxide in mitochondria of living cells

Nitric oxide (NO), a ubiquitous gaseous messenger, plays critical roles in various pathological and physiological progresses. The abnormal levels of NO in organisms are closely related to a large number of maladies. Mitochondria are the main area that produce NO in mammalian cells. Thus, detecting and real-time imaging of NO in mitochondria is of great significance for exploring the biological functions of NO. Herein, a ratiometric fluorescent biosensor (Mito-GNP-pNO520) is developed for sensitive and selective detection and real-time imaging of NO in mitochondria of living cells. The detection is achieved through the fluorescence off-on response of Mito-GNP-pNO520 toward NO. This biosensor shows excellent characteristics, such as high sensitivity toward NO with a low detection limit of 0.25 nM, exclusive selectivity to NO without interference from other substances, good biological stability and low cytotoxicity. More importantly, the biosensor is specifically located in mitochondria, enabling the detection and real-time imaging of endogenous and exogenous NO in mitochondria of living cells. Therefore, our biosensor offers a new approach for dynamic detecting and real-time imaging of NO in subcellular organelles, providing an opportunity to explore new biological effects of NO.

Strategies for gaseous neuromodulator release in chemical neuroscience: Experimental approaches and translational validation

Gasotransmitters are a group of short-lived gaseous signaling molecules displaying diverse biological functions depending upon their localized concentration. Nitric oxide (NO), hydrogen sulfide (H2S), and carbon monoxide (CO) are three important examples of endogenously produced gasotransmitters that play a crucial role in human neurophysiology and pathogenesis. Alterations in their optimal physiological concentrations can lead to various severe pathophysiological consequences, including neurological disorders. Exogenous administration of gasotransmitters has emerged as a prominent therapeutic approach for treating such neurological diseases. However, their gaseous nature and short half-life limit their therapeutic delivery. Therefore, developing synthetic gasotransmitter-releasing strategies having control over the release and duration of these gaseous molecules has become imperative. However, the complex chemistry of synthesis and the challenges of specific quantified delivery of these gases, make their therapeutic application a challenging task. This review article provides a focused overview of emerging strategies for delivering gasotransmitters in a controlled and sustained manner to re-establish neurophysiological homeostasis.

Magnetoelectric Nanodiscs Enable Wireless Transgene-Free Neuromodulation

Deep-brain stimulation (DBS) with implanted electrodes revolutionized treatment of movement disorders and empowered neuroscience studies. Identifying less invasive alternatives to DBS may further extend its clinical and research applications. Nanomaterial-mediated transduction of magnetic fields into electric potentials offers an alternative to invasive DBS. Here, we synthesize magnetoelectric nanodiscs (MENDs) with a core-double shell Fe3O4-CoFe2O4-BaTiO3 architecture with efficient magnetoelectric coupling. We find robust responses to magnetic field stimulation in neurons decorated with MENDs at a density of 1 μg/mm2 despite individual-particle potentials below the neuronal excitation threshold. We propose a model for repetitive subthreshold depolarization, which combined with cable theory, corroborates our findings in vitro and informs magnetoelectric stimulation in vivo. MENDs injected into the ventral tegmental area of genetically intact mice at concentrations of 1 mg/mL enable remote control of reward behavior, setting the stage for mechanistic optimization of magnetoelectric neuromodulation and inspiring its future applications in fundamental and translational neuroscience.

Submillimeter Multifunctional Ferromagnetic Fiber Robots for Navigation, Sensing, and Modulation

Small-scale robots capable of remote active steering and navigation offer great potential for biomedical applications. However, the current design and manufacturing procedure impede their miniaturization and integration of various diagnostic and therapeutic functionalities. Herein, submillimeter fiber robots that can integrate navigation, sensing, and modulation functions are presented. These fiber robots are fabricated through a scalable thermal drawing process at a speed of 4 meters per minute, which enables the integration of ferromagnetic, electrical, optical, and microfluidic composite with an overall diameter of as small as 250 µm and a length of as long as 150 m. The fiber tip deflection angle can reach up to 54o under a uniform magnetic field of 45 mT. These fiber robots can navigate through complex and constrained environments, such as artificial vessels and brain phantoms. Moreover, Langendorff mouse hearts model, glioblastoma micro platforms, and in vivo mouse models are utilized to demonstrate the capabilities of sensing electrophysiology signals and performing a localized treatment. Additionally, it is demonstrated that the fiber robots can serve as endoscopes with embedded waveguides. These fiber robots provide a versatile platform for targeted multimodal detection and treatment at hard-to-reach locations in a minimally invasive and remotely controllable manner.

In Situ Forming of Nitric Oxide and Electric Stimulus for Nerve Therapy by Wireless Chargeable Gold Yarn-Dynamos

Endogenous signals, namely nitric oxide (NO) and electrons, play a crucial role in regulating cell fate as well as the vascular and neuronal systems. Unfortunately, utilizing NO and electrical stimulation in clinical settings can be challenging due to NO's short half-life and the invasive electrodes required for electrical stimulation. Additionally, there is a lack of tools to spatiotemporally control gas release and electrical stimulation. To address these issues, an "electromagnetic messenger" approach that employs on-demand high-frequency magnetic field (HFMF) to trigger NO release and electrical stimulation for restoring brain function in cases of traumatic brain injury is introduced. The system comprises a NO donor (poly(S-nitrosoglutathione), pGSNO)-conjugated on a gold yarn-dynamos (GY) and embedded in an implantable silk in a microneedle. When subjected to HFMF, conductive GY induces eddy currents that stimulate the release of NO from pGSNO. This process significantly enhances neural stem cell (NSC) synapses' differentiation and growth. The combined strategy of using NO and electrical stimulation to inhibit inflammation, angiogenesis, and neuronal interrogation in traumatic brain injury is demonstrated in vivo.

Nitric Oxide: Physiological Functions, Delivery, and Biomedical Applications

Nitric oxide (NO) is a gaseous molecule that has a central role in signaling pathways involved in numerous physiological processes (e.g., vasodilation, neurotransmission, inflammation, apoptosis, and tumor growth). Due to its gaseous form, NO has a short half-life, and its physiology role is concentration dependent, often restricting its function to a target site. Providing NO from an external source is beneficial in promoting cellular functions and treatment of different pathological conditions. Hence, the multifaceted role of NO in physiology and pathology has garnered massive interest in developing strategies to deliver exogenous NO for the treatment of various regenerative and biomedical complexities. NO-releasing platforms or donors capable of delivering NO in a controlled and sustained manner to target tissues or organs have advanced in the past few decades. This review article discusses in detail the generation of NO via the enzymatic functions of NO synthase as well as from NO donors and the multiple biological and pathological processes that NO modulates. The methods for incorporating of NO donors into diverse biomaterials including physical, chemical, or supramolecular techniques are summarized. Then, these NO-releasing platforms are highlighted in terms of advancing treatment strategies for various medical problems.

New Opportunities of Electrochemistry for Monitoring, Modulating, and Mimicking the Brain Signals

In vivo electrochemistry is a powerful key for unlocking the chemical consequences in neural networks of the brain. The past half-century has witnessed the technology revolutionization in this field along with innovations in electrochemical concepts, principles, methods, and devices. Present applications of electrochemical approaches have extended from measuring neurochemical concentrations to modulating and mimicking brain signals. In this Perspective, newly reported strategies for tackling long-standing challenges of in vivo electrochemical brain monitoring (i.e., basal level measurement, electroactivity dependence, in vivo stability, neuron compatibility, multiplexity, and implantable device fabrication) are highlighted. Moreover, recent progress on neuromodulation tools and neuromorphic devices in electrochemical frameworks is introduced. A glimpse of future opportunities for electrochemistry in brain research is offered at last.

Conjugation of bone grafts with NO-delivery dinitrosyl iron complexes promotes synergistic osteogenesis and angiogenesis in rat calvaria bone defects

Craniofacial/jawbone deformities remain a significant clinical challenge in restoring facial/dental functions and esthetics. Despite the reported therapeutics for clinical bone tissue regeneration, the bioavailability issue of autografts and limited regeneration efficacy of xenografts/synthetic bone substitutes, however, inspire continued efforts towards functional conjugation and improvement of bioactive bone graft materials. Regarding the potential of nitric oxide (NO) in tissue engineering, herein, functional conjugation of NO-delivery dinitrosyl iron complex (DNIC) and osteoconductive bone graft materials was performed to optimize the spatiotemporal control over the delivery of NO and to activate synergistic osteogenesis and angiogenesis in rat calvaria bone defects. Among three types of biomimetic DNICs, [Fe2(μ-SCH2CH2COOH)2(NO)4] (DNIC-COOH) features a steady kinetics for cellular uptake by MC3T3-E1 osteoblast cells followed by intracellular assembly of protein-bound DNICs and release of NO. This steady kinetics for intracellular delivery of NO by DNIC-COOH rationalizes its biocompatibility and wide-spectrum cell proliferation effects on MC3T3-E1 osteoblast cells and human umbilical vein endothelial cells (HUVECs). Moreover, the bridging [SCH2CH2COOH]- thiolate ligands in DNIC-COOH facilitate its chemisorption to deproteinized bovine bone mineral (DBBM) and physisorption onto TCP (β-tricalcium phosphate), respectively, which provides a mechanism to control the kinetics for the local release of loaded DNIC-COOH. Using rats with calvaria bone defects as an in vivo model, DNIC-DBBM/DNIC-TCP promotes the osteogenic and angiogenic activity ascribed to functional conjugation of osteoconductive bone graft materials and NO-delivery DNIC-COOH. Of importance, the therapeutic efficacy of DNIC-DBBM/DNIC-TCP on enhanced compact bone formation after treatment for 4 and 12 weeks supports the potential for clinical application to regenerative medicine.

Recent Advances in Functional Nanomaterials for Catalytic Generation of Nitric Oxide: A Mini Review

As a gaseous second messenger, nitric oxide (NO) plays an important role in a series of signal pathways. Research on the NO regulation for various disease treatments has aroused wide concern. However, the lack of accurate, controllable, and persistent release of NO has significantly limited the application of NO therapy. Profiting from the booming development of advanced nanotechnology, a mass of nanomaterials with the properties of controllable release have been developed to seek new and effective NO nano-delivery approaches. Nano-delivery systems that generate NO through catalytic reactions exhibit unique superiority in terms of precise and persistent release of NO. Although certain achievements have been made in the catalytically active NO delivery nanomaterials, some basic but critical issues, such as the concept of design, are of low attention. Herein, an overview of the generation of NO through catalytic reactions and the design principles of related nanomaterials are summarized. Then, the nanomaterials that generate NO through catalytic reactions are classified. Finally, the bottlenecks and perspectives are also discussed in depth for the future development of catalytical NO generation nanomaterials.

Fully Biodegradable and Long-Term Operational Primary Zinc Batteries as Power Sources for Electronic Medicine

Given the advantages of high energy density and easy deployment, biodegradable primary battery systems remain as a promising power source to achieve bioresorbable electronic medicine, eliminating secondary surgeries for device retrieval. However, currently available biobatteries are constrained by operational lifetime, biocompatibility, and biodegradability, limiting potential therapeutic outcomes as temporary implants. Herein, we propose a fully biodegradable primary zinc-molybdenum (Zn-Mo) battery with a prolonged functional lifetime of up to 19 days and desirable energy capacity and output voltage compared with reported primary Zn biobatteries. The Zn-Mo battery system is shown to have excellent biocompatibility and biodegradability and can significantly promote Schwann cell proliferation and the axonal growth of dorsal root ganglia. The biodegradable battery module with 4 Zn-Mo cells in series using gelatin electrolyte accomplishes electrochemical generation of signaling molecules (nitric oxide, NO) that can modulate the behavior of the cellular network, with efficacy comparable with that of conventional power sources. This work sheds light on materials strategies and fabrication schemes to develop high-performance biodegradable primary batteries to achieve a fully bioresorbable electronic platform for innovative medical treatments that could be beneficial for health care.

Multifunctional ferromagnetic fiber robots for navigation, sensing, and treatment in minimally invasive surgery

Small-scale robots capable of remote active steering and navigation offer great potential for biomedical applications. However, the current design and manufacturing procedure impede their miniaturization and integration of various diagnostic and therapeutic functionalities. Here, we present a robotic fiber platform for integrating navigation, sensing, and therapeutic functions at a submillimeter scale. These fiber robots consist of ferromagnetic, electrical, optical, and microfluidic components, fabricated with a thermal drawing process. Under magnetic actuation, they can navigate through complex and constrained environments, such as artificial vessels and brain phantoms. Moreover, we utilize Langendorff mouse hearts model, glioblastoma microplatforms, and in vivo mouse models to demonstrate the capabilities of sensing electrophysiology signals and performing localized treatment. Additionally, we demonstrate that the fiber robots can serve as endoscopes with embedded waveguides. These fiber robots provide a versatile platform for targeted multimodal detection and treatment at hard-to-reach locations in a minimally invasive and remotely controllable manner.

Functional Fiber Materials to Smart Fiber Devices

The development of fiber materials has accompanied the evolution of human civilization for centuries. Recent advances in materials science and chemistry offered fibers new applications with various functions, including energy harvesting, energy storing, displaying, health monitoring and treating, and computing. The unique one-dimensional shape of fiber devices endows them advantages to work as human-interfaced electronics due to the small size, lightweight, flexibility, and feasibility for integration into large-scale textile systems. In this review, we first present a discussion of the basics of fiber materials and the design principles of fiber devices, followed by a comprehensive analysis on recently developed fiber devices. Finally, we provide the current challenges facing this field and give an outlook on future research directions. With novel fiber devices and new applications continuing to be discovered after two decades of research, we envision that new fiber devices could have an important impact on our life in the near future.

Targeted delivery of Nitric Oxide triggered by α-Glucosidase to Ameliorate NSAIDs-induced Enteropathy

Nonsteroidal anti-inflammatory drugs (NSAIDs) increase risks of severe small intestinal injuries. Development of effective therapeutic strategies to overcome this issue remains challenging. Nitric oxide (NO) as a gaseous mediator plays a protective role in small intestinal injuries. However, small intestine-specific delivery systems for NO have not been reported yet. In this study, we reported a small intestine-targeted polymeric NO donor (CS-NO) which was synthesized by covalent grafting of α-glucosidase-activated NO donor onto chitosan. In vitro and in vivo experiments demonstrated that CS-NO could be activated by intestinal α-glucosidase to release NO in the small intestine. Pre-treatment of mice with CS-NO significantly alleviated small intestinal damage induced by indomethacin, as demonstrated by down-regulation of the levels of pro-inflammatory cytokines and chemokines CXCL1/KC. Moreover, CS-NO also attenuated indomethacin-induced gut barrier dysfunction as evidenced by up-regulation of the levels of tight junction proteins and restoration of the levels of goblet cells and MUC2 production. Meanwhile, CS-NO effectively restored the defense function of Paneth cells against pathogens in small intestine. Our present study paves the way to develop NO-based therapeutic strategy for NSAIDs-induced small intestinal injuries.

Modulating cell signalling in vivo with magnetic nanotransducers

Weak magnetic fields offer nearly lossless transmission of signals within biological tissue. Magnetic nanomaterials are capable of transducing magnetic fields into a range of biologically relevant signals in vitro and in vivo. These nanotransducers have recently enabled magnetic control of cellular processes, from neuronal firing and gene expression to programmed apoptosis. Effective implementation of magnetically controlled cellular signalling relies on careful tailoring of magnetic nanotransducers and magnetic fields to the responses of the intended molecular targets. This primer discusses the versatility of magnetic modulation modalities and offers practical guidelines for selection of appropriate materials and field parameters, with a particular focus on applications in neuroscience. With recent developments in magnetic instrumentation and nanoparticle chemistries, including those that are commercially available, magnetic approaches promise to empower research aimed at connecting molecular and cellular signalling to physiology and behaviour in untethered moving subjects.

Electrochemical Generation of Nitric Oxide for Medical Applications

Over the past 30 years, the significance of nitric oxide (NO) has become increasingly apparent in mammalian physiology. It is biosynthesized by three isoforms of nitric oxide synthases (NOS): neuronal (nNOS), endothelial (eNOS), and inducible (iNOS). Neuronal and eNOS both produce low levels of NO (nM) as a signaling agent and vasodilator, respectively. Inducible (iNOS) is present in activated macrophages at sites of infection to generate acutely toxic (μM) levels of NO as part of the mammalian immune defense mechanism. These discoveries have led to numerous animal and clinical studies to evaluate the potential therapeutic utility of NO in various medical operations/treatments, primarily using NO gas (via gas-cylinders) as the NO source. In this review, we focus specifically on recent advances in the electrochemical generation of NO (E-NOgen) as an alternative means to generate NO from cheap and inert sources, and the fabrication and testing of biomedical devices that utilize E-NOgen to controllably generate NO for medical applications.

Protective effect of platinum nano-antioxidant and nitric oxide against hepatic ischemia-reperfusion injury

Therapeutic interventions of hepatic ischemia-reperfusion injury to attenuate liver dysfunction or multiple organ failure following liver surgery and transplantation remain limited. Here we present an innovative strategy by integrating a platinum nanoantioxidant and inducible nitric oxide synthase into the zeolitic imidazolate framework-8 based hybrid nanoreactor for effective prevention of ischemia-reperfusion injury. We show that platinum nanoantioxidant can scavenge excessive reactive oxygen species at the injury site and meanwhile generate oxygen for subsequent synthesis of nitric oxide under the catalysis of nitric oxide synthase. We find that such cascade reaction successfully achieves dual protection for the liver through reactive oxygen species clearance and nitric oxide regulation, enabling reduction of oxidative stress, inhibition of macrophage activation and neutrophil recruitment, and ensuring suppression of proinflammatory cytokines. The current work establishes a proof of concept of multifunctional nanotherapeutics against ischemia-reperfusion injury, which may provide a promising intervention solution in clinical use.

Pharmacological interventions against hepatic ischemia-reperfusion injury remain limited. Here, the authors provide a nanotherapeutics-based solution combining reactive oxygen species scavenging and nitric oxide modulation.

Nitric Oxide Induces Immunogenic Cell Death and Potentiates Cancer Immunotherapy

Tumor cells undergoing immunogenic cell death (ICD) release immunogenic damage-associated molecular patterns (DAMPs) to trigger a long-term protective antitumor response. ICD can be induced by certain pathogens, chemotherapeutics, and physical modalities. In this work, we demonstrate that a gaseous molecule, specifically nitric oxide (NO), can induce a potent ICD effect. NO exerts cytotoxic effects that are accompanied by the emission of DAMPs based on the endoplasmic reticulum stress and mitochondrial dysfunction pathways. Released DAMPs elicit immunological protection against a subsequent rechallenge of syngeneic tumor cells in immunocompetent mice. We prepare polynitrosated polyesters with high NO storage capacity through a facile polycondensation reaction followed by a postsynthetic modification. The polynitrosated polyesters-based NO nanogenerator (NanoNO) that enables efficient NO delivery and controlled NO release in tumors induces a sufficient ICD effect. In different immune-intact models of tumors, the NanoNO exhibits significant tumor growth suppression and increases the local dose of immunogenic signals and T cell infiltrations, ultimately prolonging survival. In addition, the NanoNO synergizes with the PD-1 blockade to prevent metastasis. We conclude not only that NO is a potent ICD inducer for cancer immunotherapy but also that it expands the range of ICD inducers into the field of gaseous molecules.

Delivery of nitric oxide-releasing silica nanoparticles for in vivo revascularization and functional recovery after acute peripheral nerve crush injury

Nitric oxide (NO) has been shown to promote revascularization and nerve regeneration after peripheral nerve injury. However, in vivo application of NO remains challenging due to the lack of stable carrier materials capable of storing large amounts of NO molecules and releasing them on a clinically meaningful time scale. Recently, a silica nanoparticle system capable of reversible NO storage and release at a controlled and sustained rate was introduced. In this study, NO-releasing silica nanoparticles (NO-SNs) were delivered to the peripheral nerves in rats after acute crush injury, mixed with natural hydrogel, to ensure the effective application of NO to the lesion. Microangiography using a polymer dye and immunohistochemical staining for the detection of CD34 (a marker for revascularization) results showed that NO-releasing silica nanoparticles increased revascularization at the crush site of the sciatic nerve. The sciatic functional index revealed that there was a significant improvement in sciatic nerve function in NO-treated animals. Histological and anatomical analyses showed that the number of myelinated axons in the crushed sciatic nerve and wet muscle weight excised from NO-treated rats were increased. Moreover, muscle function recovery was improved in rats treated with NO-SNs. Taken together, our results suggest that NO delivered to the injured sciatic nerve triggers enhanced revascularization at the lesion in the early phase after crushing injury, thereby promoting axonal regeneration and improving functional recovery.

Magnetic Responsive Release of Nitric Oxide from an MOF-Derived Fe3O4@PLGA Microsphere for the Treatment of Bacteria-Infected Cutaneous Wound

Nitric oxide (NO) is an essential endogenous signaling molecule regulating multifaceted physiological functions in the (cardio)vascular, neuronal, and immune systems. Due to the short half-life and location-/concentration-dependent physiological function of NO, translational application of NO as a novel therapeutic approach, however, awaits a strategy for spatiotemporal control on the delivery of NO. Inspired by the magnetic hyperthermia and magneto-triggered drug release featured by Fe₃O₄ conjugates, in this study, we aim to develop a magnetic responsive NO-release material (MagNORM) featuring dual NO-release phases, namely, burst and steady release, for the selective activation of NO-related physiology and treatment of bacteria-infected cutaneous wound. After conjugation of NO-delivery [Fe(μ-S-thioglycerol)(NO)₂]₂ with a metal-organic framework (MOF)-derived porous Fe₃O₄@C, encapsulation of obtained conjugates within the thermo-responsive poly(lactic-co-glycolic acid) (PLGA) microsphere completes the assembly of MagNORM. Through continuous/pulsatile/no application of the alternating magnetic field (AMF) to MagNORM, moreover, burst/intermittent/slow release of NO from MagNORM demonstrates the AMF as an ON/OFF switch for temporal control on the delivery of NO. Under continuous application of the AMF, in particular, burst release of NO from MagNORM triggers an effective anti-bacterial activity against both Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli). In addition to the magneto-triggered bactericidal effect of MagNORM against E. coli-infected cutaneous wound in mice, of importance, steady release of NO from MagNORM without the AMF promotes the subsequent collagen formation and wound healing in mice.

Biology-guided engineering of bioelectrical interfaces

Bioelectrical interfaces that bridge biotic and abiotic systems have heightened the ability to monitor, understand, and manipulate biological systems and are catalyzing profound progress in neuroscience research, treatments for heart failure, and microbial energy systems. With advances in nanotechnology, bifunctional and high-density devices with tailored structural designs are being developed to enable multiplexed recording or stimulation across multiple spatial and temporal scales with resolution down to millisecond-nanometer interfaces, enabling efficient and effective communication with intracellular electrical activities in a relatively noninvasive and biocompatible manner. This review provides an overview of how biological systems guide the design, engineering, and implementation of bioelectrical interfaces for biomedical applications. We investigate recent advances in bioelectrical interfaces for applications in nervous, cardiac, and microbial systems, and we also discuss the outlook of state-of-the-art biology-guided bioelectrical interfaces with high biocompatibility, extended long-term stability, and integrated system functionality for potential clinical usage.

Freestanding nanomaterials for subcellular neuronal interfaces

Current technological advances in neural probing and modulation have enabled an extraordinary glimpse into the intricacies of the nervous system. Particularly, nanomaterials are proving to be an incredibly versatile platform for neurological applications owing to their biocompatibility, tunability, highly specific targeting and sensing, and long-term chemical stability. Among the most desirable nanomaterials for neuroengineering, freestanding nanomaterials are minimally invasive and remotely controlled. This review outlines the most recent developments of freestanding nanomaterials that operate on the neuronal interface. First, the different nanomaterials and their mechanisms for modulating neurons are explored to provide a basis for how freestanding nanomaterials operate. Then, the three main applications of subcellular neuronal engineering-modulating neuronal behavior, exploring fundamental neuronal mechanism, and recording neuronal signal-are highlighted with specific examples of current advancements. Finally, we conclude with our perspective on future nanomaterial designs and applications.

Faradaic Pixels for Precise Hydrogen Peroxide Delivery to Control M-Type Voltage-Gated Potassium Channels

H2 O2 plays a significant role in a range of physiological processes where it performs vital tasks in redox signaling. The sensitivity of many biological pathways to H2 O2 opens up a unique direction in the development of bioelectronics devices to control levels of reactive-oxygen species (ROS). Here a microfabricated ROS modulation device that relies on controlled faradaic reactions is presented. A concentric pixel arrangement of a peroxide-evolving cathode surrounded by an anode ring which decomposes the peroxide, resulting in localized peroxide delivery is reported. The conducting polymer (poly(3,4-ethylenedioxythiophene) (PEDOT), is exploited as the cathode. PEDOT selectively catalyzes the oxygen reduction reaction resulting in the production of hydrogen peroxide (H2 O2 ). Using electrochemical and optical assays, combined with modeling, the performance of the devices is benchmarked. The concentric pixels generate tunable gradients of peroxide and oxygen concentrations. The faradaic devices are prototyped by modulating human H2 O2 -sensitive Kv7.2/7.3 (M-type) channels expressed in a single-cell model (Xenopus laevis oocytes). The Kv7 ion channel family is responsible for regulating neuronal excitability in the heart, brain, and smooth muscles, making it an ideal platform for faradaic ROS stimulation. The results demonstrate the potential of PEDOT to act as an H2 O2 delivery system, paving the way to ROS-based organic bioelectronics.

Nanotechnology Enables Novel Modalities for Neuromodulation

Neuromodulation is of great importance both as a fundamental neuroscience research tool for analyzing and understanding the brain function, and as a therapeutic avenue for treating brain disorders. Here, an overview of conceptual and technical progress in developing neuromodulation strategies is provided, and it is suggested that recent advances in nanotechnology are enabling novel neuromodulation modalities with less invasiveness, improved biointerfaces, deeper penetration, and higher spatiotemporal precision. The use of nanotechnology and the employment of versatile nanomaterials and nanoscale devices with tailored physical properties have led to considerable research progress. To conclude, an outlook discussing current challenges and future directions for next-generation neuromodulation modalities is presented.

Graphene nanostructures for input-output bioelectronics

The ability to manipulate the electrophysiology of electrically active cells and tissues has enabled a deeper understanding of healthy and diseased tissue states. This has primarily been achieved via input/output (I/O) bioelectronics that interface engineered materials with biological entities. Stable long-term application of conventional I/O bioelectronics advances as materials and processing techniques develop. Recent advancements have facilitated the development of graphene-based I/O bioelectronics with a wide variety of functional characteristics. Engineering the structural, physical, and chemical properties of graphene nanostructures and integration with modern microelectronics have enabled breakthrough high-density electrophysiological investigations. Here, we review recent advancements in 2D and 3D graphene-based I/O bioelectronics and highlight electrophysiological studies facilitated by these emerging platforms. Challenges and present potential breakthroughs that can be addressed via graphene bioelectronics are discussed. We emphasize the need for a multidisciplinary approach across materials science, micro-fabrication, and bioengineering to develop the next generation of I/O bioelectronics.

Nanoenabled Bioelectrical Modulation

Studying the formation and interactions between biological systems and artificial materials is significant for probing complex biophysical behaviors and addressing challenging biomedical problems. Bioelectrical interfaces, especially nanostructure-based, have improved compatibility with cells and tissues and enabled new approaches to biological modulation. In particular, free-standing and remotely activated bioelectrical devices demonstrate potential for precise biophysical investigation and efficient clinical therapies. Interacting with single cells or organelles requires devices of sufficiently small size for high resolution probing. Nanoscale semiconductors, given their diverse functionalities, are promising device platforms for subcellular modulation. Tissue-level modulation requires additional consideration regarding the device's mechanical compliance for either conformal contact with the tissue surface or seamless three-dimensional (3D) biointegration. Flexible or even open-framework designs are essential in such methods. For chronic organ integration, the highest level of biocompatibility is required for both the materials and device configurations. Additionally, a scalable and high-throughput design is necessary to simultaneously interact with many individual cells in the organ. The physical, chemical, and mechanical stabilities of devices for organ implantation may be improved by ensuring matching of mechanical behavior at biointerfaces, including passivation or resistance designs to mitigate physiological impacts, or incorporating self-healing or adaptative properties. Recent research demonstrates principles of nanostructured material designs that can be used to improve biointerfaces. Nanoenabled extracellular interfaces were frequently used for either electrical or remote optical modulation of cells and tissues. In particular, methods are now available for designing and screening nanostructured silicon, especially chemical vapor deposition (CVD)-derived nanowires and two-dimensional (2D) nanostructured membranes, for biological modulation in vitro and in vivo. For intra- and intercellular biological modulation, semiconductor/cell composites have been created through the internalization of nanowires, and such cellular composites can even integrate with living tissues. This approach was demonstrated for both neuronal and cardiac modulation. At a different front, laser-derived nanocrystalline semiconductors showed electrochemical and photoelectrochemical activities, and they were used to modulate cells and organs. Recently, self-assembly of nanoscale building blocks enabled fabrication of efficient monolithic carbon-based electrodes for in vitro stimulation of cardiomyocytes, ex vivo stimulation of retinas and hearts, and in vivo stimulation of sciatic nerves. Future studies on nanoenabled bioelectrical modulation should focus on improving efficiency and stability of current and emerging technologies. New materials and devices can access new interrogation targets, such as subcellular structures, and possess more adaptable and responsive properties enabling seamless integration. Drawing inspiration from energy science and catalysis can help in such progress and open new avenues for biological modulation. The fundamental study of living bioelectronics could yield new cellular composites for diverse biological signaling control. In situ self-assembled biointerfaces are of special interest in this area as cell type targeting can be achieved.

Customizing MRI-Compatible Multifunctional Neural Interfaces through Fiber Drawing

Fiber drawing enables scalable fabrication of multifunctional flexible fibers that integrate electrical, optical and microfluidic modalities to record and modulate neural activity. Constraints on thermomechanical properties of materials, however, have prevented integrated drawing of metal electrodes with low-loss polymer waveguides for concurrent electrical recording and optical neuromodulation. Here we introduce two fabrication approaches: (1) an iterative thermal drawing with a soft, low melting temperature (Tm) metal indium, and (2) a metal convergence drawing with traditionally non-drawable high Tm metal tungsten. Both approaches deliver multifunctional flexible neural interfaces with low-impedance metallic electrodes and low-loss waveguides, capable of recording optically-evoked and spontaneous neural activity in mice over several weeks. We couple these fibers with a light-weight mechanical microdrive (1g) that enables depth-specific interrogation of neural circuits in mice following chronic implantation. Finally, we demonstrate the compatibility of these fibers with magnetic resonance imaging (MRI) and apply them to visualize the delivery of chemical payloads through the integrated channels in real time. Together, these advances expand the domains of application of the fiber-based neural probes in neuroscience and neuroengineering.

Modular Integration of Hydrogel Neural Interfaces

Thermal drawing has been recently leveraged to yield multifunctional, fiber-based neural probes at near kilometer length scales. Despite its promise, the widespread adoption of this approach has been impeded by (1) material compatibility requirements and (2) labor-intensive interfacing of functional features to external hardware. Furthermore, in multifunctional fibers, significant volume is occupied by passive polymer cladding that so far has only served structural or electrical insulation purposes. In this article, we report a rapid, robust, and modular approach to creating multifunctional fiber-based neural interfaces using a solvent evaporation or entrapment-driven (SEED) integration process. This process brings together electrical, optical, and microfluidic modalities all encased within a copolymer comprised of water-soluble poly(ethylene glycol) tethered to water-insoluble poly(urethane) (PU-PEG). We employ these devices for simultaneous optogenetics and electrophysiology and demonstrate that multifunctional neural probes can be used to deliver cellular cargo with high viability. Upon exposure to water, PU-PEG cladding spontaneously forms a hydrogel, which in addition to enabling integration of modalities, can harbor small molecules and nanomaterials that can be released into local tissue following implantation. We also synthesized a custom nanodroplet forming block polymer and demonstrated that embedding such materials within the hydrogel cladding of our probes enables delivery of hydrophobic small molecules in vitro and in vivo. Our approach widens the chemical toolbox and expands the capabilities of multifunctional neural interfaces.

Electrochemical Modulation of Carbon Monoxide-Mediated Cell Signaling

Despite the critical role played by carbon monoxide (CO) in physiological and pathological signaling events, current approaches to deliver this messenger molecule are often accompanied by off-target effects and offer limited control over release kinetics. To address these challenges, we develop an electrochemical approach that affords on-demand release of CO through reduction of carbon dioxide (CO2 ) dissolved in the extracellular space. Electrocatalytic generation of CO by cobalt phthalocyanine molecular catalysts modulates signaling pathways mediated by a CO receptor soluble guanylyl cyclase. Furthermore, by tuning the applied voltage during electrocatalysis, we explore the effect of the CO release kinetics on CO-dependent neuronal signaling. Finally, we integrate components of our electrochemical platform into microscale fibers to produce CO in a spatially-restricted manner and to activate signaling cascades in the targeted cells. By offering on-demand local synthesis of CO, our approach may facilitate the studies of physiological processes affected by this gaseous molecular messenger.

Nano- and Microscale Optical and Electrical Biointerfaces and Their Relevance to Energy Research

Different research fields in energy sciences, such as photovoltaics for solar energy conversion, supercapacitors for energy storage, electrocatalysis for clean energy conversion technologies, and materials-bacterial hybrid for CO₂ fixation have been under intense investigations over the past decade. In recent years, new platforms for biointerface designs have emerged from the energy conversion and storage principles. This paper reviews recent advances in nano- and microscale materials/devices for optical and electrical biointerfaces. First, a connection is drawn between biointerfaces and energy science, and how these two distinct research fields can be connected is summarized. Then, a brief overview of current available tools for biointerface studies is presented. Third, three representative biointerfaces are reviewed, including neural, cardiac, and bacterial biointerfaces, to show how to apply these tools and principles to biointerface design and research. Finally, two possible future research directions for nano- and microscale biointerfaces are proposed.

Endogenous Conjugation of Biomimetic Dinitrosyl Iron Complex with Protein Vehicles for Oral Delivery of Nitric Oxide to Brain and Activation of Hippocampal Neurogenesis

Nitric oxide (NO), a pro-neurogenic and antineuroinflammatory gasotransmitter, features the potential to develop a translational medicine against neuropathological conditions. Despite the extensive efforts made on the controlled delivery of therapeutic NO, however, an orally active NO prodrug for a treatment of chronic neuropathy was not reported yet. Inspired by the natural dinitrosyl iron unit (DNIU) [Fe(NO)₂], in this study, a reversible and dynamic interaction between the biomimetic [(NO)₂Fe(μ-SCH₂CH₂OH)₂Fe(NO)₂] (DNIC-1) and serum albumin (or gastrointestinal mucin) was explored to discover endogenous proteins as a vehicle for an oral delivery of NO to the brain after an oral administration of DNIC-1. On the basis of the in vitro and in vivo study, a rapid binding of DNIC-1 toward gastrointestinal mucin yielding the mucin-bound dinitrosyl iron complex (DNIC) discovers the mucoadhesive nature of DNIC-1. A reversible interconversion between mucin-bound DNIC and DNIC-1 facilitates the mucus-penetrating migration of DNIC-1 shielded in the gastrointestinal tract of the stomach and small intestine. Moreover, the NO-release reactivity of DNIC-1 induces the transient opening of the cellular tight junction and enhances its paracellular permeability across the intestinal epithelial barrier. During circulation in the bloodstream, a stoichiometric binding of DNIC-1 to the serum albumin, as another endogenous protein vehicle, stabilizes the DNIU [Fe(NO)₂] for a subsequent transfer into the brain. With aging mice under a Western diet as a disease model for metabolic syndrome and cognitive impairment, an oral administration of DNIC-1 in a daily manner for 16 weeks activates the hippocampal neurogenesis and ameliorates the impaired cognitive ability. Taken together, these findings disclose the synergy between biomimetic DNIC-1 and endogenous protein vehicles for an oral delivery of therapeutic NO to the brain against chronic neuropathy.

Influence of Magnetic Fields on Electrochemical Reactions of Redox Cofactor Solutions

Redox cofactors mediate many enzymatic processes and are increasingly employed in biomedical and energy applications. Exploring the influence of external magnetic fields on redox cofactor chemistry can enhance our understanding of magnetic-field-sensitive biological processes and allow the application of magnetic fields to modulate redox reactions involving cofactors. Through a combination of experiments and modeling, we investigate the influence of magnetic fields on electrochemical reactions in redox cofactor solutions. By employing flavin mononucleotide (FMN) cofactor as a model system, we characterize magnetically induced changes in Faradaic currents. We find that radical pair intermediates have negligible influence on current increases in FMN solution upon application of a magnetic field. The dominant mechanism underlying the observed current increases is the magneto-hydrodynamic effect. We extend our analyses to other diffusion-limited electrochemical reactions of redox cofactor solutions and arrive at similar conclusions, highlighting the opportunity to use this framework in redox cofactor chemistry.

Near infrared II laser controlled free radical releasing nanogenerator for synergistic nitric oxide and alkyl radical therapy of breast cancer

Recently, alkyl radicals have attracted much attention in cancer therapy due to their oxygen-independent generation property. For the first time, alkyl radical and nitric oxide (NO) combined therapy is demonstrated as an effective strategy for tumor inhibition. As a proof of concept, a biocompatible free radical nanogenerator with near-infrared (NIR) II laser-induced simultaneous NO and alkyl radical release property was elaborately fabricated. In particular, an NIR II molecule (IR 1061), NO donor (BNN6) and alkyl radical initiator (AIPH) were firstly encapsulated in a natural lecithin stabilized phase change material, and then further functionalized by an amphiphile of DSPE-PEG-RGD with specific tumor targeting ability, finally obtaining biocompatible P(IR/BNN6/AIPH)@Lip-RGD. Upon NIR II laser irradiation, the photothermal effect generated from IR 1061 could trigger the phase change of the nanogenerator by releasing the encapsulated BNN6 and AIPH, and subsequently decompose them to generate highly active NO and alkyl radicals. Remarkably, NO and alkyl radical release profiles of P(IR/BNN6/AIPH)@Lip-RGD could be precisely controlled using intermittent NIR II laser irradiation. Moreover, P(IR/BNN6/AIPH)@Lip-RGD displayed a synergistic NO and alkyl radicals' anticancer effect by significantly inhibiting the growth of breast tumors, upon NIR II laser exposure. Furthermore, an in depth mechanistic study revealed that synergistic NO and alkyl radical effect induced cancer cell apoptosis through a mitochondria-mediated apoptotic pathway. The synergistic effect jointly caused a burst generation of mitochondrial ROS, which significantly down-regulated Bcl-2 protein expression, accelerated cytochrome c release and triggered a cascade of apoptosis-related proteins of Caspase-3 and Caspase-9.

Correlating 3D Surface Atomic Structure and Catalytic Activities of Pt Nanocrystals

Active sites and catalytic activity of heterogeneous catalysts is determined by their surface atomic structures. However, probing the surface structure at an atomic resolution is difficult, especially for solution ensembles of catalytic nanocrystals, which consist of heterogeneous particles with irregular shapes and surfaces. Here, we constructed 3D maps of the coordination number (CN) and generalized CN (CN_) for individual surface atoms of sub-3 nm Pt nanocrystals. Our results reveal that the synthesized Pt nanocrystals are enclosed by islands of atoms with nonuniform shapes that lead to complex surface structures, including a high ratio of low-coordination surface atoms, reduced domain size of low-index facets, and various types of exposed high-index facets. 3D maps of CN_ are directly correlated to catalytic activities assigned to individual surface atoms with distinct local coordination structures, which explains the origin of high catalytic performance of small Pt nanocrystals in important reactions such as oxygen reduction reactions and CO electro-oxidation.

Electrochemical evidence of nitrate release from the nitrooxy compound 4-((nitrooxy) methyl)-3-nitrobenzoic acid and its antinociceptive and anti-inflammatory activities in mice

Considering the many biological activities of nitric oxide (NO), some lines of research focused on the modulation of these activities through the provision of this mediator by designing and synthesizing compounds coupled with an NO donor group. Thus, the objectives of the present study were to carry out an electrochemical investigation of the nitrooxy compound 4-((nitrooxy) methyl)-3-nitrobenzoic acid (1) and evaluate its activities and putative mechanisms in experimental models of pain and inflammation. Voltammetric studies performed in aprotic medium (mimetic of membranes) showed important electrochemical reduction mechanisms: nitroaromatic reduction, self-protonation, and finally reductive elimination, which leads to nitrate release. Systemic administration of the nitrooxy compound (1) inhibited the nociceptive response induced by heat and the tactile hypersensitivity and paw edema induced by carrageenan in mice. The activities in the models of inflammatory pain and edema were associated with reduced neutrophil recruitment and production of inflammatory cytokines, such as interleukin (IL)-1β, IL-6, tumor necrosis factor-α and CXCL-1, and increased production of IL-10. Concluding, electrochemical analysis revealed unequivocally that electron transfer at the nitro group of the nitrooxy compound (1) results in the cleavage of the organic nitrate, potentially resulting in the generation of NO. This electrochemical mechanism may be compared to a biochemical electron-transfer mediated nitrate release that, by appropriate in vivo bioreduction (enzymatic or not) would lead to NO production. Compound (1) exhibits activities in models of inflammatory pain and edema that may be due to reduced recruitment of neutrophils and production of inflammatory cytokines and increased production of IL-10. These results reinforce the interest in the investigation of NO donor compounds as candidates for analgesic and anti-inflammatory drugs.