A sensitive and specific nanosensor for monitoring extracellular potassium levels in the brain

Rapid Identification of Drug Mechanisms with Deep Learning-Based Multichannel Surface-Enhanced Raman Spectroscopy

Rapid identification of drug mechanisms is vital to the development and effective use of chemotherapeutics. Herein, we develop a multichannel surface-enhanced Raman scattering (SERS) sensor array and apply deep learning approaches to realize the rapid identification of the mechanisms of various chemotherapeutic drugs. By implementing a series of self-assembled monolayers (SAMs) with varied molecular characteristics to promote heterogeneous physicochemical interactions at the interfaces, the sensor can generate diversified SERS signatures for directly high-dimensionality fingerprinting drug-induced molecular changes in cells. We further train the convolutional neural network model on the multidimensional SAM-modulated SERS data set and achieve a discriminatory accuracy toward 99%. We expect that such a platform will contribute to expanding the toolbox for drug screening and characterization and facilitate the drug development process.

Sensing patches for biomarker identification in skin-derived biofluids

In conventional clinical disease diagnosis and screening based on biomarker detection, most analysis samples are collected from serum, blood. However, these invasive collection methods require specific instruments, professionals, and may lead to infection risks. Additionally, the diagnosis process suffers from untimely results. The identification of skin-related biomarkers plays an unprecedented role in early disease diagnosis. More importantly, these skin-mediated approaches for collecting biomarker-containing biofluid samples are noninvasive or minimally invasive, which is more preferable for point-of-care testing (POCT). Therefore, skin-based biomarker detection patches have been promoted, owing to their unique advantages, such as simple fabrication, desirable transdermal properties and no requirements for professional medical staff. Currently, the skin biomarkers extracted from sweat, interstitial fluid (ISF) and wound exudate, are achieved with wearable sweat patches, transdermal MN patches, and wound patches, respectively. In this review, we detail these three types of skin patches in biofluids collection and diseases-related biomarkers identification. Patch classification and the corresponding manufacturing as well as detection strategies are also summarized. The remaining challenges in clinical applications and current issues in accurate detection are discussed for further advancement of this technology (Scheme 1).

An NIR-IIb emissive transmembrane voltage nano-indicator for the optical monitoring of electrophysiological activities in vivo

In vivo transmembrane-voltage detection reflected the electrophysiological activities of the biological system, which is crucial for the diagnosis of neuronal disease. Traditional implanted electrodes can only monitor limited regions and induce relatively large tissue damage. Despite emerging monitoring methods based on optical imaging have access to signal recording in a larger area, the recording wavelength of less than 1000 nm seriously weakens the detection depth and resolution in vivo. Herein, a Förster resonance energy transfer (FRET)-based nano-indicator, NaYbF4:Er@NaYF4@Cy7.5@DPPC (Cy7.5-ErNP) with emission in the near-infrared IIb biological window (NIR-IIb, 1500-1700 nm) is developed for transmembrane-voltage detection. Cy7.5 dye is found to be voltage-sensitive and is employed as the energy donor for the energy transfer to the lanthanide nanoparticle, NaYbF4:Er@NaYF4 (ErNP), which works as the acceptor to achieve electrophysiological signal responsive NIR-IIb luminescence. Benefiting from the high penetration and low scattering of NIR-IIb luminescence, the Cy7.5-ErNP enables both the visualization of action potential in vitro and monitoring of Mesial Temporal lobe epilepsy (mTLE) disease in vivo. This work presents a concept for leveraging the lanthanide luminescent nanoprobes to visualize electrophysiological activity in vivo, which facilitates the development of an optical nano-indicator for the diagnosis of neurological disorders.

Nanocarriers address intracellular barriers for efficient drug delivery, overcoming drug resistance, subcellular targeting and controlled release

The cellular barriers are major bottlenecks for bioactive compounds entering into cells to accomplish their biological functions, which limits their biomedical applications. Nanocarriers have demonstrated high potential and benefits for encapsulating bioactive compounds and efficiently delivering them into target cells by overcoming a cascade of intracellular barriers to achieve desirable therapeutic and diagnostic effects. In this review, we introduce the cellular barriers ahead of drug delivery and nanocarriers, as well as summarize recent advances and strategies of nanocarriers for increasing internalization with cells, promoting intracellular trafficking, overcoming drug resistance, targeting subcellular locations and controlled drug release. Lastly, the future perspectives of nanocarriers for intracellular drug delivery are discussed, which mainly focus on potential challenges and future directions. Our review presents an overview of intracellular drug delivery by nanocarriers, which may encourage the future development of nanocarriers for efficient and precision drug delivery into a wide range of cells and subcellular targets.

Fluorophore Label-Free Light-up Near Infrared Deoxyribonucleic Acid Nanosensor for Monitoring Extracellular Potassium Levels

Fluorescent DNA nanosensors have been widely used due to their unique advantages, among which the near-infrared (NIR) imaging mode can provide deeper penetration depth and lower biological background for the nanosensors. However, efficient NIR quenchers require ingenious design, complex synthesis, and modification, which severely limit the development of NIR DNA nanosensors. Label-free strategies based on G-quadruplex (G4) and NIR G4 dyes were first introduced into in situ extracellular imaging, and a novel NIR sensing strategy for the specific detection of extracellular targets is proposed. The strategy avoids complex synthesis and site-specific modification by controlling the change of the NIR signal through the formation of a G4 nanostructure. A light-up NIR DNA nanosensor based on potassium ion (K+)-sensitive G4 chain PS2.M was constructed to verify the strategy. PS2.M forms a stable G4 nanostructure in the presence of K+ and activates the NIR G4 dye CSTS, thus outputting NIR signals. The nanosensor can rapidly respond to K+ with a linear range of 5-50 mM and has good resistance to interference. The nanosensor with cholesterol can provide feedback on the changes in extracellular K+ concentration in many kinds of cells, serving as a potential tool for the study of diseases such as epilepsy and cancer, as well as the development of related drugs. The strategy can be potentially applied to the NIR detection of a variety of extracellular targets with the help of functional DNAs such as aptamer and DNAzyme.

Long-Range Epitaxial MOF Electronics for Continuous Monitoring of Human Breath Ammonia

As an important biomarker, ammonia exhibits a strong correlation with protein metabolism and specific organ dysfunction. Limited by the immobile instrumental structure, invasive and complicated procedures, and unsatisfactory online sensitivity and selectivity, current medical diagnosis fails to monitor this chemical in real time efficiently. Herein, we present the successful synthesis of a long-range epitaxial metal-organic framework on a millimeter domain-sized single-crystalline graphene substrate (LR-epi-MOF). With a perfect 30° epitaxial angle and a mere 2.8% coincidence site lattice mismatch between the MOF and graphene, this long-range-ordered epitaxial structure boosts the charge transfer from ammonia to the MOF and then to graphene, thereby promoting the overall charge delocalization and exhibiting extraordinary electrical global coupling properties. This unique characteristic imparts a remarkable sensitivity of 0.1 ppb toward ammonia. The sub-ppb detecting capability and high anti-interference ability enable continuous information recording of breath ammonia that is strongly correlated with the intriguing human lifestyle. Wearable electronics based on the LR-epi-MOF could accurately portray the active protein metabolism pattern in real time and provide personal assistance in health management.

A Nanozyme-Based Electrode for High-Performance Neural Recording

Implanted neural electrodes have been widely used to treat brain diseases that require high sensitivity and biocompatibility at the tissue-electrode interface. However, currently used clinical electrodes cannot meet both these requirements simultaneously, which hinders the effective recording of electronic signals. Herein, nanozyme-based neural electrodes incorporating bioinspired atomically precise clusters are developed as a general strategy with a heterogeneous design for multiscale and ultrasensitive neural recording via quantum transport and biocatalytic processes. Owing to the dual high-speed electronic and ionic currents at the electrode-tissue interface, the impedance of nanozyme electrodes is 26 times lower than that of state-of-the-art metal electrodes, and the acquisition sensitivity for the local field potential is ≈10 times higher than that of clinical PtIr electrodes, enabling a signal-to-noise ratio (SNR) of up to 14.7 dB for single-neuron recordings in rats. The electrodes provide more than 100-fold higher antioxidant and multi-enzyme-like activities, which effectively decrease 67% of the neuronal injury area by inhibiting glial proliferation and allowing sensitive and stable neural recording. Moreover, nanozyme electrodes can considerably improve the SNR of seizures in acute epileptic rats and are expected to achieve precise localization of seizure foci in clinical settings.

Biomimetic mesoporous carbon-silica/AAO asymmetric nanochannel array for electrochemical sensing of K+ in rat brain microdialysates and serum

Acquirement of chemical expression in practical brain system is vital to understand the molecular mechanism involved in physiological and pathological processes in brain. Though nanochannels have been demonstrated to be promising platform for electrochemical sensor, it is a great challenge for nanochannels to be employed in practical brain biofluid. In this work, we rationally designed and created the biomimetic asymmetric nanochannels for sensing of K+ through integrating in situ modification of a two-component mesoporous carbon-silica (MCS) thin film with a pore size of ∼3.6 nm at anodic alumina nanochannel array (AAO) with the ∼40 nm pores (denoted as MCS/AAO). Apparent rectification phenomenon in such functionalized nanochannel array was achieved based on diode-like ion transport. Then, 4'-aminobenzeno-18-crown-6 (SP) was selected to be chemically decorated at MCS/AAO as the specific recognition for K+ (SP/MCS/AAO). The developed SP/MCS/AAO exhibited good selectivity towards K+ detection against the coexisting interferences in brain, and possessed a good linear response to K+ concentration in the range of 0.5-10 mM with a detection limit of 0.1 mM. Combined with microdialysis technique, the variation of K+ was successfully determined in rat brain microdialysates and serums. Compared with normal rats, the concentration of K+ was found to be greatly decreased in the cerebral microdialysates and serum of rats with hypertensive model (SHR). This work unveiled a powerful platform for K+, and promised to be extended to design new strategy for detecting other chemical species, in particular non-electroactive species in biofluid related to physiological and pathological events.

Cas12a-based direct visualization of nanoparticle-stabilized fluorescence signal for multiplex detection of DNA methylation biomarkers

The CRISPR-Cas12a RNA-guided complexes hold immense promise for nucleic acid detection. However, limitations arise from their specificity in detecting off-targets and the stability of the signal molecules. Here, we have developed a platform that integrates multiplex amplification and nanomolecular-reporting signals, allowing us to detect various clinically relevant nucleic acid targets with enhanced stability, sensitivity, and visual interpretation. Through the electrostatic co-assembly of the Oligo reporter with oppositely charged nanoparticles, we observed a significant enhancement in its stability in low-pollution environments, reaching up to a threefold increase compared to the original version. Additionally, the fluorescence efficiency was expanded by three orders of magnitude, broadening the detection range considerably. Utilizing a multiplex strategy, this assay can accomplish simultaneous detection of multiple targets and single-point indication detection of nine specific targets. This significant advancement heightened the sensitivity of disease screening and improved the accuracy of diagnosing disease-related changes. We tested this assay in a colorectal cancer model, demonstrating that it can identify DNA methylation features at the aM-level within 40-60 min. Validation using clinical samples yielded consistent results with qPCR and bisulfite sequencing, affirming the assay's reliability and potential for clinical applications.

A Fiber Sensor for Long-Term Monitoring of Extracellular Potassium Ion Fluctuations in Chronic Neuropsychiatric Diseases

The extracellular potassium ion concentration in the brain exerts a significant influence on cellular excitability and intercellular communication. Perturbations in the extracellular potassium ion level are closely correlated with various chronic neuropsychiatric disorders including depression. However, a critical gap persists in performing real-time and long-term monitoring of extracellular potassium ions, which is necessary for comprehensive profiling of chronic neuropsychiatric diseases. Here, a fiber potassium ion sensor (FKS) that consists of a soft conductive fiber with a rough surface and a hydrophobic-treated transduction layer interfaced with a potassium ion-selective membrane is found to solve this problem. The FKS demonstrates stable interfaces between its distinct functional layers in an aqueous environment, conferring an exceptional stability of 6 months in vivo, in stark contrast to previous reports with working durations from hours to days. Upon implantation into the mouse brain, the FKS enables effective monitoring of extracellular potassium ion dynamics under diverse physiological states including anesthesia, forced swimming, and tail suspension. Using this FKS, tracking of extracellular potassium ion fluctuations that align with behaviors associated with the progression of depression over months is achieved, demonstrating its usability in studying chronic neuropsychiatric disorders from a new biochemical perspective.

Designing artificial ion channels with strict K+/Na+ selectivity toward next-generation electric-eel-mimetic ionic power generation

A biological potassium channel is >1000 times more permeable to K+ than to Na+ and exhibits a giant permeation rate of ∼108 ions/s. It is a great challenge to construct artificial potassium channels with such high selectivity and ion conduction rate. Herein, we unveil a long-overlooked structural feature that underpins the ultra-high K+/Na+ selectivity. By carrying out massive molecular dynamics simulation for ion transport through carbonyl-oxygen-modified bi-layer graphene nanopores, we find that the twisted carbonyl rings enable strict potassium selectivity with a dynamic K+/Na+ selectivity ratio of 1295 and a K+ conduction rate of 3.5 × 107 ions/s, approaching those of the biological counterparts. Intriguingly, atomic trajectories of K+ permeation events suggest a dual-ion transport mode, i.e. two like-charged potassium ions are successively captured by the nanopores in the graphene bi-layer and are interconnected by sharing one or two interlayer water molecules. The dual-ion behavior allows rapid release of the exiting potassium ion via a soft knock-on mechanism, which has previously been found only in biological ion channels. As a proof-of-concept utilization of this discovery, we propose a novel way for ionic power generation by mixing KCl and NaCl solutions through the bi-layer graphene nanopores, termed potassium-permselectivity enabled osmotic power generation (PoPee-OPG). Theoretically, the biomimetic device achieves a very high power density of >1000 W/m2 with graphene sheets of <1% porosity. This study provides a blueprint for artificial potassium channels and thus paves the way toward next-generation electric-eel-mimetic ionic power generation.

Fluorescent nano- and microparticles for sensing cellular microenvironment: past, present and future applications

The tumor microenvironment (TME) demonstrates distinct hallmarks, including acidosis, hypoxia, reactive oxygen species (ROS) generation, and altered ion fluxes, which are crucial targets for early cancer biomarker detection, tumor diagnosis, and therapeutic strategies. Various imaging and sensing techniques have been developed and employed in both research and clinical settings to visualize and monitor cellular and TME dynamics. Among these, ratiometric fluorescence-based sensors have emerged as powerful analytical tools, providing precise and sensitive insights into TME and enabling real-time detection and tracking of dynamic changes. In this comprehensive review, we discuss the latest advancements in ratiometric fluorescent probes designed for the optical mapping of pH, oxygen, ROS, ions, and biomarkers within the TME. We elucidate their structural designs and sensing mechanisms as well as their applications in in vitro and in vivo detection. Furthermore, we explore integrated sensing platforms that reveal the spatiotemporal behavior of complex tumor cultures, highlighting the potential of high-resolution imaging techniques combined with computational methods. This review aims to provide a solid foundation for understanding the current state of the art and the future potential of fluorescent nano- and microparticles in the field of cellular microenvironment sensing.

Advanced Temporally-Spatially Precise Technologies for On-Demand Neurological Disorder Intervention

Temporal-spatial precision has attracted increasing attention for the clinical intervention of neurological disorders (NDs) to mitigate adverse effects of traditional treatments and achieve point-of-care medicine. Inspiring steps forward in this field have been witnessed in recent years, giving the credit to multi-discipline efforts from neurobiology, bioengineering, chemical materials, artificial intelligence, and so on, exhibiting valuable clinical translation potential. In this review, the latest progress in advanced temporally-spatially precise clinical intervention is highlighted, including localized parenchyma drug delivery, precise neuromodulation, as well as biological signal detection to trigger closed-loop control. Their clinical potential in both central and peripheral nervous systems is illustrated meticulously related to typical diseases. The challenges relative to biosafety and scaled production as well as their future perspectives are also discussed in detail. Notably, these intelligent temporally-spatially precision intervention systems could lead the frontier in the near future, demonstrating significant clinical value to support billions of patients plagued with NDs.

One-step rapid colorimetric detection of K+ using silver nanoparticles modified by crown ether

Urinary potassium is an important parameter in clinical health diagnosis. Rapid and convenient detection of potassium ions (K⁺) in urine is essential for personal healthcare and health management. Here, crown ether (4-aminodibenzo-18-crown-6, ADC) modified silver nanoparticles (ADC-Ag NPs) were successfully prepared for one-step rapid colorimetric detection of urinary potassium. The detection mechanism is as follows: due to the matching sizes of the diameter of K⁺ and the cavity in crown ether 6, K⁺ is encapsulated between the cavities of two crown ethers, resulting in the clumping of ADC-Ag NPs and the color of the solution being altered. The colorimetric detection method has a fast response and is completed within 20 minutes. It also shows good selectivity and interference immunity. The lowest detectable concentration is 20 μM with the naked eye and 2.16 μM for UV-vis absorption spectroscopy. A good linear relationship (R² = 0.9931) between the absorption intensity ratio and K⁺ concentration (0-100 μM) indicates that this colorimetric probe can be used to detect K⁺. The method was also applied for quantitative analysis of K⁺ in real urine samples with recovery between 116 and 120%.

Activity-Dependent Fluctuations in Interstitial [K+]: Investigations Using Ion-Sensitive Microelectrodes

In the course of action potential firing, all axons and neurons release K⁺ from the intra- cellular compartment into the interstitial space to counteract the depolarizing effect of Na⁺ influx, which restores the resting membrane potential. This efflux of K⁺ from axons results in K⁺ accumulation in the interstitial space, causing depolarization of the K⁺ reversal potential (E_K), which can prevent subsequent action potentials. To ensure optimal neuronal function, the K⁺ is buffered by astrocytes, an energy-dependent process, which acts as a sink for interstitial K⁺, absorbing it at regions of high concentration and distributing it through the syncytium for release in distant regions. Pathological processes in which energy production is compromised, such as anoxia, ischemia, epilepsy and spreading depression, can lead to excessive interstitial K⁺ accumulation, disrupting sensitive trans-membrane ion gradients and attenuating neuronal activity. The changes that occur in interstitial [K⁺] resulting from both physiological and pathological processes can be monitored accurately in real time using K⁺-sensitive microelectrodes, an invaluable tool in electrophysiological studies.

Emerging biotransduction strategies on soft interfaces for biosensing

As a lab-on-soft biochip providing accurate and timely biomarker information, wearable biosensors can satisfy the increasing demand for intelligent e-health services, active disease diagnosis/therapy, and huge bioinformation data. As biomolecules generally could not directly produce detectable signals, biotransducers that specifically convert biomolecules to electrical or optical signals are involved, which determines the pivotal sensing performance including 3S (sensitivity, selectivity, and stability), reversibility, etc. The soft interface poses new requirements for biotransducers, especially equipment-free, facile operation, mechanical tolerance, and high sensing performance. In this review, we discussed the emerging electrochemical and optical biotransduction strategies on wearables from the aspects of the transduction mechanism, amplification strategies, biomaterial selection, and device fabrication procedures. Challenges and perspectives regarding future biotransducers for monitoring trace amounts of biomolecules with high fidelity, sensitivity, and multifunctionality are also discussed. It is expected that through fusion with functional electronics, wearable biosensors can provide possibilities to further decentralize the healthcare system and even build biomolecule-based intelligent cyber-physical systems and new modalities of cyborgs.

Neuron devices: emerging prospects in neural interfaces and recognition

Neuron interface devices can be used to explore the relationships between neuron firing and synaptic transmission, as well as to diagnose and treat neurological disorders, such as epilepsy and Alzheimer's disease. It is crucial to exploit neuron devices with high sensitivity, high biocompatibility, multifunctional integration and high-speed data processing. During the past decades, researchers have made significant progress in neural electrodes, artificial sensory neuron devices, and neuromorphic optic neuron devices. The main part of the review is divided into two sections, providing an overview of recently developed neuron interface devices for recording electrophysiological signals, as well as applications in neuromodulation, simulating the human sensory system, and achieving memory and recognition. We mainly discussed the development, characteristics, functional mechanisms, and applications of neuron devices and elucidated several key points for clinical translation. The present review highlights the advances in neuron devices on brain-computer interfaces and neuroscience research.

Stimuli-responsive crosslinked nanomedicine for cancer treatment

Nanomedicines are attractive paradigms to deliver drugs, contrast agents, immunomodulators, and gene editors for cancer therapy and diagnosis. However, the currently developed nanomedicine suffers from poor serum stability, premature drug release, and lack of responsiveness. Crosslinking strategy can be utilized to overcome these shortcomings by employing stimuli-responsive chemical bonds to tightly hold the nanostructure and releasing the payloads spatiotemporally in a highly controlled manner. In this Review, we summarize the recently ingenious design of the stimuli-responsive crosslinked nanomedicines (SCN) in the field of cancer treatment and their advances in circumventing the drawbacks of the conventional drug delivery system. We classify the SCNs into three categories based on the crosslinking strategies, including built-in, on-surface, and inter-particle crosslinking nanomedicines. Thanks to the stimuli-responsive crosslinkages, SCNs are capable of keeping robust stability during systemic circulation. They also respond to the particular tumoral conditions to experience a series of dynamic changes, such as the changes in size, surface charge, targeting moieties, integrity, and imaging signals. These characteristics allow them to efficiently overcome different biological barriers and substantially improve the drug delivery efficiency, tumor-targeting ability, and imaging sensitivities. With the examples discussed, we envision that our perspectives can inspire more attempts to engineer intelligent nanomedicine to achieve effective cancer therapy and diagnosis.

Activated astrocytes attenuate neocortical seizures in rodent models through driving Na+-K+-ATPase

Epileptic seizures are widely regarded to occur as a result of the excitation-inhibition imbalance from a neuro-centric view. Although astrocyte-neuron interactions are increasingly recognized in seizure, elementary questions about the causal role of astrocytes in seizure remain unanswered. Here we show that optogenetic activation of channelrhodopsin-2-expressing astrocytes effectively attenuates neocortical seizures in rodent models. This anti-seizure effect is independent from classical calcium signaling, and instead related to astrocytic Na+-K+-ATPase-mediated buffering K+, which activity-dependently inhibits firing in highly active pyramidal neurons during seizure. Compared with inhibition of pyramidal neurons, astrocyte stimulation exhibits anti-seizure effects with several advantages, including a wider therapeutic window, large-space efficacy, and minimal side effects. Finally, optogenetic-driven astrocytic Na+-K+-ATPase shows promising therapeutic effects in a chronic focal cortical dysplasia epilepsy model. Together, we uncover a promising anti-seizure strategy with optogenetic control of astrocytic Na+-K+-ATPase activity, providing alternative ideas and a potential target for the treatment of intractable epilepsy.

Tailoring Materials for Epilepsy Imaging: From Biomarkers to Imaging Probes

Excising epileptic foci (EF) is the most efficient approach for treating drug-resistant epilepsy (DRE). However, owing to the vast heterogeneity of epilepsies, EF in one-third of patients cannot be accurately located, even after exhausting all current diagnostic strategies. Therefore, identifying biomarkers that truly represent the status of epilepsy and fabricating probes with high targeting specificity are prerequisites for identifying the "concealed" EF. However, no systematic summary of this topic has been published. Herein, the potential biomarkers of EF are first summarized and classified into three categories: functional, molecular, and structural aberrances during epileptogenesis, a procedure of nonepileptic brain biasing toward epileptic tissue. The materials used to fabricate these imaging probes and their performance in defining the EF in preclinical and clinical studies are highlighted. Finally, perspectives for developing the next generation of probes and their challenges in clinical translation are discussed. In general, this review can be helpful in guiding the development of imaging probes defining EF with improved accuracy and holds promise for increasing the number of DRE patients who are eligible for surgical intervention.

Dynamic Detection of HbA1c Using a Silicon Nanowire Field Effect Tube Biosensor

As an emerging diabetes diagnostic indicator and a dynamic change index, HbA1c can not only reflect the average blood glucose level over a period of time but can also well predict the incidence of related microvascular complications. It is important to develop a detection method that can dynamically characterize HbA1c. Silicon nanowire (SiNW) devices were mass-produced using top-down sputtering technology, and a microdialyzer was installed in a SiNW field effect tube biosensor detection system. Finally, the detection system was used to detect HbA1c levels quantitatively and dynamically in experimental rabbits. Various measurements showed that mass-produced SiNW devices have ideal dimensions, stable structures, and good performance. A series of microscopy results showed that the SiNW surface can be functionalized for intermolecular interactions. The addition of a dialysis device can effectively overcome Debye shielding, making the blood test similar to the pure standard test. Finally, the dynamic detection of HbA1c within 40 h was realized. SiNW biosensors are capable of the dynamic detection of biomolecules, and dynamic observation of the interaction between blood glucose and HbA1c provides new ideas for the diagnosis and treatment of patients with diabetes. Therefore, the SiNW biosensor can reflect the dynamic changes in HbA1c in a shorter time, which has a certain potential value in the clinical treatment of diabetes.

Cell-Membrane-Anchored DNA Logic-Gated Nanoassemblies for In Situ Extracellular Bioimaging

Extracellular K⁺ and adenosine triphosphate (ATP) levels are significantly elevated in the tumor microenvironment (TME) and can be used as biomarkers for early cancer detection and tumor localization. Most reported TME sensors only respond to single abnormal factors, resulting in a lack of accuracy and specificity for the detection of complex environments. Thus, precisely locating the TME remains challenging. In this work, we aimed to develop an intelligent DNA nanoassembly controlled by a "YES-AND" logic circuit using a bimolecular G-quadruplex (G4) and ATP aptamer as logical control units. As a proof of concept, in the presence of K⁺ (input 1) and ATP (input 2), the YES-AND Boolean operator returned a true value and the output was the fluorescence resonance energy transfer (FRET) signal, indicating high sensitivity and selectivity. After being anchored to living cell surfaces, this logic nanosensor imaged extracellular K⁺ and ATP present at abnormal levels in situ. Owing to diverse disease markers in the TME, this novel logic sensor might hold great promise for the targeted delivery of intelligent anticancer drugs and Boolean logic-controlled treatment.

Network topology-directed design of molecular CPU for cell-like dynamic information processing

Natural cells (NCs) can automatically and continuously respond to fluctuant external information and distinguish meaningful stimuli from weak noise depending on their powerful genetic and protein networks. We herein report a network topology-directed design of dynamic molecular processing system (DMPS) as a molecular central processing unit that powers an artificial cell (AC) able to process fluctuant information in its immediate environment similar to NCs. By constructing a mixed cell community, ACs and NCs have synchronous response to fluctuant extracellular stimuli under physiological condition and in a blood vessel-mimic circulation system. We also show that fluctuant bioinformation released by NCs can be received and processed by ACs. The molecular design of DMPS-powered AC is expected to allow a profound understanding of biological systems, advance the construction of intelligent molecular systems, and promote more elegant bioengineering applications.

Versatile synthesis of dendritic mesoporous rare earth-based nanoparticles

Rare earth-based nanomaterials that have abundant optical, magnetic, and catalytic characteristics have many applications. The controllable introduction of mesoporous channels can further enhance its performance, such as exposing more active sites of rare earth and improving the loading capacity, yet remains a challenge. Here, we report a universal viscosity-mediated assembly strategy and successfully endowed rare earth-based nanoparticles with central divergent dendritic mesopores. More than 40 kinds of dendritic mesoporous rare earth-based (DM-REX) nanoparticles with desired composition (single or multiple rare earth elements, high-entropy compounds, etc.), particle diameter (80 to 500 nanometers), pore size (3 to 20 nanometers), phase (amorphous hydroxides, crystalline oxides, and fluorides), and architecture were synthesized. Theoretically, a DM-REX nanoparticle library with 393,213 kinds of possible combinations can be constructed on the basis of this versatile method, which provides a very broad platform for the application of rare earth-based nanomaterials with rational designed functions and structures.

A High-Performance Electrode Based on van der Waals Heterostructure for Neural Recording

Neural electrodes have been widely used to monitor neurological disorders and have a major impact on neuroscience, whereas traditional electrodes are limited to their inherent high impedance, which makes them insensitive to weak signals during recording neural signals. Herein, we developed a neural electrode based on the graphene/Ag van der Waals heterostructure for improving the detection sensitivity and signal-to-noise ratio (SNR). The impedance of the graphene/Ag electrode is reduced to 161.4 ± 13.4 MΩ μm², while the cathode charge-storage capacity (CSCc) reaches 24.2 ± 1.9 mC cm^-2, which is 6.3 and 48.4 times higher than those of the commercial Ag electrodes, respectively. Density functional theory (DFT) results find that the Ag-graphene interface has more doped electronic states, providing faster electron transfer and enhanced interfacial transport. In vivo detection sensitivity and SNR of graphene/Ag electrodes are significantly improved. The current work provides a feasible solution for designing brain electrodes to monitor neural signals more sensitively and accurately.

Fluorescent probes for the detection of disease-associated biomarkers

Fluorescent probes have emerged as indispensable chemical tools to the field of chemical biology and medicine. The ability to detect intracellular species and monitor physiological processes has not only advanced our knowledge in biology but has provided new approaches towards disease diagnosis. In this review, we detail the design criteria and strategies for some recently reported fluorescent probes that can detect a wide range of biologically important species in cells and in vivo. In doing so, we highlight the importance of each biological species and their role in biological systems and for disease progression. We then discuss the current problems and challenges of existing technologies and provide our perspective on the future directions of the research area. Overall, we hope this review will provide inspiration for researchers and prove as useful guide for the development of the next generation of fluorescent probes.

A K+-sensitive AND-gate dual-mode probe for simultaneous tumor imaging and malignancy identification

Although molecular imaging probes have the potential to non-invasively diagnose a tumor, imaging probes that can detect a tumor and simultaneously identify tumor malignancy remain elusive. Here, we demonstrate a potassium ion (K⁺) sensitive dual-mode nanoprobe (KDMN) for non-invasive tumor imaging and malignancy identification, which operates via a cascaded ‘AND’ logic gate controlled by inputs of magnetic resonance imaging (MRI) and fluorescence imaging (FI) signals. We encapsulate commercial K⁺ indicators into the hollow cavities of magnetic mesoporous silica nanoparticles, which are subsequently coated with a K⁺-selective membrane that exclusively permits the passage of K⁺ while excluding other cations. The KDMN can readily accumulate in tumors and enhance the MRI contrast after systemic administration. Spatial information of the tumor lesion is thus accessible via MRI and forms the first layer of the ‘AND’ gate. Meanwhile, the KDMN selectively captures K⁺ and prevents interference from other cations, triggering a K⁺-activated FI signal as the second layer of the ‘AND’ gate in the case of a malignant tumor with a high extracellular K⁺ level. This dual-mode imaging approach effectively eliminates false positive or negative diagnostic results and allows for non-invasive imaging of tumor malignancy with high sensitivity and accuracy.

Electrochemically Imaging the Response of Ion-Selective Membranes with an Ultralow Detection Limit

The development of ion-selective membranes for the selective response of a particular ion has been studied for many years; however, imaging the response of the membrane with a low detection limit is challenging. Here, high spatial-resolution electrochemical imaging of this response down to picomolar is achieved using scanning ion conductive microscopy. The detection strategy relies on the exclusion of a small amount of counter ions from the membrane in the presence of a low concentration of target ions in the solution. These excluded counter ions are adsorbed at the membrane-solution interface, leading to more positive charges at the surface. The resultant elevation of the ionic current in the approach curve behaves as the response for the target ions down to 10^-11 M, which is much more sensitive than that using potentiometric measurement. The constant-current scanning of the membrane exhibits the fluctuation of the apparent surface height that is correlated with the ionic concentration, permitting the imaging of the response at the nanoscale. The achievement of highly sensitive and spatial-resolution imaging for the ionic response enable the collection of spatial response at the ion-selective membrane, which will greatly advance the study of ion-selective electrodes.

Chemical Design of Activatable Photoacoustic Probes for Precise Biomedical Applications

Photoacoustic (PA) imaging technology, a three-dimensional hybrid imaging modality that integrates the advantage of optical and acoustic imaging, has great application prospects in molecular imaging due to its high imaging depth and resolution. To endow PA imaging with the ability for real-time molecular visualization and precise biomedical diagnosis, numerous activatable molecular PA probes which can specifically alter their PA intensities upon reacting with the targets or biological events of interest have been developed. This review highlights the recent developments of activatable PA probes for precise biomedical applications including molecular detection of the biotargets and imaging of the biological events. First, the generation mechanism of PA signals will be given, followed by a brief introduction to contrast agents used for PA probe design. Then we will particularly summarize the general design principles for the alteration of PA signals and activatable strategies for developing precise PA probes. Furthermore, we will give a detailed discussion of activatable PA probes in molecular detection and biomedical imaging applications in living systems. At last, the current challenges and outlooks of future PA probes will be discussed. We hope that this review will stimulate new ideas to explore the potentials of activatable PA probes for precise biomedical applications in the future.

In Situ Monitoring of Extracellular K+ Using the Potentiometric Mode of Scanning Electrochemical Microscopy with a Carbon-Based Potassium Ion-Selective Tip

The expression of potassium channels can be related to the occurrence and development of tumors. Their change would affect K⁺ outflow. Thus, in situ monitoring of extracellular K⁺ shows a great significance. Herein, the dual-functional K⁺ ion-selective electrode as the scanning electrochemical microscopy (SECM) tip (K⁺-ISE SECM tip) has been developed for in situ monitoring of the extracellular K⁺. Based on multi-wall carbon nanotubes as a transduction layer, the K⁺-ISE SECM tip realizes both the plotting of approach curves to position the tip for in situ detection and the recording of potential responses. It shows a near Nernstian response, good selectivity, and excellent stability. Based on these characteristics, it was used to in situ monitor K⁺ concentrations ([K⁺]_o) of three breast cancer cell lines (MCF-7, MDA-MB-231, and SK-BR-3 cells) at 3 μm above the cell, and [K⁺]_o of MDA-MB-231 cells show the highest value, followed by MCF-7 cells and SK-BR-3 cells. K⁺ outflow induced by electrical stimulation or pH changes of the culture environment (Δ[K⁺]_o) was further determined, and the possible mechanism of K⁺ outflow was investigated with 4-aminopyridin (4-AP). MCF-7 cells present the largest value of Δ[K⁺]_o, followed by MDA-MB-231 cells and SK-BR-3 cells at all the stimulation potentials, and pH 6.50 shows the greatest impact on K⁺ outflow of the three cell lines. The pretreatment of 4-AP changed K⁺ outflow, probably due to the regulation of voltage-gated channels. These findings provide insight into a deep understanding of the microenvironment influence on K⁺ outflow, thereby reflecting the possible mechanism of potassium channels.

Electron transfer-triggered imaging of EGFR signaling activity

In vivo electron transfer processes are closely related to the activation of signaling pathways, and, thus, affect various life processes. Indeed, the signaling pathway activation of key molecules may be associated with certain diseases. For example, epidermal growth factor receptor (EGFR) activation is related to the occurrence and development of tumors. Hence, monitoring the activation of EGFR-related signaling pathways can help reveal the progression of tumor development. However, it is challenging for current detection methods to monitor the activation of specific signaling pathways in complex biochemical reactions. Here we designed a highly sensitive and specific nanoprobe that enables in vivo imaging of electronic transfer over a broad range of spatial and temporal scales. By using the ferrocene-DNA polymer “wire”, the electrons transferred in a biochemical reaction can flow to persistent luminescent nanoparticles and change their electron distribution, thereby altering the optical signal of the particles. This electron transfer-triggered imaging probe enables mapping the activation of EGFR-related signaling pathways in a temporally and spatially precise manner. By offering precise visualization of signaling activity, this approach may offer a general platform not only for understanding molecular mechanisms in various biological processes but also for promoting disease therapies and drug evaluation.

Here, the authors design a nanoprobe for in vivo imaging of electronic transfer, consisting of a ferrocene-DNA polymer to transfer electrons to luminescent nanoparticles, changing their optical signal. Using this probe, they map activation of EGFR signalling during tumour treatment.

Cell-Surface-Anchored DNA Sensors for Simultaneously Monitoring Extracellular Sodium and Potassium Levels

The K⁺ and Na⁺ levels in cells have a synergistic effect on many biological processes (BPs); therefore, the simultaneous detection of them is important. Here, we propose a novel Y-shaped DNA sensor for simultaneous monitoring of Na⁺ and K⁺ in extracellular microenvironments. The designed sensor contributed to the selective response to the above two ions. In addition, it performed the imaging of the above two ions on the cell surface in a real-time, on-site manner, which would shed more light on the association of the Na⁺/K⁺ content with regulatory BPs. We believe that this new strategy will be a promising tool to investigate the synergy of Na⁺/K⁺ in regulating different BPs.

Vesicle-Based Sensors for Extracellular Potassium Detection

Introduction

The design of sensors that can detect biological ions in situ remains challenging. While many fluorescent indicators exist that can provide a fast, easy readout, they are often nonspecific, particularly to ions with similar charge states. To address this issue, we developed a vesicle-based sensor that harnesses membrane channels to gate access of potassium (K⁺) ions to an encapsulated fluorescent indicator.

Methods

We assembled phospholipid vesicles that incorporated valinomycin, a K⁺ specific membrane transporter, and that encapsulated benzofuran isophthalate (PBFI), a K⁺ sensitive dye that nonspecifically fluoresces in the presence of other ions, like sodium (Na⁺). The specificity, kinetics, and reversibility of encapsulated PBFI fluorescence was determined in a plate reader and fluorimeter. The sensors were then added to E. coli bacterial cultures to evaluate K⁺ levels in media as a function of cell density.

Results

Vesicle sensors significantly improved specificity of K⁺ detection in the presence of a competing monovalent ion, sodium (Na⁺), and a divalent cation, calcium (Ca²⁺), relative to controls where the dye was free in solution. The sensor was able to report both increases and decreases in K⁺ concentration. Finally, we observed our vesicle sensors could detect changes in K⁺ concentration in bacterial cultures.

Conclusion

Our data present a new platform for extracellular ion detection that harnesses ion-specific membrane transporters to improve the specificity of ion detection. By changing the membrane transporter and encapsulated sensor, our approach should be broadly useful for designing biological sensors that detect an array of biological analytes in traditionally hard-to-monitor environments.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12195-021-00688-7.

Dynamic nanoassembly-based drug delivery systems on the horizon

Self-assembly in nature creates matter with complex structures and unpredictable designs; disordered building blocks spontaneously organize into ordered structures to achieve specific functions. Self-assembly begins to play an important role in the design of advanced drug delivery as well. Though, the behavior of 'dynamic nanoassembly-based drug delivery systems' (DNDDS) in biological media and cells remains poorly understood, while this is highly critical for controlling spatiotemporal drug release from DNDDS in vivo. To deepen the understanding of tailor-made DNDDS, this contribution in the Oration - New Horizons section of the Journal of controlled Release aims to highlight nature-inspired designs, construction principles, and controllable functionalities of DNDDS and how they are triggered by endogenous and exogenous stimuli. Furthermore, biomedical applications of tailor-made DNDDS for accurate diagnosis and precise treatment of diseases, including tumors, neurological diseases, injuries and infections are discussed. Finally, current challenges and future perspectives of DNDDS are briefly outlined.

New advances in pharmacoresistant epilepsy towards precise management-from prognosis to treatments

Epilepsy, one of the most severe neurological diseases, is characterized by abrupt recurrent seizures. Despite great progress in the development of antiseizure drugs (ASDs) based on diverse molecular targets, more than one third of epilepsy patients still show resistance to ASDs, a condition termed pharmacoresistant epilepsy. The management of pharmacoresistant epilepsy involves serious challenges. In the past decade, promising advances have been made in the use of interdisciplinary techniques involving biophysics, bioinformatics, biomaterials and biochemistry, which allow more precise prognosis and development of drug target for pharmacoresistant epilepsy. Notably, novel experimental tools such as viral vector gene delivery, optogenetics and chemogenetics have provided a framework for promising approaches to the precise treatment of pharmacoresistant epilepsy. In this review, historical achievements especially recent advances of the past decade in the prognosis and treatment of pharmacoresistant epilepsy from both clinical and laboratory settings are presented and summarized. We propose that the further development of novel experimental tools at cellular or molecular levels with both temporal and spatial precision are necessary to make improve the management and drug development for pharmacoresistant epilepsy in the clinical arena.

Dynamic nanoassemblies for imaging and therapy of neurological disorders

The past decades have witnessed an increased incidence of neurological disorders (NDs) such as Alzheimer's disease, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, ischemic stroke, and epilepsy, which significantly lower patients' life quality and increase the economic and social burden. Recently, nanomedicines composed of imaging and/or therapeutic agents have been explored to diagnose and/or treat NDs due to their enhanced bioavailability, blood-brain barrier (BBB) permeability, and targeting capacity. Intriguingly, dynamic nanoassemblies self-assembled from functional nanoparticles to simultaneously interfere with multiple pathogenic substances and pathological changes, have been regarded as one of the foremost candidates to improve the diagnostic and therapeutic efficacy of NDs. To help readers better understand this emerging field, in this review, the pathogenic mechanism of different types of NDs is briefly introduced, then the functional nanoparticles used as building blocks in the construction of dynamic nanoassemblies for NDs theranostics are summarized. Furthermore, dynamic nanoassemblies that can actively cross the BBB to target brain lesions, sensitively and efficiently diagnose or treat NDs, and effectively promote neuroregeneration are highlighted. Finally, we conclude with our perspectives on the future development in this field.

Dynamic nanoassembly-based drug delivery system (DNDDS): Learning from nature

Dynamic nanoassembly-based drug delivery system (DNDDS) has evolved from being a mere curiosity to emerging as a promising strategy for high-performance diagnosis and/or therapy of various diseases. However, dynamic nano-bio interaction between DNDDS and biological systems remains poorly understood, which can be critical for precise spatiotemporal and functional control of DNDDS in vivo. To deepen the understanding for fine control over DNDDS, we aim to explore natural systems as the root of inspiration for researchers from various fields. This review highlights ingenious designs, nano-bio interactions, and controllable functionalities of state-of-the-art DNDDS under endogenous or exogenous stimuli, by learning from nature at the molecular, subcellular, and cellular levels. Furthermore, the assembly strategies and response mechanisms of tailor-made DNDDS based on the characteristics of various diseased microenvironments are intensively discussed. Finally, the current challenges and future perspectives of DNDDS are briefly commented.

Real-Time Visualization and Monitoring of Physiological Dynamics by Aggregation-Induced Emission Luminogens (AIEgens)

Physiological dynamics in living cells and tissues are crucial for maintenance and regulation of their normal activities and functionalities. Tiny fluctuations in physiological microenvironments can leverage significant influences on cell growth, metabolism, differentiation, and apoptosis as well as disease evolution. Fluorescence imaging based on aggregation-induced emission luminogens (AIEgens) exhibits superior advantages in real-time sensing and monitoring of the physiological dynamics in living systems, including its unique properties such as high sensitivity and rapid response, flexible molecular design, and versatile nano- to mesostructural fabrication. The introduction of canonic AIEgens with long-wavelength, near-infrared, or microwave emission, persistent luminescence, and diversified excitation source (e.g., chemo- or bioluminescence) offers researchers a tool to evaluate the resulting molecules with excellent performance in response to subtle fluctuations in bioactivities with broader dimensionalities and deeper hierarchies.

Microenvironment-tailored nanoassemblies for the diagnosis and therapy of neurodegenerative diseases

Neurodegenerative disorder is an illness involving neural dysfunction/death attributed to complex pathological processes, which eventually lead to the mortality of the host. It is generally recognized through features such as mitochondrial dysfunction, protein aggregation, oxidative stress, metal ions dyshomeostasis, membrane potential change, neuroinflammation and neurotransmitter impairment. The aforementioned neuronal dysregulations result in the formation of a complex neurodegenerative microenvironment (NME), and may interact with each other, hindering the performance of therapeutics for neurodegenerative disease (ND). Recently, smart nanoassemblies prepared from functional nanoparticles, which possess the ability to interfere with different NME factors, have shown great promise to enhance the diagnostic and therapeutic efficacy of NDs. Herein, this review highlights the recent advances of stimuli-responsive nanoassemblies that can effectively combat the NME for the management of ND. The first section outlined the NME properties and their interrelations that are exploitable for nanoscale targeting. The discussion is then extended to the controlled assembly of functional nanoparticles for the construction of stimuli-responsive nanoassemblies. Further, the applications of stimuli-responsive nanoassemblies for the enhanced diagnosis and therapy of ND are introduced. Finally, perspectives on the future development of NME-tailored nanomedicines are given.

Cellular lensing and near infrared fluorescent nanosensor arrays to enable chemical efflux cytometry

Nanosensors have proven to be powerful tools to monitor single cells, achieving spatiotemporal precision even at molecular level. However, there has not been way of extending this approach to statistically relevant numbers of living cells. Herein, we design and fabricate nanosensor array in microfluidics that addresses this limitation, creating a Nanosensor Chemical Cytometry (NCC). nIR fluorescent carbon nanotube array is integrated along microfluidic channel through which flowing cells is guided. We can utilize the flowing cell itself as highly informative Gaussian lenses projecting nIR profiles and extract rich information. This unique biophotonic waveguide allows for quantified cross-correlation of biomolecular information with various physical properties and creates label-free chemical cytometer for cellular heterogeneity measurement. As an example, the NCC can profile the immune heterogeneities of human monocyte populations at attomolar sensitivity in completely non-destructive and real-time manner with rate of ~600 cells/hr, highest range demonstrated to date for state-of-the-art chemical cytometry.

Brain neurochemical monitoring

Brain neurochemical monitoring aims to provide continuous and accurate measurements of brain biomarkers. It has enabled significant advances in neuroscience for application in clinical diagnostics, treatment, and prevention of brain diseases. Microfabricated electrochemical and optical spectroscopy sensing technologies have been developed for precise monitoring of brain neurochemicals. Here, a comprehensive review on the progress of sensing technologies developed for brain neurochemical monitoring is presented. The review provides a summary of the widely measured clinically relevant neurochemicals and commonly adopted recognition technologies. Recent advances in sampling, electrochemistry, and optical spectroscopy for brain neurochemical monitoring are highlighted and their application are discussed. Existing gaps in current technologies and future directions to design industry standard brain neurochemical sensing devices for clinical applications are addressed.

Highly Selective Detection of K+ Based on a Dimerized G-Quadruplex DNAzyme

Potassium ion (K⁺) plays a crucial role in biological systems, such as maintaining cellular processes and causing diseases. However, specifically, the detection of K⁺ is extremely challenging because of the coexistence of the chemically similar ion of Na⁺ under physiological conditions. In this work, a K⁺ specific biosensor is constructed on the basis of a dimerized G-quadruplex (GQ) DNA, which is promoted by K⁺, and the enzymatic activity of the resulting DNAzyme depends on the concentration of the K⁺. The K⁺ in a 1-200 mM concentration range can be selectively detected by visual color, UV-Vis absorbance or fluorescence even if the concentration of the accompanying Na⁺ is up to 140 mM at an ambient condition up to 45 °C. In addition, this system can also be used to selectively detect NH₄⁺ in a 5-200 mM concentration range. This dimerized DNAzyme offers a new type of biosensor with a potential application in the biological system.