Gut function is closely modulated by the synchronized mechanical activities of intestinal wall and luminal microbial-derived metabolites, and their influences are speculated to converge on serotonin (5-HT) signaling pathways. Existing knowledge mainly focuses on the isolated effect of mechanical or microbial factors on the ultimate intestinal 5-HT levels. However, it remains unclear how these coexisting factors interplay and modulate 5-HT release during dynamic peristaltic activity. Herein, leveraging the mechanical deformability and in situ measurement of stretchable electrodes, this study presents a balloon electrochemical sensor to seamlessly interface with the gut lining, initiate mechanical distension, and monitor ensuing 5-HT overflow. These tailored sensors allow systematic quantification of 5-HT release from intestinal cells and tissues exposed to mechanical distension and short-chain fatty acids (SCFAs). This results reveal that mechanical stimuli evoke Piezo2-mediated transient 5-HT release from enterochromaffin cells of the intestine. While, SCFAs stimulation triggers transient 5-HT release through G-protein coupled receptor (GPCR) activation, and prolonged SCFAs exposure enhances 5-HT biosynthesis and mechanosensitivity. These findings provide direct evidence to decipher how mechanical and microbial factors synergistically potentiate the 5-HT secretion in peristaltic intestine, as well as crucial perspectives for the complex mechano-chemical coupling in signal transduction.

Hydrogen peroxide (H2O2) monitoring in plants is essential for elucidating stress signaling and related physiology. However, the performance of current detection methods is often compromised by the complex plant matrix. Photoelectrochemical (PEC) sensing utilizing p-type semiconductors facilitates rapid electron transfer from the electrode interface to electron acceptors, resulting in a cathodic photocurrent and offering a notable anti-interferent ability for H2O2 detection. Herein, we report a novel tetraphenylethylene-equipped graphene quantum dots (TEGQDs) heterostructure to construct cathodic PEC sensors for H2O2 detection. By pi-pi stacking assembly of pi-electron-rich TPE molecules with p-type GQDs, fast electron channels are established within the heterostructure, endowing the TEGQDs with an enhanced cathodic photocurrent signal. Moreover, in the presence of H2O2, the peroxidase-like enzyme activity of TEGQDs inherited from GQDs catalyzes oxidation of 4-chloro-1-naphthol to produce an insoluble precipitate, decreasing the photocurrent response. This strategy endows the PEC sensor with exceptional selectivity and a low detection limit of 70.2 nM for H2O2. Assisted by a minimally invasive microneedle extraction, this sensor is successfully applied to investigate H2O2 fluctuations in tomato leaves subjected to various biotic (Botrytis cinerea) and abiotic (wounding, heat) stresses. This study presents a robust and versatile PEC sensor for monitoring plant health in agricultural management.

Environmental pollutant nanoplastics (NPs) cross the blood-brain barrier and induce central nervous system toxicity through multiple pathways, with oxidative stress as the core neurotoxicity initiator. However, the brain penetration depth of NPs and associated oxidative stress distribution have not yet been investigated. Herein, we developed a flexible electrochemical sensor based on platinum nanoparticle-modified carbon nanotube fiber (Pt/CNF) to minimize insertion damage. The sensor exhibits excellent mechanical compliance and high sensitivity for hydrogen peroxide (H2O2) detection. Using this sensor for real-time in situ H2O2 monitoring in human cortical organoids (COs), we systematically investigated the oxidative stress levels at depths of 100 and 300 & micro;m in COs exposed to polystyrene nanoplastics (PS-NPs) for different durations within 6 days. Our results demonstrate that oxidative stress at the same depth increased with longer exposure time, and showed distinct spatial locality, concentrating primarily in the similar to 100 & micro;m-deep penetration region. This study quantifies the spatiotemporal neurotoxicity of nanoplastics in human brain models and provides a robust technical framework for environmental health risk assessment in other tissues.

Acupuncture exerts its therapeutic effects through complex mechanical cues, including compressive forces from needle insertion and retention, and tensile stresses from extracellular matrix deformation during needle twisting. How these biomechanical stimuli regulate mast cell function at the molecular level remains poorly understood due to the lack of tools capable of replicating such multifaceted forces. Here, we report a magneto-responsive biosensor that enables multimodal simulation of stretching, compression, and combined loading in both static and cyclic modes. This allows for closely recapitulating the mechanical environment of mast cells during acupuncture, while simultaneously monitoring mechanically evoked cellular serotonin (5HT) release in real time. Using this sensor, we demonstrate that cyclic combined stimulation significantly amplifies cell responses by promoting both 5-HT release and intracellular biosynthesis. Furthermore, in vivo experiments at acupoints confirmed the "release-replenishment" phenomenon observed in vitro. Collectively, this study provides mechanistic insights into the molecular basis of acupuncture therapy and establishes a versatile tool for probing mechanobiological regulation in living systems.

Mechanotransduction exerts a profound influence on diverse cellular processes via activated signalling pathways. Although the currently established methods could reveal force-induced ultimate changes in specific biochemical cues, they fail to provide real-time and comprehensive information about the complicated signaling events. Herein, we report stretchable electrode enabled electrochemical mass spectrometry for in situ and complementary analysis of cellular mechanotransduction. The stretchable electrode functions as not only an electrochemical sensor for tracking the electroactive molecules released from stretched cells cultured thereon, but also an ionization source to ionize the intracellular metabolites for mass spectrometry analysis. As a concept application, the endothelial mechanotransduction mediated NO pathway was found to be different in transient stimulation and prolonged stimulation for the first time. This work provides a revealing strategy for in situ and comprehensive analysis of the biomolecules involved in cellular mechanotransduction.

Real-time monitoring of reactive oxygen and nitrogen species (RONS) in skeletal muscle provides crucial insights into the cause-and-effect relationships between physical activity and health benefits. However, the dynamic production of exercise-induced RONS remains poorly explored, due to the lack of sensing tools that can conform to soft skeletal muscle while monitor RONS release during exercise. Here we introduce dual flexible sensors via twisting carbon nanotubes into helical bundles of fibers and subsequent assembling electrochemical sensing components. These flexible sensors exhibit low bending stiffness, excellent H2O2 and NO sensing abilities, outstanding biocompatibility and compliance with engineered skeletal muscle tissue. This allows real-time and simultaneous monitoring of H2O2 and NO release from engineered skeletal muscle in response to different exercise-mimicking stretches, which reveals that warm-up activities before high-intensity exercise may enhance adaptive responses by down-regulating H2O2 and up-regulating NO production. The proposed sensing strategy demonstrates great versatility in monitoring multiple biomarkers of soft tissue and organs.

High-fat foods are decomposed into fatty acids during digestion and absorption, primarily occurring in the gastrointestinal tract, and numerous studies have indicated that long-term high-fat diets significantly increase the incidence of intestinal disorders. As a critical intestinal hormone, serotonin (5-hydroxytryptamine, 5-HT) is involved in regulating intestinal peristalsis, secretion, and visceral sensitivity. However, due to the lack of methods capable of reproducing intestinal mechanical activities and in situ monitoring of 5-HT levels, the influence of high-fat diets on intestinal 5-HT release remains unclear. Herein, we presented a deformable peristalsis-mimicking intestinal epithelium chip with a built-in stretchable electrochemical sensor for in situ and quantitative 5-HT detection. Two high-fat diet models were established by pretreating the intestinal epithelium with saturated fatty acid (palmitic acid, PA) and unsaturated fatty acid (oleic acid, OA), respectively. Both PA and OA could promote epithelial 5-HT synthesis and increase 5-HT release during intestinal motility, while OA exhibited a stronger stimulatory effect on 5-HT release than PA, which might be associated with the OA-enhanced intestinal epithelial barrier. These results provide important insights into the differential roles of saturated and unsaturated fatty acids in regulating intestinal function.

Plant benzylisoquinoline alkaloids (BIAs) are a group of plant-specialized metabolites with significant pharmacological properties. In lotus (Nelumbo nucifera), BIAs accumulate primarily in the leaf blade and plumule organs. The two organs, however, accumulate quite different types of BIAs, within the former primarily aporphine-type BIAs, while the latter predominantly bis-BIAs. Herein, we demonstrate that the spatial regulation of BIA biosynthesis in lotus is coordinately controlled through the NnMYC2-NnMYB14-NnCYP80 modules. Genome-wide screening of lotus CYP80 genes discovered two tandemly arrayed yet tissue-specific NnCYP80s that are identical to the previously reported NnCYP80G and NnCYP80A, respectively. NnCYP80G is expressed primarily in the lotus laminae, while NnCYP80A is expressed particularly in the plumules. Our enzyme assays confirmed the proaporphine synthase activity of NnCYP80G and the bis-BIA synthase activity of NnCYP80A, and revealed the aporphine synthase activity of NnCYP80G by efficiently converting the (R)-reticuline substrate into corytuberine. In addition, we characterized an R2R3 MYB transcription factor (TF) NnMYB14, which binds directly to the NnCYP80G and NnCYP80A promoters and positively regulates their expression. NnMYC2, the core regulator in the JA signaling pathway, acts very upstream of NnMYB14, by binding directly to the NnMYB14 promoter and inducing its expression. Our results resolved that the organ-specific accumulation of BIAs in lotus is attributed to the tissue-specially expressed NnCYP80G and NnCYP80A genes, and the NnMYC2-NnMYB14 TF module could positively regulate the NnCYP80G and NnCYP80A expression and the lotus BIA biosynthesis.

Quantifying the shape and stiffness of extracellular vesicles (EVs) is essential for understanding their biophysical properties and roles in intercellular communication. However, achieving single-particle resolution under physiological conditions remains a significant challenge. Here, we introduce an approach that integrates single-molecule diffusivity mapping (SMdM) with diffusion models for spherical and discoidal shapes to quantify the geometric and mechanical properties of individual liposomes and EVs in aqueous solution. Our findings identify charged lipids and cholesterol as critical factors that enhance liposome stiffness, driving their shapes closer to spheres. Applying this method to EVs reveals that those derived from tumor cells exhibit lower stiffness compared to EVs from normal cells, consistent with the biomechanical characteristics of their parent cells. This rapid, high-throughput strategy for characterizing the shape and stiffness of single EVs in aqueous solution offers promising applications in cancer biomarker discovery and the development of EV-based therapeutics.

For the plants with important ecological or economic values, understanding the genetic structure of their populations is crucial to inform conservation strategies. Chinese wild rice Zizania latifolia is distributed in the East China along a wide stretch of latitudinal zones (20 degrees-51 degrees N). In this study, using restriction-site associated DNA sequencing (RAD-seq), the genetic structure and local adaptation were evaluated on 60 wild samples composed of 10 Z. latifolia populations collected along a latitudinal gradient and 6 cultivated samples from different cultivars in central China. Low levels of genetic variability were found in the Z. latifolia populations (HE = 0.08-1.52). Population structure analysis showed that samples firstly divided into two major clusters (north and south groups), splitting along a temperature boundary. It was estimated that the two groups diverged during the 8.2 kiloyear event and later experienced severe genetic bottlenecks with advancement of agriculture and increase in human population 2k years later. Compared to geographical distance, environment had a higher contribution to allele frequency variations (r2=0.3467, P G 0.001 vs r2=0.4702, P G 0.001) and morphological variations of populations (r2=0.6110, P G 0.001 vs r2=0.7739, P G 0.001). Several loci were found to be correlated with environmental variables as well as morphological traits, most of which were annotated as retrotransposons. Considering the abundance of transposable elements in the Z. latifolia genome, differentiation and local adaptation was inferred to be partly driven by temperature-induced transposable elements activity. Based on these results, populations from different latitude zones should be separately protected due to their high genetic differentiation and local adaptation.

Mechanical cues are critical regulators of cell fate and behavior through the orchestrated and continual conversion of physical forces into biochemical responses. However, due to the poor compatibility between mechanical and biochemical techniques, existing methods are often limited in characterizing the occurring biochemical signals during mechanical stimulation. Herein, this work presents a magneto-responsive nanomesh (MRnM) biosensor capable of mechanically stimulating cells in vitro and tissues in vivo and simultaneously detecting the triggered biomolecules. Under external magnetic fields, the sensor exhibits excellent magnetic responsiveness with remote, controllable and tailored deformation, while maintaining prominent and stable electrochemical sensing performance. As a proof of concept, this MRnM sensor achieves the magnetically-actuated deformation of osteoblasts and real-time monitoring of the ensuing nitric oxide release, revealing the role of Piezo1 channels in nitric oxide synthase signaling pathways. Furthermore, we demonstrate the capability of MRnM sensor for in vivo applications. Ultimately, the developed MRnM biosensor holds great potential for mechanical stimulation and real-time monitoring of various biological systems, ranging from living cells to soft tissues and in vivo organs.

Highly pathogenic avian influenza (HPAI) H5N1 virus poses a continuing global public health threat due to its outbreaks in poultry farms and zoonotic transmission from birds to humans. In the quest of effective therapeutics against H5N1 infection, antibodies with broad neutralizing activity have attracted significant attention. In this study, we employed a phage display technique to select and identify VHH antibodies with specific neutralizing activity against H5N1 hemagglutinin (HA) from an immune llama-derived antibody library. Subsequently, we prepared fusions of VHH10 antibody with human Fc fragment. The chimeric antibody VHH10-hFc was characterized and evaluated for its specificity, binding affinity, serum persistence and antigen recognition epitope. Following purification from 293 F cell cultures, VHH10-hFc chimeric antibody retained its specificity to H5N1 HA. Its antigen-binding affinity was enhanced by up to 130-fold, and its serum persistence was extended by up to 170-fold compared to VHH10. The VHH10-hFc chimeric antibody demonstrated high affinity, excellent thermal stability, and broad reactivity against H5N1 HA in clades 0, 1, 2, and 4. Through epitope mapping, we identified a conformational epitope consisting amino acid residues at positions Q187, K189, L190, Y191, N193, T215, S217 and N220 located on the top region of HA, which was specific and conserved epitopes among H5N1 strains. Consequently, VHH10-hFc, with great specificity, high affinity, prolonged serum persistence and good thermal stability, recognizes a conserved neutralization epitope on the globular head of H5N1 HA, indicating great potential in therapeutic strategies against H5N1 infection.

Exposure to widely used inert fibrous nanomaterials (for example, glass fibres or carbon nanotubes) may result in asbestos-like lung pathologies, becoming an important environmental and health concern. However, the origin of the pathogenesis of such fibres has not yet been clearly established. Here we report an electrochemical nanosensor that is used to monitor and quantitatively characterize the flux and dynamics of reactive species release during the frustrated phagocytosis of glass nanofibres by single macrophages. We show the existence of an intense prolonged release of reactive oxygen and nitrogen species by single macrophages near their phagocytic cups. This continued massive leakage of reactive oxygen and nitrogen species damages peripheral cells and eventually translates into chronic inflammation and lung injury, as seen during in vitro co-culture and in vivo experiments.

Nanoplastics from air pollutants can be directly inhaled into the alveoli in the lungs and further enter blood circulation, and numerous studies have revealed the close relation between internalized nanoplastics with many physiological disorders via intracellular oxidative stress. However, the dynamic process of nanoplastics-induced oxidative stress in lung cells under breath-mimicked conditions is still unclear, due to the lack of methods that can reproduce the mechanical stretching of the alveolar and simultaneously monitor the oxidative stress response. Here, we describe a biomimetic platform by culturing alveoli epithelial cells on a stretchable electrochemical sensor and integrating them into a microfluidic device. This allows reproducing the respiration of alveoli by cyclic stretching of the alveoli epithelial cells and monitoring the nanoplastics-induced oxidative stress by the built-in sensor. By this device, we prove that cyclic stretches can greatly enhance the cellular uptake of nanoplastics with the dependencies of strain amplitude. Importantly, oxidative stress evoked by internalized nanoplastics can be quantitatively monitored in real time. This work will promote the deep understanding about the cytotoxicity of inhaled nanoplastics in the pulmonary mechanical microenvironment.

Chondrocytes, the cells that formulate the cartilage, reside in a complex microenvironment composed of extracellular matrix (ECM) and biomechanical factors. Although current cartilage models can reproduce the ECM architecture or mechanical environment, they fail to provide the transient biochemical information of chondrocytes during dynamic mechanical loading. Here, we present a cartilage-on-a-chip integrated with a stretchable electrochemical sensor, which consists of collagen-alginate hybrid hydrogel to mimic ECM-like matrices and a pneumatic actuation unit to apply controllable mechanical compression to cell-laden hydrogel. The built-in stretchable electrochemical sensor allows real-time monitoring of nitric oxide (NO) release from chondrocytes when subjected to physiological and hyperphysiological compression. This device enables the establishment of a reliable cartilage model and the assessment of the biochemical response, providing an evaluation platform for cell regulation, tissue engineering, and drug screening.

Exocytosis involving the fusion of intracellular vesicles with cell membrane, is thought to be modulated by the mechanical cues in the microenvironment. Single-cell electrochemistry can offer unique information about the quantification and kinetics of exocytotic events; however, the effects of mechanical force on vesicular release have been poorly explored. Herein, we developed a stretchable microelectrode with excellent electrochemical stability under mechanical deformation by microfabrication of functionalized poly(3,4-ethylenedioxythiophene) conductive ink, which achieved real-time quantitation of strain-induced vesicular exocytosis from a single cell for the first time. We found that mechanical strain could cause calcium influx via the activation of Piezo1 channels in chromaffin cell, initiating the vesicular exocytosis process. Interestingly, mechanical strain increases the amount of catecholamines released by accelerating the opening and prolonging the closing of fusion pore during exocytosis. This work is expected to provide revealing insights into the regulatory effects of mechanical stimuli on vesicular exocytosis.

Comprehensive SummaryIn vivo monitoring of bioelectrical and biochemical signals with implanted electrodes has received great interest over the past decades. However, this faces huge challenges because of the severe mechanical mismatch between conventional rigid electrodes and soft biological tissues. In recent years, the emergence of flexible and stretchable electrodes offers seamless and conformable biological‐electronic interfaces and has demonstrated significant advantages for in vivo electrochemical and electrophysiological monitoring. This review first summarizes the strategies for electrode fabrication from the point of substrate and conductive materials. Next, recent progress in electrode functionalization for improved performance is presented. Then, the advances of flexible and stretchable electrodes in exploring bioelectrical and biochemical signals are introduced. Finally, we present some challenges and perspectives ranging from electrode fabrication to application.Key ScientistsIn 2001, a seminal work by Kipke et al. first showed flexible polyimide‐based intracortical electrode arrays.[1] This electrode was further expanded to 252‐channel using microelectromechanical systems technology by Stieglitz et al. in 2009 and achieved large‐scale cortical recordings.[2] Later, Lieber et al. created mesh electronics that allow for seamless and minimally invasive three‐dimensional interpenetration with nerve tissues, opening up unique applications for flexible electronics.[3] Subsequently, Rogers et al. described bioresorbable electronics for transient electrical activity recordings in 2016.[4] And Frank et al. proposed polymer electrode arrays capable of resolving single neurons in 2019.[5] It wasn't until 2020 that a significant breakthrough in biochemical signals monitoring by Peng et al. demonstrated functionalized carbon nanotube fibre bundles for multiple disease biomarkers monitoring.[6] Later on, Mooney et al. established the first fully viscoelastic electrode arrays for neural recordings from the brain and heart in 2021.[7] Recently, Bao et al. presented tissue‐mimicking, stretchable neurotransmitter interfaces for monitoring the brain and gut.[8]

Alzheimer's disease (AD) is a neurodegenerative disease that causes memory loss and progressive and permanent deterioration of cognitive function. The most challenging issue in combating AD is its complicated pathogenesis, which includes the deposition of amyloid β (Aβ) plaques, intracellular hyperphosphorylated tau protein, neurofibrillary tangles (NFT), etc. Despite rapid advancements in mechanistic research and drug development for AD, the currently developed drugs only improve cognitive ability and temporarily relieve symptoms but cannot prevent the development of AD. Moreover, the blood-brain barrier (BBB) creates a huge barrier to drug delivery in the brain. Therefore, effective diagnostic tools and treatments are urgently needed. In recent years, nanomedicine has provided opportunities to overcome the challenges and limitations associated with traditional diagnostics or treatments. Various types of nanoparticles (NPs) play an essential role in nanomedicine for the diagnosis and treatment of AD, acting as drug carriers to improve targeting and bioavailability across/bypass the BBB or acting as drugs directly on AD lesions. This review categorizes different types of NPs and summarizes their applications in nanomedicine for the diagnosis and treatment of AD. It also discusses the challenges associated with clinical applications and explores the latest developments and prospects of nanomedicine for AD.

Mechanotransduction is the essential process that cells convert mechanical force into biochemical responses, and electrochemical sensor stands out from existing techniques by providing quantitative and real-time information about the biochemical signals during cellular mechanotransduction. However, the intracellular biochemical response evoked by mechanical force has been poorly monitored. In this paper, we report a method to apply local stretch on single cell and simultaneously monitor the ensuing intracellular biochemical signals. Specifically, a ferromagnetic micropipette was fabricated to locally stretch a single cell labeled with Fe3O4 nanoparticles under the external magnetic field, and the SiC@Pt nanowire electrode (SiC@Pt NWE) was inserted into the cell to monitor the intracellular hydrogen peroxide (H2O2) production induced by the local stretch. As a proof of concept, this work quantitatively investigated the elevated amount of H2O2 levels in single endothelial cell under different stretching amplitudes. This work puts forward a new research modality to manipulate and monitor the mechanotransduction at the single-cell level.

The rise of flexible and stretchable electronics has revolutionized biosensor techniques for probing biological systems. Particularly, flexible and stretchable electrochemical sensors (FSECSs) enable the in situ quantification of numerous biochemical molecules in different biological entities owing to their exceptional sensitivity, fast response, and easy miniaturization. Over the past decade, the fabrication and application of FSECSs have significantly progressed. This review highlights key developments in electrode fabrication and FSECSs functionalization. It delves into the electrochemical sensing of various biomarkers, including metabolites, electrolytes, signaling molecules, and neurotransmitters from biological systems, encompassing the outer epidermis, tissues/organs in vitro and in vivo, and living cells. Finally, considering electrode preparation and biological applications, current challenges and future opportunities for FSECSs are discussed.