Timely monitoring of volatile fatty acids (VFAs) is critical for maintaining in the stability in anaerobic digestion, however conventional chromatographic analyses delay actionable feedback. Microbial electrochemical sensors (MES) provide continuous electrical signals, yet it remains unclear how early these responses can support quantitative acetate prediction across independently operated systems and when electrochemical context becomes useful. This study investigated four strain-specific MES setups, i.e. Pseudomonas aeruginosa, Shewanella oneidensis MR-1, Bacillus subtilis, and Escherichia coli, over six acetate levels (0.1-10.0 mM). A temporal framework combining truncated voltage trajectories, eight kinetic summaries, and cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) descriptors were evaluated by nested grouped leave-one-strain-out validation. Cross-strain validation showed that acetate concentration could be quantified with R2 = 0.938 at 120 min and R2 = 0.970 at 180 min (RMSE = 0.900 and 0.593 mM, respectively), with no further improvement at 240 min otably, CV/EIS context proved essential for high accuracy at 180 min but contributed little at 120 min, revealing a shift from dynamics-driven early quantification to context-assisted later quantification. Thus, under controlled pure-culture conditions, the MES-based approach enables rapid acetate measurement within 120/180 min, with a clear trade-off between response time and accuracy.

The precise detection of CA19-9 is paramount for early cancer diagnosis and clinical monitoring. However, traditional immunoassays are often hampered by their heavy reliance on matched antibody pairs and the insufficient sensitivity of enzymatic amplification systems. To address these limitations, we report a novel, enzyme-free surface-enhanced Raman scattering (SERS) platform based on a "dual-hotspot amplification" strategy. The core innovation lies in exploiting the dual-connectivity of phenylboronic acid (PBA) to achieve precise hotspot modulation via a multi-cycle assembly. By utilizing D-glucose as a reversible molecular bridge, this strategy successfully breaks the traditional "one-to-one" linear binding limit of PBA. It facilitates a synergistic transition from heterogeneous binding, which anchors nanoprobes to a BSA@CPBA macromolecular scaffold, to homogeneous binding that drives continuous inter-particle cross-linking. This cycle-dependent assembly transforms individual immune recognition events into a highly coupled 3D dendritic plasmonic network, resulting in progressive accumulation of plasmonic hotspots and amplified macroscopic SERS signals. Under optimized conditions, the proposed sensor achieves an exceptionally low limit of detection of 6.2 × 10[-5] U/mL and a wide linear dynamic range spanning five orders of magnitude (10[-4] to 10 U/mL). Furthermore, the platform demonstrates outstanding specificity and excellent reproducibility (RSD = 8.34%). Practical utility was validated in human serum samples with near-ideal recovery rates (98.67%-103.87%) and excellent agreement with clinical chemiluminescence immunoassays. This modular and cost-effective approach not only enhances detection sensitivity but also provides a useful design concept for the ultrasensitive analysis of carbohydrate-derived biomarkers.

Monitoring butyrylcholinesterase (BuChE) activity is crucial for tracking Alzheimer's disease (AD) progression and evaluating therapeutics; however, high-performance near-infrared (NIR) probes with rapid response and clear design principles remain scarce. Here, we report a series of dicyanoisophorone-based NIR fluorescent probes engineered via a "halogen effect" to systematically tune reactivity toward BuChE. Through spectroscopic screening, the CF3-substituted probe DCNC7 emerged as the optimal candidate, benefiting from the strong electron-withdrawing and hydrophobic nature of the trifluoromethyl group, which enhances binding affinity and catalytic recognition. DCNC7 exhibits over 120-fold NIR fluorescence enhancement upon the BuChE reaction, with fast kinetics (∼15 min), high sensitivity (detection limit 0.0206 U/L), and excellent selectivity. We validated DCNC7 for in situ imaging of BuChE in AD mouse cells and brain tissues, enabling both identification of natural inhibitors and longitudinal assessment of AD progression. Moreover, the screened inhibitor was evaluated for its suppressive effect on BuChE activity in brain tissue and its therapeutic efficacy in vivo. Collectively, DCNC7 offers a reliable tool for AD monitoring, drug screening, and efficacy evaluation, and the halogen effect-based design strategy provides a generalizable route to develop rapid-response, high-affinity enzyme probes for complex disease models.

Neuroinflammation is increasingly recognized as a critical driver in the onset and progression of Parkinson's disease (PD), yet technologies capable of continuously tracking neuroinflammatory dynamics in vivo remain limited. Here, we report an implantable bioelectronic interface that integrates multiplexed aptamer based electrochemical biosensing with deep brain stimulation (DBS) for biomarker monitoring and neuromodulation in the rat brain. The biosensing platform introduces Tantalum@Au electrodes, engineered for chronic stability and biocompatibility, enabling simultaneous in vivo electrochemical monitoring of interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), α-synuclein (α-syn), and pH after DBS therapy. In freely moving PD rat models, the system maintained stable electrochemical performance for at least eight days post-implantation and captured dynamic biomarker fluctuations in response to targeted subthalamic nucleus DBS. DBS reduced IL-6 and TNF-α levels, indicating modulation of neuroinflammatory pathways, whereas α-syn level remained unchanged within the short-term window, consistent with the slower temporal dynamics of protein aggregation. DBS partially restored motor coordination though residual asymmetry persisted, paralleling clinical observations of symptom alleviation without complete functional recovery. These findings demonstrate the feasibility of integrating continuous biochemical sensing with therapeutic neuromodulation to achieve a closed-loop platform, providing direct insight into molecular responses to DBS. This bioelectronic interface establishes a foundation for future biochemical-feedback-enabled neuromodulation strategies and precision therapeutic for neurodegenerative disorders.

Rapid and sensitive determination of total bacterial count in water is essential for safeguarding water safety. In this work, an ultrasensitive electrochemical nucleic acid biosensor was developed for the detection of total bacteria in water. A conserved fragment of bacterial 16S rRNA gene (16S rDNA) was screened as the universal target, and the corresponding hairpin capture probe was designed and immobilized on magnetic particles for specific recognition and enrichment. By combining electrochemical detection with a triple signal amplification strategy-including hybridization chain reaction, G-quadruplex-assisted signal enhancement, and artificial nuclease-mediated signal activation-the sensor achieved highly sensitive quantification of aquatic bacteria. It displayed a linear response to bacterial 16S rDNA over a concentration range from 0.1 fM to 100 pM, with an ultralow detection limit of 1.0 aM. For total bacterial determination in real water, it achieved a practical detection limit of 1 CFU mL[-1], showing strong concordance with the gold-standard plate count method. It also exhibited good reproducibility and stability, satisfying the demand for total bacterial count monitoring in drinking water and environmental water bodies, and thus providing an efficient and reliable platform for water safety assurance.

The rising demand for sustainable, high-performance materials in electrochemical (bio)sensing (EB) has driven the exploration of carbon materials derived from renewable resources. While graphene, carbon nanotubes, and similar nanocarbons are currently leading the field, their widespread use is limited by energy-intensive synthesis processes, high costs, and dependence on non-renewable or geopolitically sensitive materials. In this setting, biochar, a carbon-rich, porous material produced by controlled pyrolysis of biomass, has gained attention as a versatile form of disordered carbon with inherent electrochemical properties. Beyond sustainability, biochar (BC) provides tunable surface chemistry, hierarchical porosity, and electronic properties, all influenced by feedstock type and pyrolysis conditions. These features enable effective biomolecule immobilization, defect-mediated charge transport, and competitive performance in enzymatic, immunological, and nucleic acid biosensors across various applications. This review critically explores how structure-function relationships influence biochar behavior, linking feedstock selection, thermal processing, and post-synthesis modifications, such as activation and heteroatom doping, to device performance. We examine various integration methods, from traditional electrode modifications to printed and additively manufactured devices, and discuss challenges related to reproducibility, standardization, and scalability. While the main emphasis is on BC-based biosensors, we also include selected studies on technological advancements in incorporating BC into innovative electroanalytical platforms, as these provide a valuable foundation for the future development of biosensors and bioanalytical devices. This article presents a rational framework for proposing biochar as a scalable and sustainable source for next-generation electrochemical and biosensing technologies, spanning from material design to electroanalytical needs.

Ampicillin (AMP) residues arising from widespread antibiotic use pose increasing concerns for food safety and environmental health, while their trace detection in complex matrices remains challenging. Here, we report a recognition-induced in situ plasmonic modulation strategy integrated with a near-infrared-responsive organic photoelectrochemical transistor (OPECT) for sensitive AMP detection. A Ni6MnO8/UCNPs-based photogate was employed as the near-infrared-responsive transduction interface. Target recognition regulated alkaline phosphatase-mediated generation of ascorbic acid (AA) from ascorbic acid phosphate, and the resulting AA served as an electron donor and reducing agent to promote charge separation and induce the in situ formation of Au NPs. The generated Au NPs modulated the optical absorption and interfacial charge-transfer behavior of the photogate, producing amplified channel-current responses through effective gate-voltage regulation. The proposed OPECT sensor achieved a detection limit of 0.029 pg mL[-1] and satisfactory performance in complex food samples. This study provides a promising strategy for antibiotic residue monitoring in complex matrices.

Rapid on-site monitoring of lead (Pb) contamination is often limited by the fragility of mammalian-cell biosensors in an environmental setting and the manual image analysis that is labor intensive. This work demonstrates a stable, on-site portable sensing platform based on E. coli that expresses the high-sensitivity Met-lead 1.44 M1 FRET sensor and is encapsulated in a protective gelatin hydrogel matrix. To address data processing constraints, we present a novel AI-assisted pipeline combining feature extraction and Cellpose-SAM DL segmentation. This procedure for automated pixel-shift correction and high-accuracy ROI determination (with average precision, AP of 0.945 at threshold intersection over unit, IoU of 0.5) is integrated in this work allowing us to speed up analysis time drastically by a factor of over 47 compared to laborious manual processing. Our bacterial sensor has a high linearity (R[2] > 0.93) and it performs consistently well in both aqueous and hydrogel forms. More importantly, the system exhibited a LOD of 2.0 ppb within 15 min, which is significantly below the WHO drinking water limit (10 ppb), and also all the functions remained intact after 4 h of warm environmental exposure. This AI-powered method can be used for both smartphone and microscopy imaging, allowing for real-time detection in a range of applications. Finally, a predictive "traffic-light" risk model was implemented for an easy interpretation of water quality. By closing the gap between laboratory-based sensing and field operation, this work provides a high throughput, real time, mobile solution for next generation environmental safety monitoring.

Acute liver injury is a life-threatening disorder associated with substantial morbidity and mortality worldwide, underscoring the need for convenient and minimally invasive monitoring. Here, we develop an ALI-responsive nanoprobe that dissociates into renal-clearable gold nanoparticles, facilitating minimally invasive acute liver injury diagnosis through colorimetric urinalysis. This nanoprobe is constructed as a simple nanoaggregate of self-assembled ultrasmall AuNPs linked via a responsive moiety (2,2'-[propane-2,2-diylbis(thio)]diacetic acid). Elevated endogenous reactive oxygen species in the injured liver trigger the dissociation of Au-TKs accumulated in hepatic tissue. The released AuNPs are subsequently excreted into urine and can be quantified by leveraging their peroxidase-like activity and renal-clearable property. This platform outperforms conventional serum-based methods in terms of sensitivity and accuracy for early prediction of acetaminophen-induced liver injury in mice. To enhance practicality, a smartphone application with color capture capability was developed, demonstrating excellent linearity (R[2] > 0.95) compared with microplate reader detection. This smartphone-based colorimetric biosensing system, featuring convenient, minimally invasive operation, holds strong potential to transform ALI monitoring through urinary readouts and may provide additional benefits for rapid detection of a broad range of inflammatory diseases by targeting disease-specific pathological signatures.

The Werner syndrome helicase (WRN) is a critical synthetic lethal target in microsatellite instability cancers, essential for resolving complex genomic structures like replication bubbles and R-loops. However, strategies to simultaneously discriminate WRN activity on DNA versus DNA-RNA substrates in living cells are lacking. Here, we developed a structure-specific CRISPR/Cas12a biosensing strategy to visualize WRN functional activity by engineering bubble-structure probes. These probes were rationally designed to structurally mimic DNA replication bubbles and R-loop associated DNA-RNA hybrids. Upon specific unwinding by WRN, the probes release a sequestered activator strand that triggers Cas12a trans-cleavage, effectively converting the unwinding event into an amplified fluorescent signal. This assay achieves low picomolar sensitivity (LODs: 5.6-6.0 pM) and exceptional selectivity against homologous RecQ helicases. Uniquely, this strategy enables the parallel quantification of WRN activity on both substrate types, providing insights into distinct WRN-mediated pathways for resolving genomic stress. We further demonstrated the strategy's utility by visualizing endogenous WRN dynamics in living cells and profiling the efficacy of small-molecule inhibitors. This work offers a powerful molecular toolkit for dissecting WRN biology and facilitating high-throughput drug screening in targeted cancer therapy.

Herein, a novel signal-off photoelectrochemical (PEC) biosensor was rationally constructed by integrating a Bi2S3/RuO2 heterojunction with the multiple tetrahedral DNA nanonet (mTDN) for ultrasensitive and accurate lead ions detection. This photoactive Bi2S3/RuO2 composite was synthesized through a simple ultrasonic-assisted mixing method, in which the RuO2 not only functioned as an efficient electron conductor and a protective layer for Bi2S3, but also formed a typical p-n heterojunction with Bi2S3, effectively promoting the separation of photogenerated electron-hole pairs for achieving an extremely high initial photocurrent that twelve-times higher than individual component. Afterwards, the present of target lead ions (Pb[2+]) led to the specific DNAzyme cleavage on electrode, thus exposing abundant binding sites for immobilizing mTDN. Compared with traditional DNA nanostructures, the designed mTDN prone to form a continuous, dense, and uniform three-dimensional rigid network film, and thus endowed the effective obstructing of electronic transfer derived from non-conductive characteristic and spatial steric hindrance, significantly depressing the photocurrent for achieving sensitive and accurate Pb[2+] detection. As a result, the proposed PEC biosensor exhibited excellent analytical performance with a low detection limit down to 0.82 fM (S/N = 3), providing a sensitive and reliable approach for environmental pollution monitoring and drinking water safety controlling.

Flexible electrodes have emerged as key bioelectronic interfaces for recording, modulation, and sensing in complex biological environments. Their mechanical compliance, conformal contact, and tunable electrochemical properties enable effective coupling between soft biological tissues and rigid electronic systems. However, the fabrication strategies and interface requirements governing flexible electrode performance differ substantially across biological domains, and this cross-domain design landscape has not been systematically addressed. This review comprehensively examines preparation and optimization strategies for flexible electrodes, covering structure-driven designs, material selection, and surface functionalization approaches targeting charge transfer, selectivity, and biostability. We further survey applications across four biomedical domains: brain interfaces, peripheral nerve interfaces, gastrointestinal tract, and wearable health monitoring, spanning epidermal, visceral, and neural environments in both in vitro and in vivo settings. By mapping design strategies onto diverse biological interface requirements, this review provides a cross-domain reference framework to guide application-specific electrode design. Remaining challenges in scalable fabrication, chronic biointegration, closed-loop operation, and clinical translation are critically discussed, with future directions emphasizing convergence across neuroscience, materials science, and intelligent bioelectronics.

Nitrogen-rich zeolitic imidazolate frameworks (ZIFs) are promising for rapid small-molecule sensing due to their tunable porosity. Yet, their practical application is often hindered by mass transfer limitations and low metal utilization caused by intrinsic microporosity. Herein, a hierarchically porous Co-ZIF nanozyme (HP ZIF-67) possessing a three-dimensionally ordered macro-microporous architecture was constructed via in situ crystallization within a 3D ordered hard template using a double-solvent system. Its regularly interconnected macroporous channels and large specific surface area accelerate mass transfer, exposes abundant accessible active sites, and provide confined catalytic environment, leading to remarkably enhanced peroxidase-like activity. Crucially, to facilitate the colorimetric sensing of vanillin (a ubiquitous food additive), phytic acid (PA) was introduced as an enrichment linker to capture vanillin on the HP ZIF-67 surface through cation-bridging. This interaction triggers a pronounced shielding effect on the typical TMB-H2O2 chromogenic reaction, allowing for specific colorimetric recognition of vanillin. The developed sensor, which supports both portable smartphone-assisted digital image readout and accurate absorbance-based measurement, delivers a low detection limit of 0.184 μM across a broad linear range of 2-250 μM, and exhibits good practical utility in real food sample analysis. This work provides a robust and straightforward strategy for flavor quality control and food safety supervision.

Self-powered photoelectrochemical (PEC) sensing features no external power supply, fast response, strong anti-interference and high sensitivity, providing a powerful strategy for ultrasensitive detection of β-site amyloid precursor protein cleaving enzyme 1 (BACE1), a key biomarker for early Alzheimer's disease (AD). In this work, a dual-photoelectrode self-powered PEC biosensor with ultralow background signal was constructed. ZnIn2S4 was grown in situ on fluorine-doped tin oxide (FTO) via hydrothermal reaction, and CdS quantum dots were loaded through successive ionic layer adsorption and reaction to fabricate ZnIn2S4@CdS/FTO photoanode. The obtained photoanode delivered a photocurrent of 279 μA, which was 2.3 times higher than pure ZnIn2S4/FTO, benefiting from superior visible light absorption and charge separation capacity. Bi2WO6@polydopamine (Bi2WO6@PDA) probes were anchored on peptide substrates in 96-well plates. When BACE1 existed, enzymatic cleavage released Bi2WO6@PDA heterojunction probes onto bare FTO photocathode to generate obvious photocurrent. In the absence of BACE1, the photocathode remained equivalent to bare FTO without Bi2WO6@PDA probe. Under visible light and zero bias, the sensor realized sensitive BACE1 detection with a linear range of 1 fg mL[-1]-500 pg mL[-1] with a limit of detection of 0.30 fg mL[-1]. The biosensor possessed favorable selectivity and stability with serum sample recoveries of 96.9%-102.5%, and it could be applied to screen BACE1 inhibitors. This self-powered biosensor with near-zero background shows great application prospect in early AD clinical diagnosis.

Nanozymes are known for their exceptional stability under extreme pH conditions, yet this property has never been exploited to overcome practical analytical limitations. Here, we report the first utilization of the extreme acid tolerance to address a long-standing challenge in wash-free assays - background signal caused by endogenous peroxidases. By performing in situ signal amplification at pH 1.0, we selectively inactivate natural peroxidases while preserving sufficient catalytic activity of Au@Pt nanozyme, thereby eliminating false-positive signals without additional washing steps. We applied this strategy to lateral flow immunoassay (LFIA) using monoclonal antibodies and nanobodies for the detection of paraquat in spinach characterized by high endogenous peroxidase activity. Under standard pH conditions, strong background interference prevented reliable visual readout. In contrast, low-pH amplification completely suppressed matrix-induced background, significantly improved the signal-to-noise ratio, and enabled detection limits (60 pg/mL) unachievable with conventional protocols and yielded satisfactory paraquat recoveries of 90-130% This work establishes a new design paradigm in biosensing and chemical engineering: instead of avoiding harsh conditions, they can be served on purpose to gain selectivity against biological background.