Emerging biosensing and transducing techniques for potential applications in point-of-care diagnostics

A colorimetric and SERS-based LFIA for sensitive and simultaneous detection of three stroke biomarkers: An ultra-fast and sensitive point-of-care testing platform

Stroke ranks as the second leading cause of disability and mortality globally. Biomarker detection represents a promising avenue for predicting disease severity and prognosis. The expression levels of metalloproteinase-9 (MMP-9), neuron-specific enolase (NSE), and N-terminal pro-brain natriuretic peptide (NT-pro BNP) in blood correlate with stroke severity. Hence, monitoring these biomarkers is crucial for stroke diagnosis and management. Point-of-care testing (POCT) offers on-site diagnostic capabilities, with lateral flow immunoassay (LFIA) being the most widely used method currently. However, traditional LFIA sensitivity requires enhancement. This study introduces an ultra-sensitive surface-enhanced Raman scattering-based lateral flow immunoassay (SERS-based LFIA) strip for simultaneous detection of the three stroke biomarkers using SERS immune tags. Bimetallic core-shell structured SERS immune tags leverage the advantages of two metals, ensuring stability and enhancing Raman signals through plasmon resonance. This development of a POCT based on SERS-based LFIA strips offers rapid, sensitive, and multiplex detection of stroke biomarkers. The limits of detection (LODs) for MMP-9, NSE, and NT-pro BNP were 0.00020 ng mL-1, 0.00016 ng mL-1, and 0.00012 ng mL-1, respectively. Furthermore, enzyme-linked immunosorbent assay (ELISA) validated the accuracy of SERS-based LFIA. Clinical sample analysis demonstrated consistency between outcomes obtained by SERS-based LFIA and ELISA. Thus, SERS-based LFIA presents a novel POCT approach for stroke diagnosis.

Simultaneous detection of dengue virus serotypes in a dual-serotype-detection nucleic acid based lateral flow assay

Dengue virus (DENV) is an important arthropod-borne viral disease, with four antigenically and genetically diverse serotypes (DENV-1, DENV-2, DENV-3, and DENV-4). Timely and accurate diagnosis of dengue virus serotypes is crucial for the management of outbreaks. This study focussed on the development of a RT-PCR based lateral flow strip assay to detect DENV serotypes in a dual detection manner without using gel electrophoresis. The assay uses anti-biotin/streptavidin colloidal gold conjugates with fluorescent/enzymatic tagged DENV serotype specific antibodies for the direct detection of DENV infected serum samples on a nitrocellulose membrane using biotin-BSA as control line. The detection limit of the assay was up to 10 copies of cDNA for DENV-1 and 100 copies for DENV-2, DENV-3, and DENV-4. In house evaluation of DENV LFIA demonstrated 100 % sensitivity in all the serotypes compared to conventional RT-PCR, 100 % specificity for DENV-1, DENV-2, DENV-3, and 95 % specificity for DENV-4 detection. DENV serotyping was assessed in a dual detection manner (DENV-1/DENV-3 and DENV-2/DENV-4 at two test lines) on the strip. The limitation of the assay is the requirement of PCR for initial amplification and confirmation of individual serotype in case of DENV-1/DENV-3 and DENV-2/DENV-4 detection, besides the field evaluation of the assay detected DENV-2 and DENV-3 serotypes, and no other serotype was detected in line with RT-PCR findings.

Ultrasensitive detection of holoTC for analysis of Vitamin B12 levels using Ag2MoO4 deposited PEDOT sensing platform

Vitamin B12 is an essential micronutrient required for the proper functioning of the human body. Vitamin B12 deficiency is primarily causative of various neurolological disorders alongwith recurrence of oral ulcers and burning sensations which are early signs of condition such as pernicious anemia. Other complications associated with Vitamin B12 deficiency include risk of heart failure due to anemia, risk of developing autoimmune disorders and gastric cancer. Therefore, to obstruct these communal health issues, early detection of Vit B12 is highly needed. However, screening of vitamin B12 insufficiency is hindered by the low sensitivity of the conventional vitamin B12 test. Holotranscobalamin (holoTC) is an early indicator of the negative vitamin B12 balance as it is the first protein to decline in the serum. We report a novel impedimetric immunosensor based on flower-like poly (3,4-ethylenedioxythiophene) (PEDOT) nanostructural film impregnated with silver molybdate nanoparticles (Ag2MoO₄ NPs) deposited on fluorine-doped tin oxide electrode. The prepared electrodes were characterized by Field emission scanning electron microscopy (FE-SEM) with energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and electrochemical studies. The activated anti-holoTC antibody was immobilized and optimized to capture the target in a response time of 15 min. The electrochemical performance of the sensor was carried out by using the electrochemical impedance spectroscopy technique (EIS) and a good linear relationship between ΔRct and holoTC was obtained in the range from 0.1 pg mL-1 to 100 ng mL-1 with a detection limit of 0.093 pg mL-1. The proposed sensor was successfully applied in human serum samples for holoTC detection. The experimental results showed that the immunosensor is highly selective towards holoTC and presented an acceptable stability of 20 days with reproducibility RSD ≤4%. To the best of our knowledge, this is the first developed electrochemical immunosensor for holoTC detection.

Exploring the diffusion of DNA strands into nanoporous structures for establishing a universal electrochemical biosensor

The development of universal electrochemical sensing platforms with high sensitivity and specificity is of great significance for advancing practical disease diagnostic methods and devices. Exploring the structural properties of electrode materials and their interaction with biomolecules is essential to developing novel and distinctive analytical approaches. Here, we innovatively investigated the effect of DNA length and configuration on DNA molecule transfer into the nanostructure of a nanoporous gold (NPG) electrode. The NPG electrode can not only distinguish and quantify short DNA strands but can also prevent the diffusion of long DNA, thereby minimizing or eliminating background interference. Leveraging these findings, we developed a universal DNA-based NPG electrochemical biosensing platform for the detection of different types of biomolecules. As a proof-of-concept, this sensing platform was integrated with nuclease-assisted target-recycling recognition and amplification reactions to achieve sensitive and specific detection of single-stranded DNA, microRNA-21, and carcino-embryonic antigen, with detection limits of 4.09, 27.4, and 0.28 fM, respectively. The demonstrated universality, sensitivity, specificity, and capability for analyzing complex samples ensure a comprehensive and robust detection approach for nucleic acid-based molecular diagnosis.

Pathogen-Specific Electrochemical Real-Time LAMP Detection Using Universal Solid-Phase Probes on Carbon Electrodes

Epidemic infections and spreading antibiotic resistance require diagnostic tests that can be rapidly adopted. To reduce the usually time-consuming adaptation of molecular diagnostic tests to changing targets, we propose the novel approach of a repurposable sensing electrode functionalization with a universal, target-independent oligonucleotide probe. In the liquid phase covering the electrode, the target sequence is amplified by MD LAMP (mediator-displacement loop-mediated isothermal amplification) releasing a generic methylene blue-labeled mediator, which specifically hybridizes to the solid-phase probe. To demonstrate the universality of the approach, two different pathogens, Staphylococcus aureus (crude lysate) and Treponema pallidum, are detected using the same solid-phase probe. The reactions reach a limit of detection of 1 × 103 and 4 × 102 copies per reaction within 30 min, respectively. The solid-phase probes carry a carboxymethyl aniline modification to form covalent C-C bonds on low-cost carbon electrodes. Maximum surface coverage and maximum hybridization signals are observed at grafting concentrations of ≥2 μM solid-phase probes. Successful detection of spiked target DNA in real swab samples and with three different commercial amplification buffers proved the broad applicability of this assay approach. The electrochemical MD LAMP is fast, compatible with dsDNA targets, and requires only minimal adaptation of an established amplification method. It is easily transferable to existing analytical electrochemical platforms, allowing the consumable to be synergistically used for different targets. The suggested approach of repurposable functionalized electrodes can also be considered to increase the preparedness for future epidemic or pandemic outbreaks as well as rapidly evolving resistance patterns or variants.

Emerging Combination of Hydrogel and Electrochemical Biosensors

Electrochemical sensors are among the most promising technologies for biomarker research, with outstanding sensitivity, selectivity, and rapid response capabilities that make them important in medical diagnostics and prognosis. Recently, hydrogels have gained attention in the domain of electrochemical biosensors because of their superior biocompatibility, excellent adhesion, and ability to form conformal contact with diverse surfaces. These features provide distinct advantages, particularly in the advancement of wearable biosensors. This review examines the contemporary utilization of hydrogels in electrochemical sensing, explores strategies for optimization and prospective development trajectories, and highlights their distinctive advantages. The objective is to provide an exhaustive overview of the foundational principles of electrochemical sensing systems, analyze the compatibility of hydrogel properties with electrochemical methodologies, and propose potential healthcare applications to further illustrate their applicability. Despite significant advances in the development of hydrogel-based electrochemical biosensors, challenges persist, such as improving material fatigue resistance, interfacial adhesion, and maintaining balanced water content across various environments. Overall, hydrogels have immense potential in flexible biosensors and provide exciting opportunities. However, resolving the current obstacles will necessitate additional research and development efforts.

Capillarity-powered and CRISPR/Cas12a-responsive DNA hydrogel distance sensor for highly sensitive visual detection of HPV DNA

The rapid and specific identification and sensitive detection of human papillomavirus (HPV) infection is critical for preventing cervical cancer, particularly in resource-limited regions. In this work, we hope to propose a capillarity-powered and CRISPR/Cas12a-responsive DNA hydrogel distance sensor for point-of-care (POC) DNA testing. Using the thermal reversibility of DNA hydrogel and capillarity, the novel DNA hydrogel distance sensor can be rapidly and simply constructed by loading an ultra-thin CRISPR/Cas12a-responsive DNA-crosslinked hydrogel film at the end of the capillary tube. The target DNA-specific recombinase polymerase reaction (RPA) amplicons activate the trans-cleavage activity of the Cas12a enzyme, cleaving the crosslinked DNA in hydrogel film, and causing an increase of hydrogel's permeability. As a result, a sample solution containing target DNA travels into the capillary tube at a longer distance compared to the negative samples. Reading the solution traveling distance in capillary tubes, the novel sensor realizes target DNA detection without any special equipment. Benefiting from the exponential target amplification of RPA and multiple turnover response of trans-cleavage of CRISPR/Cas12a, the developed sensor can visually and specifically detect as low as 1 aM HPV 16 DNA within 30 min. These outstanding features, including exceptional sensitivity and specificity, simple and portable design, mild measurement conditions, quick turnaround time, and user-friendly read-out, make the novel distance sensor a promising option for POC diagnostic applications.

Noncontact 3D Bioprinting of Proteinaceous Microarrays for Highly Sensitive Immunofluorescence Detection within Clinical Samples

Immunofluorescence assays are extensively used for the detection of disease-associated biomarkers within patient samples for direct diagnosis. Unfortunately, these 2D microarrays suffer from low repeatability and fail to attain the low limits of detection (LODs) required to accurately discern disease progression for clinical monitoring. While three-dimensional microarrays with increased biorecognition molecule density stand to circumvent these limitations, their viscous component materials are not compatible with current microarray fabrication protocols. Herein, we introduce a platform for 3D microarray bioprinting, wherein a two-step printing approach enables the high-throughput fabrication of immunosorbent hydrogels. The hydrogels are composed entirely of cross-linked proteins decorated with clinically relevant capture antibodies. Compared to two-dimensional microarrays, these proteinaceous microarrays offer 3-fold increases in signal intensity. When tested with clinically relevant biomarkers, ultrasensitive single-plex and multiplex detection of interleukin-6 (LOD 0.3 pg/mL) and tumor necrosis factor receptor 1 (LOD 1 pg/mL) is observed. When challenged with clinical samples, these hydrogel microarrays consistently discern elevated levels of interleukin-6 in blood plasma derived from patients with systemic blood infections. Given their easy-to-implement, high-throughput fabrication, and ultrasensitive detection, these three-dimensional microarrays will enable better clinical monitoring of disease progression, yielding improved patient outcomes.

Inclusive and Accurate Clinical Diagnostics Using Intelligent Computation and Smartphone Imaging

Smartphone-based colorimetry has been widely applied in clinical analysis, although significant challenges remain in its practical implementation, including the need to consider biases introduced by the ambient imaging environment, which limit its potential within a clinical decision pathway. In addition, most commercial devices demonstrate variability introduced by manufacturer-to-manufacturer differences. Here, we undertake a systematic characterization of the potential imaging interferences that lead to this limited performance in conventional smartphones and, in doing so, provide a comprehensive new understanding of smartphone color imaging. Through derivation of a strongly correlated parameter for sample quantification, we enable real-time imaging, which for the first time, takes the first steps to turning the mobile phone camera into an analytical instrument - irrespective of model, software, and the operating systems used. We demonstrate clinical applicability through the imaging of patients' skin, enabling rapid and convenient diagnosis of cyanosis and measurement of local oxygen concentration to a level that unlocks clinical decision-making for monitoring cardiovascular disease and anemia. Importantly, we show that our solution also accounts for the differences in individuals' skin tones as measured across the Fitzpatrick scale, overcoming potential clinically significant errors in current optical oximetry.

CRISPR-Driven Biosensors: A New Frontier in Rapid and Accurate Disease Detection

This comprehensive review delves into the advancements and challenges in biosensing, with a strong emphasis on the transformative potential of CRISPR technology for early and rapid detection of infectious diseases. It underscores the versatility of CRISPR/Cas systems, highlighting their ability to detect both nucleic acids and non-nucleic acid targets, and their seamless integration with isothermal amplification techniques. The review provides a thorough examination of the latest developments in CRISPR-based biosensors, detailing the unique properties of CRISPR systems, such as their high specificity and programmability, which make them particularly effective for detecting disease-associated nucleic acids. While the review focuses on nucleic acid detection due to its critical role in diagnosing infectious diseases, it also explores the broader applications of CRISPR technology in detecting non-nucleic acid targets, thereby acknowledging the technology's broader potential. Additionally, the review identifies existing challenges, such as the need for improved signal amplification and real-world applicability, and offers future perspectives aimed at overcoming these hurdles. The ultimate goal is to advance the development of highly sensitive and specific CRISPR-based biosensors that can be used widely for improving human health, particularly in point-of-care settings and resource-limited environments.

Exonuclease III/Cas12a Cascade Amplification Strategy and Smartphone-Based Portable Fluorescence Detector to Repurpose the Commercial AFP Strip for the POCT of Multiple RNAs

Point of care testing (POCT) of nucleic acid (NA) contributes to the timely disease diagnosis, like bacteria and virus screening in households or resource-constrained areas, but its development has always been stagnant. Herein, we proposed an exonuclease III cascaded with CRISPR/Cas12a (Exo-III/Cas12a) amplification strategy and constructed a smartphone-based portable fluorescence detector (SPFD) to repurpose the commercial alpha-fetoprotein (AFP) strip for the ultrasensitive and hand-held detection of NA samples. In detail, the target-initiated-Exo-III/Cas12a strategy realizes the signal amplification and liberates AFP from magnetic beads through the trans-cleavages of activated Cas12a toward the AFP aptamer. After magnetic separation and migration, the fluorescence signals of the test (FT) and control (FC) lines on the AFP strip were digitally output by the SPFD, and the FT/FC was employed for the quantitative analysis to minimize external disturbances and improve accuracy. We experimentally assessed the universe applicability of the proposed NA-POCT platform toward miRNA-155, 16S rRNA of Staphylococcus aureus, and ORF1a/b RNA of Covid-19 pseudovirus, achieving favorable detection limits of 42 aM, 18 CFU/mL, and 87 copies/μL, respectively. Moreover, its simplicity, universality, and admirable detection performance demonstrate a great potential in the aspect of rapidly transforming the existing POCT devices for multiple new applications at the time of need.

Innovations in Biosensor Technologies for Healthcare Diagnostics and Therapeutic Drug Monitoring: Applications, Recent Progress, and Future Research Challenges

This comprehensive review delves into the forefront of biosensor technologies and their critical roles in disease biomarker detection and therapeutic drug monitoring. It provides an in-depth analysis of various biosensor types and applications, including enzymatic sensors, immunosensors, and DNA sensors, elucidating their mechanisms and specific healthcare applications. The review highlights recent innovations such as integrating nanotechnology, developing wearable devices, and trends in miniaturisation, showcasing their transformative potential in healthcare. In addition, it addresses significant sensitivity, specificity, reproducibility, and data security challenges, proposing strategic solutions to overcome these obstacles. It is envisaged that it will inform strategic decision-making, drive technological innovation, and enhance global healthcare outcomes by synthesising multidisciplinary insights.

Harnessing cerium-based biomaterials for the treatment of bone diseases

Bone, an actively metabolic organ, undergoes constant remodeling throughout life. Disturbances in the bone microenvironment can be responsible for pathologically bone diseases such as periodontitis, osteoarthritis, rheumatoid arthritis and osteoporosis. Conventional bone tissue biomaterials are not adequately adapted to complex bone microenvironment. Therefore, there is an urgent clinical need to find an effective strategy to improve the status quo. In recent years, nanotechnology has caused a revolution in biomedicine. Cerium(III, IV) oxide, as an important member of metal oxide nanomaterials, has dual redox properties through reversible binding with oxygen atoms, which continuously cycle between Ce(III) and Ce(IV). Due to its special physicochemical properties, cerium(III, IV) oxide has received widespread attention as a versatile nanomaterial, especially in bone diseases. This review describes the characteristics of bone microenvironment. The enzyme-like properties and biosafety of cerium(III, IV) oxide are also emphasized. Meanwhile, we summarizes controllable synthesis of cerium(III, IV) oxide with different nanostructural morphologies. Following resolution of synthetic principles of cerium(III, IV) oxide, a variety of tailored cerium-based biomaterials have been widely developed, including bioactive glasses, scaffolds, nanomembranes, coatings, and nanocomposites. Furthermore, we highlight the latest advances in cerium-based biomaterials for inflammatory and metabolic bone diseases and bone-related tumors. Tailored cerium-based biomaterials have already demonstrated their value in disease prevention, diagnosis (imaging and biosensors) and treatment. Therefore, it is important to assist in bone disease management by clarifying tailored properties of cerium(III, IV) oxide in order to promote the use of cerium-based biomaterials in the future clinical setting. STATEMENT OF SIGNIFICANCE: In this review, we focused on the promising of cerium-based biomaterials for bone diseases. We reviewed the key role of bone microenvironment in bone diseases and the main biological activities of cerium(III, IV) oxide. By setting different synthesis conditions, cerium(III, IV) oxide nanostructures with different morphologies can be controlled. Meanwhile, tailored cerium-based biomaterials can serve as a versatile toolbox (e.g., bioactive glasses, scaffolds, nanofibrous membranes, coatings, and nanocomposites). Then, the latest research advances based on cerium-based biomaterials for the treatment of bone diseases were also highlighted. Most importantly, we analyzed the perspectives and challenges of cerium-based biomaterials. In future perspectives, this insight has given rise to a cascade of cerium-based biomaterial strategies, including disease prevention, diagnosis (imaging and biosensors) and treatment.

A High-Avidity, Thermostable, and Low-Cost Synthetic Capture for Ultrasensitive Detection and Quantification of Viral Antigens and Aerosols

Lateral flow assays (LFAs) are currently the most popular point-of-care diagnostics, rapidly transforming disease diagnosis from expensive doctor checkups and laboratory-based tests to potential on-the-shelf commodities. Yet, their sensitive element, a monoclonal antibody, is expensive to formulate, and their long-term storage depends on refrigeration technology that cannot be met in resource-limited areas. In this work, LCB1 affibodies (antibody mimetic miniproteins) were conjugated to bovine serum albumin (BSA) to afford a high-avidity synthetic capture (LCB1-BSA) capable of detecting the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein and virus like particles (VLPs). Substituting the monoclonal antibody 2B04 for LCB1-BSA (stable up to 60 °C) significantly improved the thermal stability, shelf life, and affordability of plasmonic-fluor-based LFAs (p-LFAs). Furthermore, this substitution significantly improved the sensitivity of p-LFAs toward the spike protein and VLPs with precise quantitative ability over 2 and 3 orders of magnitude, respectively. LCB1-BSA sensors could detect VLPs at 100-fold lower concentrations, and this improvement, combined with their robust nature, enabled us to develop an aerosol sampling technology to detect aerosolized viral particles. Synthetic captures like LCB1-BSA can increase the ultrasensitivity, availability, sustainability, and long-term accuracy of LFAs while also decreasing their manufacturing costs.

Photoelectrochemical sensor for the detection of Escherichia coli O157:H7 based on TPA-NO2 and dual-functional polythiophene films

The detection of Escherichia coli (E. coli) is of great significance for the environment and human health. Herein, a photoelectrochemical (PEC) detection strategy based on molecularly imprinted polymers (MIPs) was proposed for the sensitive detection of E. coli. 4,4',4″-Trinitrotriphenylamine (TPA-NO2) was prepared using a simple nitration reaction. Subsequently, MIP films were polymerized on the surface of TPA-NO2 using 1,3-dihydrothieno[3,2-d]pyrimidine-2,4-dione as the functional monomer with the dual functions of specific recognition and sensitization. The linear range was 10-108 CFU/mL and the limit of detection was 10 CFU/mL. It showed favorable recoveries in real sample tests of milk, orange juice and tomato. Additionally, the ability of functional monomers to bind excellently with E. coli was verified using molecular docking techniques. This research provided broader possibilities for constructing MIPs-PEC sensors and analyzing the interaction mechanism between E. coli and functional monomers.

Fluorescence Multi-Detection Device Using a Lensless Matrix Addressable microLED Array

A Point-of-Care system for molecular diagnosis (PoC-MD) is described, combining GaN and CMOS chips. The device is a micro-system for fluorescence measurements, capable of analyzing both intensity and lifetime. It consists of a hybrid micro-structure based on a 32 × 32 matrix addressable GaN microLED array, with square LEDs of 50 µm edge length and 100 µm pitch, with an underneath wire bonded custom chip integrating their drivers and placed face-to-face to an array of 16 × 16 single-photon avalanche diodes (SPADs) CMOS. This approach replaces instrumentation based on lasers, bulky optical components, and discrete electronics with a full hybrid micro-system, enabling measurements on 32 × 32 spots. The reported system is suitable for long lifetime (>10 ns) fluorophores with a limit of detection ~1/4 µM. Proof-of-concept measurements of streptavidin conjugate Qdot™ 605 and Amino PEG Qdot™ 705 are demonstrated, along with the device ability to detect both fluorophores in the same measurement.

Recent advances in microfluidic-based spectroscopic approaches for pathogen detection

Rapid identification of pathogens with higher sensitivity and specificity plays a significant role in maintaining public health, environmental monitoring, controlling food quality, and clinical diagnostics. Different methods have been widely used in food testing laboratories, quality control departments in food companies, hospitals, and clinical settings to identify pathogens. Some limitations in current pathogens detection methods are time-consuming, expensive, and laborious sample preparation, making it unsuitable for rapid detection. Microfluidics has emerged as a promising technology for biosensing applications due to its ability to precisely manipulate small volumes of fluids. Microfluidics platforms combined with spectroscopic techniques are capable of developing miniaturized devices that can detect and quantify pathogenic samples. The review focuses on the advancements in microfluidic devices integrated with spectroscopic methods for detecting bacterial microbes over the past five years. The review is based on several spectroscopic techniques, including fluorescence detection, surface-enhanced Raman scattering, and dynamic light scattering methods coupled with microfluidic platforms. The key detection principles of different approaches were discussed and summarized. Finally, the future possible directions and challenges in microfluidic-based spectroscopy for isolating and detecting pathogens using the latest innovations were also discussed.

Nucleic acid-based electrochemical biosensor for detection of influenza B by gold nanoparticles

The influenza virus is a pervasive pathogen that exhibits increased prevalence during colder seasons, resulting in a significant annual occurrence of infections. Notably, pharmaceutical interventions effective against influenza A strains often exhibit limited efficacy against influenza B variants. Against this backdrop, the need for innovative approaches to accurately and swiftly differentiate and detect influenza B becomes evident. Biosensors play a pivotal role in this detection process, offering rapid, specific, and sensitive identification of the virus, facilitating timely intervention and containment efforts. Oligonucleotide sequences targeting the conserved B/Victoria/2/87 influenza virus NP region were designed. Nasopharyngeal swabs were collected from patients suspected of influenza virus infection, and viral RNA was extracted. RNA quality was assessed through one-step PCR. cDNA synthesis was performed using random hexamers, and real-time PCR quantified the influenza genome. Gold nanoparticles were immobilized on a surface to immobilize the specific DNA probe, and electrochemical hybridization was electrochemically followed. The biosensor exhibited high selectivity and effective distinction of complementary sequences from mismatches and influenza virus cDNA genome. The biosensor successfully detected the influenza B virus genome in real samples. Non-influenza samples yielded no significant hybridization signals. The comparison between the results obtained from the biosensor and real-time PCR revealed full agreement of these methods. The biosensor utilized electrochemical detection of hybridization and proved effective in detecting the influenza B virus genome with high specificity, sensitivity, and selectivity. Comparative analysis with real-time PCR underscored the accuracy and potential applicability of the biosensor in rapid and specific virus detection. This innovative approach holds promise for future diagnostic and epidemiological applications in detecting influenza B virus and other pathogens.

Application of Pt@ZIF-8 nanocomposite-based electrochemical biosensor for sensitive diagnosis of tau protein in Alzheimer's disease patients

Alzheimer's disease (AD) is a progressive brain disorder characterized by the ongoing decline of brain functions. Studies have revealed the detrimental effects of hyperphosphorylated tau (p-tau) protein fibrils in AD pathogenesis, highlighting the importance of this factor in the early-stage detection of AD conditions. We designed an electrochemical immunosensor for quantitative detection of the cis conformation of the p-tau protein (cis-p-tau) employing platinum nanoparticles (Pt NPs) supported on zeolitic imidazolate frameworks (ZIF) for modifying the glassy carbon electrode (GCE) surface. Under optimum conditions, the immunosensor selectively and sensitively detected cis-p-tau within the broad linear range of 1 fg mL-1 to 10 ng mL-1 and the low limit of detection (LOD) of 1 fg mL-1 with desired reproducibility and stability. Furthermore, the fabricated immunosensor's performance was examined for the cis-p-tau analysis in the serum of AD patients, indicating its accuracy and feasibility for real-sample analysis. Notably, this is the first application of Pt@ZIF-8 nanocomposite in fabricating a valid immunosensor for selective cis-p-tau detection, even in the presence of trans-p-tau. It is worth mentioning that the enzyme-linked immunosorbent assay (ELISA) reference technique is not able to evaluate pico- or femtomolar concentrations of cis-p-tau, making the fabricated immunosensor superior for early-stage measurement and screening of AD.

Tablet-Based Sensor: A Stable and User-Friendly Tool for Point-of-Care Detection of Glucose in Urine

The colorimetric detection of glucose in urine through enzymatic reactions offers a low-cost and non-invasive method to aid in diabetes management. Nonetheless, the vulnerability of enzymes to environmental conditions, particularly elevated temperatures, and their activity loss pose significant challenges for transportation and storage. In this work, we developed a stable and portable tablet sensor as a user-friendly platform for glucose monitoring. This innovative device encapsulates glucose oxidase and horseradish peroxidase enzymes with dextran, transforming them into solid tablets and ensuring enhanced stability and practicality. The enzymatic tablet-based sensor detected glucose in urine samples within 5 min, using 3,3',5,5'-tetramethylbenzidine (TMB) as the indicator. The tablet sensor exhibited responsive performance within the clinically relevant range of 0-6 mM glucose, with a limit of detection of 0.013 mM. Furthermore, the tablets detected glucose in spiked real human urine samples, without pre-processing, with high precision. Additionally, with regard to thermal stability, the enzyme tablets better maintained their activity at an elevated temperature as high as 60 °C compared to the solution-phase enzymes, demonstrating the enhanced stability of the enzymes under harsh conditions. The availability of these stable and portable tablet sensors will greatly ease the transportation and application of glucose sensors, enhancing the accessibility of glucose monitoring, particularly in resource-limited settings.

Urine protein quantification in human urine on boron-doped diamond electrodes based on the electrochemical reaction of Coomassie brilliant blue

Urinalysis is attracting interest in personal healthcare management as part of a general move to improve quality of life. Urine contains various metabolites and the protein level in urine is an indicator of kidney function. In this study, a novel electrochemical sensing system based on boron-doped diamond (BDD) electrodes was developed for the detection of protein concentrations in human urine. BDD electrodes have the advantages of a wide electrochemical potential window and low non-specific adsorption, making them ideal for simple, rapid, and compact devices for home detection of bio-relevant substances. Coomassie brilliant blue (CBB), a dye that selectively and strongly binds to urine proteins, was found to be a redox-active indicator to show a decrease in its redox currents in relation to the concentration of protein in urine samples. Our detailed studies of BDD electrodes showed their limit of detection to be 2.57 μg mL-1 and that they have a linear response that ranges from 0 to 400 μg mL-1 in urine samples. We also investigated the detection of urine protein in different urine samples. Our results agreed with those obtained using conventional colorimetric analysis. We believe this to be the first study of electrochemical detection of urine protein in urine samples on BDD electrodes, which is of great significance to be able to obtain results with electrical signals rapidly compared to conventional colorimetric analysis. This CBB-BDD technique has the potential to assist healthcare management in the form of a rapid daily diagnostic test to judge whether a more detailed examination is needed.

Post-Vaccination Detection of SARS-CoV-2 Antibody Response with Magnetic Nanoparticle-Based Electrochemical Biosensor System

Here, we report magnetic nanoparticle-based biosensor platforms for the rapid detection of SARS-CoV-2 antibody responses in human serum. The use of the proposed system enabled the detection of anti-SARS-CoV-2 spike (S) and nucleocapsid (N) proteins at a concentration of ng/mL in both buffer and real serum samples. In particular, the protocol, which is considered an indicator of innate immunity after vaccination or post-infection, could be useful for the evaluation of antibody response. We included a total of 48 volunteers who either had COVID-19 but were not vaccinated or who had COVID-19 and were vaccinated with CoronoVac or Biontech. Briefly, in this study, which was planned as a cohort, serum samples were examined 3, 6, and 12 months from the time the volunteers' showed symptoms of COVID-19 with respect to antibody response in the proposed system. Anti-S Ab and anti-N Ab were detected with a limit of detection of 0.98 and 0.89 ng/mL, respectively. These data were confirmed with the corresponding commercial an electrochemiluminescence immunoassay (ECLIA) assays. Compared with ECLIA, more stable data were obtained, especially for samples collected over 6 months. After this period, a drop in the antibody responses was observed. Our findings showed that it could be a useful platform for exploring the dynamics of the immune response, and the proposed system has translational use potential for the clinic. In conclusion, the MNP-based biosensor platform proposed in this study, together with its counterparts in previous studies, is a candidate for determining natural immunity and post-vaccination antibody response, as well as reducing the workload of medical personnel and paving the way for screening studies on vaccine efficacy.

Illuminating Progress: The Contribution of Bioluminescence to Sustainable Development Goal 6-Clean Water and Sanitation-Of the United Nations 2030 Agenda

The United Nations Agenda 2030 Sustainable Development Goal 6 (SDG 6) aims at ensuring the availability and sustainable management of water and sanitation. The routine monitoring of water contaminants requires accurate and rapid analytical techniques. Laboratory analyses and conventional methods of field sampling still require considerable labor and time with highly trained personnel and transport to a central facility with sophisticated equipment, which renders routine monitoring cumbersome, time-consuming, and costly. Moreover, these methods do not provide information about the actual toxicity of water, which is crucial for characterizing complex samples, such as urban wastewater and stormwater runoff. The unique properties of bioluminescence (BL) offer innovative approaches for developing advanced tools and technologies for holistic water monitoring. BL biosensors offer a promising solution by combining the natural BL phenomenon with cutting-edge technologies. This review provides an overview of the recent advances and significant contributions of BL to SDG 6, focusing attention on the potential use of the BL-based sensing platforms for advancing water management practices, protecting ecosystems, and ensuring the well-being of communities.

Mapping the Potential of Microfluidics in Early Diagnosis and Personalized Treatment of Head and Neck Cancers

Head and neck cancers (HNCs) account for ~4% of all cancers in North America and encompass cancers affecting the oral cavity, pharynx, larynx, sinuses, nasal cavity, and salivary glands. The anatomical complexity of the head and neck region, characterized by highly perfused and innervated structures, presents challenges in the early diagnosis and treatment of these cancers. The utilization of sub-microliter volumes and the unique phenomenon associated with microscale fluid dynamics have facilitated the development of microfluidic platforms for studying complex biological systems. The advent of on-chip microfluidics has significantly impacted the diagnosis and treatment strategies of HNC. Sensor-based microfluidics and point-of-care devices have improved the detection and monitoring of cancer biomarkers using biological specimens like saliva, urine, blood, and serum. Additionally, tumor-on-a-chip platforms have allowed the creation of patient-specific cancer models on a chip, enabling the development of personalized treatments through high-throughput screening of drugs. In this review, we first focus on how microfluidics enable the development of an enhanced, functional drug screening process for targeted treatment in HNCs. We then discuss current advances in microfluidic platforms for biomarker sensing and early detection, followed by on-chip modeling of HNC to evaluate treatment response. Finally, we address the practical challenges that hinder the clinical translation of these microfluidic advances.

Fluorescence intensity coded DNA frameworks based on the FRET effect enable multiplexed miRNA imaging in living cells

miRNA analysis has played an important role in precise diagnosis, treatment and prognosis of cancer, especially multiplexed miRNA imaging. In this work, a novel fluorescence emission intensity (FEI) encoding strategy was developed based on a tetrahedron DNA framework (TDF) carrier and the FRET effect between Cy3 and Cy5. Six FEI-encoded TDF (FEI-TDF) samples were constructed by tuning the labeling number of Cy3 and Cy5 at the vertexes of the TDF. For fluorescence characterization in vitro, distinct FEIs in the spectra and different colors under ultraviolet (UV) irradiation of FEI-TDF samples were observed. By dividing the ranges of FEIs of samples, the stability of FEIs was highly improved. Based on the ranges of FEIs in each sample, five codes with good discrimination were finally developed. Before the application of intracellular imaging, the excellent biocompatibility of the TDF carrier was proved by CCK-8 assay. The barcode probes based on samples 12, 21 and 11 were designed as example models to realize multiplexed imaging of miRNA-16, miRNA-21 and miRNA-10b in MCF-7 cells with obviously different fluorescence merged colors. FEI-TDFs provide a new research perspective for the development of fluorescence multiplexing strategies in the future.

Self-regulating bioinspired supramolecular photonic hydrogels based on chemical reaction networks for monitoring activities of enzymes and biofuels

Inspired by the way many living organisms utilize chemical/biological reactions to regulate their skin and respond to stimuli in the external environment, we have developed a self-regulating hydrogel design by incorporating chemical reaction networks (CRNs) into biomimetic photonic crystal hydrogels. In this hydrogel system, we used host-guest supramolecular non-covalent bonds between beta-cyclodextrin (β-CD) and ferrocene (Fc) as partial crosslinkers and designed a CRN involving enzyme-fuel couples of horseradish peroxidase (HRP)/H₂O₂ and glucose oxidase (GOD)/d-glucose, by which the responsive hydrogel was transformed into a glucose-driven self-regulating hydrogel. Due to the biomimetic structural color in the hydrogel, the progress of the chemical reaction was accompanied by a change in the color of the hydrogel. Based on this principle, the designed supramolecular photonic hydrogel (SPH) can not only achieve naked-eye detection of H₂O₂ and glucose concentrations with the assistance of a smartphone but also monitor the reactions of HRP and GOD enzymes and determine their activity parameters. The sensitivity and stability of the sensor have been proven. In addition, due to the reversibility of the chemical reaction network, the sensor can be reused, thus having the potential to serve as a low-cost point-of-care sensor. The SPH was ultimately used to detect glucose in human plasma and H₂O₂ in liver tumor tissue. The results are comparable with commercial assay kits. By redesigning the chemical reaction network in the hydrogel, it is expected to be used for detecting other enzymes or fuels.

Photoelectrochemical sensors based on paper and their emerging applications in point-of-care testing

Point-of-care testing (POCT) technology is urgently required owing to the prevalence of the Internet of Things and portable electronics. In light of the attractive properties of low background and high sensitivity caused by the complete separation of excitation source and detection signal, the paper-based photoelectrochemical (PEC) sensors, featured with fast in analysis, disposable and environmental-friendly have become one of the most promising strategies in POCT. Therefore, in this review, the latest advances and principal issues in the design and fabrication of portable paper-based PEC sensors for POCT are systematically discussed. Primarily, the flexible electronic devices that can be constructed by paper and the reasons why they can be used in PEC sensors are expounded. Afterwards, the photosensitive materials involved in paper-based PEC sensor and the signal amplification strategies are emphatically introduced. Subsequently, the application of paper-based PEC sensors in medical diagnosis, environmental monitoring and food safety are further discussed. Finally, the main opportunities and challenges of paper-based PEC sensing platforms for POCT are briefly summarized. It provides a distinct perspective for researchers to construct paper-based PEC sensors with portable and cost-effective, hoping to enlighten the fast development of POCT soon after, as well as benefit human society.

Classification of Pericarpium Citri Reticulatae (Chenpi) age using surface-enhanced Raman spectroscopy

Pericarpium Citri Reticulatae (PCR) is used in food and medical herbal formula, and its quality is determined by its age. Raman spectroscopy is a laser technology for molecular fingerprinting. The feasibility of using surface-enhanced Raman spectroscopy (SERS) to determine the PCR age was investigated. The Raman peaks were acquired using a Raman spectrometer with a 785 nm diode laser and were analyzed using principal component analysis (PCA) followed by linear discriminant analysis (PCA-LDA). There were six major peaks at 600, 730, 990, 1370, 1607, and 1742 cm^-1 in the SERS spectra, and their intensity, especially the peak at 1607 cm^-1, was inversely correlated with the PCR age. The different ages of PCR could be correctly classified with over 90 % accuracy by using PCA-LDA based on the SERS spectra. In conclusion, a Raman spectrometer may be used as a novel method to identify the age of PCR products.

Trends in Molecular Diagnosis of Nosocomial Pneumonia Classic PCR vs. Point-of-Care PCR: A Narrative Review

Nosocomial pneumonia is one of the most frequent hospital-acquired infections. One of the types of nosocomial pneumonia is ventilator-associated pneumonia, which occurs in endotracheally intubated patients in intensive care units (ICU). Ventilator-associated pneumonia may be caused by multidrug-resistant pathogens, which increase the risk of complications due to the difficulty in treating them. Pneumonia is a respiratory disease that requires targeted antimicrobial treatment initiated as early as possible to have a good outcome. For the therapy to be as specific and started sooner, diagnostic methods have evolved rapidly, becoming quicker and simpler to perform. Polymerase chain reaction (PCR) is a rapid diagnostic technique with numerous advantages compared to classic plate culture-based techniques. Researchers continue to improve diagnostic methods; thus, the newest types of PCR can be performed at the bedside, in the ICU, so-called point of care testing-PCR (POC-PCR). The purpose of this review is to highlight the benefits and drawbacks of PCR-based techniques in managing nosocomial pneumonia.

Wearable Smart Bandage-Based Bio-Sensors

Bandage is a well-established industry, whereas wearable electronics is an emerging industry. This review presents the bandage as the base of wearable bioelectronics. It begins with introducing a detailed background to bandages and the development of bandage-based smart sensors, which is followed by a sequential discussion of the technical characteristics of the existing bandages, a more practical methodology for future applications, and manufacturing processes of bandage-based wearable biosensors. The review then elaborates on the advantages of basing the next generation of wearables, such as acceptance by the customers and system approvals, and disposal.

Direct, precise, enzyme-free detection of miR-103–3p in real samples by microgels with highly specific molecular beacons

Low abundance, small size, and sequence similarities render microRNA (miRNAs) detection challenging, particularly in real samples, where quantifying weakly expressed miRNAs can be arduous due to interference of more abundant molecules. The standard quantitative reverse transcription polymerase chain reaction (qRT-PCR) requires multiple steps, thermal cycles, and costly enzymatic reactions that can negatively affect results. Here we present a direct, precise, enzyme-free assay based on microgels particles conjugating molecular beacons (MB) capable of optically detecting low abundant miRNAs in real samples. We validate the applicability of microgels assay using qRT-PCR as a reference technology. As a relevant case, we chose miR-103-3p, a valuable diagnostic biomarker for breast cancer, both in serum samples and MCF7 cells. As a result, microgels assay quantifies miRNA molecules at room temperature in a single step, 1 h (vs. 4 hrs for qRT-PCR) without complementary DNA synthesis, amplification, or expensive reagents. Microgels assay exhibits femtomolar sensitivity, single nucleotide specificity, and a wide linear range (10²-10⁷ fM) (wider than qRT-PCR), with low sample consumption (2 μL) and excellent linearity (R²= 0.98). To test the selectivity of the microgel assay in real samples, MCF7 cells were considered where the pool of 8 other miRNAs were further upregulated with respect to miRNA 103-3p. In such complex environments, microgels assay selectively detects the miRNA target, mainly due to MB advanced stability and specificity as well as high microgel antifouling properties. These results show the reliability of microgels assay to detect miRNAs in real samples.

Multiplex Identification of Post-Translational Modifications at Point-of-Care by Deep Learning-Assisted Hydrogel Sensors

Multiplex detection of protein post-translational modifications (PTMs), especially at point-of-care, is of great significance in cancer diagnosis. Herein, we report a machine learning-assisted photonic crystal hydrogel (PCH) sensor for multiplex detection of PTMs. With closely-related PCH sensors microfabricated on a single chip, our design achieved not only rapid screening of PTMs at specific protein sites by using only naked eyes/cellphone, but also the feasibility of real-time monitoring of phosphorylation reactions. By taking advantage of multiplex sensor chips and a neural network algorithm, accurate prediction of PTMs by both their types and concentrations was enabled. This approach was ultimately used to detect and differentiate up/down regulation of different phosphorylation sites within the same protein in live mammalian cells. Our developed method thus holds potential for POC identification of various PTMs in early-stage diagnosis of protein-related diseases.

Electrophoresis-Assisted Multilayer Assembly of Nanoparticles for Sensitive Lateral Flow Immunoassay

Lateral flow immunoassay (LFIA) is a rapid, simple, and inexpensive point-of-need method. A major limitation of LFIA is a high limit of detection (LOD), which impacts its diagnostic sensitivity. To overcome this limitation, we introduce a signal-enhancement procedure that is performed after completing LFIA and involves controllably moving biotin- and streptavidin-functionalized gold nanoparticles by electrophoresis. The nanoparticles link to immunocomplexes forming multilayer aggregates on the test strip, thus, enhancing the signal. Here, we demonstrate lowering the LOD of hepatitis B surface antigen from approximately 8 to 0.12 ng mL^-1 , making it clinically acceptable. Testing 118 clinical samples for hepatitis B showed that signal enhancement increased the diagnostic sensitivity of LFIA from 73 % to 98 % while not affecting its 95 % specificity. Electrophoresis-driven enhancement of LFIA is universal (antigen-independent), takes two minutes, and can be performed by an untrained person.

Multifunctional Composite Hydrogels for Bacterial Capture, Growth/Elimination, and Sensing Applications

Hydrogels are cross-linked networks of hydrophilic polymer chains with a three-dimensional structure. Owing to their unique features, the application of hydrogels for bacterial/antibacterial studies and bacterial infection management has grown in importance in recent years. This trend is likely to continue due to the rise in bacterial infections and antimicrobial resistance. By exploiting their physicochemical characteristics and inherent nature, hydrogels have been developed to achieve bacterial capture and detection, bacterial growth or elimination, antibiotic delivery, or bacterial sensing. Traditionally, the development of hydrogels for bacterial/antibacterial studies has focused on achieving a single function such as antibiotic delivery, antibacterial activity, bacterial growth, or bacterial detection. However, recent studies demonstrate the fabrication of multifunctional hydrogels, where a single hydrogel is capable of performing more than one bacterial/antibacterial function, or composite hydrogels consisting of a number of single functionalized hydrogels, which exhibit bacterial/antibacterial function synergistically. In this review, we first highlight the hydrogel features critical for bacterial studies and infection management. Then, we specifically address unique hydrogel properties, their surface/network functionalization, and their mode of action for bacterial capture, adhesion/growth, antibacterial activity, and bacterial sensing, respectively. Finally, we provide insights into different strategies for developing multifunctional hydrogels and how such systems can help tackle, manage, and understand bacterial infections and antimicrobial resistance. We also note that the strategies highlighted in this review can be adapted to other cell types and are therefore likely to find applications beyond the field of microbiology.

Nanomaterials-based portable electrochemical sensing and biosensing systems for clinical and biomedical applications

Miniaturized electrochemical sensing systems are employed in day-to-day uses in the several area from public health to scientific applications. A variety of electrochemical sensor and biosensor systems may not be effectively employed in real-world diagnostic laboratories and biomedical industries due to their limitation of portability, cost, analytical period, and need of skilled trainer for operating devices. The design of smart and portable sensors with high sensitivity, good selectivity, rapid measurement, and reusable platforms is the driving strength for sensing glucose, lactate, hydrogen peroxide, nitric oxide, mRNA, etc. The enhancement of sensing abilities of such sensor devices through the incorporation of both novel sensitive nanomaterials and design of sensor strategies are evidenced. Miniaturization, cost and energy efficient, online and quantitative detection and multiple sensing ability are the beneficial of the nanostructured-material-based electrochemical sensor and biosensor systems. Owing to the discriminating catalytic action, solidity and biocompatibility for designing sensing system, nanoscale materials empowered electrochemical detection systems are accomplished of being entrenched into/combined with portable or miniaturized devices for specific applications. In this review, the advance development of portable and smart sensing/biosensing systems derived from nanoscale materials for clinical and biomedical applications is described.

Graphical Abstract

Leveraging Nanomechanical Perturbations in Raman Spectro-Immunoassays to Design a Versatile Serum Biomarker Detection Platform

While immunoassays are pivotal to medical diagnosis and bioanalytical chemistry, the current landscape of public health has catalyzed an important shift in the requirements of immunoassays that demand innovative solutions. For example, rapid, label-free, and low-cost screening of a given analyte is required to inform the best countermeasures to combat infectious diseases in a timely manner. Yet, the current design of immunoassays cannot accommodate such requirements as constraint by accumulative challenges, such as repeated incubation and washing, and the need of two types of antibodies in the sandwich format. To provide a potential solution, herein, a plasmonic Raman immunoassay with single-antibody, multivariate regression, and shift-of-peak strategies, coined as the PRISM assay, for serum biomarkers detection, is reported. The PRISM assay relies on Raman reporter-antibody conjugates to capture analytes on a plasmonic substrate. The ensuing nanomechanical perturbations to vibration of Raman reporters induce subtle but characteristic spectral changes that encode rich information related to the captured analytes. By fusing Raman spectroscopy and chemometric analysis, both Raman frequency shift- and multivariate regression models for sensitive detection of biomarkers are developed. The PRISM assay is expected to find a wide range of applications in clinical diagnosis, food safety surveillance, and environmental monitoring.

Elucidating Sensitivity and Stability Relationship of Gold-Carbon Hybrid LSPR Sensors Using Principal Component Analysis

Sensitive localized surface plasmon resonance (LSPR) sensing is achieved using nanostructured geometries of noble metals which typically have dimensions less than 100 nm. Among the plethora of geometries and materials, the spherical geometries of gold (Au) are widely used to develop sensitive bio/chemical sensors due to ease of manufacturing and biofunctionlization. One major limitation of spherical-shaped geometries of Au, used for LSPR sensing, is their low refractive index (RI) sensitivity which is commonly addressed by adding another material to the Au nanostructures. However, the process of addition of new material on Au nanostructures, while retaining the LSPR of Au, often comes with a trade-off which is associated with the instability of the developed composite, especially in harsh chemical environments. Addressing this challenge, we develop a Au-graphene-layered hybrid (Au-G) with high stability (studied up to 2 weeks here) and enhanced RI sensitivity (a maximum of 180.1 nm/RIU) for generic LSPR sensing applications using spherical Au nanostructures in harsh chemical environments, involving organic solvents. Additionally, by virtue of principal component analysis, we correlate stability and sensitivity of the developed system. The relationship suggests that the shelf life of the material is proportional to its sensitivity, while the stability of the sensor during the measurement in liquid environment decreases when the sensitivity of the material is increased. Though we uncover this relationship for the LSPR sensor, it remains evasive to explore similar relationships within other optical and electrochemical transduction techniques. Therefore, our work serves as a benchmark report in understanding/establishing new correlations between sensing parameters.

Dual-Modulated Heterojunctions for Anti-Interference Sensing of Heavy Metals in Seawater

Trace analyte detection in a complex environment such as in seawater is usually challenging for classic redox-based electrochemical sensors since the matrix effect of high salinity and various interfering species with similar redox properties can generate false positive/negative signals, thus impacting the sensitivity and specificity of the sensors. In this work, unlike redox-based approaches, we propose a novel sensing mode that relies on dual-modulated interfacial energy barriers of heterojunctions. By constructing the hierarchical structure of Ni/TiO₂/porous-reduced graphene oxide/chitosan (CS), we introduce interfacial energy barriers of Schottky junctions into the electrochemical sensors for Cu²⁺. Most importantly, we found that two factors, light and the electrostatic interactions between the heterojunctions and Cu²⁺, can be coupled to regulate the height of the interfacial energy barrier and at last exponentially magnify the sensing signals in response to Cu²⁺. Since the electrostatic interaction is inert to redox, the proposed sensor is robust against most interfering species even in seawater. Illumination further enhances its sensitivity by 6.23 times and endows it a limit of detection of 0.22 nM. Such a dual-modulated sensing mode is also valid in other heterojunctions such as in the p-n junctions of Ni/NiO/MoS₂/CS, demonstrating its potential in more universal applications.