However, sweat antibody detection remains particularly challenging because antibody concentrations are substantially lower than those of common sweat markers such as cortisol and glucose. By integrating ultra-sensitive interfacial capacitive sensing with ultra-fast AC electrothermal target enrichment, we develop detachable monolithic biosensors for sweat antibodies, which are based on antigen probe functionalized flexible electrode arrays. A wearable biosensing system, incorporating a pressure-regulated PDMS sweat-collection patch and a wristwatch-style microcapacitance detector, is further constructed to enable real-time quantitation of ultra-trace antibodies in sweat. SARS-CoV-2 N protein antibody and Hepatitis B surface antibody in sweat are tested with a limit of 10-6 ng/mL, a linear range of 10-5~10-1 ng/mL, and a responding time of 30 s. In response to the fluctuations of sweat biomarker levels, adaptive stratification algorithms are implemented by leveraging the sensor’s high dynamic range through machine learning. Validated on 25 volunteers with a stratification balanced accuracy exceeding 0.74, this system provides a versatile wearable platform capable of quantifying and stratifying a broader range of highly fluctuating, low-abundance sweat biomarkers.

The biological accumulation of microcontaminants and associated antibiotic resistance in food poses significant threats to both human and environmental health. Therefore, it is particularly crucial to design and develop methods of efficient identification and detection. Recently, molecularly imprinted polymers (MIPs) and aptamers (Apts), as novel hybrid recognition elements, have received widespread attention from researchers. Because the dual recognition-based sensors have demonstrated enhanced performance and desirable characteristics, including high sensitivity, strong binding affinity, a low detection limit, and excellent stability under harsh environmental conditions, which are expected to be applied in food safety fields. This paper compares the characteristics of MIP and Apt, highlighting the significant advantages of molecularly imprinted polymer–aptamer (MIP-Apt) dual recognition in selectivity, sensitivity, and stability, which stems from their symmetric integration, akin to an extension of the ‘lock-and-key’ model. It then systematically discusses three synthetic strategies for MIP-Apt hybrid recognition systems and their applications for food safety detection, focusing on analyzing their detection strategies, sensing mechanisms, construction methodologies, performance evaluations, and potential application value. It also offers substantive perspectives on both the prevailing limitations and promising developmental pathways for MIP-Apt hybrid recognition-based sensing platforms.

A flexible electrochemical sensor with high sensitivity and specificity is developed using gold nanoparticles (AuNPs) and a reduced graphene oxide/molybdenum disulfide (rGo-MoS2) composite modified screen printed carbon electrode (SPCE), with L-cysteine (L-Cys) as a probe for Cu2+ target recognition. Owing to the AuNPs/rGo-MoS2, the electron transference ability is improved by increasing the specific surface area of the working electrode, and a high sensitivity is achieved. Meanwhile, the bidentate chelation of L-Cys to Cu2+ contributes to a good selectivity. Using differential pulse voltammetry (DPV) for spiked standard Cu2+, the test results show a dynamic range from 0.1 μM to 100 μM, a detection limit of 0.020 μM, and a high sensitivity of 1.190 μA μM-1. Furthermore, detection in both environmental water and human plasma samples demonstrates a wide applicability of this sensor in various matrices, and an excellent feasibility for environmental and clinical applications.

A nanozyme-based aptasensor combines the unique properties of nanozymes with the specificity of aptamers for the detection of various biomolecules. Nanozymes are nanomaterials that possess enzyme-like properties, demonstrating substantial potential for enhancing the sensing capabilities of biosensors. In recent years, the incorporation of nanozymes into biosensors has opened new avenues for the detection of tumor biomarkers. The unique attributes of nanozymes and aptamers lead to biosensors characterized by high sensitivity, specificity, reproducibility and accuracy in analytical performance. This article reviews the research progress of nanozyme-based aptasensors in tumor biomarker detection over the past decade. We categorize these sensors based on their sensing modes and target types, and examine the properties and applications of the nanozymes employed in these devices, providing a thorough discussion of the strengths and weaknesses associated with each sensor type. Finally, the review highlights the strengths and challenges associated with nanozyme-based biosensors and envisions future developments and applications in this field. The objective is to provide insights for improving biosensor performance in tumor biomarker detection, thereby contributing to advancements in precision cancer diagnosis and treatment.

Escherichia coli (E. coli) is one of the most common strains that produce Shiga toxin, which can contaminate food and water, causing serious diseases and even endangering life. Therefore, the detection of E. coli is crucial for protecting public health. At present, most traditional methods have disadvantages such as long detection cycles, high cost, and complex operations. This article proposed a novel commercial Rayleigh surface acoustic wave (R-SAW) biosensor for the detection of trace amounts of E. coli, which utilized the coordination reaction between carboxyl (-COOH) groups and aluminum ions (Al3+) to form the bio-enhanced probes, enabling the 5-terminal -COOH-modified aptamers to be preferentially enriched and directionally immobilized on the electrode surface. The biosensor could complete the detection within 100 s, with a linear detection range of 103–108 cells/mL, a limit of detection (LOD) as low as 732 cells/mL, and a selectivity ratio of 3270:1. This article conducted spiked detection on six types of food, indicating that the biosensor had the advantages of rapid speed, high sensitive, wide detection range, low LOD, strong specificity, and low cost, providing an economical and convenient solution for detecting trace amounts of E. coli in food.

Kanamycin (KanR) is a widely used antibiotic in human and veterinary medicine, as well as in food production and livestock breeding. However, its environmental residue and bioaccumulation in the food chain pose a great threat to human health. A real-time and sensitive aptasensor is developed for KanR detection based on a gold interdigitated electrode (IDE). A microfluidic alternating current electrothermal (ACET) effect is employed for rapid directional manipulation and enrichment of KanR molecules. As an ultrasensitive indicator, solid–liquid capacitance is adopted to reflect the tiny change on the IDE surface caused by target adsorption. The overall detection takes only 60 s from sample to result, and a wide linear detection range of 0.1 fM~1 pM, an ultra-low detection limit of 16.56 aM, and a high selectivity of 7752:1 are simultaneously achieved, with 5 times of repeated use and the shelf life of 10 days. Furthermore, the aptasensor shows excellent practicability in milk samples, with the spiked recovery rate ranging from 86.90% to 116.17%. This aptasensor with the detecting strategy provides a rapid, convenient, and cost-effective solution for real-time monitoring of KanR.

Perfluorooctanoic acid (PFOA) is one of the most persistent and bioaccumulative water contaminants. Sensitive, rapid, and in-field analysis is needed to ensure safe water supplies. Here, we present a single step (one shot) and rapid sensor capable of measuring PFOA at the sub-quadrillion (ppq) level, 4.5 × 10−4 ppq, within 10 s. This innovative sensor employs a synergistic combination of a molecularly imprinted polymer (MIP)-modified gold interdigitated microelectrode chip and AC electrothermal effects (ACETs), which enhance detection sensitivity by facilitating the accelerated movement of PFOA molecules towards specific recognition sites on the sensing surface. The application of a predetermined AC signal induces microfluidic enrichment and results in concentration-dependent changes in interfacial capacitance during the binding process. This enables real-time, rapid quantification with exceptional sensitivity. We achieved a linear dynamic range spanning from 0.4 to 40 fg/L (4 × 10−7–4 × 10−5 ppt) and demonstrated good selectivity (~1:100) against other PFAS compounds, including perfluorooctanoic acid (PFOS), in PBS buffer. The sensor’s straightforward operation, cost-effectiveness, elimination of the need for external redox probes, compact design, and functionality in relatively resistant environmental matrices position it as an outstanding candidate for deployment in practical applications.

The development of point-of-use sensors capable of rapidly detecting per- and polyfluoroalkyl substances (PFAS) is crucial for real-time monitoring and effective management of PFAS contamination in the aquatic environment. Addressing current limitations in existing techniques for sensitive in-field analysis, this work employs a multifaceted approach to develop a rapid, ultra-sensitive, and single-step sensing platform for perfluorooctanesulfonic acid (PFOS). The approach integrates self-referencing interfacial capacitance sensing with microfluidic enrichment by AC electrothermal (ACET) effect. A molecular imprinted polymer (MIP) on gold interdigitated microelectrode chip is employed as a robust recognition element for the affinity-based capture of PFOS. A predetermined AC signal applied to the sensor will not only accelerate PFOS molecules towards the sensing surface for binding, but also track the interfacial capacitance change during binding, enabling real-time detection with extremely high sensitivity. The resulting single-step and rapid assay demonstrates detection as low as 0.5 fg/L (5x10- 7 ppt) in 10 s, a linear range of 0.5-500 fg/L (5x10- 7-5x10- 4 ppt), and high selectivity (105:1) in Phosphate-buffered saline (PBS) media against other PFAS compounds including perfluorooctanoic acid (PFOA). The success of this work will potentially provide a routine PFOS monitoring test for drinking water.

Foodborne bacteria like Escherichia coli threaten global food security, necessitating affordable, on-site detection methods, especially in resource-limited settings. This study optimized loop-mediated isothermal amplification (LAMP) integrated with peroxidase-mimicking G-quadruplex DNA structures (DNAzyme), termed DNAzyme-LAMP which was designed to incorporate two different catalytic DNAzymes per amplification unit, enabling colorimetric detection of E. coli in leafy vegetables and milk samples. Additionally, we introduce a novel electrochemical method that enhances analytical sensitivity. The optimized DNAzyme-LAMP achieved a detection limit below 6.3 CFU per reaction or 0.1 aM gene copies. This system lays the groundwork for the development of on-site biosensors and can be adapted for detecting other foodborne pathogens.

The rapid and sensitive detection of foodborne pathogens is crucial for ensuring food safety. Among virus testing methods, polymerase chain reaction (PCR) has served as the gold-standard technique in most food safety regulation organizations. However, to enhance the speed and efficiency of PCR, novel approaches are continually being explored. In this work, leveraging the photothermal effects and high thermal conductivity of gold nanoparticles, we have significantly improved the heating and cooling rates of thermal cycles, enabling ultra-fast PCR detection. Specifically, we present a pre-degassing multiplex digital PCR chip integrated with gold nanoparticles. We further developed a portable system with a light source for photothermal heating cycling, along with an optoelectronic sensor to analyze PCR amplification products after rapid thermal cycling. As proof of concept, the proposed chip and portable device was applied for the on-site detection of several types of foodborne pathogens, including Escherichia coli, Listeria monocytogenes, Staphylococcus aureus, and Salmonella. The whole system could distinguish those pathogens within 20 min, showing good potential for the rapid detection of multiple types of foodborne pathogens.

Rapidly identifying and quantifying Gram-positive bacteria are crucial to diagnosing and treating bacterial lower respiratory tract infections (LRTIs). This work presents a field-deployable biosensor for detecting Gram-positive bacteria from exhaled breath condensates (EBCs) based on peptidoglycan recognition using an aptamer. Dielectrophoretic force is employed to enrich the bacteria in 10 s without additional equipment or steps. Concurrently, the measurement of the sensor's interfacial capacitance is coupled to quantify the bacteria during the enrichment process. By incorporation of a semiconductor condenser, the whole detection process, including EBC collection, takes about 3 min. This biosensor has a detection limit of 10 CFU/mL, a linear range of up to 105 CFU/mL and a selectivity of 1479:1. It is cost-effective and disposable due to its low cost. The sensor provides a nonstaining, culture-free and PCR-independent solution for noninvasive and real-time diagnosis of Gram-positive bacterial LRTIs.

Aflatoxin B1 (AFB1) is a highly toxic substance found in food, necessitating rapid and sensitive detection methods. Combining interfacial capacitive sensing with AC electrothermal (ACET) enrichment, an aptasensor based on a PCB electrode array is developed for real-time detection of trace AFB1. Owing to the sensitive solid-liquid capacitance with a pF-level resolution, AFB1 detection at sub-femtomolar level is achieved. The induced ACET flows enrich AFB1 molecules towards the electrode surface during capacitance measurement, enabling a one-step detection containing target enrichment, with an overall time of 20 s without any extra concentrating devices or processes. This sensor has a low detection limit of 620 aM, a selectivity of 2262:1 against interferences, and a wide semi-log linear range from 1 fM to 10 pM. It is with a cost below 1 US dollar for disposable detection and a convenient operation for on-site application. The detection of AFB1 in three types of quality control samples demonstrates a good feasibility for food safety inspection.

Lead ion (Pb2+) pollution is a critical global issue due to its ability to accumulate in the human body, resulting in severe health problems. Despite extensive research efforts devoted to the detection of Pb2+ contamination, practical, rapid, and field-deployable sensors for Pb2+ is yet to be developed to effectively safeguard the environment and public health. Herein, a label-free affinity-based sensing device is developed based on printed circuit board (PCB) for low-cost, easy-to-use, and real-time on-site detection of Pb2+ ions. The sensors are prepared by forming a self-assembled monolayer of glutathione (GSH) on the surface of gold-plated PCB electrodes, which serves as a molecular probe to recognize Pb2+. Rapid and sensitive detection is achieved by using capacitance sensing integrated with microfluidic enrichment. The sensor’s interfacial capacitance is used to indicate specific binding, while the capacitance reading process simultaneously induces alternating current electrothermal (ACET) acceleration of analyte’s travel towards the probes. Thus, the enrichment and detection are integrated into a single step, making pre-concentration unnecessary and shortening the assay time to 30 s. This Pb2+ sensor has demonstrated one of the lowest limits of detection reported so far (1.85 fM) with a linear range of 0.01–10 pM. To evaluate the sensor’s specificity, non-target metal ions are tested, all showing negligible responses. Testing of tap water sample also yields reasonable results, validating the sensor’s robustness. The above-mentioned features, together with a commercial portable readout, make this sensor well-suited for point-of-use Pb2+ detection at low cost.

Due to the genetic mutation (fa) in the gene encoding for leptin receptor, homozygous Zucker rats (fa−/−) develop excessive adiposity and become an experimental animal model in obesity and metabolic-related diseases research. Based on tetra-primer amplification refractory mutation system-polymerase chain reaction (ARMS-PCR), we developed a method to quickly genotype Zucker rats with a mutated fa allele from their wildtype littermates. The three genotypes are clearly discriminated on 2.0% agarose gel. Our method can be used as a reliable tool to set up and maintain the breeding colony in animal facilities as well as assign animals to control and treatment groups based on their genotypes for animal studies.

In this work, we proposed a chamber-based digital PCR (cdPCR) microfluidic device that is compatible with fluorescence imaging systems for milk adulteration detection. The device enables the digitalization of PCR reagents, which are loaded into microchambers, and subsequent thermocycling for DNA amplification. Then, fluorescence images of the microchambers are captured and analyzed to obtain the total number of positive chambers, which is used to calculate the copy numbers of the target DNA, enabling accurate quantitative detections to determine intentional milk adulteration from accidental contaminations. The validation of this device is performed by camel milk authentication. We performed 25,600-chamber virtual multiplexing cdPCR tests using 40 × 40 chamber devices for the detection of DNA templates extracted from pure or mixed milk with different dilutions. Then, the cdPCR chip was used to authenticate blind milk samples, demonstrating its efficacy in real biotechnical applications.

With the ever-increasing proliferation of edge devices for applications, such as home automation and vehicle systems, their security vulnerabilities have received additional attention. A recent type of attack, physical fault injections, are particularly powerful as they can compromise these devices by skipping necessary instructions through physical methods, such as induced voltage glitches. Hence, they can trigger a wide range of software behavior anomalies and vulnerabilities not caused by the programs themselves. These attacks allow adversaries to carry out severe security breaches such as control flow hijacking and information leakage, even if the original device firmware has been well tested. To defend against physical fault injections, this paper develops an innovative approach based on a runtime attestation of code execution, i.e., given a sequence of instructions, they should be executed thoroughly and correctly in a verified manner. Hence, instruction anomalies can be detected and reported if faults are injected. This protection mechanism does not require additional hardware or specialized instructions. Instead, it leverages a lightweight virtual machine to protect critical code segments such as password-related operations. It integrates two techniques: blockchain-based instruction integrity assurance and memory randomization-based data protection. We fully implemented this framework on an AVR-based microcontroller, and our evaluation results demonstrate that our methodology is practical enough to effectively prevent a wide range of hardware-based fault injection attacks, paving the way for more secure edge applications.

Cell viability is an essential physiological status for drug screening. While cell staining is a conventional cell viability analysis method, dye staining is usually cytotoxic. Alternatively, impedance cytometry provides a straightforward and label-free sensing approach for the assessment of cell viability. A key element of impedance cytometry is its sensing electrodes. Most state-of-the-art electrodes are made of expensive metals, microfabricated by lithography, with a typical size of ten microns. In this work, we proposed a low-cost microfluidic impedance cytometry device with 100-micron wide indium tin oxide (ITO) electrodes to achieve a comparable performance to the 10-micron wide Au electrodes. The effectiveness was experimentally verified as 7 μm beads can be distinguished from 10 μm beads. To the best of our knowledge, this is the lowest geometry ratio of the target to the sensing unit in the impedance cytometry technology. Furthermore, a cell viability test was performed on MCF-7 cells. The proposed double differential impedance cytometry device has successfully differentiated the living and dead MCF-7 cells with a throughput of ~1000 cells/s. The label-free and low-cost, high-throughput impedance cytometry could benefit drug screening, fundamental biological research and other biomedical applications.

Meat adulteration detection is a common concern of consumers. Here, we proposed a multiplex digital polymerase chain reaction method and a low-cost device for meat adulteration detection. Using a polydimethylsiloxane microfluidic device, polymerase chain reaction reagents could be pump-free loaded into microchambers (40 x 40 chambers) automatically. Due to the independence of multiplex fluorescence channels, deoxyribonucleic acid templates extracted from different animal species could be distinguished by one test. In this paper, we designed primers and probes for four types of meat (beef, chicken, pork, and duck) and labeled each of the four fluorescent markers (hexachlorocyclohexane [HEX], 6-carboxyfluorescein [FAM], X-rhodamine [ROX], and cyanine dyes 5 [CY5]) on the probes. Specific detection and mixed detection experiments were performed on four types of meat, realizing a limit of detection of 3 copies/mu L. A mixture of four different species can be detected by four independent fluorescence channels. The quantitative capability of this method is found to meet the requirements of meat adulteration detections. This method has great potential for point-of-care testing together with portable microscopy equipment.

Hepatocellular carcinoma (HCC) is the main pathological type of liver cancer. Due to its insidious onset and the lack of specific early markers, HCC is often diagnosed at an advanced stage, and the survival rate of patients with partial liver resection is low. Non-coding RNAs (ncRNAs) have emerged as valuable biomarkers for HCC detection, with microRNAs (miRNAs) being a particularly relevant class of short ncRNAs. MiRNAs play a crucial role in gene expression regulation and can serve as biomarkers for early HCC detection. However, the detection of miRNAs poses a significant challenge due to their small molecular weight and low abundance. In recent years, biosensors utilizing electrochemical, optical, and electrochemiluminescent strategies have been developed to address the need for simple, rapid, highly specific, and sensitive miRNA detection. This paper reviews the recent advances in miRNA biosensors and discusses in detail the probe types, electrode materials, sensing strategies, linear ranges, and detection limits of the sensors. These studies are expected to enable early intervention and dynamic monitoring of tumor changes in HCC patients to improve their prognosis and survival status.

Mercury (Hg2+) is one of the most toxic heavy metals in farm products, so rapid detection of trace Hg2+ has always been sought after with high interest. Herein, we report a biosensor to specifically recognize Hg2+ in leaching solutions of brown rice flour. This sensor is simple and of low cost, with a very short assay time of 30 s. Another merit is the ultra-low limit of detection (LOD) at fM level. In addition, the specific aptamer probe realizes a good selectivity above 105: 1 against the interferences. This sensor is developed based on an aptamer-modified gold electrode array (GEA) for capacitive sensing. Alternating current electrothermal (ACET) enrichment is induced during the AC capacitance acquirement. Thus, the enrichment and detection are coupled as a single step, and pre-concentration is needless. Owing to the sensing mechanism of solid-liquid interfacial capacitance and ACET enrichment, Hg2+ level can be sensitively and rapidly reflected. Also, the sensor has a wide linear range from 1 fM to 0.1 nM and a shelf life of 15 days. This biosensor shows advantages on overall performance, enabling easy-to-operate, real-time, and large-scale Hg2+ detection in farm products.