Search Results (534)

Acrylamide (AA) is a common contaminant in foods processed at high temperatures and has attracted significant attention due to its potential neurotoxicity and carcinogenicity. Therefore, the development of a highly sensitive, highly selective sensing technology suitable for on-site detection is of great importance for ensuring food safety. In this study, an aptamer (Apt)-based capacitive AA sensor was developed based on the alternating current electrokinetics (ACEK) effect. The sensor utilizes an aptamer as the biomimetic recognition element, which can specifically recognize AA, thereby enabling quantitative detection. Additionally, a detachable detection fixture and data acquisition system were designed to enhance the detection stability and convenience of sensor. Within the linear range of 1 nmol/L to 10 µmol/L, the sensor response (dC/dt) exhibited a good linear relationship with AA concentration, with a detection limit as low as 0.4235 nmol/L. The sensor exhibits good selectivity toward structural analogs of AA, with a recovery relative standard deviations (RSDs) of less than 5.42% in spiked coffee samples. This portable detection system provides a sensitive and user-friendly tool for the analysis of acrylamide in food and holds great potential for application in food safety. Full article

Rare earth-doped upconversion nanoparticles (UCNPs) can emit upconversion luminescence under infrared light excitation and have been widely applied in the field of biosensing. In this study, upconversion nanoparticles were loaded onto porous silicon (PSi), and the detection of isocarbophos concentration was realized by virtue of nucleic acid aptamers. Firstly, the PSi was prepared by electrochemical etching and further functionalized. Nucleic acid aptamers were immobilized on the inner wall of PSi. Subsequently, the aptamer complementary strands labeled with UCNPs hybridized with the immobilized nucleic acid aptamers, enabling the indirect attachment of UCNPs to the inner wall of PSi. Then, isocarbophos solutions with different concentrations were added. The upconversion fluorescence images of samples before and after biological reaction were collected by an image acquisition device. The variation in average gray value of the images was obtained by image processing software, thereby achieving the quantitative detection of isocarbophos concentration. The limit of detection of this method for isocarbophos is 0.73 µg/L, which indicates that the proposed method can realize low-cost, high-sensitivity, and convenient biological detection of isocarbophos, with a fast and equipment-free signal readout. Full article

Kanamycin (KANA), a widely used aminoglycoside antibiotic in animal husbandry, is associated with residue accumulation in foods due to improper use, threatening food safety. Detecting trace KANA in complex food systems such as dairy, meat, and apicutural products remains challenging because of matrix interferences (e.g., proteins, lipids, and co-existing ions) and limitations of conventional methods, which require labor-intensive pretreatment and sophisticated instrumentation. Aptamer-based fluorescent biosensors have emerged as promising tools for rapid, sensitive KANA detection with high specificity and on-site analysis potential. DNA aptamers act as selective recognition elements that bind KANA and undergo conformational changes for efficient signal transduction. This review summarizes recent advances in fluorescent aptasensors for KANA detection, with an emphasis on food system applications. Aptamer selection strategies are outlined, highlighting split aptamers’ advantages in binding precision and structural stability. Labeled and label-free sensing modes are compared in terms of design principles, analytical performance, and suitability for complex food matrices. Attention is paid to strategies for mitigating matrix interference and improving detection reliability in real samples. Despite progress, challenges remain in sensor stability, reproducibility, and on-site deployment. Overall, aptamer-based fluorescent biosensors provide a powerful platform for rapid antibiotic residue monitoring and advance food safety-oriented sensing technologies. Full article

Precise quantitative monitoring of 17β-estradiol (E2) is important for reproductive management in precision livestock farming. However, E2 determination in complex biological matrices remains challenging because of matrix-derived background and signal variability. Here, we developed a nanoconfinement-assisted solid-state ratiometric fluorescent aptasensor integrating target-induced strand displacement (TISD), magnetic separation, and anodic aluminum oxide (AAO) nanochannel confinement. The sensing probe consisted of streptavidin-coated magnetic nanoparticles (MNPs) carrying a FAM-labeled cDNA internal reference and a Texas Red-labeled E2 aptamer reporter. E2 binding promoted dissociation of the Texas Red-labeled aptamer from the magnetic probe. Magnetic separation and washing reduced soluble matrix-derived interference, while subsequent deposition of the sensing complexes onto an AAO membrane mitigated coffee-ring-associated nonuniformity and produced a more spatially uniform dual-color fluorescence distribution for ratiometric analysis. Under matrix-matched calibration conditions, linear ranges of 5.0–50.0 pM were obtained in tap water and sow saliva, 5.0–40.0 pM in whole milk, and 5.0–15.0 pM in post-estrus sow urine. The LOD determined in tap water was 3.62 pM. The different calibration slopes obtained among the four matrices indicated that residual matrix-dependent effects remained and that matrix-specific calibration was required for quantitative analysis. Matrix-matched spike recoveries ranged from 86.92% to 119.54% across the investigated matrices. The aptasensor exhibited the strongest response toward 17β-E2 among the tested compounds; however, cross-reactivities of 77.3% for E3 and 47.3% for 17α-E2 indicated preferential rather than exclusive recognition. Molecular docking suggested a putative binding pose but did not experimentally establish the molecular recognition mechanism. Overall, the platform demonstrated laboratory-scale analytical feasibility in pretreated tap water, sow saliva, whole milk, and post-estrus sow urine. Further development of sample preparation, magnetic handling, membrane loading, probe selectivity, and portable fluorescence readout will be required before in situ or on-site application. Full article

Rapid, point-of-care detection of Escherichia coli O157:H7 remains an unmet clinical need, as culture and molecular methods are slow and poorly suited to decentralized or emergency settings. A label-free, monolithic aptasensor biochip was fabricated in a standard 65 nm CMOS process, featuring three aptamer-functionalized gold sensing pads with matched reference pads for differential readout. A 37-mer DNA aptamer targeting the E. coli O157:H7 lipopolysaccharide was immobilized via thiol–gold self-assembled monolayer chemistry. Binding events were transduced into surface-potential shifts, amplified by an on-chip analog front-end (~100 V/V gain, 101.5 µW), and evaluated using calibration standards, patient specimens, and hospital environmental samples, with fluorescence microscopy for validation. The sensor achieved 47.42 mV/decade sensitivity across 1–10,000 CFU/mL, an IUPAC detection limit near 3.74 CFU/mL, and an empirical LOD of about 11 CFU/mL, with outputs tracking bacterial load and ~5.7% matrix-related deviation. Hospital samples were detectable to 28 CFU/mL. Because the patient-derived and hospital-acquired cohorts (n = 10 and n = 6, respectively) were assembled for pilot analytical and matrix-tolerance characterization rather than for diagnostic-accuracy determination, these results establish detectability and matrix robustness in real clinical and environmental specimens rather than clinical diagnostic sensitivity or specificity, which will require a larger, prospectively enrolled cohort in future work. Sensor kinetics followed Langmuir-type adsorption, saturating within 16–25 min for target pathogens versus slower responses for non-target strains. Selectivity tests against six bacterial species showed discrimination, with cross-reactivity decreasing from related E. coli pathotypes to Enterobacteriaceae to Gram-positive species. Inter-pad variability stayed below 1.5 mV, supporting this compact, low-power platform for scalable, enrichment-free point-of-care pathogen detection. Full article

Anthracycline agents, principally doxorubicin and daunorubicin, are widely used in oncology yet carry a narrow therapeutic index and pronounced interindividual pharmacokinetic variability that exposes patients simultaneously to the risk of subtherapeutic dosing and cumulative cardiotoxicity. Conventional therapeutic drug monitoring (TDM) based on periodic venous sampling and offline high-performance liquid chromatography cannot resolve the sub-minute concentration dynamics that determine organ-specific drug exposure. Electrochemical aptamer-based (EAB) sensors couple nucleic-acid aptamers, self-assembled monolayers, and methylene blue redox reporters on gold microelectrodes to convert binding-induced conformational changes into real-time, reagent-free electrochemical signals. Recent advances in this field fall into five areas: signal interrogation strategies, from kinetic differential measurement to calibration-free Fourier-transform impedance spectroscopy (FFT-EIS); interface engineering including nanostructured electrodes and AI-guided aptamer design; in vivo multi-compartment pharmacokinetic monitoring and closed-loop feedback drug delivery; the mechanisms of in vivo signal drift alongside antifouling countermeasures spanning hydrogel barriers, zwitterionic brushes, and xenonucleic acid backbone substitution; and FDA premarket pathways and clinical translation, including Premarket Approval requirements and the emerging Real-Time Clinical Trial (RTCT) framework. In live rodents, dual-compartment monitoring has resolved a reproducible 30–60 min plasma-to-ISF lag for doxorubicin at 12 s temporal resolution; calibration-free FFT-EIS interrogation achieves inter-animal coefficients of variation below 12% without individual pre-calibration; and xenonucleic acid backbone substitution has extended continuous in vivo operation to seven consecutive days. Unlike prior EAB reviews that survey general molecular targets or benchtop aptasensors, this review uniquely integrates anthracycline-specific in vivo pharmacokinetics, multi-compartment plasma–ISF monitoring, calibration-free interrogation, XNA-enabled long-term stability, and FDA/RTCT regulatory translation into a single clinical roadmap. Three gaps still separate rodent proof-of-concept work from chemotherapy patients: clinical-context validation, tumor microenvironment calibration, and anthracycline-specific XNA aptamer design. Full article

Sulfadimethoxine (SDM) is a sulfonamide antibiotic widely used in the aquaculture of aquatic organisms. Its excessive residues in animal-derived food products can cause irreversible harm to human health and the environment. Current primary detection methods for SDM, such as instrumental methods and Immunoassay techniques, demonstrate high sensitivity and accuracy. However, their industrial application is impeded by laborious sample pretreatment, reliance on specific equipment, and dependence on specially trained personnel. Therefore, there is an urgent need to develop a simple and rapid method for detecting SDM residues. In this study, we constructed a novel colorimetric sensing platform based on functional nucleic acids for SDM detection. This sensor incorporates a nucleic acid aptamer capable of specifically recognizing SDM, a G-quadruplex/Hemin complex with peroxidase-like catalytic activity, and a shielding sequence that suppresses catalytic activity while undergoing SDM-induced conformational changes. The colorimetric signal was generated using a 3,3′,5,5′-Tetramethylbenzidine (TMB) chromogenic substrate, and the sensor’s performance was evaluated via absorbance measurements with a microplate reader. After optimizing detection conditions, the sensor exhibited a linear response to SDM concentrations ranging from 0.155 to 3.10 ng/mL, with a detection limit of 0.0796 ng/mL. Furthermore, the sensor demonstrated excellent selectivity and achieved recoveries of 83.0% to 107% in spiked aquaculture water and fish samples, with coefficients of variation below 10.4%, confirming its superior practicality for real-world sample analysis. Full article

Gold nanoparticles (AuNPs) are widely used in aptasensors because of their high extinction coefficient and aggregation-dependent color differences. However, recent studies have indicated that nonspecific interactions between target molecules and AuNPs may dominate the detection signal rather than aptamer–target specific binding. This study systematically investigated the interactions between 13 aminoglycoside antibiotics and AuNPs. We found that all aminoglycoside antibiotics interacted strongly with AuNPs, considerably reducing their salt stability. Furthermore, methoxy polyethylene glycol thiol reversed AuNP aggregation induced by aminoglycoside antibiotics, indicating that it occurs at the secondary minimum. Using density functional theory, we analyzed the molecular structures and charge distribution characteristics of the aminoglycoside antibiotics, elucidating that they replace citrate ions on AuNP surfaces via a ligand exchange mechanism, thereby inducing aggregation. Additionally, both aptamer targets and complementary DNA struggled to desorb the aptamer (KAN6-1) from the AuNP surfaces. Our study demonstrates that the label-free colorimetric assay based on aggregation of unmodified citrate–AuNPs is neither suitable for characterizing the binding affinity of aminoglycoside aptamers nor viable for constructing corresponding colorimetric sensors to detect this class of antibiotics. Thus, researchers should incorporate mechanistic verification and rigorous controls when employing this system to ensure reliable results. Full article

The presence of aflatoxin B1 (AFB1) is ubiquitous in the environment, and it is considered one of the most powerful natural carcinogenic substances. In this study, a highly sensitive electrochemical aptasensor was designed to detect aflatoxin B1 (AFB1) in peanuts. Iron–cobalt-doped magnetic carbon (Fe-Co/NPC) was used to enhance the conductivity of the electrode and catalytic performance, providing an increased specific surface area. Gold nanoparticles (AuNPs) were used to immobilize an aptamer. And cDNA-polyacrylic acid (cDNA-PAA) nanogels served as a high-density carrier for cDNA and an active signal amplification unit, significantly increasing the charge transfer resistance (Rct) through steric hindrance and electrostatic repulsion. Unlike traditional aptasensors that relied on passive blocking agents, we designed a competitive displacement mechanism. AFB1 competed with cDNA-PAA during detection in order to bind to the aptamer, which resulted in the removal of the non-conductive complex and a substantial increase in the electrochemical signal. Under the optimal conditions, the aptasensor had a linear response range of 1–1000 ng/L and a limit of detection (LOD) of 0.3 ng/L. It displayed high specificity, reproducibility, and stability. In spiked peanut samples, the recoveries ranged from 98.04% to 100.86%. Due to its sensitivity and reliability, this aptasensor has a great determination of AFB1 in food safety applications. Full article

The accurate and sensitive detection of toxin contamination remains a pressing challenge for food safety, environmental integrity, and public health, because conventional analytical methods suffer from high costs, poor field stability, and inadequate sensitivity for trace-level emerging contaminants. In this review, we provide a comprehensive overview of biosensor technologies for toxin detection, with a dedicated focus on nucleic acid aptamers and SELEX (Systematic Evolution of Ligands by Exponential Enrichment) technology. We systematically categorize nine SELEX variants developed for toxin detection, covering target-immobilized, library-immobilized, non-immobilized, cell-based, and high-throughput platforms, with an emphasis on their selection principles, applicability, and limitations. This review discusses computationally assisted aptamer discovery (e.g., AI-based sequence generation and molecular docking) as well as experimental post-SELEX optimization strategies such as cyclization, multivalent assembly, and structure-switching design. We then discuss key challenges and future perspectives, highlighting the shift from method-oriented to demand-oriented aptamer development through integrated SELEX strategies and AI-assisted design. Overall, this review covers mainstream SELEX technologies, aptamer selection, computational design, experimental optimization, and sensor integration to serve as a reference for next-generation toxin detection applications. Full article

Neuropeptide Y (NPY) is a stress-modulating neuropeptide and a promising biomarker for non-invasive assessment. Herein, a sensitive electrochemical aptasensor was developed on reduced graphene oxide/gold nanoparticle (rGO/AuNP)-modified screen-printed electrodes for selective NPY detection. A methylene blue (MB)-labeled NPY-specific aptamer was immobilized on the electrode surface through Au–S chemistry, and square-wave voltammetry (SWV) was used for signal readout. The rGO/AuNP-modified interface provided high conductivity and a large effective surface area, facilitating electron transfer and probe immobilization. Under optimized conditions, the aptasensor exhibited a linear detection range of 10–10,000 pg mL⁻¹ in PBS with a low detection limit of 1.17 pg mL⁻¹ and good linearity (R² = 0.991). In addition, the sensor showed satisfactory selectivity, reproducibility, and mechanical stability. Recovery tests in artificial sweat yielded recoveries of 91.8–107.8% with relative standard deviations below 5%, demonstrating good analytical accuracy in complex matrices. Combined with an agarose-hydrogel-assisted sampling interface and a reverse-iontophoresis-compatible wearable platform, this low-cost and facile sensing strategy provides a portable proof-of-concept approach for NPY analysis in artificial sweat and shows potential for future wearable-oriented biofluid monitoring. Full article

Cortisol, as a crucial biomarker reflecting psychological stress and physiological status, requires rapid and sensitive detection for health assessment and disease diagnosis. Conventional methods are time-consuming, operationally complex, and costly, limiting their use for point-of-care testing. This study reports a flexible, aptamer-based capacitive biosensor that exploits alternating current electrokinetics for ultrafast detection of cortisol in small-volume samples. Aptamers are immobilized via Au-S self-assembly on gold interdigitated electrodes on a PET substrate, and ACEK-induced fluid motion and dielectrophoresis rapidly enrich cortisol at the electrode interface, producing measurable interfacial capacitance changes ΔC/C₀. The experimental results demonstrate that the sensor achieves a detection limit of 0.337 ng/mL in artificial sweat, with a response time within 1 min and a good linear response across the concentration range of 1 to 1000 ng/mL. Requiring only 10 μL of sample, the sensor exhibits good repeatability, specificity, and interference resistance, making it suitable for rapid cortisol level detection. To enhance detection stability, this study designed and integrated a microfluidic chip, enabling efficient sample delivery and stable detection. The system demonstrates strong interference resistance, revealing potential applications in health management and disease monitoring. Full article

The rapid and sensitive quantification of antibiotic residues in aquatic animals is crucial for ensuring food safety and protecting public health. Electrochemical (bio)sensors show great potential in this field due to their quick response time, low cost, and ease of miniaturization. This paper presents a systematic review of advances in the electrochemical detection of eight classes of antibiotics: fluoroquinolones, sulfonamides, amphenicols, tetracyclines, nitrofurans, macrolides, aminoglycosides, and β-lactams in aquatic animal samples. It covers four types of sensors: direct electrochemical sensors, immunosensors, aptasensors, and molecularly imprinted sensors. The review emphasizes the electrochemical behavior of the targets, interface design, recognition elements, signal amplification strategies, and validation using real samples. It also summarizes the sample pretreatment methods for different classes of antibiotics. Finally, the paper analyzes key challenges related to adaptability to complex matrices, consistency in sample preparation, and validation with real-world samples. Additionally, it proposes future directions for development in this field. Full article

Gold is considered the most widely used surface for the development of aptamer-based layers. However, its high cost, laborious surface-cleaning protocols, and susceptibility of receptor layers to degradation in complex samples, including biological fluids, enforce the search for alternative transducers. One solution is the application of carbon materials, which are inexpensive and allow for the use of a wide potential range when electrochemical measurements are performed. Herein, we present studies on the elaboration of aptamer receptor layers formed on carbon macroelectrodes. To achieve this, a one-step procedure for aptamer molecules containing a pyrene or anthracene group at the 5′ end was used, with immobilization via adsorption facilitated by Π–Π interactions between the anchor group and the carbon surface. It was evidenced that using anthracene-modified aptamer and sodium anthraquinone-2-sulfonic acid (AQMS) redox indicator enabled the detection of a model analyte–vancomycin below the millimolar concentration range. It was also revealed that vancomycin can be successfully detected in serum samples, and the aptasensor exhibits good selectivity towards vancomycin. The latter was observed by comparison of responses in PBS containing solely vancomycin and a solution spiked with vancomycin and a mixture of antibiotics. Full article

We designed a label-free fluorescent aptasensor assisted by exonuclease III (Exo III) for sensitive insulin (Ins) detection. The method has high sensitivity, anti-interference properties and repeatability. Additionally, the label-free fluorescent aptasensor assisted by Exo III used to detect Ins has not been reported on yet. In this study, we connected a modified DNA sequence to the 5′ end of an aptamer, modifying it into a hairpin structure and exposing 11 nucleotides at the 3′ end containing the base adenine (A). The A was substituted with base 2-aminopurine (2AP) to provide a label-free stable hairpin fluorescent probe (2AP-hairpin probe). This strategy took advantage of the high binding affinity of the Ins aptamer and the susceptibility of 2AP to the local base stacking environment. When Ins is added to the detection system, the 2AP-hairpin probe binds to Ins, adopts a folded state, and blocks Exo III’s access to the binding site for cutting DNA. 2AP cannot be released, and the fluorescence of the 2AP-hairpin probe/cDNA/Ins/Exo III system cannot be restored. Ins detection is achieved by comparing changes in the fluorescent intensity before and after adding Ins to the detection system. The detection limit of the aptasensor is as low as 1.62 nM with a linear range of 3–130 nM. Furthermore, it is able to selectively and directly detect Ins in biological fluids, demonstrating significant clinical application value and research significance. Full article