Search Results (87)

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

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

Salmonella enteritidis (SE) is recognized as a primary etiological agent of foodborne infection and food poisoning. Selective and sensitive determination of SE in animal-derived products is of great importance for ensuring safety in the food industry. Here, we report a highly sensitive and specific competition assay for detecting SE in eggs without interference from background fluorescence, by using persistent luminescent nanoparticles (PLNPs) as luminescent probes in combination with aptamer recognition and magnetic separation. Initially, the SE-specific aptamer (SEapt), as previously reported, was conjugated onto the surface of Fe₃O₄ magnetic nanoparticles to serve as both the recognition and separation unit. Meanwhile, the ZnGa₂O₄:Cr (PLNPs) were functionalized with the aptamer-complementary DNA (cDNA), serving as the PL signal generator. The constructed PL aptasensor is composed of the aptamer-conjugated MNPs (MNPs-SEapt) and cDNA-functionalized PLNPs (PLNPs-cDNA), integrating the merits of the long-lasting luminescence of PLNPs, the magnetic separation ability of MNPs and the selectivity of the aptamer. This integration offers a promising approach for autofluorescence-free determination of SE in food samples. The proposed aptasensor exhibited excellent linearity in the range from 1.0 × 10²–1.0 × 10⁷ CFU mL⁻¹ with a limit of detection as low as 32 CFU mL⁻¹. The precision for 11 replicate determinations of 1.0 × 10³ CFU mL⁻¹ SE was 3.4% (relative standard deviation). The developed aptasensor achieved recoveries ranging from 98.8% to 102.8% for the determination of SE in the presence of common foodborne bacterial interferents. The method was successfully applied to the analysis of Salmonella genus in egg samples. In principle, the proposed platform may be adapted to other food matrices by substituting the target-specific aptamer, pending target-dependent optimization and validation. Full article

Pseudomonas aeruginosa is an important waterborne pathogen that is harmful to food safety and human health. Therefore, the detection of Pseudomonas aeruginosa has become an essential item in food sampling. This article constructs a fluorescent aptamer sensor based on Tb-MOFs, using Tb-MOFs as the fluorescence signal source, colloidal gold (AuNPs) as the signal conversion switch, and aptamers as the target recognition element, to establish a quantitative detection method for Pseudomonas aeruginosa. The constructed sensor exhibits a good linear relationship within the concentration range of Pseudomonas aeruginosa from 1 to 10⁶ CFU/mL, with a detection limit of 0.63 CFU/mL. Moreover, the sensor was also applied to the detection of Pseudomonas aeruginosa in actual samples of bottled drinking water and orange juice. The fluorescent aptasensor based on Tb-MOFs provides a rapid and sensitive new sensing method for the detection of Pseudomonas aeruginosa in food. Full article

Fumonisin B1 (FB1) is a secondary metabolite produced by Fusarium species, exhibiting strong toxicity and classified as a Group 2B carcinogen by the International Agency for Research on Cancer. It poses a significant threat to both human and animal health. Therefore, developing a simple and reliable method for FB1 detection and analysis is imperative. In this study, a biosensor based on nucleic acid aptamers was developed, utilizing plasma-modified graphene oxide (mGO) as a fluorescence quencher for FB1 detection. This system leverages the interaction between mGO and FAM-APT (a nucleic acid aptamer labeled with 5-carboxyfluorescein, FAM), achieving fluorescence quenching through fluorescence resonance energy transfer (FRET) under excitation at 490 nm and emission at 520 nm. In the presence of FB1, FAM-APT specifically binds to FB1 and dissociates from the mGO surface, resulting in fluorescence recovery. Quantitative detection of FB1 was achieved by measuring the differential fluorescence intensity. The biosensor demonstrated excellent linearity over a concentration range of 10 to 5 × 10⁶ ng/L, with a detection limit (LOD) as low as 0.16 μg/L. Additionally, the sensor exhibited high specificity for FB1 among six common mycotoxins. In practical sample analysis, recovery rates ranged from 95.8% to 104.7% in corn samples and from 89.3% to 94.5% in rice samples. This aptamer-based biosensor features a simple structure, high sensitivity, and a wide detection range, providing important technical support for advancing mycotoxin research. Full article

In recent years, harmful algal blooms have led to frequent occurrences of shellfish toxin contamination, posing a significant threat to the safety of aquatic products and public health. As a potent neurotoxin, domoic acid (DA) can accumulate in shellfish, highlighting the urgent need for rapid and highly sensitive detection methods. In this study, we developed a fluorescent aptasensor based on a dual-signal amplification system by combining G-quadruplex (G4) dimers with multi-walled carbon nanotubes (CNTs). The sensor is designed with a hairpin-structured aptamer as the recognition probe, where short multi-walled CNTs serve as both a fluorescence quencher and platform, and G4 dimers are incorporated into the sensing interface to enhance signal output. In the absence of the target, the hairpin-structured aptamer remains closed, keeping the fluorescence signal “off”. Upon binding to DA, the aptamer undergoes a specific conformational change that exposes the G4-dimer sequence. The exposed sequence then binds to thioflavin T (ThT), which in turn generates a greatly enhanced fluorescence signal, leading to a substantial fluorescence enhancement and completing the second stage of the cascade amplification. Under optimal conditions, the constructed sensor achieves rapid detection of DA within 5 min, with a low detection limit of 1.1 ng/mL. This work presents a valuable tool for the rapid and sensitive detection of DA in shellfish, with promising applications in marine environmental monitoring and food safety regulation. Full article

The presence of hazardous substances in food poses a serious threat to our health. It is important to develop fast, convenient, and inexpensive assays for on-site sensitive analysis of various hazards in food. With the emergence and popularization of aptamers and biosensors, aptasensors have gradually become one of the most important detection techniques for substances such as nucleic acids and small molecules. This paper reviews the recent research progress in the field of aptasensor based on different technologies (such as electrochemistry, fluorescence, colorimetry, among others) for the rapid detection of hazards (such as foodborne pathogens, mycotoxins, pesticides, among others) in food. In addition, the current challenges of different aptasensors are described for the readers, and the future direction of aptasensors is envisioned by comparing the different technologies in order to develop a more suitable aptasensor. This review will not only promote the advancement of aptasensors but also their practical application in daily life to safeguard human health and food safety. Full article

Despite the substantial human health risks posed by ochratoxin A (OTA), a potent mycotoxin, simple, low-cost methods for its sensitive and selective detection in foods are lacking. To address this gap, we herein developed a label-free OTA aptasensor based on deoxyribonucleic acid (DNA)-scaffolded silver nanoclusters (AgNCs) with an intense red fluorescence. As the DNA template fragment used for AgNC fabrication was derived from the complementary sequence of the OTA aptamer (Apt-OTA), Apt-OTA complexed the AgNCs in the absence of OTA, quenching their fluorescence. OTA inhibited this quenching by strongly binding Apt-OTA and thus precluding its binding to the AgNCs. The OTA aptasensor exhibited a high selectivity and low detection limit (0.38 ng/mL), eliminating the need for expensive reagents, complicated pre-treatments, and advanced equipment, and was successfully used to quantify mycotoxins in food under real-life conditions, thus holding promise for mycotoxin control. Full article

The combination of rGO-FETs (reduced Graphene Oxide Field-Effect Transistors) and DNA-oligonucleotide aptamers to sense analytes has been shown to be a promising technological approach, achieving high sensitivity and selectivity. With human adenovirus type 5 (HAdV-5) particles as the target, we here demonstrate the application of the aptamer/FET combination for detection of this medically and biotechnologically relevant viral vector. A focused anti-HAdV-5 aptamer library was evolved in a nine-round SELEX process, allowing for the specific fluorescent labeling of HAdV-5 and related subtypes. Moreover, this library was already sufficient to serve as the binding entity on a gFET sensor for sensitive quantification of the virus particles. Adenoviruses have been widely used as gene delivery vectors for gene therapy and genetic vaccination. The use of adenoviral vectors within the vaccination campaign against COVID-19 emphasized the need for robust biotechnological production processes, which additionally require sensitive product formation monitoring. We believe that these type of gFET-based aptasensors can serve as the technological monitoring basis in virus production processes in the near future. Full article

Antibiotics can accumulate in the body via ingestion, presenting serious health and safety risks to humans, and have garnered extensive international attention in recent years. Meanwhile, aptamers have been applied in the detection of antibiotics, mainly because of their good stability, high specificity, easy synthesis, and low cost. Among various kinds of aptasensors, fluorescent dye-based or nanomaterial-based fluorescent aptasensors serve as highly efficient tools for the rapid quantification of antibiotics owing to their remarkable sensitivity, specificity, and selectivity. In addition, some novel techniques such as aptamer tailoring, signal amplification, and artificial intelligence for aptasensors are also presented. This paper provides a detailed and comprehensive review of fluorescent aptasensors for antibiotic detection. Moreover, it pinpoints the challenges encountered during the development of the aforesaid fluorescent aptasensors and puts forward future research directions. Full article

Aflatoxin B₁ (AFB₁) exhibits high toxicity and has the potential to induce cancer, deformities, and mutations. It is therefore highly desirable that sensitive and straightforward methods for detecting AFB₁ be developed. In this study, due to the high specific adsorption capacity of AFB₁ aptamers, we applied a sensing strategy based on quantum dots (QDs) and carboxyl-functionalized graphene oxide (FGO) to construct a simple fluorescence quenching platform. FGO and CdTe QDs modified with AFB₁ aptamers cause a FRET effect that produces CdTe QDs with yellow-green fluorescence quenching. When AFB₁ is present, aptamers form complexes with it and CdTe QDs leave the quenching platform, resulting in fluorescence recovery. In this study, we used a fluorescence aptasensor with a wide detection range of 0.05 to 150 ng/mL and a low limit of detection (LOD) of 8.2 pg/mL. The average recoveries of AFB₁ in peanut and pure milk samples ranged from 94.5% to 107.0%. The aptasensor also exhibited the advantages of simple operation, low cost, and good stability. The sensing strategy reported here can thus serve as a potential candidate for the rapid detection of AFB_1. Full article

Point-of-care (POC) antigen detection plays a crucial role in curbing the spread of viruses. Paper-based fluorescence aptasensors are expected to offer a low-cost tool to meet the needs of decentralized POC diagnosis. Herein, we report on a fluorescent paper-based sensing system for detecting the SARS-CoV-2 spike protein. The sensing system was constructed by loading multi-layer Nb₂C MXene nano-quenchers and carbon-dot-labeled aptamer (G-CDs@Apt) probes onto a mixed cellulose ester (MCE) paper substrate. On the Nb₂C MXene/G-CDs@Apt sensing paper, abundant G-CDs@Apt probes were attached to the multilayer MXene nano-quenchers and kept in a fluorescence-off state, while recognition of the target detached the G-CDs@Apt probes formed the nano--quenchers, resulting in fluorescence recovery of the sensing paper. The developed paper-based sensor performed well in the one-step detection of the SARS-CoV-2 S1 protein with a detection limit of 0.067 ng/mL (0.335 pg/test). The assay exhibited good selectivity and anti-interference in the detection of the SARS-CoV-2 S1 protein in artificial saliva. Moreover, the paper-based aptasensor was successfully used to detect the SARS-CoV-2 S1 protein in actual environmental samples with recoveries of 90.87–100.55% and relative standard deviations of 1.52–3.41%. The proposed technology provides a cost-effective alternative to traditional antibody test strips for a wide range of POC diagnostic applications. Full article