Search

After optimizing the original aptamer sequence by truncation strategy, a magnetic separation-assisted DNAzyme-driven 3D DNA walker fluorescent aptasensor was developed for detecting the food-borne pathogen Cronobacter species. Iron oxide magnetic nanoparticles (MNPs) modified with a hybrid of truncated aptamer probe and DNAzyme strand (AP-E1) denoted as MNPs@AP-E1, were employed as capture probes. Simultaneously, a DNAzyme-driven 3D-DNA walker was utilized as the signal amplification element. The substrate strand (Sub) was conjugated with the gold nanoparticles (AuNPs), resulting in the formation of AuNPs@Sub, which served as a 3D walking track. In the presence of the target bacteria and Mg2+, E1-DNAzyme was activated and moved along AuNPs@Sub, continuously releasing the signal probe. Under optimized conditions, a strong linear correlation was observed for Cronobacter sakazakii (C. sakazakii) in the concentration range 101 to 106 CFU mL−1, with a low detection limit of 2 CFU mL−1. The fluorescence signal responses for different Cronobacter species exhibited insignificant differences, with a relative standard deviation of 3.6%. Moreover, the aptasensor was successfully applied to determine C. sakazakii in real samples with recoveries of 92.86%—108.33%. Therefore, the novel method could be a good candidate for ultra-sensitive and selective detection of Cronobacter species without complex manipulation. [ABSTRACT FROM AUTHOR]

A novel ternary Y-DNA walker amplification strategy designed fluorescence aptasensor based on Au@SiO2@Fe3O4 nanomaterials for ultrasensitive and specific ochratoxin A detection in food samples is presented. Au@SiO2@Fe3O4 nanomaterials provide the loading platform as well as separation and recovery properties for the ternary Y-DNA walker. The ternary Y-DNA walker is designed to be driven by Nb.BbvCI cleaving a large number of FAM probes to achieve signal amplification. Since Ochratoxin A (OTA) can bind to the constituent aptamer in the ternary Y-DNA walker, adding OTA will destroy the structure of the ternary Y-DNA walker, thereby inhibiting the driving process of the walker. After optimization of various parameters, a standard curve was obtained from 100 to 0.05 ng·mL−1 of OTA with the limit of determination of 0.027 ng·mL−1. The spiked recovery of peanut samples by this method was 82.00–93.30%, and the aptasensor showed excellent specificity and long-term stability. This simple, robust, and scalable oligonucleotide chain-based ternary Y-DNA walker can provide a general signal amplification strategy for trace analysis. [ABSTRACT FROM AUTHOR]

Dynamic DNA nanodevices have gained tremendous attention due to their extraordinary inherent functionality and advantages, however, dynamic DNA nanodevices-based biosensors are still challenging due to their high reliance on proteases and limited amplification capabilities. Herein, exploiting bispecific aptamer as initiators for the first time, we developed a three-dimensional (3D) DNA nanomotor biosensor powered by DNAzyme and entropy-driven circuit for sensitive and specific detection of lysozyme, in which walking and rolling strategies are efficiently integrated to achieve excellent signal amplification capability. Benefiting from the high selectivity of bispecific aptamer, the 3D DNA nanomotor biosensor can respond to lysozyme with high specificity and operate at high speed to release signals. The whole process is independent of protease, avoiding the influence of adverse environment on the operation stability. Under optimal conditions, it can achieve a limit of detection as low as 0.01 pg/mL with an excellent linear range of 0.05 pg/mL–500 ng/mL for lysozyme. Furthermore, the proposed strategy revealed high accuracy in the analysis of real samples, indicating a great potential for the application of nanomotor biosensors to the detection of non-nucleic acid targets. [ABSTRACT FROM AUTHOR]

Aflatoxin B 1 (AFB 1) is an extremely toxic food contaminant that has serious effects on human health. In published aptamer-based lateral flow chromatography test strips, the detection results are mostly inversely proportional to the concentration of AFB 1 , which is a serious violation of intuition. An aptamer sensor based on the "turn on" mode for AFB 1 detection has been reported in this paper. In this paper, we use gold nanoparticles (AuNPs) to present colorimetric signals and link capture sequences (SH-poly A-cDNA) to design AuNPs@SH-poly A-cDNA nanoprobes. The test strip relies on AFB 1 and AuNPs@SH-poly A-cDNA competing aptamers for rapid detection of AFB 1. In the absence of AFB 1 , the aptamer binds to AuNPs@SH-poly A-cDNA, preventing the cDNA from binding to the complementary fragment of the test line (DNA T), resulting in the disappearance of the red signal. However, in the presence of AFB 1 , the aptamer binds to AFB 1 , allowing some AuNPs@SH-poly A-cDNA not bound to the aptamer to be captured by DNA T , leading to the generation of a red signal. Regardless of the presence or absence of AFB 1 , the poly-A fragment of AuNPs@SH-poly A-cDNA consistently binds to the complementary sequence of the control line (DNA C) and presents a red signal. The detection results are proportional to the concentration of AFB 1 , which is in line with human intuitions. The development of this test strip provides a novel design idea for the detection of small molecules such as mycotoxins. • Innovative application of aptamer in test strips for the detection of AFB 1. • The first "turn on" mode for AFB 1 detection using AuNPs as signal labels. • "Turn on" mode meets the intuitive impression and has comparable detection limits. • The aptamer and complementary sequences on detection results was investigated. [ABSTRACT FROM AUTHOR]

To identify the target of an adipose specific aptamer adipo-8, predict the potential interaction between adipo-8 and its target, and investigate lipid-lowering effect of adipo-8 in vitro and in vivo. Distinct membranous protein of 3T3-L1 adipocyte pulled-down by adipo-8 was mass-spectrometry analyzed as target candidate(s), and affinity of adipo-8 to target protein-silent adipocyte was detected to validate it. Interaction between adipo-8 and target was predicted by bioinformatic analysis, further confirmed by aptamer truncation and competitive binding assay. To investigate lipid-lowering effect of adipo-8 and mechanism behind, 250 nmol/L adipo-8 or library was incubated with 3T3-L1 adipocyte or target-protein-silent adipocyte for 24 h, and 0.01 μg/g/day adipo-8 or library was administrated to high-fat-fed male mice for 21 days. APMAP (Adipocyte Plasma Membrane Associated Protein) was identified as adipo-8 target, and adipo-8 affinity to adipocytes was in proportional to APMAP expression. Docking model between the stem-loop structure of adipo-8 and APMAP were predicted that adipo-8 was likely to interact with APMAP at its amino-acid 275–411 sequence. Moreover, adipo-8 could ameliorate fat deposition through interaction with APMAP in vitro , and administration of adipo-8 in high-fat-diet fed mice resulted in body weight loss and blood triglyceride decrease without liver or renal dysfunction. Adipo-8 could recognize APMAP specifically and interact with its targets to ameliorate fat deposition in vitro and in vivo. Aptamer adipo-8 has potential to act as an effective and safe targeted drug for obesity and obesity related diseases. [ABSTRACT FROM AUTHOR]

Food safety has become the focus of social attention with the rapid development of economic society and the improvement of living standards. Food detection plays an important role in food safety. In recent years, efficient and rapid detection technology is one of the conventional means of food safety screening, effectively preventing the occurrence of food safety events. Because of the advantages of short detection time, simple operation, high sensitivity, and economy, lateral flow assay (LFA) provides an ideal platform for on-site detection. The key to developing a lateral-flow biosensor is to identify biorecognition molecules, design strategies, and labels according to the target. Aptamers have comparable specificity and affinity to antibodies, making them a viable alternative. Nanoparticles can not only be used as labels for qualitative and quantitative detection, but also their rigidity can stabilize the spatial structure of aptamers, ensuring maintenance of their affinity and specificity in complex matrices. A review of the field finds that the application of nanoparticles is mainly focused on GNPs. Aptamer-based dipstick detection still lags behind antibody-based dipstick detection in actual field detection. It is conceivable that the application of aptamer and nanoparticle combination in LFA has both challenges and opportunities. In this paper, the above content is briefly introduced and reviewed in order to provide help for the development of LFA based on aptamer-functionalized nanoparticles. [ABSTRACT FROM AUTHOR]

In this work, the aptamer of melamine was truncated and mutated. Based on isothermal titration calorimetry, circular dichroism and molecular dynamics, the thermodynamic information, structural changes and binding pocket of the truncated aptamer SJs32 with 32 bases to melamine were systematically studied. Meanwhile, a novel aptasensor coupled with CRISPR/Cas14a1 and Exo III was developed for melamine detection. SJs32 was first hybridized with the complementary DNA (cDNA) to form SJs32-cDNA. In the presence of melamine, SJs32 recognized melamine to form SJs32-melamine and performed structural transformation, which resulted in the releasing of cDNA into the solution. Exo III digested the SJs32-melamine and the released melamine led to the dissociation of more cDNA from SJs32-cDNA complex. Finally, the combination of cDNA and sgRNA activated the trans-cleavage activity of Cas14a1. According to the change of fluorescence intensity, the sensitive and rapid detection of melamine was realized with the linear detection range of 4 nmol/L-1 µmol/L. The developed strategy broadened the application of melamine aptamer in food safety and provided a new insight for the development of CRISPR/Cas14a1 aptasensor. • The binding mechanism of aptamer to melamine was explored. • The vital bases of aptamer in recognition was confirmed by molecular dynamics. • The introduction of Exo III improved the sensitivity of CRISPR/Cas14a1 detection platform. • The combination of aptamer, CRISPR/Cas14a1 and Exo III guaranteed the selectivity of detection. [ABSTRACT FROM AUTHOR]

Aflatoxin B 1 (AFB 1) is a typical food contaminant. A truncated DNA aptamer of AFB 1 was reported by our team in previous work. However, the recognition mechanism between aptamer and AFB 1 was lacking, which was crucial for the design of related aptasensor. Herein, the binding of aptamer to AFB 1 was systematically studied and found that it was an exothermic process and the conformation of aptamer changed during the recognition process. Loop bases in the secondary structure of aptamer formed a special binding pocket to recognize AFB 1. Van der Waals and electrostatic interaction were the main driving forces. By blocking the stem bases guided by the structural investigation, a rationally designed CRISPR/Cas12a-Exo III aptasensor for AFB 1 detection was constructed, and the sensitivity was improved by target recycling. Under optimal conditions, the linear detection range for AFB 1 was 0.01–20 ng/mL, and AFB 1 was accurately determined in corn and wheat samples. This work laid a theoretical foundation for the design of AFB 1 aptasensor, and the developed detection model came up with new ideas for the development of CRISPR/Cas12a-based aptasensor. [ABSTRACT FROM AUTHOR]

Co-contamination of multiple mycotoxins produces synergistic toxic effects, leading to more serious hazards. Therefore, the simple, rapid and accurate simultaneous detection of multiple mycotoxins is crucial. Herein, a three-channel aptamer-based lateral flow assay (Apt-LFA) was established for the detection of aflatoxin M 1 (AFM 1), aflatoxin B 1 (AFB 1) and ochratoxin A (OTA). The multi-channel Apt-LFA utilized gold‑iridium nanozyme to catalyze the chromogenic substrate, which effectively achieved signal amplification. Moreover, the positions and lengths of the complementary sequences were screened by changes in fluorescence intensity. After grayscale analysis, the semi-quantitative results showed that the detection limits of AFM 1 , AFB 1 and OTA were 0.39 ng/mL, 0.36 ng/mL and 0.82 ng/mL. The recoveries of the multiplexed competitive sensors in complex matrices of real samples were 93.33%–97.01%, 95.72%–102.67%, and 106.88%–109.33%, respectively. In conclusion, the assembly principle of the three-channel Apt-LFA is simple, which can provide a new idea for the simultaneous detection of small molecule targets. • Simultaneous detection of mycotoxins by three-channel Apt-LFA without interference. • Peroxidase activity of nanozymes effectively improved detection sensitivity. • "Turn on" mode met the intuitive impression and improved detection performance. [ABSTRACT FROM AUTHOR]

Patulin (PAT) is a mycotoxin-produced secondary metabolite that can contaminate foods, causing toxic effects on animal and human health. Therefore, for the first time, we have constructed a "turn-on" dual-mode aptamer sensor for PAT using oleic acid-coated upconversion nanomaterials (OA-UCNPs) and G-Quadruplex-hemin DNAzyme (G4-DNAzyme) as fluorescent and colorimetry probes. The sensor employs aptamers binding to PAT as recognition elements for specific molecule detection. Mxene-Au can be used as a biological inducer to assist OA-UCNPs in controlling fluorescence intensity. In addition, colorimetric signal amplification was performed using the trivalent G4-DNAzyme to increase detection sensitivity and reduce false positives. Under optimal conditions, the dual-mode aptasensor has a detection limit of 5.3 pg mL−1 in fluorescence and 2.4 pg mL−1 in colorimetric methods, respectively, with the wider linear range and limit of detection (LOD) of the colorimetric assay. The combination aptasensor can detect PAT with high sensitivity and high specificity and has broad application prospects in the field of food safety detection. [Display omitted] • A dual-mode aptasensor was developed for patulin (PAT). • The UCNPs and Mxene-Au provides the ideal platform for biosensing applications. • The affinity of PAT for the aptamer ensures the accuracy and selectivity of the assay. • The superior catalytic ability of G4-DNAzyme greatly improved the colorimetric sensitivity (2.4 pg mL−1). [ABSTRACT FROM AUTHOR]

In recent years, the conventional preparation of silver nanoclusters (AgNCs) has attracted much attention due to their ultra-small size, tunable fluorescence, easy-to-engineer, as well as biocompatible material. Moreover, its great affinity towards cytosine bases on single-stranded DNA has led to the construction of biosensors, especially aptamers, for a broad variety of applications in food safety and environmental protection. In past years, numerous researchers paid attention to the construction of AgNCs aptasensor. Therefore, this review will be an effort to summarize the synthetic strategy along with the influences of factors on synthesis, categorize the sensing mechanism of aptamer-functionalized AgNCs biosensors, as well as their specific applications in food safety detection including heavy metal, toxin, and foodborne pathogenic bacteria. Furthermore, a brief conclusion and outlook regarding the prospects and challenges of their applications in food safety were drawn in line with the developments in DNA-AgNCs. [Display omitted] • Concise introduction of fluorescent DNA-AgNCs in food safety. • Brief classification of the detection mechanism and signal amplification strategy. • DNA-AgNCs advance food safety monitoring with versatile and potent sensing capabilities. • The summarization and outlook of way forward strategies, challenges and future prospect. [ABSTRACT FROM AUTHOR]

DNA nanostructures, with their fascinating luminescent and detecting capabilities, provide a basis that can accommodate a wide range of applications. The unique electronic configurations, and physical and chemical properties of aptamer-assembled gold nanoclusters (apt-AuNCs) as a novel type of fluorophore have gradually piqued the interest of the scientific community. Bending DNA sequences and other templates/legends as a stabilizing agent with Au metal has produced an abundance of biosensors, along with catalytic and imaging properties. This review article summarizes the synthesis, conjugation tactics, advantages, and sensing mechanisms of AuNCs aptasensor after providing a brief introduction to the topic. Moreover, the application of DNA/aptamer functionalization has been briefly discussed in the fields of food safety and quality, catalysis, clinical diagnosis, cancer cell bioimaging, detection of cancer cell indicators, and therapy. We also concluded the current obstacles and made recommendations about the future prospects of AuNCs for fundamental research and applications in line with the developments in DNA/aptamer-AuNCs. [Display omitted] • This review briefly concise the aptamer functionalized AuNCs sensor with respective to their sensing principal. • The synthesis, conjugation chemistry, sensing mechanism and advantages to explore its widespread application. • Aptamer-AuNCs stratagem as an emerging nanoprobe in food safety, catalysis, clinical diagnosis and cancer cell indication. • The summarization of aptamer-AuNCs, challenges and future prospects. [ABSTRACT FROM AUTHOR]

Patulin (PAT) and ochratoxin A (OTA) are the two main mycotoxins present in apples. Herein, a sensitive aptasensor for simultaneous detection of PAT and ochratoxin OTA was developed. Dual-color gold nanoclusters (AuNCs) with enhanced fluorescence properties were synthesized and employed as fluorescence amplifiers. Two separated fluorescence peaks at 650 nm and 530 nm were monitored simultaneously by employing single excitation (405 nm), corresponding to the aptamer probes of Cys@BSA-AuNCs-Apt PAT and Arg@ATT-AuNCs-Apt OTA , respectively. The fluorescent aptasensor demonstrated satisfying specificity, storage ability and accuracy. Under the optimal experimental conditions, the linear detection range for PAT and OTA was 0.10–50 ng/mL, with the limit of detection of 0.09 ng/mL and 0.06 ng/mL, respectively. Most importantly, practicability of the constructed aptasensor were confirmed by conducting the determination of PAT and OTA in apple juice sample, indicating the great potential of the aptasensor in practical detection applications. [Display omitted] • A simultaneous aptasensor for detecting PAT and OTA in apple juice was developed. • Sensitivity were enhanced by amino acid modification to gold nanoclusters. • Dual-color nanoclusters were used to modify aptamer probes. • The aptasensor was good in specificity, storage stability and reproducibility. [ABSTRACT FROM AUTHOR]

Capsaicin (CAP), a prominent indicator, has been identified for detecting the gutter oil in adulterated edible oils. In view of the limited availability of efficient and reliable methods for detecting gutter oil, the present study employed the Capture-SELEX technology, which utilizes a high-throughput sequencing (HTS) platform, to facilitate the precise tracking of screening rounds and facilitate the isolation of aptamers with specific affinity for CAP. Isothermal titration calorimetry (ITC) determined the highest affinity and K d value of 15.5 ± 4.69 nM for aptamer Cap-1. A colorimetric dual-mode aptasensor was designed for CAP detection based on graphene oxide (GO)@gold nanoparticles (AuNPs) composite. A high-sensitivity assay can be achieved using a Synergy™ H1 multimode zymography instrument and a smartphone. Under optimal conditions, the colorimetric dual-mode aptasensor has a detection range of 0.5 ∼ 120 ng mL−1 and a low limit of detection (LOD) of 0.14 ng mL−1. The quantitative recovery of the sensor for CAP in edible oil was 86.25∼98.12 %. Compared with the conventional single-mode aptasensor, the dual-mode aptasensor has independent signal conversion, which provides suitable detection solutions for different scenarios and improves detection accuracy and reliability. [Display omitted] • The first conventional SELEX-based aptamer Cap-1 that specifically binds capsaicin (CAP) was developed. • Monitor the enrichment rate of the aptamer during the screening process by high-throughput sequencing (HTS). • Design a colorimetric dual-mode aptasensor based on CAP-1 to detect CAP. • GO/ AuNPs form more stable suspensions with synergistic properties that maximize their functionality. • The dual-mode aptasensor detecting CAP has independent signal conversion, which improves accuracy and reliability. [ABSTRACT FROM AUTHOR]

Aptasensors being versatile sensing platforms presented higher sensitivity toward target detection. However, lacking theoretical basis of recognition between most targets and their corresponding aptamers has impeded their applications. Herein, we conducted a study to explore the binding mechanism of aptamer to kanamycin (Kana) and developed rapid fluorescent aptasensing methods. Based on the fluorescence polarization results, base mutations were performed at different sites of the aptamer. The key binding nucleotides of Kana was identified as T7, T8, C13 and A15 by using isothermal titration calorimetry (ITC). The Kmut3 (2.18 μM) with lower dissociation constants (Kd), one-third of the native aptamer (6.91 μM), was also obtained. In addition, the lower K+ concentration and temperature were found to be conducive to Kana binding. Circular dichroism (CD) results revealed that the binding of Kana can trigger the change of base stacking force and helix force. On the aforementioned basis, a fluorescent sensor was designed with the native aptamer and Kmut3 as recognition elements. The comparison results proved that the Kmut3 presented a 3 times lower limit of detection of 59 nM compared to the native aptamer (148 nM). Notably, this developed aptasensor can be finished in 45 min and was convenient to operate. (a) Fluorescence polarization to confirm possible binding regions; (b) Base mutations at different sites to confirm key binding nucleotides; (c) A rapid fluorescent aptasensor based on FRET. [Display omitted] • The direct binding nucleotides of aptamer of kanamycin were confirmed. • A mutant called Kmut3 that had better affinity than the native aptamer was obtained via base mutations. • Study of the conformational change of aptamers via circular dichroism. • A rapid and convenient fluorescent aptasensor that can be finished in an hour was developed. [ABSTRACT FROM AUTHOR]

Zearalenone (ZEN) is a kind of mycotoxin with estrogen-like effect. The presence of ZEN in cereals is potentially harmful to the health of humans. Herein, for the first time, the binding mechanism of ZEN aptamer with 19 bases (Z19) were systematically studied by molecular dynamics, circular dichroism and isothermal titration calorimetry. The binding driving forces, key bases of Z19 to ZEN, the conformational changes and thermodynamic information were originally found. On this basis, by employing the inherent rapid nature of fluorescence polarization and target recycling induced by Exo III, a novel fluorescence polarization aptasensor was constructed. The realized "add and measure" detection mode can be completed within one hour. Under the optimal conditions, the detection platform showed excellent analytical performance with a linear range of 0.01–100 ng/mL and a limit of detection as low as 0.004 ng/mL. Moreover, the practicability and reliability of the constructed strategy were confirmed with standard HPLC-MS method in corn and wheat samples. The established aptasensor with enhanced sensitivity broaden the application scope of fluorescence polarization technique, especially in detection targets of low molecular weight. • The zearalenone (ZEN) aptamer was first truncated to 19 bases. • The structure and vital bases of aptamer to ZEN were originally found. • Low molecular target was detected by fluorescence polarization technique. • The developed fluorescence polarization aptasensor was reliable and sensitive. [ABSTRACT FROM AUTHOR]

A DNA tweezers fluorescence aptasensor based on split aptamer assisted-magnetic nanoparticles (MNPs) and magnetic separation was established for the detection of Enrofloxacin (ENR). The DNA tweezers' fluorescence aptasensor consists of two arms with fluorophores (FAM) and quenchers (BHQ 1) connected at both ends. Meanwhile, the high fluorescence signal can be generated with FAM and BHQ 1 being spatially separated. Split aptamer 1 (SPA 1) of ENR was annealed and incubated with avidin-coated MNPs. ENR and split aptamer 2 (SPA 2) were added to form a sandwich structure with two split aptamer strands (MNPS-SPA 1 /ENR/SPA 2). After magnetic separation, the supernatant did not interact with DNA tweezers, which made DNA tweezers a "turn-on" aptasensor to enhance the fluorescence signal. In the absence of ENR, SPA 2 was free in the supernatant to dramatically quench the fluorescence which made DNA tweezers a "turn-off" aptasensor. The linear range of ENR detection was 0.01–100 ng/mL with a limit of detection of 0.008 ng/mL. The prepared DNA tweezers fluorescence aptasensors were applied to detect ENR in spiked milk samples, which showed good recoveries between 90.27% and 106.62%. In addition, the present method showed great potential for the target, employing a split aptamer detection platform in practical application. • A novel fluorescence aptasensor assay for Enrofloxacin (ENR) detection was established. • The sandwich structure is formed by specific target recognition of split aptamer to achieve sensitive detection. • The "turn-on/turn-off" structure of DNA tweezers offers significant fluorescence signals. [ABSTRACT FROM AUTHOR]

Aptamers, as recognition molecules, play an important role in the field of detection and control. Screening is the key procedure to obtain aptamers. Improving the aptamer screening rate involves two aspects, one is to shorten the cycle time required for the screening process, and the other is to obtain high-performance aptamers through screening. This review summarizes approaches to aptamer screening constructed to improve aptamer screening rates, starting from the four most basic steps that make up a SELEX process round. The selection of appropriate screening methods for different targets and the provision of sequencing and monitoring tools for the screening process can not only help to reduce the required screening cycle, but also obtain high-performance aptamers through screening. Shortening the screening cycle time can also be achieved by pre-reducing the library and applying high separation efficiency techniques to the SELEX segment. High-performance aptamers are aptamers that have high affinity and specificity while maintaining their structural stability in the actual assay environment. The complexity of the aptamer structure affects its binding affinity and specificity to the target. Therefore, it is important to obtain high-performance aptamers for the design of the library and the complexity of the screening system. Methods based on improving the screening rate of key steps. [Display omitted] • Aptamer screening methods based on improving the screening rate of key steps have been summarized. • The methods of pre-reduction of library capacity and design of library have been discussed. • Different separation techniques affecting the screening cycle have been summarized. • The importance of monitoring techniques and the complexity of screening systems have been discussed. • This review will facilitate the development of novel and efficient aptamer screening methods. [ABSTRACT FROM AUTHOR]

Zearalenone (ZEN) is a highly toxic non-steroidal mycotoxin produced via some Fusarium species that intimidate the agricultural and food industry. Therefore, it is an intense need for different groups to develop some novel, rapid, reliable, and precise analytical methods for ZEN detection to ensure food safety. Although various analytical techniques have been fabricated for ZEN detection, hindrances including high price instruments, time-consuming and labor-intensive, have restricted their application. Aptamers are a new class of bioreceptors designated via a process named SELEX (systematic evolution of ligands by exponential enrichment). Recently, advanced nanomaterials (NMs) have gained much attention in the construction of aptasensors due to their creditable optical, electrical, magnetic, and structural characteristic. This article briefly summarized ZEN occurrence, metabolism, and toxicity caused by ZEN and also enumerate the aptamers selected for ZEN. Most importantly this review article mainly focuses on the recently published articles on the NMs-based aptasensors for ZEN detection. So far, optical (colorimetric fluorescence and localized surface plasmon resonance) and electrochemical (conventional electrochemical and electrochemiluminescence) aptasensors with different detection strategies have been fabricated for ZEN detection in different food and feed samples. Among them, electrochemical aptasensor gained special attention due to their high sensitivity, simplicity, and easy operation. Hence, this article intends to sum up the various advanced NMs-based aptasensors, their detection design, and the complete working principle used for ZEN detection. Moreover, the intrinsic worth of each detection strategy has been investigated and the finest performance gained from each strategy was highlighted. Furthermore, the current contests and the future outlooks for emerging novel aptasensor for ZEN/other target's detection have also been discussed. Nanomaterial-based aptasensors for ZEN detection. [Display omitted] [ABSTRACT FROM AUTHOR]

DNA walker machines, as one of the dynamic DNA nanodevices, have attracted extensive interest in the field of analysis due to their inherent superiority. Herein, we reported a split aptamer remodeling-initiated target-self-service 3D-DNA walker for ultrasensitive, specific, and high-signal-background ratio determination of 17β-estradiol (E2) in food samples. Two split probes (STWS-a and STWS-b) were rationally designed that can undergo structural reassembled to serve as walking strands (STWS) under the induction of the target. Meanwhile, an intact E6-DNAzyme region was formed and activated at the tail of STWS. The activated E6-DNAzyme then continuously drives the 3D-DNA walker for signal amplification and specific detection of E2. Under optimal conditions, the proposed DNA walker-based biosensor exhibited excellent linearity in the range of 1 pM to 50 nM with a low limit of detection (LOD) of 0.28 pM, and good precision (2.7%) for 11 replicate determinations of 1 nM of E2. Furthermore, the developed DNA walker-based biosensor achieved excellent sensitive analysis of E2 in the complex food matrix with recoveries of 95.6–106.5%. This newly proposed split aptamer-based strategy has the advantages of ultrasensitive, high signal-to-background ratio, and high stability. Noteworthy, the successful operation of the DNA walker initiated by the split aptamer expands the principles of DNA walker design and provides a universal signal amplification platform for trace analysis. [Display omitted] • A novel 3D-DNA walker was developed for ultrasensitive detection of 17β-estradiol. • Bifunctionality split probe was designed as walking strand in walker machine. • Integration of split aptamers significantly improved the sensitivity and specificity. • DNA walker powered by DNAzyme, which greatly ensures the stability of aptasensor. [ABSTRACT FROM AUTHOR]

Zearalenone (ZEN) is a widespread nonsteroidal mycotoxin with estrogen-like activity. Sensitive and reliable quantification of ZEN in food is critical to ensure food safety and safeguard agricultural production. Herein, by combining the metal-organic frameworks-based nanozyme (MOFzyme) and hyaluronic acid (HA)-DNA hydrogel, a well-designed colorimetric aptasensor was developed. The HA-DNA hydrogel was deposited on the surface of the bimetallic MOFzyme via strand-induced hybridization chain reaction (HCR). Relying on the ZEN-specific aptamer integrated in hydrogel structure, the disintegration of the hydrogel network and the concomitant exposure of the encapsulated MOFzyme could be specifically triggered by the introduction of ZEN molecules. Moreover, the magnitude of hydrogel disintegration was positively correlated with the amount of ZEN, by which the quantification of ZEN can be effortlessly achieved. Benefiting from the delicate design, the satisfactory catalytic performance and stability of bimetallic MOFzyme and the appealing stimuli-responsiveness of DNA hydrogel, the developed aptasensor demonstrated superior analytical performance and ease of use. Under optimal conditions, the linear range of the aptasensor fell between 0.001 and 200 ng mL−1 with a limit of detection (LOD) of 0.8 pg mL−1. Furthermore, the aptasensor was successfully applied for the quantitative detection of ZEN in corn and soybean samples with recoveries ranging from 94.0% to 109.0%. The developed aptasensor is expected to be a prospective universal platform for accurately quantifying food or environmental hazards. [ABSTRACT FROM AUTHOR]

Ochratoxin A (OTA) is known as an important mycotoxin that is widely distributed in food products. The increasing requirement for sensitive and convenient OTA detection has promoted the development of aptasensors based on nanomaterials and elegant design strategy for aptamer probes. Ratiometric fluorescence aptasensors greatly reduce the probability of generating false-positive signals, compared to one-signal detection methods. In this work, an efficient ratiometric aptasensor was constructed, based on the dual-emission fluorescence of N -methyl mesoporphyrin IX (NMM) and copper nanoclusters (CuNCs). The key binding region of aptamer was obtained by theoretical results of molecular docking, and experiments of optimizing the length of complementary DNA (cDNA) verified the conjecture. With the addition of OTA, CuNCs-cDNA dissociated from the aptamer sequence, and the fluorescence of CuNCs (λ em =510 nm) decreased. Meanwhile, the aptamer contained G-quadruplex structure and enhanced the fluorescence of NMM (λ em =610 nm). In this way, fluorescence intensity at the emission wavelength of 610 nm and 510 nm were monitored and I 610 /I 510 was set as the signal output of this aptasensor. Stability tests indicated that the established aptasensor can reduce the interference of pH and storage time. The limit of detection (LOD) was as low as 0.045 ng/mL, with a wide linear range of 0.05–100 ng/mL. Moreover, specificity tests provided excellent selectivity towards other common mycotoxins, and the applicability was confirmed by performing real sample analysis, indicating that the NMM/CuNCs ratiometric biosensor for OTA detection has practical application prospects in food samples. [Display omitted] • A sensitive and reliable ratiometric aptasensor was constructed for OTA detection. • NMM and CuNCs were used as dual-emission fluorescent signals with same excitation. • Key binding bases of the aptamer were studied by molecular docking. • The established aptasensor displayed satisfying specificity, accuracy and precision. [ABSTRACT FROM AUTHOR]

Aptamers are short single-stranded DNA or RNA oligonucleotides isolated from randomized libraries, presenting high affinity and specificity toward targets with similar to antibodies. Recently, aptamers have demonstrated their outstanding application potential ranging from biosensors, bioimaging, and therapeutics due to various advantages including low immunogenicity, ease of large-scale synthesis, low batch-to-batch variation, easily chemical modification, and programmability. However, the current overall success rate of aptamer is far from being satisfactory, and still needs to overwhelm the major obstacle in affinity, specificity, and stability for practical application. The efficient strategy of manipulating the binding performance of aptamers, and improving their performance in practical application is of great significance. Herein, we review the challenges and advances in manipulating the binding performance (e.g., affinity, specificity, and stability) of aptamers to obtain high-quality aptamers by comprehensive analyzing their structure and properties. This mainly includes interfering with the SELEX protocol to obtain excellent parental aptamers, engineering aptamers in post-SELEX process and matching the optimal working microenvironment. Moreover, the perspectives of future direction are also summarized. We hope to provide researchers with alternative strategies for enhancing the performance of aptamers in practical applications and promoting the explosive development of aptamers in related fields. [Display omitted] • Systematically elaborate the origin, development and current application status of aptamers • The obstacles faced by aptamers in practical application are explained in depth. • Intervention strategies in SELEX to obtain high-quality aptamer • Comprehensive Post-SELEX strategies for engineering or remodeling the aptamers [ABSTRACT FROM AUTHOR]

• 1. A colorimetric aptasensor was established initially for the rapid detection of ZEN. • 2. MOF nano-container provided an ideal platform for the biosensing. • 3. The affinity of ZEN aptamer guaranteed the accuracy and selectivity of detection. • 4. The superb catalytic ability of G4-DNAzyme greatly improved the sensitivity (0.36 pg mL−1). Zearalenone (ZEN) poses a serious threat to human and animal health. The development of sensitive determination methods for ZEN is of great significance for ensuring the quality and safety of food. Herein, based on a stimuli-responsive aptamer-functionalized metal–organic framework (MOF) nano-container and trivalent DNA peroxidase mimicking enzyme (DNAzyme), an efficient aptasensor was constructed initially for the colorimetric determination of ZEN. The proposed aptasensor only required simple operations but exhibited outstanding specificity, reproducibility, storage stability and reusability simultaneously. Under the optimal conditions, there was a good linear relationship between the changed absorbance and logarithm concentration of ZEN within 0.01–100 ng mL−1, and the limit of detection (LOD) could reach 0.36 pg mL−1. Moreover, the proposed aptasensor was reliable in quantifying ZEN in spiked food samples. The current bioassay provides a promising scheme for constructing stable, specific and rapid colorimetric platforms with potential applications in the fields of food safety. [ABSTRACT FROM AUTHOR]