Highly sensitive electrochemiluminescence aptasensor based on dual-signal amplification strategy for kanamycin detection

"Two-in-One" PtPdCu Trimetallic Multifunctional Nanoparticles-Mediated Dual-Signal-Integrated Aptasensor for Ultradetection of Enrofloxacin

Balancing the accuracy and simplicity of aptasensors is a challenge in their construction. This study addresses this issue by leveraging the remarkable loading capacity and peroxidase-like catalytic activity of PtPdCu trimetallic nanoparticles, which reduces the reliance on precious metals. A dual-signal readout aptasensor for enrofloxacin (ENR) detection is designed, incorporating DNA dynamic network cascade reactions to further amplify the output signal. Exploiting the strong loading capacity of PtPdCu nanoparticles, they are self-assembled with thionine (Thi) to form a signal label capable of generating signals in two independent modes. The label exhibits excellent enzyme-like catalytic activity and enhances electron transfer capabilities. Differential pulse voltammetry (DPV) and square-wave voltammetry (SWV) are employed to independently read signals from the oxidation-reduction reaction of Thi and the catalytic oxidation of hydroquinone (HQ) to benzoquinone (BQ) by H2O2. The introduced DNA dynamic network cascade reaction modularizes sample processing and electrode surface signal generation, avoiding electrode contamination and efficiently increasing the output of the catalyzed hairpin assembly (CHA) cycle. Under optimized conditions, the developed aptasensor demonstrates detection limits of 0.112 (DPV mode) and 0.0203 pg/mL (SWV mode). Additionally, the sensor successfully detected enrofloxacin in real samples, expanding avenues for designing dual-mode signal amplification strategies.

Novel electrochemiluminescence aptasensor based on AuNPs-ABEI encapsulated TiO2 nanorod for the detection of acetamiprid residues in vegetables

Gold nanoparticles (AuNPs)@N-(4-aminobutyl)-N-ethylisoluminol (ABEI)@Titanium dioxide nanorods (TiO2NRs) were used as sensing materials to produce a unique encapsulated nanostructure aptasensor for the detection of acetamiprid residues in this work. ABEI, an analog of luminol, was extensively used as an electrochemiluminescence (ECL) reagent. The ECL mechanism of ABEI- hydrogen peroxide (H2O2) system had connections to a number of oxygen-centered free radicals. TiO2NRs improved ECL response with high electron transfer and a specific surface area. AuNPs were easy to biolabel and could catalyze H2O2 to enhance ECL signal. AuNPs were wrapped around TiO2NRs by utilizing the reduction property of ABEI to form wrapped modified nanomaterials. The sulfhydryl-modified aptamer bound to the nanomaterial by forming gold-sulfur (Au-S) bonds. The aptamer selectively bound to its target with the addition of acetamiprid, which caused a considerable decrease in ECL intensity and enabled quantitative detection of acetamiprid. The aptasensor showed good stability, repeatability and specificity with a broad detection range (1×10-2-1×103 nM) and a lower limit of detection (3 pM) for acetamiprid residues in vegetables. Overall, this aptasensor presents a simple and highly sensitive method for ECL detecting acetamiprid, with potential applications in vegetable safety monitoring.

Current Trends in Nanomaterials-Based Electrochemiluminescence Aptasensors for the Determination of Antibiotic Residues in Foodstuffs: A Comprehensive Review

Veterinary pharmaceuticals have been recently recognized as newly emerging environmental contaminants. Indeed, because of their uncontrolled or overused disposal, we are now facing undesirable amounts of these constituents in foodstuff and its related human health concerns. In this context, developing a well-organized environmental and foodstuff screening toward antibiotic levels is of paramount importance to ensure the safety of food products as well as human health. In this case, with the development and progress of electric/photo detecting, nanomaterials, and nucleic acid aptamer technology, their incorporation-driven evolving electrochemiluminescence aptasensing strategy has presented the hopeful potentials in identifying the residual amounts of different antibiotics toward sensitivity, economy, and practicality. In this context, we reviewed the up-to-date development of ECL aptasensors with aptamers as recognition elements and nanomaterials as the active elements for quantitative sensing the residual antibiotics in foodstuff and agriculture-related matrices, dissected the unavoidable challenges, and debated the upcoming prospects.

Portable biosensor for on-site detection of kanamycin in water samples based on CRISPR-Cas12a and an off-the-shelf glucometer

On-site and cost-effective monitoring of antibiotic residue in water samples using a ubiquitous device that is readily available to the general public is a big challenge. Herein, we developed a portable biosensor for kanamycin (KAN) detection based on a glucometer and CRISPR-Cas12a. The aptamer-KAN interactions liberate the trigger C strand, which can initiate the hairpin assembly to produce numerous double-stranded DNA. After recognition by CRISPR-Cas12a, Cas12a can cleave the magnetic bead and invertase-modified single-stranded DNA. After magnetic separation, the invertase can convert sucrose into glucose, which can be quantified by a glucometer. The linear range of the glucometer biosensor is from 1 pM to 100 nM and the detection limit is 1 pM. The biosensor also exhibited high selectivity and the nontarget antibiotics had no significant interference with KAN detection. The sensing system is robust and can work in complex samples with excellent accuracy and reliability. The recovery values were in the range of 89-107.2 % for water samples and 86-106.5 % for milk samples. The relative standard deviation (RSD) was below 5 %. With the advantages of simple operation, low cost, and easy accessibility to the public, this portable pocket-sized sensor can realize the on-site detection of antibiotic residue in resource-limited settings.

A molecularly imprinted electrochemical sensor for specific and ultrasensitive determination of an aminoglycoside drug: the role of copper ions in the determination

Herein, a molecularly imprinted polymer (MIP) was fabricated for specific sensing of an aminoglycoside e.g. kanamycin (KANA). Carbon paste modified with a MIP specific to Cu²⁺-KANA was first introduced. Copper (Cu²⁺) as a metal ion was used as a signal tracer and an amplifier, producing a current response measured by differential pulse voltammetry (DPV). Introducing the aminoglycoside drug into the solution containing Cu²⁺ did not affect the current response of the NIP/CPE. Under the optimum conditions, the as-fabricated sensor exhibited an increase in the current response in the range of 0.55-550 nM with a good limit of detection (LOD, S/N = 3) of 161 pM. The sensor exhibited many advantages including high sensitivity and selectivity, good stability and reproducibility, and cost-effectiveness. Moreover, it was successfully applied for the determination of KANA in milk and honey samples with RSD % not more than 3.3%, suggesting the reliability of the as-designed sensor.

Enhanced anode electrochemiluminescence in split aptamer sensor for kanamycin trace monitoring

Covalently modifying electrochemiluminescence (ECL) luminophores to alter their energy levels or generate energy/electron transfer processes for improved performance is hindered by the complex design and fabrication processes. In this study, non-covalent bond self-assembly was employed to enhance the ECL property of gold nanoclusters with tryptophan (Try) and mercaptopropionic acid (MPA) as ligands (Try-MPA-gold nanoclusters). Specifically, through the molecular recognition of Try by cucurbit[7]uril, some non-radiative transition channels of the charge carriers on the surface of the Try-MPA-gold nanoclusters were restricted, resulting in a significant enhancement of the ECL intensity of the nanoclusters. Furthermore, rigid macrocyclic molecules acted on the surface of the nanoclusters through self-assembly, forming a passive barrier that improved the physical stability of the nanoclusters in the water-phase and indirectly improved their luminescent stability. As an application, cucurbit[7]uril-treated Try-MPA-gold nanoclusters (cucurbit[7]uril@Try-MPA-gold nanoclusters) were used as signal probes, and Zn-doped SnO₂ nanoflowers (Zn-SnO₂ NFs) with high electron mobility were used as electrode modification material to establish an ECL sensor for kanamycin (KANA) detection, utilizing split aptamers as capture probes. The advanced split aptamer sensor demonstrated excellent sensitivity analysis for KANA in complex food substrates with a recovery rate of 96.2 to 106.0%.

Electrochemical aptasensor based on the target-induced strand displacement strategy-driven for T-2 toxin detection

Herein, an aptasensor based on target-induced strand displacement (TISD) strategy was developed for sensitive detection of T-2 toxin. Gold nanoparticles@ aminated manganese dioxide (AuNPs@NH₂-MnO₂) exhibited excellent electrical conductivity and provided more binding sites for aptamer (Apt). Besides, polyethyleneimine-reduced graphene oxide/gold‑platinum core-shell nanorods composites (PEI-rGO/Pt@Au NRs) were used to be carriers for signaling tags, as their sufficiently large specific surface area improved the loading capacity for signal molecules. In the presence of T-2, the Apt sequence was more inclined to form an Apt-T-2 complex, and the cDNA was displaced from the Apt-cDNA duplex, while the signal tag was released, resulting in a weakened MB signal, differential pulse voltammetry (DPV) was used to record the signal change. Under optimal conditions, the signal response of the constructed electrochemical aptasensor exhibited a good linear relationship with the concentration of T-2. The detection limit was 8.74 × 10^-7 ng mL^-1over a wide range of concentration from 5 × 10^-6 ng mL^-1 to 5 ng mL^-1. Furthermore, the proposed aptasensor had excellent specificity, good stability and can be well applied to the detection of real samples. It provided a new avenue for the research and development of sensitive aptasensors in food detection and analysis.

Construction of a dual-model aptasensor based on G-quadruplexes generated via rolling circle amplification for visual/sensitive detection of kanamycin

A dual-model colorimetric and electrochemical aptasensor was designed using a large number of G-quadruplexes generated by rolling circle amplification (RCA). Specific binding between target and aptamer during RCA yielded large numbers of G-quadruplexes. A colorimetric sensor was fabricated based on the interaction between the G-quadruplex and hemin, which altered the 3,3',5,5'-Tetramethylbenzidine (TMB)-catalyzed color reaction and facilitated the visual and semi-quantitative detection of kanamycin. An electrochemical sensor was constructed based on the strong interaction between the G-quadruplex and the methylene blue electrical signal molecule. Combining nanocomposites multi-walled carbon nanotubes-chitosan/gold nanoparticles (MWCNTs-CS/AuNPs) and RCA realized double-amplified electrochemical signals. Under optimized conditions, a linear relationship was obtained as the logarithm of different concentrations of kanamycin (KAN). The colorimetric aptasensor had a linear range of 1 × 10² nM to 1 × 10³ nM with a detection limit of 1.949 nM. The electrochemical aptasensor had wider a linear range from 1 × 10^-3 nM to 2.5 × 10³ nM and a lower detection limit of 0.333 pM. The sensor combined the advantages of simple colorimetric visualization with the ultra-precision of electrochemical methods. Aptasensor showed good specificity and prevented interference. Furthermore, the prepared dual-model aptasensor facilitated the practical monitoring of KAN in milk.

Interference-resistant aptasensor with tetrahedral DNA nanostructure for profenofos detection based on the composites of graphene oxide and polyaniline

In this work, an interference-resistant electrochemical aptasensor that could detect profenofos in vegetables was constructed based on complexes of graphene oxide and polyaniline (GO@PANI) and gold nanoparticles-tetrahedral DNA nanostructure (Au-TDN). Compared with a single chain aptamer, the tetrahedral DNA nanostructure is highly stable and allows the aptamer on this structure to stand in a highly ordered position on an electrode surface. Moreover, the AuNPs are biocompatible and can protect the activity of the aptamer, which can improve the assembly success rate of Au-TDN. Besides, the conductivity of PANI had been tremendously enhanced thanks to the existence of GO, which improved the dispersion of PANI. The GO@PANI was prepared by a chemical synthesis method, which had a large surface area and was able to adsorb many Au-TDN. Under optimal working parameters, the constructed aptasensor exhibited good electrochemical sensing performance with a detection limit of 10.50 pg/mL and a linear range of 1.0 × 10²-1.0 × 10⁷ pg/mL. In addition, it was employed in detecting profenofos in vegetables with a good recovery rate of 90.41-116.37 %. More importantly, the aptasensor also has excellent stability and high selectivity. This study provides a promising method to avoid interference in the detection of profenofos by sensors.

A competitive colorimetric aptasensor for simple and sensitive detection of kanamycin based on terminal deoxynucleotidyl transferase-mediated signal amplification strategy

We developed a rapid and sensitive colorimetric biosensor based on competitive recognition between kanamycin (KAN), magnetic beads-kanamycin (MBs-KAN) and aptamer and terminal deoxynucleotidyl transferase (TdT)-mediated signal amplification strategy. In the absence of KAN, aptamers recognize MBs-KAN. TdT can amplify oligonucleotides to the 3'-OH ends of aptamers, with biotin-dUTP being embedded in the long single stranded DNA (ssDNA). Then the assay produced visual readout due to the horseradish peroxidase (HRP)-catalyzed color change of the substrate after the linkage between biotin and streptavidin (SA)-HRP. In the presence of KAN, however, aptamers tend to bind free KAN rather than MBs-KAN. In this case, aptamers are isolated by magnetic separation, resulting in the failure of signal amplification and catalytic signals. This competitive colorimetric sensor showed excellent selectivity toward KAN with the limit of detection (LOD) as low as 9 pM. And recovery values were between 93.8 and 107.8% when spiked KAN in milk and honey samples.

Development of label-free fluorescent biosensor for the detection of kanamycin based on aptamer capped metal-organic framework

The abuse of antibiotics has caused serious threat to human health, so it is of great significance to develop a simple and sensitive method for the detection of trace residues of antibiotics in the environment and food. Herein, a novel label-free fluorescent biosensing platform based on the fluorescence change of aptamers-capped zeolitic imidazolate framework-8 (ZIF-8) @ 2,2',2″,2‴-((ethene-1,1,2,2-tetrayltetrakis (benzene-4,1-diyl)) tetrakis (oxy)) tetraacetic acid (TPE) through ATP-assisted competitive coordination reaction was designed for such an end. ZIF-8@TPE/Aptamer (Apt) emits strong fluorescence at 425 nm in HEPES buffer due to the aggregation induced luminescence properties of TPE molecules in confined state. Once kanamycin was added, the conformation of aptamer capped on the surface of ZIF-8@TPE changes because of the specific recognition of kanamycin with aptamer, leading to the collapse of ZIF-8 and release of TPE, accompanied with a dramatic decrease of fluorescence intensity. Under the optimal conditions, a good correlation was obtained between the fluorescence intensity of ZIF-8@TPE/Apt and the concentration of kanamycin ranging from 10 to 10³ ng/mL with a detection limit of 7.3 ng/mL. The satisfactory analytical performance of the assay for kanamycin detection suggests good prospect for its application in food safety analysis.

Target biorecognition-triggered assembly of a G-quadruplex DNAzyme-decorated nanotree for the convenient and ultrasensitive detection of antibiotic residues

The abuse of kanamycin (Kana) in many fields has led to increasing antibiotic pollution problems and serious threats to public health. Therefore, determining how to develop methods to realize the convenient detection of antibiotics in complicated environmental matrices is highly desirable. In this study, we utilized a target biorecognition-triggered hybridization chain reaction (HCR) assembly of a G-quadruplex DNAzyme (G-DNAzyme)-decorated nanotree to develop a novel homogeneous colorimetric biosensing method for the convenient and ultrasensitive detection of Kana antibiotic residues in real samples. Through the designed aptamer-recognition reaction, an Mg²⁺-dependent DNAzyme (MNAzyme) strand can be liberated. Thus, its catalyzed cleavage of the hairpin substrates anchored at a DNA nanowire will cause the assembled formation of an HCR-initiator; this process can be greatly amplified by the exonuclease III-assisted target recycling and the MNAzyme-catalyzed release of another MNAzyme strand. Based on the DNA-nanowire-accelerated HCR assembly of many G-DNAzyme-decorated DNA duplexes on the two sides of the nanowire, a DNA nanotree decorated by numerous G-DNAzymes will form to realize the ultrasensitive colorimetric signal output. Under the optimal conditions, this method exhibited a wide five-order-of-magnitude linear range and a very low detection limit of 28 fg mL^-1. In addition, excellent selectivity, repeatability, and reliability were also demonstrated for this homogeneous bioassay method. These unique features along with its automatic manipulation and low assay cost show promise for practical applications.

A CdSe@CdS quantum dots based electrochemiluminescence aptasensor for sensitive detection of ochratoxin A

In this work, a CdSe@CdS quantum dots (QDs) based label-free electrochemiluminescence (ECL) aptasensor was developed for the specific and sensitive detection of ochratoxin A (OTA). Chitosan (CHI) could immobilize abundant QDs on the surface of an Au electrode as the luminescent nanomaterials. Glutaraldehyde was used as the crosslinking agent for coupling a large number of OTA aptamers. Thanks to the excellent stability, good biocompatibility, and strong ECL intensity of CdSe@CdS QDs, as well as the quick reactions of the generated SO₄•- in the electrolyte, strong ECL signals were measured. Because of the specific recognition of aptamer toward OTA, the reduced ECL signals caused by OTA in the samples were recorded for quantify the content of OTA. After optimizing a series of crucial conditions, the ECL aptasensor displayed superior sensitivity for OTA with a detection limit of 0.89 ng/mL and a wide linear concentration range of 1-100 ng/mL. The practicability and viability were verified through the rapid and facile analysis of OTA in real Lily and Rhubarb samples with recovery rates (n = 3) of 98.1-105.6% and 97.3-101.5%, respectively. The newly-developed QDs-based ECL aptasensor provided a new universal analytical tool for more mycotoxins in safety assessment of foods and feeds, environmental monitoring, and clinical diagnostics.

Novel electrochemiluminescent assay for the aptamer-based detection of testosterone

This work presents a proof-of-concept assay for the detection and quantification of small molecules based on aptamer recognition and electrochemiluminescence (ECL) readout. The testosterone-binding (TESS.1) aptamer was used to demonstrate the novel methodology. Upon binding of the target, the TESS.1 aptamer is released from its complementary capture probe - previously immobilized at the surface of the electrode - producing a decrease in the ECL signal after a washing step removing the released (labeled) TESS.1 aptamer. The analytical capability of the ECL assay towards testosterone detection was investigated displaying a linear range from 0.39 to 1.56 μM with a limit of detection of 0.29 μM. The selectivity of the proposed assay was assessed by performing two different negative control experiments; i) detection of testosterone with a randomized ssDNA sequence and ii) detection of two other steroids, i.e. deoxycholic acid and hydrocortisone with the TESS.1 aptamer. In parallel, complementary analytical techniques were employed to confirm the suggested mechanism: i) native nano-electrospray ionization mass spectrometry (native nESI-MS) was used to determine the stoichiometry of the binding, and to characterize aptamer-target interactions; and, ii) isothermal titration calorimetry (ITC) was carried out to elucidate the dissociation constant (K_d) of the complex of testosterone and the TESS.1 aptamer. The combination of these techniques provided a complete understanding of the aptamer performance, the binding mechanism, affinity and selectivity. Furthermore, this important characterization carried out in parallel validates the real functionality of the aptamer (TESS.1) ensuring its use towards selective testosterone binding in further biosensors. This research will pave the way for the development of new aptamer-based assays coupled with ECL sensing for the detection of relevant small molecules.

Aptasensors for mycotoxins in foods: Recent advances and future trends

Mycotoxin contamination in foods has posed serious threat to public health and raised worldwide concern. The development of simple, rapid, facile, and cost-effective methods for mycotoxin detection is of urgent need. Aptamer-based sensors, abbreviated as aptasensors, with excellent recognition capacity to a wide variety of mycotoxins have attracted ever-increasing interest of researchers because of their simple fabrication, rapid response, high sensitivity, low cost, and easy adaptability for in situ measurement. The past few decades have witnessed the rapid advances of aptasensors for mycotoxin detection in foods. Therefore, this review first summarizes the reported aptamer sequences specific for mycotoxins. Then, the recent 5-year advancements in various newly developed aptasensors, which, according to the signal output mode, are divided into electrochemical, optical and photoelectrochemical categories, for mycotoxin detection are comprehensively discussed. A special attention is taken on their strengths and limitations in real-world application. Finally, the current challenges and future perspectives for developing novel highly reliable aptasensors for mycotoxin detection are highlighted, which is expected to provide powerful references for their thorough research and extended applications. Owing to their unique advantages, aptasensors display a fascinating prospect in food field for safety inspection and risk assessment.

Ultrasensitive ECL aptasensing of kanamycin based on synergistic promotion strategy using 3,4,9,10-perylenetetracar-boxylic-l-cysteine/Au@HKUST-1

Herein, a sensitive and selective electrochemiluminescence (ECL) aptasensor was designed using Au@HKUST-1 as accelerator towards the perylene derivative (PTC-Cys)/peroxydisulfate (S₂O₈^2-) system for kanamycin (KAN) assay. Firstly, the PTC-Cys was prepared by covalently binding l-cysteine to 3,4,9,10-perylenete-tracarboxylic acid, which was acted as the luminophore. Then Au@HKUST-1could play the part of effective catalyst to accelerate the electrochemical reduction process of S₂O₈^2-to produce more sulfate radical anions (SO₄^•-), thus the ECL signal of the compound was noticeably raised by 2.4 times in comparison with that in which only luminophore and S₂O₈^2- are present, achieving signal amplification of the ECL system. In the presence of KAN, aptamer was pulled down from the sensing interface, achieving a considerable enhancement of ECL intensity in S₂O₈^2- solution. Upon the optimal condition, our proposed strategy can quantify the concentration of KAN from 1.0 × 10^-13 to 1.0 × 10^-8 M with low limit of detection of 4.2 × 10^-14 M (S/N = 3).Besides, our proposed ECL aptasensor exhibited excellent sensitivity, stability and specificity, and could be successfully applied to detect KAN in practical samples, which proved its potential to detect other antibiotics in food security.

Electrochemiluminescence biosensor for thrombin detection based on metal organic framework with electrochemiluminescence indicator embedded in the framework

Ru(dcbpy)₃²⁺-polyethyleneimine-L-lysine (Ru-PEI-L-lys) had been immobilized on metal organic frameworks (ZIF-8) to form an electrochemiluminescent(ECL) indicator (Ru-PEI-L-lys-ZIF-8). In this ECL indicator, PEI-L-lys is used as a co-reactant. Platinum nanoparticles (PtNPs) has been mixed with Ru-PEI-L-lys-ZIF-8 to form a thin film to increase the electron transfer rate and enhanced the ECL response of the system. The prepared material had been characterized carefully and been combined with high selectivity of aptamer to develop a ECL biosensor for thrombin detection. RecJ_f exonuclease (an ssDNA specific exonuclease) assistant target recycling amplification has been adopted to enhance the sensitivity of the system. The ECL response of the system has a linear relationship with logarithm of thrombin concentration in the range of 1 fM to 10 pM with a detection limit of 0.02 aM. This work not only provides a new strategy for the design and synthesis of high performance and stable ECL indicator, but also opens up a new approach for the development of highly sensitive ECL sensors for biological analysis.

Recent advances in aptamer-based sensors for aminoglycoside antibiotics detection and their applications

Aminoglycoside antibiotics (AAs) have been extensively applied in medical field and animal husbandry owing to desirable broad-spectrum antibacterial activity. Excessive AAs residues in the environment can be accumulated in human body through food chain and cause detrimental effect on human health. The establishment of highly specific, simple and sensitive detection methods for monitoring AAs residues is highly in demand. Aptasensor using aptamer as the biological recognition element is the efficient and promising sensing method for detection of AAs. In this review, we have made a summary of specific aptamers sequences against AAs. Subsequently, we provide a systematical and comprehensive overview of modern techniques in aptasensors for detection of AAs according to optical aptasensors as well as electrochemical aptasensors and further summarize their advantages and disadvantages to compare their applications. In addition, we present an overview of practical applications of aptasensors in sample detection of AAs. Moreover, the current challenges and future trends in this field are also included to reveal a promising perspective for developing novel aptasensors for AAs.