Aptamer Self-Assembly-Functionalized Nanochannels for Sensitive and Precise Detection of Chloramphenicol

Highly sensitive antibiotic sensing based on optical weak value amplification: A case study of chloramphenicol

The public health concern of antibiotic residues in animal-origin food has been a long-standing issue. In this work, we present a novel method for antibiotic detection, leveraging optical weak value amplification and harnessing an indirect competitive inhibition assay, which significantly boosts the system's sensitivity in identifying small molecule antibiotics. We chose chloramphenicol as a model compound and mixed it with chloramphenicol-bovine serum albumin conjugates to bind to the chloramphenicol antibody competitively. We achieved a broad linear detection range of up to 3.24 ng/mL and a high concentration resolution of 33.20 pg/mL. To further validate the universality of our proposed detection methodology, we successfully applied it to testing gibberellin and tetracycline. Moreover, we conducted regeneration experiments and real-sample correlation studies. This study introduces a novel strategy for the label-free optical sensing of small molecule antibiotics, greatly expanding the range of applications for sensors utilizing optical weak value amplification.

Design of Self-Standing Chiral Covalent-Organic Framework Nanochannel Membrane for Enantioselective Sensing

Nanochannel membranes are promising materials for enantioselective sensing. However, it is difficult to make a compromise between the selectivity and permeability in traditional nanochannel membranes. Therefore, new types of nanochannel membranes with high enantioselectivity and excellent permeability should be explored for chiral analysis. Here, asymmetric catalysis strategy is reported for interfacial polymerization synthesis of chiral covalent-organic framework (cCOF) nanochannel membrane for enantioselective sensing. Chiral phenylethylamine (S/R-PEA) and 2,4,6-triformylphloroglucinol (TP) are used to prepare chiral TP monomer. 4,4',4″-triaminotriphenylamine (TAPA) is then condensed with chiral TP to obtain cCOF nanochannel membrane via a C═N Schiff-base reaction. The molar ratio of TP to S/R-PEA is adjusted so that S/R-PEA is bound to the aldehyde only or both the aldehyde and hydroxyl groups on TP to obtain chiral-induced COF (cCOF-1) or both chiral-induced and modified COF (cCOF-2) nanochannel membrane, respectively. The prepared cCOF-2 nanochannel membrane showed two times more selectivity for limonene enantiomers than cCOF-1 nanochannel membrane. Furthermore, cCOF-2 nanochannel platform exhibited excellent sensing performance for other chiral molecules such as limonene, propanediol, methylbutyric acid, ibuprofen, and naproxen (limits of detection of 19-42 ng L-1, enantiomer excess of 63.6-86.3%). This work provides a promising way to develop cCOF-based nanochannel enantioselective sensor.

Dual emitting aggregation-induced electrochemiluminescence from tetrastyrene derivative for chloramphenicol detection

Chloramphenicol (CAP) poses a threat to human health due to its toxicity and bioaccumulation, and it is very important to measure it accurately and sensitively. This work explored a host-guest recognition strategy to mediate dual aggregation-induced electrochemiluminescence (AIECL) of 1,1,2,2-tetrakis(4-(pyridin-4-yl) phenyl)-ethene (TPPE) for ratio detection of CAP, in which, cucurbit[8]uril (CB[8]) served as host to assemble guest TPPE. The resulting supramolecular complex CB[8]-TPPE exhibited excellent dual-AIECL-emission with signal strength approximately four times that of TPPE aggregates and black hole quencher-1 (BHQ1) could efficiently quench dual-AIECL signal. CB[8]-TPPE coupled dual-function quencher BHQ1 and high-efficiency DNA reactor to achieve ultra-sensitive detection of CAP, exhibiting a linearity range of 10 fmol·L-1-100 nmol·L-1 and limit of detection of 1.81 fmol·L-1. CB[8]-TPPE provides a novel way to improve the dual-emission of TPE derivatives and sets up a promising platform for CAP detection, demonstrating a good practical application potential.

Aptamer-Conjugated Covalent-Organic Framework Nanochannels for Selective and Sensitive Detection of Aflatoxin B1

Sensitive and selective detection of trace aflatoxin B1 (AFB1) in foods is of great importance to guarantee food safety and quality but still challenging because of its trace amount and the interference from the complex food matrix. Here, we report the integration of aptamer (Apt) and an ordered 2D covalent organic framework (COF) to solid-state anodic aluminum oxide (AAO) nanochannels (Apt/COF/AAO) for selective and sensitive detection of trace AFB1. The high specificity of Apt for AFB1 led to a selective change in the surface charge of Apt/COF/AAO and in turn the current change of the nanochannel, permitting the selective and sensitive determination of trace AFB1 in complex food samples. The developed nanofluidic sensor gave a wide linear range (1-500 pg mL-1), low detection limit (0.11 pg mL-1), and good precision (relative standard deviation of 1.5% for 11 replicate determinations of 100 pg mL-1). In addition, the developed sensor was successfully used for the detection of AFB1 in food samples with the recovery of 86.9%-102.5%. The coupling of Apt-conjugated 2D COF with an AAO nanochannel provides a promising way for sensitive and selective determination of food contaminants in complex samples.

Antenna effect enhanced ECL immunoassay using microfloral europium porphyrin coordination polymers based on Eu3+ and TCPP for the detection of chloramphenicol in foods

The "antenna effect" is one of the most important energy transfer modes in lanthanide light-emitting polymers. In this study, novel luminescent nanostructured coordination polymers (Eu-PCP) were synthesized in one step using Eu3+ as the central metal ion and 5,10,15,20-tetrakis (4-carboxyphenyl) porphyrin (TCPP) as the organic ligand. The unique "antenna effect" observed between Eu3+ and TCPP leads to a substantial improvement in the electrochemiluminescence (ECL) emission efficiency. Eu-PCP exhibits good cathodic ECL characteristics. Additionally, Au@SnS2 nanosheets exhibit favorable electrical conductivity, biocompatibility, and a significant specific surface area. This makes them a suitable choice as substrate materials for the modification of electrode surfaces and capturing antigens. Being well known, the development of sensitive and rapid methods to detect chloramphenicol is essential for food safety. Based on this, we report a novel competitive electrochemiluminescence immunoassay to achieve ultra-sensitive and highly specific detection of chloramphenicol. The linear range was 0.0002-500 ng mL-1 and the detection limit was 0.09 pg mL-1. Apart from that, the experimental results proved that it provided a new analytical tool for the detection of antibiotic residues in food safety.

A novel chemiluminescence sensor for alpha-fetoprotein detection based on an aptamer-luminol modified magnetic graphene oxide and copper-based MOF composite

Herein, an aptamer-luminol modified magnetic graphene oxide and copper-based MOF composite was prepared and used to build a novel target-triggered "turn on" chemiluminescence (CL) sensor for alpha-fetoprotein (AFP) detection. Magnetic graphene oxide (MGO) was functionalized with the complementary sequence of the AFP aptamer (cDNA), and then MGO-cDNA was linked to aptamer modified luminol (Apt-luminol) through the complementary base pairing effect. The functionalized magnetic graphene oxide (MGO-cDNA/Apt-luminol) was prepared as a specific magnetic separation and signal switch material. ZnONPs-Au@CuMOFs shows excellent catalytic performance and was used as a catalyst for the luminol-H2O2 reaction. AFP will specifically recognize and bind to Apt on MGO-cDNA/Apt-luminol when AFP is present, which causes luminol release and triggers the CL reaction. The released luminol encounters ZnONPs-Au@CuMOFs and produces strong CL intensity. Therefore, a novel target-triggered "turn on" CL method with high selectivity and sensitivity for detecting AFP has been established. The linear range and detection limit were 1.0 × 10-4-50 ng mL-1 and 4.2 × 10-5 ng mL-1, respectively. The sensor also exhibited good selectivity, reproducibility and stability, and was finally used for AFP detection in serum samples.

Recent Advances of Food Hazard Detection Based on Artificial Nanochannel Sensors

Food quality and safety are related to the health and safety of people, and food hazards are important influencing factors affecting food safety. It is strongly necessary to develop food safety rapid detection technology to ensure food safety. As a new detection technology, artificial nanochannel-based electrochemical and other methods have the advantages of being real-time, simple, and sensitive and are widely used in the detection of food hazards. In this paper, we review artificial nanochannel sensors as a new detection technology in food safety for different types of food hazards: biological hazards (bacteria, toxins, viruses) and chemical hazards (heavy metals, organic pollutants, food additives). At the same time, we critically discuss the advantages and disadvantages of artificial nanochannel sensor detection, as well as the restrictions and solutions of detection, and finally look forward to the challenges and development prospects of food safety detection technology based on the limitations of artificial nanochannel detection. We expect to provide a theoretical basis and inspiration for the development of rapid real-time detection technology for food hazards and the production of portable detection equipment in the future.

Pore-Size-Dependent Role of Functional Elements at the Outer Surface and Inner Wall in Single-Nanochannel Biosensors

Biological nanopores feature functional elements on the outer surfaces (FEOS) and inner walls (FEIW), enabling precise control over ions and molecules with exceptional sensitivity and specificity. This provides valuable inspiration to scientists for the development of intelligent artificial nanochannel-based platforms, with a wide range of potential applications, including biosensors. Much effort has been dedicated to investigating the distinct contribution of FEOS and FEIW of multichannel membrane biosensors. However, the intricate interactions among neighboring pores in multichannel biosensors have presented challenges. This underscores the untapped potential of single nanochannels as ideal candidates in this field. Here, we employed single nanochannel membranes with different pore sizes to investigate the distinct contributions of FEIW and FEOS to single-nanochannel biosensors, combined with numerical simulations. Our findings revealed that alterations in the negative charges of FEIW and FEOS, induced by target binding, have differential effects on ion transport, contingent upon the degree of nanoconfinement. In the case of smaller pores, such as 20 nm, the ion concentration polarization driven by FEIW can independently control ion transport through the surface's electric double layer. However, as the pore size increases to 40-60 nm, both FEIW and FEOS become essential for effective ion concentration polarization. When the pore size reaches 100 nm, both FEIW and FEOS are ineffective and thus unsuitable for biosensors. Simulations demonstrate that the observed phenomena can be attributed to the interactions between the charges of FEIW and FEOS within the overlapping electric double layer under confinement. These results underscore the critical role of pore size as a key parameter in governing the functionality of probes within or on nanopore-based biosensors as well as in the design of nanopore-based devices.

Outer-Surface Functionalized Solid-State Nanochannels for Enhanced Sensing Properties: Progress and Perspective

Solid-state nanochannel-based sensing systems have been established as vigorous tools for sensing plentiful biomarkers due to their label-free, highly sensitive, and high-throughput screening. However, research on solid-state nanochannels has predominantly centered on the functional groups modified on the inner wall, neglecting investigations into the outer surface. Actually, the outer surface, as a part of the nanochannels, also plays a key role in regulating ionic current. When the target nears the entrance of the nanochannel and prepares to pass through, it would also interact with functional groups located on the nanochannel's outer surface, leading to subsequent alterations in the ionic current. Recently, the probes on the outer surface have experimentally demonstrated their ability to independently regulate ionic current, unveiling advantages in in situ target detection, especially for targets larger than the diameter of the nanochannels that cannot pass through them. Here, we review the progress over the past decade in nanochannels featuring diverse outer-surface functionalization aimed at enhanced sensing performance, including charge modification, wettability adjustment, and probe immobilization. In addition, we present the promises and challenges posed by outer-surface functionalized nanochannels and discuss possible directions for their future deployments.

Simultaneous Determination of Amphenicols in Animal-Derived Foods by Solvent and Solid Phase Extraction With Ultrahigh-Performance Liquid Chromatography Tandem Mass Spectrometry

BACKGROUND

The consumption of foods containing amphenicols, a type of antibiotic, is a major concern for human health. A stable and accurate detection method can provide technical support for food-safety monitoring.

OBJECTIVE

An effective and efficient method was established for determining amphenicols in animal-derived foods through the simultaneous use of solid-phase extraction (SPE) cleanup and ultrahigh-performance liquid chromatography/mass spectrometry (UPLC-MS/MS).

METHOD

Samples were extracted using 1.0% ammoniated ethyl acetate solution, degreased with n-hexane, and then concentrated and cleaned using a C18 SPE column. Next, gradient elution was performed using methanol and 0.05% aqueous ammonia as the mobile phase, followed by separation using a C18 column. The target compound was detected using electrospray ionization, both in positive and negative modes, through multiple reaction monitoring, and quantified using an internal-standard method.

RESULTS

The content of chloramphenicol (CAP), florfenicol (FF), and florfenicol amine (FFA) (content range: 0.2-8.0 µg/kg) as well as that of thiamphenicol (TAP; content range: 1.0-40.0 µg/kg) show a good linear relationship, with a correlation coefficient of r > 0.999. Furthermore, recoveries of 86.7-111.9% and relative standard deviations of <9.0% were achieved. The limits of detection and quantification are obtained as 0.03-0.33 and 0.1-1.0 μg/kg, respectively.

CONCLUSIONS

The proposed method has excellent stability and accuracy, and can be successfully used for the qualitative and quantitative determination of amphenicols, i.e., CAP, TAP, FF, and FFA residues in 210 animal-derived food samples, of which FF and FFA were detected in four samples.

HIGHLIGHTS

A stable and accurate method was successfully established for the simultaneous determination of CAP, TAP, FF, and FFA in animal-derived foods using UPLC-MS/MS. Effective sample pretreatment was established, lipids were removed using n-hexane, concentration and cleanup were achieved with the C18 SPE column, and matrix effects were effectively reduced, thus improving the method's accuracy and stability. The method was validated for eight common animal-source foods, including beef, lamb, pork, chicken, egg, milk, fish, and honey. This method has good applicability for CAP, TAP, FF, and FFA in animal-derived foods.

Pure Covalent-Organic Framework Membrane as a Label-Free Biomimetic Nanochannel for Sensitive and Selective Sensing of Chiral Flavor Substances

Chiral flavor substances play an important role in the human perception of different tastes. Here, we report a pure covalent-organic framework (COF) membrane nanochannel in combination with a chiral gold nanoparticles (AuNPs) selector for sensing chiral flavor substances. The pure COF membrane with a proper pore size is selected as the nanochannel, while l-cysteine-modified AuNPs (l-Cys-AuNPs) are used as the chiral selector. l-Cys-AuNPs show stronger binding to the S-enantiomer than the R-enantiomer, causing current reduction to different degrees for the R- and S-enantiomer to achieve chiral sensing due to the synergistic effect of the size exclusion of the COF nanochannel and the chiral selectivity of l-Cys-AuNPs. The developed COF membrane nanochannel sensing platform not only allows an easy balance of the permeability and selectivity, which is difficult to achieve in traditional polymer membrane nanochannel sensors, but also exhibits better chiral performance than commercial artificial anodic aluminum oxide (AAO) nanochannel sensors. The developed nanochannel sensor is successfully applied for sensing flavor enantiomers such as limonene, propanediol, methylbutyric acid, and butanol with the enantiomer excess values of 55.2% (propanediol) and 72.4% (limonene) and the low detection limits of 36 (limonene) and 71 (propanediol) ng L-1. This study provides a new idea for the construction of nanochannel platforms based on the COF for sensitive and selective chiral sensing.

Solid-state nanochannels for bio-marker analysis

Bio-markers, such as ions, small molecules, nucleic acids, peptides, proteins and cells, participate in the construction of living organisms and play important roles in biological processes. It is of great significance to accurately detect these bio-markers for studying their basic functions, the development of molecular diagnosis and to better understand life processes. Solid-state nanochannel-based sensing systems have been demonstrated for the detection of bio-markers, due to their rapid, label-free and high-throughput screening, with high sensitivity and specificity. Generally, studies on solid-state nanochannels have focused on probes on the inner-wall (PIW), ignoring probes on the outer-surface (POS). As a result, the direct detection of cells is difficult to realize by these inner-wall focused nanochannels. Moreover, the sensitivity for detecting ions, small molecules, nucleic acids, peptides and proteins requires further improvement. Recent research has focused on artificial solid-state nanochannels with POS, which have demonstrated the ability to independently regulate ion transport. This design not only contributes to the in situ detection of large analytes, such as cells, but also provides promising opportunities for ultra-high sensitivity detection with a clear mechanism. In this tutorial review, we present an overview of the detection principle used for solid-state nanochannels, inner-wall focused nanochannels and outer-surface focused nanochannels. Furthermore, we discuss the remaining challenges faced by current nanochannel technologies and provide insights into their prospects.

Two colors, one-step, self-drive fluorescent strategy for chloramphenicol detection base on DNAzyme cleavage triggered hybridization chain reaction

A two colors, one-step, self-drive fluorescent strategy was developed for chloramphenicol (CAP) detection based on cyclic cleavage of molecular beacon (MB) by pincer DNA sequences. CAP can bind with its aptamer and active the enzyme-strand (E-DNA). Then the E-DNA can circularly cleave the MB on the both side of pincer DNA sequences. The cleaved fragments can self-assembly to form a long duplex and cause the great recovery of the two colors fluorescent signal. The limit of detection was as low as 0.7 pM. Importantly, the whole detection process is very simple with only one-step operation. Moreover, the two colors fluorescent signals can greatly enhance the accuracy of the result. It was also successfully used to detect CAP in actual samples.

Solid-State Nanopore/Nanochannel Sensing of Single Entities

Solid-state nanopores/nanochannels, with their high stability, tunable geometry, and controllable surface chemistry, have recently become an important tool for constructing biosensors. Compared with traditional biosensors, biosensors constructed with solid-state nanopores/nanochannels exhibit significant advantages of high sensitivity, high specificity, and high spatiotemporal resolution in the detection single entities (such as single molecules, single particles, and single cells) due to their unique nanoconfined space-induced target enrichment effect. Generally, the solid-state nanopore/nanochannel modification method is the inner wall modification, and the detection principles are the resistive pulse method and the steady-state ion current method. During the detection process, solid-state nanopore/nanochannel is easily blocked by single entities, and interfering substances easily enter the solid-state nanopore/nanochannel to generate interference signals, resulting in inaccurate measurement results. In addition, the problem of low flux in the detection process of solid-state nanopore/nanochannel, these defects limit the application of solid-state nanopore/nanochannel. In this review, we introduce the preparation and functionalization of solid-state nanopore/nanochannel, the research progress in the field of single entities sensing, and the novel sensing strategies on solving the above problems in solid-state nanopore/nanochannel single-entity sensing. At the same time, the challenges and prospects of solid-state nanopore/nanochannel for single-entity electrochemical sensing are also discussed.

Smartphone-integrated tri-color fluorescence sensing platform based on acid-sensitive fluorescence imprinted polymers for dual-mode visual intelligent detection of ibuprofen, chloramphenicol and florfenicol

The abuse of multiple antibiotics and anti-inflammatory drugs can harm the ecological environment and human health. Herein, a smartphone-integrated tri-color fluorescence sensing platform based on acid-sensitive fluorescence imprinted polymers was proposed for dual-mode visual intelligent detection of ibuprofen (IP), chloramphenicol (CAP), and florfenicol (FF). In this research, the dual-mode of tri-color ratiometric fluorescence imprinted sensor (TC-FMIPs) was realized at different pH environments for the detection IP, CAP, and FF. The fluorescence peak at 551 nm of TC-FMIPs was quenched in the presence of IP solution and fluorescence peak at 687 nm was quenched in the presence of CAP phosphate buffer solution (PBS, pH 7.0), while the fluorescence peak at 433 nm kept stable. Interestingly, the TC-FMIPs has a peroxidase-like activity, in which a new fluorescence peak at 561 nm was quenched and the fluorescence peak at 433 nm increased gradually with the addition of FF solution in pH 4.0 PBS. The TC-FMIPs showed a low detection limit of 10 pM, 8.5 pM, and 5.5 nM for IP, CAP, and FF, respectively. Additionally, a smartphone was used to capture of fluorescence colors and read out the RGB values for intelligent detection of IP, CAP, and FF, in which the detection limit was calculated as 15 pM, 12 pM and 7 nM toward IP, CAP and FF, respectively. The smartphone-integrated tri-color fluorescence sensing platform was developed for dual-mode visual intelligent detection of IP, CAP and FF successfully, which provided a new strategy for multi-target detection in the complex environment.

Self-coordinated nanozyme on Cu3BiS3 nanorods for high-performance aptasensing

A novel strategy is reported to access high-performance nanozymes via the self-coordination of ferrocyanides ([Fe(CN)₆]^4-) onto the surface of the Cu₃BiS₃ (CBS) nanorods. Notably, the in situ formed nanozymes had high catalytic activity, good stability, low cost, and easy mass production. The formed nanozyme catalyzed the oxidation of the typical chromogenic substrate of 3,3',5,5'-tetramethylbenzidine (TMB) with a distinctive absorption peak at 652 nm, accompanied by a blue color development. Moreover, the attachment of deoxyribonucleoside 5'-monophosphates (dNMP) beforehand onto the surface of CBS prevented coordination of ferrocyanides and resulted in the tunable formation of the nanozyme, thereby enabling the construction of an exquisite biosensing platform. Taking the aptasensing of chloramphenicol (CAP) as an example, the engineered nanozyme allowed the construction of a homogenous, label-free, and high-performance bioassay in terms of its convenience and high sensitivity. Under the optimal conditions, changes in the absorption intensity at 652 nm for the oxidized TMB provides a good linear correlation with the logarithm of CAP concentrations in the range 0.1 pM to 100 nM, and the limit of detection was 0.033 pM (calculated from 3σ/s). Considering a vast number of bioreactions can be connected to dNMP production, we expect the engineerable nanozyme as a universal signal transduction scaffold for versatile applications in bioassays. Through the attachment of deoxyribonucleoside 5'-monophosphate (dNMP) on the surface of CBS to regulate the generation of self-coordinated nanozyme CBS/BiHCF, a homogeneous, label-free, and high-performance universal aptasensing platform was constructed.

Integrating Ordered Two-Dimensional Covalent Organic Frameworks to Solid-State Nanofluidic Channels for Ultrafast and Sensitive Detection of Mercury

Grafting specific recognition moieties onto solid-state nanofluidic channels is a promising way for selective and sensitive sensing of analytes. However, the time-consuming interaction between recognition moieties and analytes is the main hindrance to the application of nanofluidic channel-based sensors in rapid detection. Here, we show the integration of ordered two-dimensional covalent organic frameworks (2D COFs) to solid-state nanofluidic channels to achieve rapid, selective, and sensitive detection of contaminants. As a proof of concept, a thiourea-linked 2D COF (JNU-3) as the recognition unit is covalently bonded on the stable artificial anodic aluminum oxide nanochannels (AAO) to fabricate a JNU-3@AAO-based nanofluidic sensor. The rapid and selective interaction of Hg(II) with the highly ordered channels of JNU-3 allows the JNU-3@AAO-based nanofluidic sensor to realize ultrafast and precise determination of Hg(II) (90 s) with a low limit of detection (3.28 fg mL^-1), wide linear range (0.01-100 pg mL^-1), and good precision (relative standard deviation of 3.8% for 11 replicate determination of 10 pg mL^-1). The developed method was successfully applied to the determination of mercury in a certified reference material A072301c (rice powder), real water, and rice samples with recoveries of 90.4-99.8%. This work reveals the great potential of 2D COFs-modified solid-state nanofluidic channels as a sensor for the rapid and precise detection of contaminants in complicated samples.

Triple-Helix Molecular Switch Triggered Cleavage Effect of DNAzyme for Ultrasensitive Electrochemical Detection of Chloramphenicol

The abuse of chloramphenicol (CAP) in animal-derived products leads to serious food safety problems, so the sensitive and accurate determination of CAP residues has great noteworthiness for public health. Herein, we present a novel electrochemical aptasensor that incorporates a poly(diallyldimethylammonium chloride) functionalized graphene/Ag@Au nanosheets (PDDA-Gr/Ag@Au NSs) composite modified electrode and a DNAzyme signal amplification effect triggered by a triple-helix molecular switch (THMS) for detecting CAP. The PDDA-Gr/Ag@Au NSs composite has the advantages of high surface area, great conductivity, and dispersibility and has successfully improved the electrochemical performance of the electrode. Specific interaction with CAP will cause the signal transduction probe (STP) to be released from the THMS. After that, the DNAzyme will be activated with the help of Pb²⁺ and remove the immobilized signal probe on the electrode surface. The signal change was recorded by square wave voltammetry (SWV) and led to an accurate quantification of CAP. With all these features, the proposed sensing strategy yielded a satisfactory analytical performance with linearity between 1 pM and 1 μM and a limit of detection of 18.6 fM. Furthermore, the aptasensor shows excellent specificity for CAP in the presence of other antibiotics and resists interference with other common metal ions. Importantly, the performance is not diminished when the constructed aptasensor is applied to measuring CAP in milk powder. This THMS-based method is easy to design, and alteration to different targets can be achieved by simply replacing the aptamer sequence in the THMS. Therefore, this method shows significant prospects as a flexible platform for accurate monitoring of antibiotic residues in foodstuffs.

An aptamer-assisted biological nanopore biosensor for ultra-sensitive detection of ochratoxin A with a portable single-molecule measuring instrument

Biological nanopore-based single-molecule detection technology has shown ultrahigh sensitivity to various target analyte. But the detection scope of interesting targets is limited due to the lack of effective signal conversion strategies. In addition, conventional nanopore detection instruments are cumbersome, resulting nanopore detection can only be performed in laboratory. Herein, a customizable nanopore current amplifier is constructed to lower the cost and increase the portability of the nanopore instrument, and then an immobilized aptamer-based signal conversion strategy is proposed for α-hemolysin (α-HL) nanopore to detect small molecules (ochratoxin A, OTA). The presence of OTA in sample would trigger the release of probe single-strand DNA (ssDNA) from magnetic beads, which could subsequently cause current blockage in nanopore. The results show that the signal frequency of probe ssDNA has a linear relationship with the OTA concentration in the range of 2 × 10¹～2 × 10³ pmol/L. Compared to other methods, our sensing system has achieved an ultra-sensitive detection of OTA with the detection limit as low as 1.697 pmol/L. This strategy could broaden the scope of nanopore detection and have the potential for rapid and in-situ detection of other food contaminants in the future.