Mesoporous DNA-Co@C nanofibers knitted aptasensors performing onsite determination of trace kanamycin residues.

The abuse of kanamycin (KAN) poses an increasing threat to human health by contaminating agricultural and animal husbandry products, drinking water, and more. Therefore, the sensitive detection of trace KAN residues in real samples is crucial for monitoring agricultural pollution, ensuring food safety, and diagnosing diseases. However, traditional assay techniques for KAN rely on bulky instruments and complicated operations with unsatisfactory detection limits. Herein, we developed a novel label-free aptasensor to achieve ultrasensitive detection of KAN by constructing mesoporous DNA-cobalt@carbon nanofibers (DNA-Co@C-NFs) as the recognizer. Leveraging the extended π-conjugation structure, prominent surface area, and abundant pores, the Co@C-NFs can effectively load aptamer strands via π-π stacking interactions, serving as KAN capturer and reporter. Due to the change in DNA configuration upon binding KAN, this aptasensor presented an ultralow detection limit and ultra-wide linear range, along with favorable precision and selectivity. Using real tap water, milk, and human serum samples, the aptasensor accurately reported trace KAN levels. As a result, this convenient and rapid autosensing technique holds promise for onsite testing of other antibiotic residues in agriculture, food safety, and clinical diagnosis.

Simultaneous screening of multiple diarrhetic shellfish poisons with group-specific split aptamers and silver nanocluster beacon.

Poisoning events concerning diarrhetic shellfish poisons (DSPs) are increasing continually. It is extremely necessary to develop simple analysis methods for screening simultaneously different types of DSPs from food-related samples. Okadaic acid (OA) and its analogues, i.e., dinophysistoxin-1 (DTX-1) and dinophysistoxin-2 (DTX-2), are the prevalent DSPs. Herein, a facile and label-free fluorescent aptasensor targeting the three DSPs was constructed with a pair of group-specific split aptamers and silver nanocluster beacon. In presence of the targets, the DNA templates attached at the ends of the split aptamers would be dragged close to trigger enhanced fluorescence signals from silver nanoclusters. The aptasensor offered high sensitivity and good selectivity, with limit of detection of 2.282 nmolL-1, 19.38 nmolL-1, and 13.61 nmolL-1 for OA, DTX-1, and DTX-2, respectively. Moreover, the applicability of aptasensor was well verified with shellfish and seawater samples. This study provides good reference for further exploration on analysis methods for food-related molecules.

One-step impedimetric NT-proBNP aptasensor targeting cardiac insufficiency in artificial saliva.

Currently, sensitive and accurate approaches for diagnosis, rapid assessment, and cardiac biomarker monitoring in patients with heart failure are needed. In this context, the advantages of aptamers over traditional antibodies have been employed to fabricate a single-step impedimetric N-terminal pro b-type natriuretic peptide (NT-proBNP)-modified gold microelectrode array. The development of an electrochemical aptasensing platform was based on the coimmobilization of alkanethiol self-assembled monolayers and amine-terminated aptamer that specifically recognized cardiac NT-proBNP protein resulting in charge electron transfer. Electroimpedimetric signals of the sensor were observed to be linear to the NT-proBNP concentrations in the range of 5.0 × 10-3 to 1.0 pg mL-1 (R2 = 0.9624), while achieving a low detection limit of 5.0 × 10-3 pg mL-1. Clinically relevant detection levels for NT-proBNP were achieved in a simple, rapid, and label-free measurement using artificial saliva, which was highlighted to be specific, regenerative, and selective over potential interferers occurring during the processes of cardiac insufficiency, Therefore, the novel NT-proBNP aptasensor is a promising point-of-care tool exhibiting safe, non-invasive, affordable, and non-prescription home use accessible to overcome the limitations associated with conventional ELISA and previous aptasensing.

A highly selective and sensitive competitive aptasensor capable of quantifying thrombin elevated with side effects in severe COVID-19.

To protect critical injury from blood clots with side effects in severe COVID-19, a highly selective and sensitive biosensor was developed for the quantification of trace levels of thrombin using the combination of a DNA aptamer (TBA) of thrombin and a complementary strand of TBA. TBA rapidly binds with thrombin, whereas it slowly binds with the complementary strand to form a double stranded DNA (dsDNA). SFC green intercalated into dsDNA cannot emit light in 1,1'-oxalyldiimidazole chemiluminescence (ODI-CL) reaction because high-energy intermediates formed from ODI-CL reaction cannot transfer energy to SFC trapped in dsDNA. However, SFC freely existing with the formation of G-quadruplex from the reaction of thrombin and TBA emits bright chemiluminescence because the high-energy intermediates can transfer energy to SFC (or camel) in solution. Thus, the brightness of light emitted in ODI-CL reaction was proportionally enhanced with the increase of thrombin in a sample due to the increase of G-quadruplex and reduction of dsDNA. The limit of detection (LOD) of the label free aptasensor operated with good linear calibration curve (10-320 mU/ml) was as low as 3 mU/ml (or 43 pM). Also, the biosensor was quantified trace levels of thrombin with good accuracy, precision, and reliability.

Label free aptasensor for ultrasensitive detection of tobramycin residue in pasteurized cow's milk based on resonance scattering spectra and nanogold catalytic amplification.

TOB aptamer can be adsorbed on the AuNPs surface to form AuNPs-aptamer complexation to prevent AuNPs aggregation in high salt solution. When TOB was added to the AuNPs solution, the aptamer would bind with TOB and depart from the AuNPs surface. The amount of the AuNPs-aptamer complexation depends on the TOB concentration. Different concentration of AuNPs-aptamer can catalyze the reduction reaction of CuSO4 to produce different size Cu2O particle. The resonance scattering peak intensities are correlated with the Cu2O size. Large size Cu2O particle as a resonance scattering spectroscopy probe can remarkable improve the TOB detection sensitivity. We have succeeded to detect the trace TOB in aqueous solutions. The linear range and limit of detection were 0.50-17 nM and 0.19 nM, respectively. This simple and inexpensive method exhibited high sensitivity and selectivity, which was successfully used to detect TOB in milk. The results indicated the accuracy and precision were satisfied.

Covalent organic framework-based electrochemical aptasensors for the ultrasensitive detection of antibiotics.

We designed and synthesized a novel covalent organic framework (COF) by condensation polymerization of 1,3,6,8-tetrakis(4-formylphenyl)pyrene and melamine through imine bonds (represented by Py-M-COF). The basic characterizations revealed that the Py-M-COF not only exhibited an extended π-conjugation framework, a large specific surface area (495.5 m2 g-1), big pore cavities, and nanosheet-like structure but also possessed rich functional groups, such as CË­C, CË­N, CË­O, and NH2. These features endowed the Py-M-COF with high charge carrier mobility, further improving the strong immobilization of DNA aptamer strands via π-π stacking interaction and electrostatic interaction. As such, the Py-M-COF-based electrochemical aptasensors are ultrasensitive in detecting different antibiotics, including enrofloxacin (ENR) and ampicillin (AMP), yielding extremely low detection limits of 6.07 and 0.04 fg mL-1 (S/N = 3) toward ENR and AMP, respectively, along with other excellent sensing performances. This biosensing platform based on Py-M-COF has potential applications for the sensitive detection of antibiotics or other analytes by replacing the corresponding aptamers.

Selection of a DNA Aptamer against Zearalenone and Docking Analysis for Highly Sensitive Rapid Visual Detection with Label-Free Aptasensor.

Contamination of feed with zearalenone (ZEN) presents a significant risk to animal health. Here, a visible, rapid, and cost-effective aptamer-based method is described for the detection of ZEN. After 8 rounds of SELEX (systematic evolution of ligands by exponential enrichment) with an affinity-based monitor and counter-screening process, the ssDNA aptamer Z100 was obtained, which had high affinity (dissociation constant = 15.2 ± 3.4 nM) and good specificity. Docking analysis of Z100 indicated that noncovalent bonds (π-π interactions, hydrogen bonds, and hydrophobic interactions) helped ZEN to anchor in the binding sites. Finally, a label-free detection method based on gold nanoparticles and Z100 at 0.25 µM was developed for ZEN determination. Excellent linearity was achieved, and the lowest detection limit was 12.5 nM. This rapid and simple method for ZEN analysis has high sensitivity and can be applied for on-site detection of ZEN in animal feeds.

Selection of an aptamer against Muscovy duck parvovirus for highly sensitive rapid visual detection by label-free aptasensor.

Muscovy duck parvovirus (MDPV) causes high mortality and morbidity in ducks. This study investigated a novel aptamer-based, label-free aptasensor detection of MDPV. In this study, we developed an ssDNA aptamer using the filtration partition and lambda exonuclease method with an affinity-based monitor and counter-screening process. After 15 rounds of SELEX (systematic evolution of ligands by exponential enrichment), the ssDNA aptamer Apt-10, which specifically bound to MDPV with high affinity (Kd = 467nM) was successfully screened, and the aptamer was also found to be good specific to MDPV. The selected Apt-10 aptamer can be used to distinguish MDPV and goose parvovirus (GPV). Three-dimensional structural analysis of the Apt-10 aptamer indicated that it folded into a compact stem-loop motif, which was related to its high affinity. Finally, a label-free detection method based on unmodified gold nanoparticles and Apt-10 aptamer was developed for MDPV determination. The concentration of Apt-10 aptamer at 5µM was optimal for MDPV determination in the label-free aptasensor. Excellent linearity was acquired and the lowest detection limit was 1.5 or 3 EID50 (50% egg infection dose) of MDPV, respectively, depending upon spectrophotometry or the naked eye were used. These results show the potential of the aptamer for the rapid detection of MDPV and antiviral research.

An ultrasensitive aptasensor for hemin and hemoglobin based on signal amplification via electrocatalytic oxygen reduction.

The present study aims at the fabrication of a novel electrochemical aptasensor, Ap-GA-AMSN-GCE, for the label-free determination of hemin and hemoglobin (Hb). Basically, the electrochemical reduction current of hemin or Hb incubated on Ap-GA-AMSN-GCE in the presence of oxygen serves as an excellent signal for quantitative determination of these analytes. By differential pulse voltammetry, the calibration plot was linear in the concentration range of 1.0 × 10-19-1.0 × 10-6 M of hemin and Hb. Also, the detection limits, DL, of hemin and Hb were found to be 7.5 × 10-20 M and 6.5 × 10-20 M respectively. According to the experimental results, using the proposed aptasensor in the absence of any oxygen molecule in the analytical solution, the DL value of hemin was 1.0 × 10-12 M. The very low DL obtained in the presence of oxygen is due to the excellent electrocatalytic activity of hemin and Hb incubated on the aptasensor for oxygen reduction. This electrocatalytic activity has a key role in bringing about excellent low detection limits, DL, and wide linear concentration ranges of analytes. Finally, this aptasensor was satisfactorily used for the determination of Hb in human blood samples.

Petal-like CdS nanospheres-based electrochemiluminescence aptasensor for detection of IgE with gold nanoparticles amplification.

A facile label-free electrochemiluminescence (ECL) aptasensor was designed for sensitive detection of human immunoglobulin E (IgE) using petal-like CdS nanospheres and Au nanoparticles (AuNPs) as sensing platform. To construct the aptasensor, petal-like CdS nanospheres as ECL emitter were firstly synthesized and immobilized on the chitosan-coated glassy carbon electrode (GCE) surface. Chitosan was coated on the CdS/CS/GCE again with two coating numbers to produce a stable ECL signal and facilitate subsequent AuNPs immobilization. The construction of aptasensor was achieved after IgE aptamer was adsorbed onto the AuNPs. The detection of IgE was performed upon the incubation of the interface with target protein IgE. Under the optimum conditions, the ECL signal decreased depending linearly on the logarithmic value of IgE concentration ranging from 5.0×10(-13) to 1.0×10(-9)M with a regression equation of I=-15254.8-2129.3 logc (R(2)=0.996). The detection limit was experimentally found to be 8.0×10(-14)M. The applicability of the constructed aptasensor was demonstrated in the determination of IgE in human serum samples.